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The medicinal importance, natural rarity, and challenges associated with the synthesis of C3-functionalized 1 H -indazoles have propelled the development of novel and practical 1 H -indazole N-oxides for the production of diverse arrays of C3-functionalized 1 H -indazoles. The use of 1 H -indazole N-oxides has been remarkably effective for the selective introduction of diverse functional groups, including amino (NHAr), chloro (Cl), hydroxy (OH), sulfonyl (SO2 Ar), aromatic (Ar), olefin, alkyl, and N-formyl (NRCHO) groups, to indazole pharmacophore molecules. This review offers a concise overview of the synthetic approaches and practical applications of 1 H -indazole N-oxides, including recent studies conducted by the authors. Transformative reactions involving 1 H -indazole N-oxides not only offer strategies for synthesizing C3-functionalized 1 H -indazoles but also hold significant potential in medicinal chemistry. 1 Introduction 2 Synthetic Approaches and Applications of 1 H -Indazole N -Oxides 3 Summary and Outlook [ABSTRACT FROM AUTHOR]

This document provides information on the synthesis and characterization of various compounds belonging to the imidazo[2,1-b][1,3]thiazine family. The compounds were synthesized using a specific method and characterized using various techniques such as NMR and HRMS. The document includes details on the physical properties, yields, and spectral data of each compound. The document also acknowledges the contribution of M. Malikėnas for HRMS measurements and provides a link to supporting information. [Extracted from the article]

An efficient radical cyclization of suitably functionalized ynamides to nitrogen-containing heterocycles is reported. Upon reaction with tributyltin hydride in the presence of catalytic amounts of AIBN in toluene at 80 °C, a range of ynamides bearing a N -iodopropyl chain could be smoothly cyclized, in a highly regio- and stereoselective manner, to the corresponding 2-arylidenepyrrolidines in good to excellent yields. The exocyclic double bond was in addition shown to be an excellent anchor for further chemical diversification and the generality of this radical cyclization could be highlighted by its extension to the synthesis of other nitrogen heterocycles including piperidines, azepanes, pyrazolidines and hexahydropyridazines. [ABSTRACT FROM AUTHOR]

In the course of the synthesis of fused-ring analogues of the antidepressant drug tianeptine, representatives of three new heterocyclic ring systems, indolo[1,7- bc ][1,2]benzothiazepines (and their 4,5-dihydro analogues), 5,6-dihydroquino[1,8- bc ][1,2]benzothiazepines, and [1,2]benzothiazepino[4,3,2- jk ]carbazoles, as well as their intermediates, have been prepared. The tetracyclic and pentacyclic ring systems containing either an oxo or a hydroxy functional group are suitable for introducing various side chains, including potential pharmacophores. For this latter transformation, examples are demonstrated by conversion of the hydroxy group into a chloro moiety and subsequent reaction with amines or with primary alcohols bearing a tertiary amino side chain. Two fused-ring derivatives exhibiting the side-chain characteristics of tianeptine have also been synthesized. Altogether 40 compounds are described in the present manuscript, eight of them are also characterized by single-crystal X-ray diffraction. [ABSTRACT FROM AUTHOR]

The significant pharmacological activity of 2,3-benzodiazepine-4-ones led to an increased interest in this compound family. However, the literature of the closely related 2,3,4-benzothiadiazepine 2,2-dioxides is rather scarce. Earlier we elaborated a synthesis of 5-aryl congeners variously substituted at the aromatic ring. In the present study, a new synthetic route was investigated via highly versatile intermediates, to extend the reaction to a wider aromatic substitution pattern and to the preparation of 5-alkyl and 5-H derivatives. The essence of this approach is, starting from benzaldehyde acetals, acetophenone and benzophenone ketals, to synthesize ortho -formyl- and ortho -acyl-arylmethanesulfonyl chlorides, which are suitable precursors of the target compounds. The synthesis was implemented as follows: ortho -lithiation of the corresponding acetals and ketals and subsequent treatment with paraformaldehyde, or alternatively in two steps, with DMF or ethyl formate, followed by reduction with NaBH4 , led to the corresponding hydroxymethyl derivatives. Reaction of these latter with methanesulfonyl chloride gave mesylates that were used to S -alkylate thiourea to afford S -alkylisothiouronium salts. The final steps of the synthesis were carried out in a telescoped reaction. Treatment of the S -alkylisothiouronium salts with N -chlorosuccinimide resulted in the corresponding arylmethanesulfonyl chlorides. Subsequent reaction with hydrazine hydrate followed by an acidic treatment gave 2,3,4-benzothiadiazepine 2,2-dioxides. [ABSTRACT FROM AUTHOR]

