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Graphical abstract Highlights • Methods of reduction based on borane complexes afford to obtain derivatives protected from reoxidization. • Silanes are the most widespread reagents which are used for the reduction of compounds with P O bond. • The catalytic methods for the reduction of phosphine oxides were described. • Organocatalysis in the reduction of phosphine oxides is possible. Abstract The digest is devoted to the most widespread reducing agents which are used for the reduction of tertiary and secondary phosphine oxides, phospholene oxides, phospholane oxides, phosphonates, phosphinates, α- and β-hydroxy and thiomethyl phosphine oxides, α-aminophosphine oxides. Stereoselectivity of reactions is described. Methods of stabilization of phosphines which are prone to re-oxidation by the formation of borane-adduct or metal complexes are considered. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Triacylated guanidines are reduced to orthoamides by borohydride. • TriBOC guanidine was over-reduced by borohydride to aminal. • Guanidine tricarbamates also reduce to orthoamides by borohydride. Abstract N , N ′, N ″-Triacylguanidines and N , N ′, N ″-tri(alkoxycarbonyl)guanidines were prepared and reduced with borohydride salts in a mixture of tetrahydrofuran and acetic acid to give triacyl and tri(alkoxycarbonyl) orthoamides in yields of 40–85%. However, similar reduction of N , N ′, N ″-tri(t -butoxycarbonyl)guanidine did not give orthoamide but the aminal di(t -butyl) methylenedicarbamate. [ABSTRACT FROM AUTHOR]

An unprecedented approach toward synthesis of α -substituted ethylphosphonates based on CuH-catalyzed conjugate reduction of vinylphosphonates has been successfully developed. This protocol features mild conditions, broad substrate scope, good functional group compatibility, high overall efficiencies, and easy gram-scale synthesis. The Cu-catalyzed reduction takes place in a highly selective manner on the phosphono substituted C C bond in the case of the reaction of alkenylphosphonates bearing both phosphono and alkyl or aryl substituted alkene moieties. Furthermore, the result of competitive reaction indicates that the Cu-catalyzed conjugate reduction of vinylphosphonate is more challenging and reproducible than the corresponding acrylate’s reaction. [ABSTRACT FROM AUTHOR]

A synthetically simple mixed metal hydride, diisobutylaluminum borohydride [( i Bu) 2 AlBH 4 ], is easily generated from a 1:1 mixture of borane-dimethylsulfide (BMS) and diisobutylaluminum hydride (DIBAL). The reduction of tertiary amides using ( i Bu) 2 AlBH 4 is complete within five minutes under ambient conditions and the product tertiary amines were isolated in 70–99% yields by a simple acid-base extraction. This new methodology, reported herein, works well for reduction of tertiary aliphatic and aromatic amides as well as lactams to the corresponding amines and product isolation and purification does not require column chromatography. [ABSTRACT FROM AUTHOR]

A highly chemoselective reduction of aryl, heteroaryl, acyl and sulfonyl azides to the corresponding amines has been achieved by Fe(0) nanoparticles in water at room temperature in the absence of external hydride source. Several readily reducible functionalities including alkene, alkyne, S-S linkage, OTBDMS remain unaffected during reduction. [ABSTRACT FROM AUTHOR]

The total carbon framework with all chiral carbons of proposed structure of baulamycin A is synthesized using Evans’ aldol and Grubbs’ cross-metathesis as key reactions. This strategy enables one to access all the isomers of this natural product. [ABSTRACT FROM AUTHOR]

Tin reduction of 3,4,4,5-tetrachloro-4 H -1,2,6-thiadiazine afforded perchloro-9-thia-1,5,8,10-tetraazaspiro[5.5]undeca-1,4,7,10-tetraene (10%) and 3,5-dichloro-4 H -1,2,6-thiadiazine-4-thione (27%), the structures of which were supported by single crystal X-ray crystallography. Treating the tetrachlorothiadiazine with Ph 3 P (1 equiv.) afforded the corresponding spirocycle in a useful 66% yield, the degradation of which with BnEt 3 NCl (0.5 equiv.) afforded densely functionalized 4,5,6-trichloropyrimidine-2-carbonitrile in 81% yield. Rational mechanisms for the formation of products are proposed. [ABSTRACT FROM AUTHOR]

