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Birch reactions employing alkali metals in ammonia have been a well‐established method for the reduction and functionalisation of aromatic compounds for nearly 100 years. Speculations regarding intermediates in the reaction pathway have been discussed since the beginning. We hereby report the isolation of NMe4(HNaph) (1), a kinetically trapped intermediate of the Birch reaction of naphthalene and sodium in liquid ammonia. 1 has been fully characterised and has been shown to continue to react to 1,2/1,4‐dihydronaphthalene – the Birch product of the reduction of naphthalene. The reactivity of 1 was investigated towards activity as an electron and hydride transfer agent with both, elements and small organic molecules. 1 demonstrates a tamed reduction potential which allows for controlled reactions such as the selective formation of hexasulphide and hexaselenide anions. [ABSTRACT FROM AUTHOR]

Birch reductions are well‐known transformations of arenes, applied for large scale synthesis of 1,4‐cyclohexadienes. Herein, we describe first reactions of benzoic acids in the presence of carbonyl compounds, affording aldol products in moderate to high yields. Alkyl aldehydes give the expected nonconjugated dienes by reaction at the α‐position. Interestingly, the intermediately formed enolate attacks aryl aldehydes and ketones from its γ‐position, which can be explained by steric hindrance. This opens the door for the one‐pot synthesis of 1,3‐cyclohexadienes, which are not accessible by classical Birch reductions. Our method is applicable to benzoic, m‐ and p‐toluic acid and various carbonyl compounds, and more than 25 new products were isolated in up to 93 % yield. Prochiral aryl aldehydes afford diastereomeric mixtures in ratios of about 4 : 1, but in the cyclohexadiene ring only trans isomers are formed with high selectivity. Finally, the 1,3‐cyclohexadienes are suitable precursors for further transformations, which we have demonstrated in first examples. Thus, aromatization affords products of a formal meta selective Friedel–Crafts alkylation, and four new stereocenters were generated by cycloaddition of singlet oxygen with excellent selectivity. [ABSTRACT FROM AUTHOR]

This document provides information on the synthesis of the dopamine agonist Rotigotine, which is used to treat Parkinson's disease and restless leg syndrome. The authors discuss different synthetic approaches and successfully synthesized Rotigotine using reductive amination with a high yield. The document also includes information on the synthesis and characterization of three compounds related to Rotigotine, along with their spectral data. Additionally, it provides details on the synthesis and chiral separation of (±)-Rotigotine, including its chemical structure, physical properties, and analytical data. The authors acknowledge Chemveda Life Sciences for their assistance in the separation process. [Extracted from the article]

α,β-Doymamış karbonil bileşikleri olan iki asit, bir ester ve bir kalkon bileşikleri farklı şartlarda Birch indirgemeleri incelendi. Ayrıca, gerilimli izole çift bağlar içeren norbornadien ve benzonorbornadien bileşiklerinin de farklı şartlarda Birch indirgemeleri incelendi.

In this contribution, we present "Birch‐type", and other reductions of simple arenes by the potassium salt of an anionic magnesium dinitrogen complex, [{K(TCHPNON)Mg}2(μ‐N2)] (TCHPNON=4,5‐bis(2,4,6‐tricyclohexylanilido)‐2,7‐diethyl‐9,9‐dimethyl‐xanthene), which acts as a masked dimagnesium(I) diradical in these reactions. This reagent is non‐hazardous, easy‐to‐handle, and in some cases provides access to 1,4‐cyclohexadiene reduction products under relatively mild reaction conditions. This system works effectively to reduce benzene, naphthalene and anthracene through magnesium‐bound "Birch‐type" reduction intermediates. Cyclohexadiene products can be subsequently released from the magnesium centres by protonolysis with methanol. In contrast, the reduction of substituted arenes is less selective and involves competing reaction pathways. For toluene and 1,3,5‐triphenylbenzene, the structural authentication of "Birch‐type" reduction intermediates is conclusive, although the formation of corresponding 1,4‐cyclohexadiene derivatives was low yielding. Reduction of anisole did not yield an isolable "Birch‐type" intermediate, but instead gave a C−O activation product. Treating triphenylphosphine with [{K(TCHPNON)Mg}2(μ‐N2)] resulted in the extrusion of both biphenyl and dinitrogen to afford a magnesium(II) phosphanide [{K(TCHPNON)Mg(μ‐PPh2)}2]. Reduction of fluorobenzene proceeded via C−F activation of the arene, and isolation of the magnesium(II) fluoride [{K(TCHPNON)Mg(μ‐F)}2]. Finally, the two‐electron reduction of 1,3,5,7‐cyclooctatetraene (COT) with [{K(TCHPNON)Mg}2(μ‐N2)] yielded a complex, [{K(TCHPNON)Mg}2(μ‐COT)], incorporating the aromatic dianion (COT2−). [ABSTRACT FROM AUTHOR]