A new approach to the synthesis of 2-(pyrimidin-2-yl)benzoic acids based on the ring contraction of the 2-carbamimidoylbenzoic acid [(2-amidinobenzoic) acid] with 1,3-dicarbonyl compounds and their synthetic equivalents has been developed. The intramolecular condensation of the obtained acids with 1,3-dielectrophiles proceeds with the formation of the 4,6-dihydropyrimido[2,1- a ]isoindole-4,6-dione system, the pyrrolidone ring of which is easily opened under the action of weak nucleophiles. The reaction of 2-amidinobenzoic acid with chromones, which have an aryloxy group at 3-position does not stop at the step of pyrimidine ring formation and undergoes further spontaneous cyclization into 2-(benzo[4,5]furo[3,2- d ]pyrimidin-2-yl)benzoic acids. [ABSTRACT FROM AUTHOR]

Cyclopropenone 1,3-propanediol ketal is an increasingly versatile building block for the introduction of various C3 and dioxaspiro units due to the emergence of numerous methodologies for the application of strained hydrocarbons. This Practical Synthetic Procedure gives an updated synthesis for a basic ketal of cyclopropenone with lowered solvent toxicity and a detailed step-by-step guide for the safe production of potassium amide in liquid ammonia and for its application in the synthesis of the cyclopropene ring. [ABSTRACT FROM AUTHOR]

2-Pyridone is characterized by a very wide range of reactivity of a different nature, ranging from electrophilic aromatic substitution, CH–metal-mediated reactions, and NH/OH functionalization of both possible lactam/lactim tautomers, through cycloaddition, to nucleophilic addition and transformation of the tautomeric C=O/C–OH moiety. The high availability of 2-pyridones and the possibility of their far-reaching functionalization additionally increased their values. Therefore, they are very useful building blocks for the synthesis of structurally diverse piperidine and pyridine compounds, including naturally occurring 2-pyridones. This review reports on the use of simple 2-pyridones in the synthesis of alkaloids and alkaloids-inspired compounds based on the piperidine or pyridine framework. 1 Introduction 2 Structure, Availability, and Reactivity of 2-Pyridones 3 Monocyclic Piperidine Alkaloids from 2-Pyridones 4 Polycyclic Alkaloids, Their Derivatives, and Alkaloid-Inspired Compounds from 2-Pyridones 4.1 New Ring Formation Involving C/N Atoms of the 2-Pyridone Ring 4.1.1 Indolizine-Fused 2-Pyridones: Camptothecins and Related Compounds 4.1.2 Other Indolizines from 2-Pyridones 4.1.3 Compounds Bearing the Quinolizine Ring System 4.2 New Ring Formation Involving C/C Atoms of the 2-Pyridone Ring 4.2.1 C-2/C-3 Ring Fusion 4.2.2 C-3/C-4 Ring Fusion 4.2.3 C-4/C-5 Ring Fusion 4.2.4 C-5/C-6 Ring Fusion 4.2.5 C-2/C-4 Ring Bridge 4.2.6 C-2/C-6 Ring Bridge 4.2.7 C-3/C-5 Ring Bridge 4.2.8 C-3/C-6 Ring Bridge 4.2.9 C-4/C-6 Ring Bridge 5 Conclusion [ABSTRACT FROM AUTHOR]