An operationally simple and rapid purification of MIDA boronates is described. This method allows separation of MIDA boronates containing basic centers from those that are neutral as well as separation from species that do not contain the MIDA moiety using a single “catch and release” purification medium. Application of this method to the purification of reductive amination products is described. It is hoped that this facile, rapid and conceptually new isolation will stimulate further investigation of other functionalized silica gel media for the isolation of MIDA boronate building blocks. [ABSTRACT FROM AUTHOR]

Reductive ring opening of isoxazolidine moiety of chromano–piperidine-fused isoxazolidines ( 3a – c ) with HCOONH 4 and 10% Pd/C in a mixture of solvents (THF/MeOH) at ambient temperature, affords novel 2-(methylamino)-4-oxo- N -phenyl- N -propyl-4 H -chromene-3-carboxamide ( 4 ), which is apparently derived from reductive N O bond cleavage followed by tandem intramolecular rearrangements. Plausible mechanistic rationale for the formation of compound 4 is proffered. [ABSTRACT FROM AUTHOR]

A procedure to exclusively obtain 3′ S -cyanoanhydrovinblastine 12 from two naturally occurring vinca-alkaloids (catharanthine and vindoline) in one step with good yield is described. Stereoselective reductions of 12 , providing straightforward access to three new vinca-alkaloids, including two diastereomers 3′ S -cyano-(4′ R ,5′-dihydro)-anhydrovinblastine and 3′ S -cyano-(4′ S ,5′-dihydro)-anhydrovinblastine as well as (3′ S -aminomethyl)-(4′ S ,5′-dihydro)-anhydrovinblastine in good yields is also reported. [ABSTRACT FROM AUTHOR]

Sonogashira coupling of 17β-acetoxy-4,5-secoandrost-3-yn-5-one with 2-iodobenzyl alcohol, followed by NABH 4 reduction afforded two epimeric steroid alkynediols that after separation underwent palladium-catalyzed spirocyclization to produce the corresponding benzannulated steroid spiroketals. The hitherto unknown spiroketals were characterized their NMR spectra and the structures were confirmed by X-ray diffraction studies. [ABSTRACT FROM AUTHOR]

The first total synthesis of Pestalotioprolide C and C7- epi -Pestalotioprolide C adopting Noyori asymmetric reduction, HWE Olefination and Shiina macrolactonization as the key steps has been described. [ABSTRACT FROM AUTHOR]

Synthesis of 8-aryl-3,5,7,3′,4′- penta - O -methylcyanidins from the corresponding quercetin derivatives by reduction with LiAlH 4 is reported. Regioselective iodination at the 8-position of penta - O -methylquercetin followed by a Suzuki-Miyaura reaction gave the 8-arylated quercetin derivatives. By the reduction of 8-arylated quercetins using 4 equiv. of LiAlH 4 at room temperature for 30 min, the corresponding anthocyanidins were obtained with a good yield. [ABSTRACT FROM AUTHOR]

An efficient FeCl 3 -mediated approach for reduction of ketones by NHC-BH 3 has been developed. A series of ketones were smoothly converted to the corresponding alcohols in good to excellent yields through NHC-BH 3 reductive process. [ABSTRACT FROM AUTHOR]

The cyclic hydroxamic acid functional group is critical to the biological activity of numerous natural products and drug candidates. Efficient, reliable, and green synthetic methods to produce cyclic hydroxamic acids are needed. Herein, flow hydrogenation has been explored as a novel approach toward achieving the selective partial reduction of 2-nitrophenylacetic acid to 1-hydroxyindolin-2-one. The bidentate ligand, 1,10-phenanthroline, has been identified as a unique inhibitor for modulating product selectivity in this Pt/C-catalyzed process. Under the newly optimized reaction conditions, the targeted hydroxami c acid is produced with high selectivity (49:1) over the lactam by-product. The scope of the reaction is demonstrated for a variety of 2-nitrophenylacetic acid derivatives. [ABSTRACT FROM AUTHOR]