Dearomative partial reduction is an extraordinary approach for transforming benzenoid arenes and has been well‐known for many decades, as exemplified by the dehydrogenation of Birch reduction and the hydroarylation of Crich addition. Despite its remarkable importance in synthesis, this field has experienced slow progress over the last half‐century. However, a revival has been observed with the recent introduction of electrochemical and photochemical methods. In this Minireview, we summarize the recent advancements in dearomative partial reduction of benzenoid arenes, including dihydrogenation, hydroalkylation, arylation, alkenylation, amination, borylation and others. Further, the intriguing utilization of dearomative partial reduction in the synthesis of natural products is also emphasized. It is anticipated that this Minireview will stimulate further progress in arene dearomative transformations. [ABSTRACT FROM AUTHOR]

Birch reduction and similar dissolved metal‐type transformations hold significant importance in the organic synthesis toolbox. Historically, the field has been dominated by alkali metal reductants. In this study, we report that largely neglected, low‐reactive alkaline earth metals can become powerful and affordable reductants when used in a ball mill under essentially solvent‐free conditions, in the presence of ethylenediamine and THF as liquid additives. Calcium can reduce both electron‐deficient and electron‐rich arenes, with yields of products similar to those obtained with lithium metal. Magnesium reveals enhanced reducing power, enabling the reduction of benzoic acids while keeping electron‐rich aromatic moieties intact and allows for chemoselective transformations. The developed mechanochemical approach uses readily available and safer‐to‐handle metals, operates under air and ambient temperature conditions, and can be used for gram‐scale preparations. Finally, we demonstrate that the developed conditions can be used for other dissolved metal‐type reductive transformations, including reductive amination, deoxygenation, dehalogenation, alkene and alkyne reductions. [ABSTRACT FROM AUTHOR]

In this study, we report a mechanochemical protocol for highly efficient and air-tolerant calcium-based Birch reduction. The developed mechanochemical approach allows the use of readily available calcium metal as a safer-to-handle reductant for Birch reduction of various aromatic compounds. The reaction was rapid and the desired dearomatization products were obtained in good yields within 15 min at ambient temperature. Notably, all synthetic operations can be performed under ambient conditions without a complicated reaction setup involving inert gases. The feasibility of the gram-scale synthesis was demonstrated, further highlighting the practical utility of this protocol. [ABSTRACT FROM AUTHOR]

Group 1 elements exhibit the lowest electronegativity values in the Periodic Table. The chemical reduction of Group 1 metal cations M+ to M(0) is extremely challenging. Common tetraaryl borates demonstrate limited redox properties and are prone to decomposition upon oxidation. In this study, by employing simple yet versatile bipyridines as ligands, we synthesized a series of redox-active borate anions characterized by NMR and X-ray single-crystal diffraction. Notably, the borate anion can realize the reduction of Li+, generating elemental lithium metal and boron radical, thereby demonstrating its potent reducing ability. Furthermore, it can serve as a powerful two-electron-reducing reagent and be readily applied in various reductive homo-coupling reactions and Birch reduction of acridine. Additionally, this borate anion demonstrates its catalytic ability in the selective two-electron reduction of CO2 into CO. Chemical reduction of alkali cations to their metals is extremely challenging. Here, the authors synthesized a series of redox-active borate anions stabilized by bipyridine ligands which can reduce lithium ions generating elemental lithium metal and borate radicals. [ABSTRACT FROM AUTHOR]