Because of their biological relevance, cyclic β-amino acids have generated increasing interest and had significant impact in drug research over the past two decades. Their preparation and further functionalization towards new types of molecular entities have received large interest in synthetic and medicinal chemistry. Various types of metathesis reactions, such as ring-opening (ROM), ring-closing (RCM), or cross metathesis (CM) are used widely for access to either alicyclic β-amino acids or other densely functionalized derivatives of this group of compounds. This account intends to provide an insight into the most relevant synthetic routes to this class of derivatives with the application of metathesis reactions. The review focuses on the presentation of selective and stereocontrolled methodologies in view of versatility, robustness, limitations and efficiency. 1 Introduction 2 Synthesis and Transformation of Cyclic β-Amino Acids through Metathesis Reactions 2.1 Synthesis of Five- and Six-Membered Cyclic β-Amino Acids by Ring-Closing Metathesis 2.2 Synthesis of Five- and Six-Membered Cyclic β-Amino Acids by Cross Metathesis 2.3 Synthesis of β-Amino Acids with Larger Ring Systems by Ring- Closing Metathesis 2.4 Synthesis of β-Amino Acids with Condensed Ring Systems by Ring-Rearrangement Metathesis 2.5 Stereocontrolled One-Step Synthesis of Functionalized Cispentacin and Transpentacin Derivatives 2.5.1 Stereocontrolled Synthesis of Functionalized Cispentacin and Transpentacin Derivatives through Ring-Opening Metathesis of Norbornene β-Amino Acid Derivatives 2.5.2 Stereocontrolled Synthesis of Functionalized Azetidinones and β-Amino Acid Derivatives from Condensed Ring β-Lactams by Ring-Opening Metathesis 2.5.3 Carbon–Carbon Double Bond Functionalization of β-Amino Acid Derivatives and β-Lactams with α,β-Unsaturated Carbonyl Compounds through Cross Metathesis 2.5.4 Synthesis of Functionalized β-Amino Acid Derivatives and β-Lactams through Chemoselective Cross Metathesis 3 Conclusions and Outlook. [ABSTRACT FROM AUTHOR]

An improved and scalable synthesis of azulene has been developed by the application of pyrrolidine as a reagent and continuous steam distillation and extraction for workup. Applications for the coloration of perfluorinated media and silicones were demonstrated. [ABSTRACT FROM AUTHOR]

A new efficient synthesis of racemic anatabine is reported. The title target was obtained in an excellent overall yield of 70%, by a five-step synthesis, using cheap reagents and mild reaction conditions. [ABSTRACT FROM AUTHOR]

The C-nor-D-homo-steroidal alkaloid cyclopamine was discovered in the 1969 and in 2000 it was shown to act as an inhibitor of the hedgehog signaling (Hh) pathway, which is aberrantly activated in some tumors. Subsequently it was revealed that this natural occurring alkaloid has also antidiabetic and antiviral properties. In this review we present syntheses of selected C-nor-D-homo-steroidal alkaloids and their analogues and also discuss a general access to C-nor-D-homo-steroids. Some historical as well as biomedical aspects are also presented. 1 Introduction 2 Total Synthesis of Cyclopamine 2.1 Synthesis of exo-Cyclopamine and Further Cyclopamine Analogues 2.2 Synthesis of a Carbacyclopamine Analogue 3 D-Homocyclopamine: Saridegib (IPI-926) 4 Synthesis of Nakiterpiosin 5 Lewis Acid Mediated Nazarov Cyclization as a Versatile Method for C-Nor-D-homo-steroid Synthesis 6 Conclusion. [ABSTRACT FROM AUTHOR]

General routes for the synthesis of 1,3-oxazin-4-ones are discussed, with particular attention paid to recent developments in the field. The syntheses of amine functionalised cyclopropyl carbinols via a hydride-mediated reduction of various 5-chloroethyl-1,3-oxazin-4-enones in moderate to good yield are disclosed. This new method provides an opportunity to access greater structural diversity within these useful synthetic building blocks. [ABSTRACT FROM AUTHOR]

An efficient and flexible four-component route to substituted 1,7,9-decatrien-3-ones was established by alkylation of sodium dialkyl malonates with a chloro-substituted phosphorane followed by a Wittig reaction with the corresponding carbonyl compound. The resulting enones were alkylated at their malonate unit with sorbyl bromide to give the title compounds in good overall yields. In an attempt to improve the overall yield by using in situ generated sorbyl tosylate we discovered the formation of an unusual bicyclic product with a 3-oxocyclopenta[b]furan core that is formally generated by an oxidative dimerization of the employed precursor enone. The structure of this compound was unambiguously determined by an X-ray crystal analysis. [ABSTRACT FROM AUTHOR]

A copper-catalyzed formation of C-N/N-N bonds using N-phenylbenzamidines with aryl nitriles has been developed and affords a route to 1,3,5-trisubstituted 1H-1,2,4-triazoles in moderate to excellent yields. The method is operationally simple and environmentally benign with a large substrate scope available and represents an economical path for numerous C-N/N-N bond formations. [ABSTRACT FROM AUTHOR]