Magnesium-promoted reductive carboxylation of ethyl benzoate in the presence of chlorotrimethylsilane in N , N -dimethylformamide brought about a new carbon-carbon bond formation between the carbonyl carbon atom and carbon dioxide to give the corresponding benzoylformic acid in good yield. It is noteworthy that only ethyl benzoates with substituents at the meta -position were converted into benzoylformic acid derivatives. Moreover, no mandelic acid was detected even under the reductive conditions. This result indicates that benzoylformic acid was obtained after hydrolysis of a carboxylated intermediate, which would be alive as a stabilized structure in the reaction media. [ABSTRACT FROM AUTHOR]

Reduction of 2-methoxy-2, 4-hexadienoates with Dibal-H in toluene at −78 °C resulted in a facile formation of 5-hydroxyl cyclopentenone derivatives. This novel transformation was proposed as a variant of the oxy-Nazarov cyclization of the corresponding 2-methoxy aldehyde intermediate via the cationic Al-chelate as depicted in Fig. 2a. [ABSTRACT FROM AUTHOR]

Polystyrene-supported ruthenium nanoparticles enable the selective hydrazine-mediated reduction of nitroarenes to hydroxylamine products in high yield and selectivity. Key to obtaining the hydroxylamine product in good yield was the use of organic solvents capable of solubilizing the polystyrene-supported nanoparticle catalyst. N -aryl and N -heteroaryl hydroxylamines are generated under exceptionally mild conditions and in the presence of a various easily reduced functional groups. [ABSTRACT FROM AUTHOR]

We describe herein a diastereoselective approach to access substituted-4-aminopiperidines from pyridine precursors. This methodology has successfully been applied to synthesize 2-alkyl substrates as well as more complex molecular entities of interest to the pharmaceutical industry. [ABSTRACT FROM AUTHOR]

Vasicine, a quinazoline alkaloid, from the leaves of Adhatoda vasica , has been utilized as an efficient catalyst for metal and base free Henry reaction of various aldehydes with nitro alkanes. The method can be used in the synthesis of various β-nitro alcohols under mild reaction conditions without use of hazardous organic solvents and expensive catalysts. Vasicine is also applied successfully for one pot synthesis of 2,1-benzisoxazoles from o -nitroacylbenzenes in good yields under mild conditions. [ABSTRACT FROM AUTHOR]

The stereoselective synthesis of the right-hand segment of enfumafungin, a potent antifungal agent isolated from a Hormonema sp., was achieved. The contiguous two quaternary carbon atoms at the angular positions of the trans -fused CD ring system was constructed through the stereoselective reduction of 4-cyano-3,4-dimethyl-2-cyclohexen-1-one and the Johnson–Claisen rearrangement. After elongation of the side chains, the D ring was formed via a stereoselective intramolecular conjugate addition reaction which was originally developed by our laboratory. [ABSTRACT FROM AUTHOR]

Catalytic hydrogenolysis of carbon–carbon sigma bond in organic substrates represents an interesting, yet less common reduction methodology in chemical transformations. In the past few decades, there are impressive works aiming at mechanistic understanding via strategic reaction design. Efforts to expand synthetic usefulness have been observed. This digest summarizes the recent achievements in transition metal catalyzed reductive C–C sigma bond cleavage to give C–H bonds by hydrogenolysis. [ABSTRACT FROM AUTHOR]

A convenient method for highly diastereoselective synthesis of bexagliflozin 7a and its carbon-13 labeled analogue 7b was developed. The main feature is the stereoselective reduction of 16 catalyzed by BF 3 ·OEt 2 . Furthermore, the cocrystallization skill was firstly used for the purification of bexagliflozin and its analogue. The carbon-13 labeled bexagliflozin 7b was firstly prepared in five steps and in 57% overall chemical yield starting from the commercially available d -gluconolactone-[ 13 C 6 ]. [ABSTRACT FROM AUTHOR]