Cyclohexane (CHA), cyclohexene (CHE), and 1,4-cyclohexadiene (CHD) derivatives have a wide variety of applications and scope in synthetic and industrial organic chemistry. These cyclic hydrocarbons are found in a variety of natural products, including herbal plants and fruits as basic fragrance components. The extraction and isolation of these essential hydrocarbons are too complex and difficult to pursue. However, the reduction of benzene and its derivatives is an essential and effective approach for producing CHA, CHE, and CHD derivatives. To obtain CHA, CHE, and CHD derivatives, several types of reduction techniques for benzene and its derivatives have been developed over the years, including various forms of catalytic hydrogenation, Benkeser reduction, classic and many modified Birch reductions such as ammonia-free, metal-free photochemical, solvent-free, electrochemical and electride-mediated Birch reduction. In this study, the comparison of chemoselectivity, regioselectivity, reaction conditions, reduction efficiency, and environmentally acceptable approaches of these techniques used for benzene reduction are summarized. [ABSTRACT FROM AUTHOR]

Routes to the framework of perylenequinone‐derived mycotoxins of the dihydroanthracene type are described. Starting with anthracene derivatives, attachment of C3 units at positions 9 and 10 and twofold cyclization would furnish the required pentacycle. Heck‐type couplings, SN2 additions of enolates, alkynyl and allyl additions turned out to be not successful, while addition of a Grignard reagent prepared from acetal‐protected 3‐bromopropionaldehyde to anthraflavic acid methyl ester, subsequent acetal cleavage, and Birch reduction furnished octahydroperylene in only four steps. [ABSTRACT FROM AUTHOR]

Enantioselective total synthesis of the aglycone of burnettramic acid A, an antifungal pyrrolizidinedione with a terminally mannosylated long acyl chain produced by Aspergillus fungi, has been achieved from a known carboxylic acid by a 14-step sequence. The key steps include 2 types of asymmetric alkylation, coupling of an acetylide intermediate with (S)-epichlorohydrin to provide an acetylenic epoxide in 1 pot, and the Birch reduction to effect desulfonylation, semi-reduction of triple bond, and debenzylation in a concurrent manner. Good agreement of the synthetic aglycone with naturally occurring one in 1 H and 13 C nuclear magnetic resonance (NMR) spectra, coupled with previously reported unambiguous stereochemical assignment of the sugar moiety, has confirmed the structure of burnettramic acid A. [ABSTRACT FROM AUTHOR]

(Hetero)arene reduction is one of the key avenues for synthesizing related cyclic alkenes and alkanes. While catalytic hydrogenation and Birch reduction are the two broadly utilized approaches for (hetero)arene reduction across academia and industry over the last century, both methods have encountered significant chemoselectivity challenges. We hereby introduce a highly chemoselective quinoline and isoquinoline reduction protocol operating through selective energy transfer (EnT) catalysis, which enables subsequent hydrogen atom transfer (HAT). The design of this protocol bypasses the conventional metric of reduction reaction, that is, the reductive potential, and instead relies on the triplet energies of the chemical moieties and the kinetic barriers of energy and hydrogen atom transfer events. Many reducing labile functional groups, which were incompatible with previous (hetero)arene reduction reactions, are retained in this reaction. We anticipate that this protocol will trigger the further advancement of chemoselective arene reduction and enable the current arene‐rich drug space to escape from flatland. [ABSTRACT FROM AUTHOR]