In this study, a one-pot, three-component reaction of two molecules of indane-1,3-dione with aromatic aldehydes for the synthesis of spirocyclopropylindanediones using poly(N-bromo-N-ethylbenzene-1,3-disulfonamide) (PBBS), N,N,N′,N′-tetrabromobenzene-1,3-disulfon­amide (TBBDA), poly(N-chloro-N-ethylbenzene-1,3-disulfonamide) (PCBS), and N,N,N′,N′-tetrachlorobenzene-1,3-disulfonamide (TCBDA) as novel reagents has been developed. In addition, an effective and simple domino procedure for the preparation of spirodicyanocyclopropylindanediones from indane-1,3-dione and 2-arylidenemalononitriles is reported. These reactions involve Michael addition, halogenation, and intramolecular ring-closing (MHIRC) reaction sequences. [ABSTRACT FROM AUTHOR]

Sulfonamides are common building blocks in organic synthesis. They have a wide range of medical applications. This review aims to delineate recent efforts towards the functionalization of primary sulfonamides during last three years and to provide an overview of the synthesis of N-alkylated, N-acylated, and N-arylated sulfonamides from primary sulfonamides. Among other reactions, the sulfonamide-directed C-H functionalization is highlighted. 1 Application of Sulfonamides 2 Synthesis of N-Alkylated Sulfonamides 3 Synthesis of N-Acylated Sulfonamides 4 Synthesis of N-Arylated Sulfonamides 5 Other Chemistry 6 Summary and Perspective [ABSTRACT FROM AUTHOR]

Treatment of α-hydroxy-substituted methoxyallene derivatives with meta-chloroperbenzoic acid provided acyloxy-substituted 1,2-diketones in moderate yields. A mechanism for the formation of these unexpected products is proposed. The configuration of the enantiopure compound (S)-1-(3-methylquinoxalin-2-yl)-1-(4- nitrobenzoyloxy)propan-2-yl 3-chlorobenzoate - determined by X-ray crystal structure analysis - indicates the intermediacy of a carbenium ion during formation of the 1,2-diketones. The functionalized 1,2-diketones are valuable starting materials for a variety of products as demonstrated by the synthesis of quinoxalines, an imidazole derivative, and electrondeficient alkenes. [ABSTRACT FROM AUTHOR]

A simple synthesis of new enantiomeric benzimidazoles was developed. Starting from readily available enantiomeric trans-1,2-diaminocyclohexane, the respective products were obtained in 3-4 steps in moderate to fair yields. A series of ten benzimidazoles substituted at the position 2 with alkyl, aryl, and heteroaryl groups were prepared. [ABSTRACT FROM AUTHOR]

Results from efforts aimed at the synthesis of polyhydroxylated jatropha-5,12-dienes are unveiled. An apparently pre-qualified plot consisting of successive aldol addition and ring-closing metathesis was pursued in order to construct the fully oxidized trans-bicyclo[ 10.3.0]pentadecane scaffold of naturally occurring jatrophanoids. [ABSTRACT FROM AUTHOR]

An efficient synthesis of furo[3,4-d]pyrimidine-2,4-diones has been accomplished via a straightforward three-step pathway. Curtius rearrangement of 4-(methoxycarbonyl)furan-3-carboxylic acid and subsequent reaction with a variety of amines resulted in the corresponding intermediate ureids, which could be ring closed to the bicyclic scaffold in good yields. Functionalization of N-1 afforded a small library of new heterocycles. (Partial) hydrogenation of the furo[3,4-d]pyrimidine-2,4-diones led to the 5,7-dihydro- and tetrahydrofuro[3,4-d]pyrimidine-2,4-diones. [ABSTRACT FROM AUTHOR]

The synthesis of postulated 2H,6H-1,5-dithiocines from isonitriles and acetylenedicarboxylates or dibenzoylacetylene in the presence of elemental sulfur was repeated. The products do not possess the structure of eight-membered sulfur heterocycles, but isothiazole-3(2H)-thiones were formed instead. This structural corrigendum was confirmed not only by a critical consideration of the 13C NMR spectroscopic data and by the correction of the MS spectra and the values of the elemental analyses but also by X-ray crystallographic structure determination. Several reaction mechanisms are discussed to explain the generation of the observed isothiazole-3(2H)-thiones. [ABSTRACT FROM AUTHOR]