Attempted reductive cleavage of indolyl-bicyclic-isoxazolidines ( 4a , b ; R = benzyl, phenyl) with ammonium formate, methanol-THF solvents, at ambient temperature, in the presence of Pd/C lead to facile synthesis of indolyl-α-hydroxy-γ-lactams ( 5a – b ), derived from reductive cleavage of the N O bond of bicyclic-isoxazolidines, followed by intramolecular recyclization. On the other hand, reaction of 4c (R = ethyl) under identical conditions follows a different course affording 6 , an analogue of naturally occurring marine alkaloid, aplysinopsin. A mechanistic rationale of observed reactivity behavior, supported by DFT calculations, is provided. [ABSTRACT FROM AUTHOR]

A highly efficient synthesis of ( S )-1-(furan-2-yl)pent-4-en-1-ol, known to be an initial precursor of Ipomoeassin family of compounds and C1–C15 domain of halichondrins has been achieved via a sequence involving the use of Weinreb amide formation followed by Weinreb ketone synthesis and finally CBS (Corey–Bakshi–Shibata) reduction. Detailed study on improvement of each step is described. The title compound was converted to a potential cytotoxic agent for further pharmacological studies. [ABSTRACT FROM AUTHOR]

The methylation of amines by paraformaldehyde in the presence of calcium hydride as a source of hydrogen and palladium on charcoal as catalyst was studied. Depending on the quantity of paraformaldehyde, monomethylated and dimethylated amines were selectively and efficiently prepared in one pot with good yields. [ABSTRACT FROM AUTHOR]

A straightforward, efficient, and highly diastereoselective method for the synthesis of 3,4-cyclopenta-1-tetralones has been realized via the copper-catalyzed coupling of 2-vinyl benzaldehydes with 3-alkenyl 2-bromocarbonyls. Subsequent reduction with l -selectride leads to the formation of benzannulated tricyclic alcohols, possessing four continuous stereogenic centers, in high yields with excellent diastereoselectivity. [ABSTRACT FROM AUTHOR]

Concomitant cathodic reduction of 9,10-phenanthrenequinone and 1,1,1-trichloro-2,2-bis(4-chlorophenyl) ethane (DDT), under constant potential conditions, led to new and interesting [1,3]dioxoles through two possible and simultaneous reaction pathways: (1) an electron-transfer from the quinone dianion to DDT molecules, and (2) electrogeneration of a carbene from DDT and further reaction with the 9,10-phenanthrenequinone dianion. Mechanism proposals are discussed. [ABSTRACT FROM AUTHOR]

A simple and straightforward method for the synthesis of α-substituted ethylphosphonates via diimide reduction strategy is described. With K 3 PO 4 or Na 2 CO 3 as the basic additive, a range of terminal alkenylphosphonates underwent efficient reduction by diimide generated from 2-nitrobenzenesulfonylhydrazide (NBSH) under room temperature. The high functional group tolerance of this methodology is also demonstrated. Moreover, our method features high safety, mild reaction condition, low requirement on equipment, and high chemoselectivity. [ABSTRACT FROM AUTHOR]

Lactols II , obtained by DIBAL reduction of their corresponding lactones I , in equilibrium with their hydroxyaldehyde tautomers III were used in a three-component reductive alkylation with 2-hydroxy-1,4-naphthoquinone to give a series of 3-alkylated 2-hydroxy-1,4-naphthoquinone derivatives IV . [ABSTRACT FROM AUTHOR]

An efficient method for the deoxygenation of sulfoxides into their corresponding sulfides at room temperature using NaHSO 3 in the presence of catalytic I 2 has been reported. [ABSTRACT FROM AUTHOR]

Described herein is that the selective reduction of aromatic/aliphatic secondary amides using a combination of InI 3 and TMDS (1,1,3,3-tetramethyldisiloxane), which led to the production of the corresponding secondary amines. This reducing system showed a relatively high tolerance to a variety of functional groups, such as an alkyl, an alkoxy, a halogen, a cyano, an ether, a thioether, a heterocyclic ring, and a terminal alkene group. [ABSTRACT FROM AUTHOR]