The typical Birch reduction transforms arenes into cyclohexa‐1,4‐dienes by using alkali metals, an alcohol as a proton source, and an amine as solvent. Capitalizing on the strong photoreductive properties of peri‐xanthenoxanthene (PXX), herein we report the photocatalyzed "Birch‐type" reduction of acenes by employing visible blue light irradiation at room temperature in the presence of air. Upon excitation at 405 or 460 nm in the presence of a mixture of N,N‐diisopropylethylamine (DIPEA) and trifluoromethanesulfonimide (HNTf2) in DMSO, PXX photocatalyzes the selective reduction of full‐carbon acene derivatives (24–75 %). Immobilization of PXX onto polydimethylsiloxane (PDMS) beads (PXX‐PDMS) allowed the use of the catalyst in heterogeneous batch reactions, giving 9‐phenyl‐9,10‐dihydroanthracene in high yield (68 %). The catalyst could easily be recovered and reused, with no notable drop in performance observed after five reaction cycles. Integration of the PXX‐PDMS beads into a microreactor enabled the reduction of acenes under continuous‐flow conditions, thereby validating the sustainability and scalability of this heterogeneous‐phase approach. [ABSTRACT FROM AUTHOR]

Herein, we show that the combination of the Birch reduction of readily available anisole derivatives and the catalytic asymmetric inverse‐electron‐demand Diels–Alder reaction of 2‐pyrones can serve as a powerful platform for the diverse synthesis of synthetically important cis‐decalin scaffolds. Enabled by a well‐modified chiral bis(oxazoline) ligand/CuII complex, a wide range of polysubstituted cis‐decalin scaffolds with up to six contiguous stereocenters were generated efficiently. The synthetic potential of this method is demonstrated by the concise synthesis of the sesquiterpene (+)‐occidentalol and a key intermediate for seven triterpenes. Mechanistic studies suggest the 1,3‐cyclohexadienes formed in situ are the key intermediates, and efficient kinetic resolution occurs when C2‐ and/or C3‐substituted 1,4‐cyclohexadienes are utilized as substrates. DFT calculations elucidated that the Diels–Alder reaction proceeds in a stepwise fashion and revealed the origins of the stereoselectivities. [ABSTRACT FROM AUTHOR]

Highly oxygenated cardiotonic steroids, such as ouabain, possess a wide spectrum of biological functions and remain significant synthetic challenges. Herein, we have applied an unsaturation‐functionalization strategy and developed a synthetic method in addressing the C19‐hydroxylation issue for efficient synthesis of polyhydroxylated steroids. An effective asymmetric dearomative cyclization allowed the construction of the C19‐hydroxy unsaturated steroidal skeleton in only four steps from the Hajos‐Parrish ketone ketal 7. The synthetic sequence featured C3−OH‐directed hydrogenation/epoxidation, m‐CPBA‐triggered epoxidation/SN2′ nucleophilic substitution, Birch reduction of an enone, and regioselective LiAlH4 reduction to furnish the polyhydroxy functionalities on the steroid skeleton with high stereochemical control and efficiency. This approach ultimately enabled the total synthesis of 19‐hydroxysarmentogenin and ouabagenin in 18 and 19 steps, respectively, overall. The synthesis of these polyhydroxylated steroids offers synthetic versatility and practicality in the search for new therapeutic agents. [ABSTRACT FROM AUTHOR]

Birch reduction has been widely used in organic synthesis for over half a century as a powerful method to dearomatize arenes into 1,4‐cyclohexadiene derivatives. However, the conventional Birch reduction reaction using liquid ammonia requires laborious procedures to ensure inert conditions and low temperatures. Although several ammonia‐free modifications have been reported, the development of an operationally simple, efficient, and scalable protocol remains a challenge. Herein, we report an ammonia‐free lithium‐based Birch reduction in air without special operating conditions using a ball‐milling technique. This method is characterized by its operational simplicity and an extremely short reaction time (within 1 min), probably owing to the in situ mechanical activation of lithium metal, broad substrate scope, and no requirement for dry bulk solvents. The potential of our flash Birch reaction is also demonstrated by the efficient reduction of bioactive target molecules and gram‐scale synthesis. [ABSTRACT FROM AUTHOR]