A generally applicable multicomponent method has been established for the synthesis of pyridines. In the reactions, thioacetamide is used as a cheap and efficient ammonium source in a multicomponent reaction with aldehydes and electron-deficient enamines or alkynes to give 3,4,5-trisubstituted pyridines in moderate to good yields and with a high product diversity. [ABSTRACT FROM AUTHOR]

A relay strategy is described that permits ring-closing metathesis and bifunctional chiral amine (thio)urea-catalyzed Michael addition reactions to proceed in a one-pot fashion. The process offers an alternative approach to the synthesis of structurally diverse chiral cyclopentanes in good yields and good enantioselectivities. [ABSTRACT FROM AUTHOR]

The Cu(I)-catalyzed Huisgen [3+2] cycloaddition is the basis of click chemistry to synthesize triazole derivatives by coupling azides with ethynyl blocks. In the development of new compounds inspired by bioactive natural products, the synthesis of new oxazole building blocks containing azide moiety and coupling them with aromatic alkynes via triazole linker is described. These oxazole building blocks are synthesized using amino acids as chiral and inexpensive starting materials. Using this approach, 16 new triazole- oxazole hybrids were synthesized. [ABSTRACT FROM AUTHOR]

The synthesis of the first 4-methoxy-substituted 1,3-benzazaphosphole was accomplished by using a C,O-dilithium intermediate generated from N-(3-methoxyphenyl)-2,2-dimethylpropanamide and butyllithium. This intermediate was subjected either to direct phosphonylation or to a bromination and phosphonylation sequence; subsequent reductive cyclization with excess lithium aluminum hydride led to the desired product. In addition, N-(2,2-dimethylpropyl)-3-methoxy-2-phosphinoaniline, formed in a side reaction, was cyclized with (dimethoxymethyl)dimethylamine to give 1-(2,2-dimethylpropyl)-4-methoxy-1H-1,3- benzazaphosphole. The behavior of these +M-substituted n-excess aromatic σ²P-heterocycles towards moisture is reported, together with their ¹H, 13C, and 31P solution NMR spectra and a crystal-structure analysis. The new compounds represent potential σ²P,O hybrid or chelate ligands with a high μ-density at the phosphorus atom. [ABSTRACT FROM AUTHOR]

This work describes the synthesis of compounds including both thiazolidine and 1,3,4-oxadiazole heterocyclic systems. The preparation is realized following a new synthesis route consisting of two multicomponent reactions. First 3-thiazolines are formed by an Asinger four-component reaction. Conversion of these cyclic imines into a-amino-1,3,4-oxadiazoles is subsequently achieved by a three-component reaction involving (isocyanoimino)triphenylphosphorane and a carboxylic acid. The synthesis route is characterized by mild reaction conditions and it tolerates many functional groups. As shown by the conversion into urea derivatives the prepared a-amino-1,3,4-oxadiazoles are marked by their potential in subsequent reactions. [ABSTRACT FROM AUTHOR]

Metal enolates and enamides bearing difluoroallylic moieties underwent nucleophilic 5-endo-trig cyclization, a process considered to be disfavored according to Baldwin's rules. Whereas no C-cyclization was observed in these reactions, O- and N-cyclization proceeded exclusively to afford 5-fluorinated 2-alkylidene-2,3- dihydrofurans and -2,3-dihydropyrroles, respectively. [ABSTRACT FROM AUTHOR]

A total synthesis of 6-O-benzoylzeylenol from diacetone glucose is described. The key steps were a crossed aldol-Cannizzaro reaction to create a quaternary carbon stereocenter, and cyclization through ring closure metathesis (RCM). Of the four stereogenic centers, two were derived from diacetone glucose, the quaternary stereocenter was created by means of the crossed aldol-Cannizzaro reaction, and the fourth stereogenic center was produced by a Sharpless asymmetric epoxidation. Finally, cyclization through RCM and deprotection by removal of a benzyl group with titanium( IV) chloride gave the target molecule. [ABSTRACT FROM AUTHOR]

An overview of the most important synthetic strategies currently available for the preparation of cyclopent-2-enones is presented and illustrated with recent applications. [ABSTRACT FROM AUTHOR]