The use of sodium in alumina and silica gels for the reductive cleavage of the N–O bond of N -methoxy- N -methylamides, commonly referred to as Weinreb amides, has been investigated. This method reduces a diverse set of Weinreb amides with different functional groups to give modest to excellent yields. In the course of the studies to explore mechanisms and functional group tolerance, an apparently novel group transfer emerged, implying base-promoted cleavage of the Weinreb amide to form formaldehyde, followed by aldol condensation. [ABSTRACT FROM AUTHOR]

2-Amino-6-nitrophenol derivatives 5A and 5B have been prepared from the bromonitro phenol derivative 4 using the Buchwald conditions. While attempting one pot reduction of nitro group and deprotection of phenolic benzyl group of the compounds 5A and 5B separately using Pd/C in methanol under H 2 atmosphere, an unexpected C(aryl)–N bond cleavage reaction had occurred which was followed by formation of a known compound Questiomycin A (2-amino-3 H -phenoxazin-3-one) 1 from both the compounds. In the present study, the danger of deamination of Buchwald products 5A and 5B under the conditions of catalytic hydrogenation and the simultaneous formation of phenoxazine 1 is disclosed. [ABSTRACT FROM AUTHOR]

Reductive Pictet Spengler cyclization was used for the synthesis of naturally occurring β-carbolines, eudistomin U, and canthine. Other biologically important β-carbolines as well as tetrahydro-β-carboline, such as (±)-harmicine were also synthesized using the same strategy. [ABSTRACT FROM AUTHOR]

Crispatanolide, which was isolated from Makinoa crispata (liverwort) in 1980, was synthesized in its chiral form starting from 3-substituted-2-bromocyclohex-2-en-1-one using CBS reduction. The absolute configuration was established using the modified Mosher method on the CBS reduction product. This synthesis established the absolute configuration of the natural product, which is presumably derived from a 10β-methyl-7-βH-eudesmane type precursor. [ABSTRACT FROM AUTHOR]

We have developed an exceptional one-pot domino cyclization process, in which a nitroarene reduction step initiates an endocyclic Nicholas reaction followed by an intramolecular Pauson–Khand cyclization. Remarkably, all reactions in this process can be mediated by a cobalt carbonyl complex under mild conditions. [ABSTRACT FROM AUTHOR]

The complete hydrogenolysis of compounds containing the geminal diazido functionality is described. Using hydrogen over palladium on charcoal, the diazides are reduced, and primary amines are obtained. For example, aminomalonates and glycines are generated in a straightforward manner. A protocol that provides direct access to acetylated amines derived from 2-amino-1,3-diketones in good to excellent yields, via hydrogenation in the presence of acetic anhydride, is also presented. [ABSTRACT FROM AUTHOR]

Facile synthetic routes to bromo- and iodo-1,2,3-triazoles were achieved. Diiodo-1,2,3-triazole was directly obtained from 1,2,3-triazole, and dihalo-1,2,3-triazoles were converted to halo-1,2,3-triazoles in good yields without protection by NH. Unsymmetrical 4-bromo-5-iodo-1,2,3-triazole was synthesized from bromo-1,2,3-triazole. These halo-1,2,3-triazoles can be readily prepared using common reagents and solvents and are useful building blocks for the analogous synthesis of 1,2,3-triazole derivatives. [ABSTRACT FROM AUTHOR]

Micellar nanoreactors derived from commercially available ‘Nok’ (SPGS-550-M), in the presence of Fu’s catalyst and a mild hydride source (NaBH 4 ), are useful for facile debromination of functionalized aromatic derivatives. This mild and environmentally responsible process is utilized in water at room temperature, and the reaction mixtures can be smoothly recycled. [ABSTRACT FROM AUTHOR]

The impact of N,N -dimethyl-2-aminoethanol (DMAE) on the reactivity of SmI 2 is presented. The SmI 2 –DMAE reagent system is capable of reducing a range of substrates including alkyl halides, ketones, lactones, and arenes. Mechanistic studies on anthracene reduction are consistent with a system that proceeds through a highly ordered, early transition state requiring 2 equiv of DMAE and 1 equiv of anthracene and Sm(II). [ABSTRACT FROM AUTHOR]