Functionalization of graphene's two-dimensional sheets can be used to modify the physical properties of graphene, such as changing its conductivity or inducing ferromagnetism, which is of broad interest for a myriad of applications. However, functionalized graphene can possess significant structural disorder that is often overlooked and is difficult to characterize quantitatively. Here we investigate hydrogenated graphene nanopowder (H-Gr) produced by Birch reduction of graphene oxide. By combining complementary x-ray and neutron diffraction, we show how to quantitatively characterize the H-Gr nanostructure, including the hydrogen content. We show that the majority of the H-Gr consists of highly disordered molecular-scale carbon while a small portion of the sample contains few-layered graphene having an expanded interlayer spacing. Modeling the coherent diffuse scattering for both x-ray and neutron diffraction, and comparing it with the incoherent neutron scattering, the hydrogen to carbon ratio was measured and it was determined that most of the hydrogen resides within the disordered carbon rather than in the graphene. Evidence is presented for hydrogen clustering as well as for hydrogen bonded perpendicular to the plane of molecular-carbon bonds. Our quantitative approach to characterizing carbon nanopowders has broad relevance to understanding disorder and bonding of hydrogen in graphitic carbons and other nanomaterials. [Display omitted] [ABSTRACT FROM AUTHOR]

The Birch reduction of biaryls generally converts one of the two arenes into a cyclohexa-1,4-diene. Biaryls are more reactive than monocyclic arenes under the Birch conditions. Unlike the reduction of monocyclic arenes, biaryl reduction proceeds through two consecutive electron transfer steps before the protonation of the dianion intermediate. The biaryl reductions and subsequent alkylations in one pot rapidly increase the molecular complexity and thus have been used in the synthesis of natural products and drug-like molecules. 1 Introduction 2 The Physical Organic Chemistry of the Birch Reduction of Biaryls 3 Biaryls as the Mediators of Electron Transfer 4 Methods for the Dissolving-Metal Reduction of Biaryls 5 Intercepting the Biaryl Reduction Intermediates with Electrophiles 6 Synthetic Applications of the Dissolving-Metal-Mediated Reductions of Biaryls 7 Outlook [ABSTRACT FROM AUTHOR]

An established concept to create radical intermediates is photoexcitation of a catalyst to a higher energy intermediate, subsequently leading to a photoinduced electron transfer (PET) with a reaction partner. The known concept of consecutive photoinduced electron transfer (con-PET) leads to catalytically active species even higher in energy by the uptake of two photons. Generally speaking, increased photon uptake leads to a more potent reductant. Here, we report the concept of multi-photoinduced electron transfer catalysis (>2 photons), termed multi-PET, which is enabled by photoinduced one-electron reductions of an organic dye. Further irradiation of the doubly reduced species leads to a photoexcited dianionic super-reductant, which is more potent than Li metal - one of the strongest chemical reductants known. This multi-photon process which is enabled by 390 nm LEDs allows the cleavage of strong carbon-fluorine bonds and reduction of other halides even in very electron-rich substrates. The resulting radicals are quenched by hydrogen atoms or engaged in carbon-carbon and carbon-phosphorus bond formations, highlighting the utility of multi-PET for organic chemistry. In addition, multi-PET enabled Birch-type reductions. Spectroscopic, chemical and computational investigations are presented to gain mechanistic insights., (© 2024 Wiley‐VCH GmbH.)

This article discusses the advances in electrosynthesis for a greener chemical industry. It highlights the potential of renewable electricity in powering chemical plants and driving thermocatalytic processes, as well as its role in reducing the environmental footprint of the chemical industry. Electrosynthesis, which uses electrons as an energy source and green reagent, offers opportunities for increased selectivity, green reaction pathways, and reduced chemical waste. The article also explores the modular nature of electrochemical reactors and their suitability for distributed chemical manufacturing. Various studies on electrosynthesis and electrochemical manufacturing are presented, including their applications in the production of green hydrogen, ammonia, hydrogen peroxide, and commodity chemicals. The article concludes by discussing the importance of electrosynthesis in environmental remediation, waste treatment, and computational methods for chemical transformation. [Extracted from the article]