The synthesis of dimethoxytriazine-containing V-aryl substituted pyrrolidinones is realized for the first time. Three new modes of reactivity for these substrates possessing a 4,6-dimethoxy-1,3,5-triazine unit are discussed. Their treatment with acid leads to complete O-demethylation of the methoxy groups, while similar re-action in a basic medium leads to partial O-demethylation. In con-trast, heating in the presence of dimethyl sulfate as the catalyst induces migration of the methyl groups from the oxygen atoms to the triazine nitrogens (Hilbert-Johnson transposition). These new scaffolds may demonstrate biological potential. [ABSTRACT FROM AUTHOR]

A two-step sequence for the conversion of heterocyclic imines to saturated and unsaturated polycyclic chlorinated ∊-lactams is disclosed. In the first step, an acyl chloride addition followed by a substitution is used to achieve unsaturated methoxyamides. The final lactamization to two different classes of polycyclic ∊-lactams via formation of a C-C bond is realized by the use of metal chlorides as Lewis acid and as a source of chloride. The potential of the ∊-lactams in subsequent reactions is demonstrated by an elimination reaction. [ABSTRACT FROM AUTHOR]

The synthesis of the pseudopterosin A-F aglycone from 3-methylcatechol features (a) the use of asymmetric Ireland- Claisen and aryl Claisen rearrangements to install three of the four stereocentres present in the molecule and (b) an A→AB→ABC annulation strategy using ring-closing metathesis and cationic cyclisation reactions as the key steps. [ABSTRACT FROM AUTHOR]

The synthesis of trisubstituted pyrrolidines and tetrahydrofurans from boronic acids, allenes, and imines or aldehydes via a five- and a three-step protocol, respectively, is described. The assignment of the relative stereochemistry in the pyrrolidines and tetrahydrofurans confirmed the mechanistically significant stereochemical divergence of the palladium-catalyzed three-component coupling reaction. The methodology is applicable to the preparation of combinatorial libraries of pyrrolidines related to pharmaceutical agents and bioactive natural products. [ABSTRACT FROM AUTHOR]

Diethyl 2-alkyl-2-(benzyloxycarbonylamino)malonates were saponified, activated with oxalyl chloride, and treated with primary aromatic amines. This gave 3,5-disubstituted hydantoin-5- carboxamides. As second products, 2-alkyl-2-formamido-N1,N3- bis(aryl)malonamides were isolated. The formation of both types of products is expected to include a cyclization to 2-alkoxyoxazol- 5(4H)-ones, acting as precursor for the hydantoins, or a further transformation to N-carboxy anhydrides, their chloride-promoted ring opening, and subsequent conversion to give the bis(aryl)malonamides [ABSTRACT FROM AUTHOR]

A synthetic strategy based on the sequential application of an aromatic aza-Claisen rearrangement and an intramolecular Heck reaction as the key steps has been developed for the synthesis of various new coumarin- and quinolone-annulated benzazocinone derivatives in 60-70% yields. [ABSTRACT FROM AUTHOR]

A variety of 3-arylated di- and tetrahydro-2H-2-benzazepin- 1-ones were efficiently assembled through a sequence involving a Suzuki-Miyaura cross-coupling reaction with enol phosphates derived from the corresponding benzazepine-1,3-diones. This technique has been further exploited for the construction of the homoprotoberberine skeleton, which was readily accessed by intramolecular carbocationic annulation reaction applied to a suitably substituted precursor. [ABSTRACT FROM AUTHOR]

A new synthesis to bis-butenolide derivatives from inexpensive divinylglycol is described, employing a sequential double acylation followed by a double ring-closing metathesis. The selectivity is affected by the choice of catalyst. [ABSTRACT FROM AUTHOR]

A new method for the synthesis of pyrrolo[1,2- d][1,4]benzodiazepines is described. The method is based on the acid-catalyzed recyclization of N-[2-(5-alkyl-2-furyl)phenyl]-2- aminoacetamides and permits the formation of both diazepine and pyrrole rings in one pot. The reaction proceeds via furan ring opening to give the diketone moiety followed by consecutive reactions of the free amino group with both carbonyl functions. [ABSTRACT FROM AUTHOR]

Cascade cyclization of bromoenynes bearing an aryl group with catalytic amounts of palladium(II) acetate and cesium carbonate led to the direct construction of tri- or tetracyclic heterocycles. Direct arylation of a pyrrole, furan or thiophene ring in the cascade reaction affords the corresponding fused heteroarenes in moderate to good yields. [ABSTRACT FROM AUTHOR]

new approach to highly functionalized quinolines is proposed. This approach is based on the electrophilic recyclization of 2-[2-(acylamino)benzyl]furans under the Bischler-Napieralski reaction conditions. [ABSTRACT FROM AUTHOR]