In this Letter, we report a novel, general, convenient, and inexpensive method for the reduction of aromatic aldehydes to the corresponding benzylic alcohols. Various aromatic aldehydes were reduced in good to excellent yields by using well-defined iron-complex as the catalyst precursor and using paraformaldehyde and water as the hydrogen source. [ABSTRACT FROM AUTHOR]

Mg-promoted reductive silylation of 4-phenyl-3-butyn-2-one in N , N -dimethylformamide (DMF) in the presence of chlorotrimethylsilane brought about double silylation at the β-carbon and oxygen atoms of the carbonyl group to give a multifunctionalized allene with a vinylsilane moiety and a silyl enol ether moiety. A variety of allenes can be synthesized through this simple methodology. Acid-catalyzed hydrolysis of an allene derived from the trimethylsilylation of 4-phenyl-3-butyn-2-one resulted in the formation of the corresponding benzalacetone with a trimethylsilyl group at the β-position of the carbonyl group in high yield. [ABSTRACT FROM AUTHOR]

Diethyl (1,2-dibromoethyl)phosphonate was found to undergo cyclopropanation with nitromethane in good yield. The resulting trans β-nitrocyclopropylphosphonate was converted to the trans N-protected aminocyclopropylphosphonate through a reduction–protection sequence. Subsequent hydrolysis gave the free β-aminocyclopropylphosphonic acid without any formation of ring-opening byproduct. Cyclopropanation of 1,2-dibromoethylphosphonates with nitroalkanes and their reduction are also discussed. [ABSTRACT FROM AUTHOR]

A fungal system belonging to Mucoraceae family ( Mucor piriformis ) was explored for the asymmetric reduction of a prochiral ketone, 3-quinuclidinone ( I ) in an efficient manner to produce an important pharmaceutical precursor ( R )-(−)-3-quinuclidinol ( II ) with ∼96% enantiomeric excess. The efficiency of the process was improved by developing a cation exchange resin (Amberlite IR-120) which assisted the purification of water soluble metabolite II from fermentation media. [ABSTRACT FROM AUTHOR]

The development of a calcium-mediated stereoselective reduction of α,β-epoxy ketones is reported. The corresponding α,β-epoxy alcohols are obtained in very good anti diastereoselectivity using Ca(OTf) 2 and NaBH 4 . Furthermore, we have shown that our method can diastereoselectively reduce α,β-aziridinyl ketones. [ABSTRACT FROM AUTHOR]

The chemoselectivity of hydrodechlorination in 2-chloropyridine derivatives possessing reduction-sensitive functionalities is examined. The reaction conditions employed tolerate a variety of functionalities illustrating highly chemoselective hydrodechlorination in the presence of nitrile, allyl, terminal olefin, and nitroamine functionalities in excellent yield. Chemoselective deprotection of carboxybenzyl ethers is illustrated in moderate yield. [ABSTRACT FROM AUTHOR]

A new method was adopted for the synthesis of benzo[b]carbazoles by Claisen condensation followed by Fischer indole cyclization. Newly synthesized benzo[b]carbazoles were treated with ethanol amine in the presence of polyphosphoric acid which leads to the formation of pyrazino carbazoles. All the synthesized compounds were characterized by all spectral means. [ABSTRACT FROM AUTHOR]

A unique synthesis of aryl methyl sulfides is reported proceeding via reduction of dimethylsulfoxide to dimethylsulfide at elevated temperature in the presence of Hunig’s base followed by nucleophilic aromatic substitution and demethylation. Activated aryl fluorides, chlorides, and nitrobenzenes are suitable substrates with 13 examples provided. Dimethylsulfoxide serves as a simple and inexpensive formal source of the thiomethyl moiety. [ABSTRACT FROM AUTHOR]

The secondary amines synthesized by the reaction between 2-aminophenols and aromatic aldehydes, via the reduction of the corresponding imines, were employed in the synthesis of new 2-hydroxy-2 H -1,4-benzoxazine derivatives through a one-pot Petasis multicomponent reaction in good to excellent yields. [ABSTRACT FROM AUTHOR]