Aromatic [5,5]-rearrangement can in principle be an ideal protocol to access dearomative compounds. However, the lack of competent [5,5]-rearrangement impedes the advance of the protocol. In this Article, we showcase the power of [5,5]-rearrangement recently developed in our laboratory for constructing an intriguing dearomative sulfonium specie which features versatile and unique reactivities to perform nucleophilic 1,2- and 1,4-addition and cyclization, thus achieving dearomative di- and trifunctionalization of easily accessible aryl sulfoxides. Impressively, the dearomatization products can be readily converted to sulfur-removed cyclohexenones, naphthalenones, bicyclic cyclohexadienones, and multi-substituted benzenes. Mechanistic studies shed light on the key intermediates and the remarkable chemo-, regio- and stereoselectivities of the reactions. In contrast with well-established dearomatization protocols such as the Birch reduction, sigmatropic rearrangement-based dearomatizations are a less-explored but potentially effective route to saturated compounds. Here, the authors show a [5,5]-rearrangement-enabled dearomatization of aryl sulfoxides. [ABSTRACT FROM AUTHOR]

New materials are the backbone of their technology‐driven modern civilization and at present carbon nanostructures are the leading candidates that have attracted huge research activities. Diamanes and diamanoids are the new nanoallotropes of sp3 hybridized carbon which can be fabricated by proper functionalization, substitution, and via Birch reduction under controlled pressure using graphitic system as a precursor. These nanoallotropes exhibit outstanding electrical, thermal, optical, vibrational, and mechanical properties, which can be an asset for new technologies, especially for quantum devices, photonics, and space technologies. Moreover, the features like wide bandgap, tunable thermal conductivity, excellent thermal insulation, etc. make diamanes and diamanoids ideal candidates for nano‐electrical devices, nano‐resonators, optical waveguides, and the next generation thermal management systems. In this review, diamanes and diamanoids are discussed in detail in terms of its historical prospect, method of synthesis, structural features, broad properties, and cutting‐edge applications. Additionally, the prospects of diamanes and diamanoids for new applications are carefully discussed. This review aims to provide a critical update with important ideas for a new generation of quantum devices based on diamanes and diamanoids which are going to be an important topic in the future of carbon nanotechnology. [ABSTRACT FROM AUTHOR]

The [Ir]-catalysed carbenoid insertion and cyclization of N-arylpyrazolones has been carried out with α-diazotized Meldrum's acid to access tricyclic pyrazolone fused 1,4-dihydrocinnolin-3-one derivatives. Further, the selective reduction of these tricyclic derivatives has been studied under Birch reduction conditions. [ABSTRACT FROM AUTHOR]

In the title compound, two tert-butyl groups replace the two hydrogen atoms at the C2 and C3 positions of the cyclohexadiene, respectively, and the electrophilic ester group replaces the hydrogen atom at the benzene ring position, as shown in the figure. Since all hydrogen atoms in this structure are not conformational isomers, * is used to distinguish all hydrogen atoms. [Extracted from the article]

In the title compound, two tert-butyl groups replace the two hydrogen atoms at the C2 and C3 positions of the cyclohexadiene, respectively, and the electrophilic ester group replaces the hydrogen atom at the benzene ring position, as shown in the figure. Since all hydrogen atoms in this structure are not conformational isomers, * is used to distinguish all hydrogen atoms. [Extracted from the article]

A convenient method for the synthesis of γ‐spirolactones in only 2–3 steps is described. Birch reduction of inexpensive and commercially available aromatic carboxylic acids in the presence of ethylene oxide affords hydroxy acids, which undergo direct lactonization during work‐up. Suitable precursors are methyl‐substituted benzoic acids, naphthoic, and dicarboxylic acids. Subsequent hydrogenation proceeds smoothly with Pd/C as catalyst and saturated γ‐spirolactones are isolated in excellent yields and stereoselectivities. Thus, up to 3 new stereogenic centers can be constructed as sole diastereomers from achiral benzoic acids. Furthermore, it is possible to control the degree of saturation with Raney nickel or Wilkinson's catalyst to obtain products with 1 double bond. Overall, more than 30 new γ‐spirolactones have been synthesized in analytically pure form. [ABSTRACT FROM AUTHOR]