In this paper, a novel route for the synthesis of (+)- (1R,3S)-cis-chrysanthemic acid is described. The use of readily available (-)-D-pantolactone as a starting point, application of ringclosing metathesis to form the cyclopentene intermediate, and Haller-Bauer/Grob-type fragmentation to form the target compound are the highlights of the present synthesis. [ABSTRACT FROM AUTHOR]

This review highlights advances in the synthesis of morphan compounds from 1980 to the present day. [ABSTRACT FROM AUTHOR]

An efficient access for the synthesis of substituted pyrazino[2',3':4,5]thieno[3,2-d]pyrimidines and pyrazino[2',3':4,5]thieno[3,2-d]-1,2,3-triazines, heteroaromatic nitrogen ligands, is reported. The title compounds were obtained by functionalization of the corresponding chloro precursors, synthesized by reaction between 7-aminothieno[2,3-b]pyrazine-6-carbonitrile and N,N-dimethyldichloromethyleniminium chloride (Viehe's salt) or sodium nitrite/hydrochloric acid, respectively. Moreover, this procedure provided a convenient synthetic route to bis(pyrazino[ 2',3':4,5]thieno[3,2-d]pyrimidines), functionalized molecules that are not readily available by other synthetic methods. [ABSTRACT FROM AUTHOR]

A series of diversely substituted 2H-2-benzazepine-1,3- diones were efficiently prepared from the unsaturated precursors, N-acyl-o-vinylbenzamides, through a ring-closing metathesis reaction. The parent compounds were easily obtained from the appropriate o-vinylbenzoic acids. [ABSTRACT FROM AUTHOR]

A highly convergent, stereoselective total synthesis of a ten-membered lactone, stagonolide G, is described. Epoxide ringopening with vinyl Grignard, Yamaguchi esterification and ringclosing metathesis are the key steps involved in the present approach. D-Mannitol was used as a chiral pool material for the construction of both of the key fragments – the olefinic acid and the olefinic alcohol moieties. [ABSTRACT FROM AUTHOR]

Many natural products are characterized by the existence of a five-membered vinylogous acid ring, named tetronic acid, in their structure. The intense synthetic interest on such compounds has led to the development of several innovative methodologies for the construction of tetronic subunits, as well as to inspired strategies towards the total synthesis of the compounds themselves. The synthetic progress on the field of naturally occurring tetronic acids is reviewed herein. [ABSTRACT FROM AUTHOR]

One version of the tert-amino effect operating in tertanilines possessing an ortho-vinyl substituent affords a fused tetrahydropyridine ring by an isomerization process with the formation of a new carbon-carbon bond between the vinyl and tert-amino moieties. Since its discovery in 1984, this type of cyclization has been efficiently used for the construction of fused-ring systems. However, it has been found that the electron-deficient heterocyclic analogues of tert-anilines, such as diazines, may undergo isomerization at considerably lower reaction rates and, as a consequence, their reactions may require harsh conditions. Recent synthetic studies have indicated that the rate and yield may be improved by incorporating the γ-vinylic carbon atom into an electron-deficient ring and/or buttressing the tert-amino group, and/or performing the reaction by means of microwave irradiation. This review describes relatively recent synthetic transformations involving this type of tert-amino effect and devotes special attention to structure-reactivity relationships including regio- and stereochemical aspects. [ABSTRACT FROM AUTHOR]

A stereoselective synthesis of functionalized 2-oxo-1-azabicyclo[5.3.0]alkane is presented. Key events of the synthetic sequence were the stereoselective propenylation of an N-acyliminium ion and a ring-closing metathesis reaction forming a 7-membered lactam. [ABSTRACT FROM AUTHOR]

The Strecker reaction of (2R,4R)-2-phenyl-3-phenoxy-carbonylthiazolidine-4-carbaldehyde (4b), which was readily prepared from L-cysteine, with benzylamine and trimethylsilyl cyanide provided α-amino nitrile 5b stereoselectively (syn-anti, 2:1). Amidation of 5b and subsequent cyclization gave bicyclic compound 6, which, upon reduction with zinc dust, hydrolysis and subsequent cyclization, furnished thiolactone 2, a key intermediate for (+)-biotin (1). [ABSTRACT FROM AUTHOR]