An easy-to-handle sodium dispersion in paraffin oil (SD), in combination with inexpensive and environmentally benign 1,3-dimethyl-2-imidazolidinone (DMI) as an additive enables the Birch-type reduction of a variety of arenes with high yields, selectivity, and tolerance of functionality such as ether, alcohol, amine, amide, and carboxylic acid. [ABSTRACT FROM AUTHOR]

In this study, we have developed a variable pressure operating hollow cathode discharge (HCD) ion source to investigate the gas phase ion-molecule reactions of nitroaromatic explosive compounds. The developed HCD ion source coupled MS system has also been validated as an analytical method to analyze explosives at trace levels. The ion source was designed in such a way that the plasma can be generated alternatively at high pressure (~30 Torr), medium pressure (~5 Torr) and low pressure (~1 Torr) regions. The plasma contains a sufficient amount of reactant ions, electrons and excited species, thus the gaseous analyte molecules were efficiently ionized when they passed through the plasma. In the ion-molecule reactions of the nitroaromatic explosives, the discharge products of NO x − (x = 2,3), O 3 and HNO 3 originating from the plasma-excited air were suggested to contribute to the formation of mostly [M − H]-, [M − NO]-, [M+NO 3 –HNO 2 ]- and [M-NO+HNO 3 ]- adduct ions at the higher ion source pressures (~5 and 28 Torr) while the electron rich plasma leads to the formation of molecular ion, M−•, at the lower ion source pressure (~1 Torr). Formation of the hydride-adduct ions of the nitroaromatic compounds reveals the surface-assisted Birch type reduction in the HCD plasma. The variety of spectral patterns in the air-assisted glow discharge would be useful for high through-put detection of TNT and TNT-related explosives. An ambient helium dielectric barrier discharge (DBD) ion source was also used and gave identical mass spectra of the nitroaromatic explosive compounds to those observed by the HCD ion source, but did not give any hydride-adduct ions of the explosive compounds. Ion formation mechanism of these ions is also discussed. Gas phase ion-molecule reactions of nitroaromatic explosive compounds studied by hollow cathode discharge ionization-mass spectrometry. [Display omitted] • Development of variable pressures hollow cathode discharge ion source. • Gas phase ion-molecule reactions of nitroaromatic explosives by mass spectrometry. • High ion source pressure facilitates adduct ion, low pressure provides molecular ion. • Metallic surface leads Birch reduction type reactions that lead hydride-adduct ions. • High through-put detection of TNT and TNT-related explosives. [ABSTRACT FROM AUTHOR]

Monocyclic ß-lactams (azetidin-2-ones) exhibit a wide range of biological activities, the most important of which are antibacterial, anticancer, and cholesterol absorption inhibitory activities. The synthesis of decorated monocyclic ß-lactams is challenging because their ring is highly constrained and consequently reactive, which is also an important determinant of their biological activity. We present the optimized synthesis of orthogonally protected 3-amino-4-substituted monocyclic ß-lactams. Among several possible synthetic approaches, Staudinger cycloaddition proved to be the most promising method for initial ring formation, yielding monocyclic ß-lactams with different substituents at the C-4 position, a phthalimido-protected 3-amino group, and a (dimethoxy)benzyl protected ring nitrogen. Challenging deprotection methods were then investigated. Oxidative cleavage with cerium ammonium nitrate and ammonia-free Birch reduction was found to be most effective for selective removal of ring nitrogen protection. Hydrazine hydrate was used for deprotection of the phthalimido group, and the procedure had to be modified by the addition of HCl in the case of aromatic substituents at the C-4 position. The presented methods and the synthesized 3-amino-4-substituted monocyclic ß-lactam derivatives are an important step toward new ß-lactams with potential pharmacological activities. [ABSTRACT FROM AUTHOR]