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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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

Abstract: The selective cleavage of different benzyl bonds within tetrahydroquinazoline and dihydroquinazolinone derived structures can be achieved by the usage of different reduction and debenzylation conditions thereby providing selective removal of O-benzyl protection groups as well as the cleavage of the ring structure within the quinazoline and quinazolinone systems. [Copyright &y& Elsevier]

Abstract: Titanium(IV) halides are extensively used in carbon carbon bond forming reactions as a Lewis acid and low valent titanium halides promote reductive coupling reactions of carbonyl compounds. In most of these reactions, ligands of titanium halides are chloride or bromide. On the other hand, titanium(IV) tetraiodide had been rarely used in organic synthesis until the late 1990s. Since 2000 several useful synthetic reactions have been developed utilizing a moderate Lewis acidity, reducing and iodination abilities of titanium(IV) tetraiodide. This digest summarizes examples of chemoselective reductions and iodinations using titanium(IV) tetraiodide (TiI4). [Copyright &y& Elsevier]

Abstract: A simple and convenient method for the chemoselective reduction of nitriles into aldehydes using a 1,1,3,3-tetramethyldisiloxane (TMDS)/triisopropoxyvanadium(V) oxide reducing system is described. Aromatic as well as aliphatic nitriles are reduced into the corresponding aldehydes in moderate to good yields. [Copyright &y& Elsevier]

Abstract: The reaction of dihydroartemisinin (DHA) with solvated electrons ( ) generated under radiolytic conditions showed high pH dependence. The reduction performed under neutral conditions led to the formation of compound P1 deriving from the initial alkoxyl radical as the only detectable product. [Copyright &y& Elsevier]

Abstract: A series of enantiomerically pure tridentate ligands based on the 1,2-diphenylethane-1,2-diamine structure, containing additional pyridine groups, was prepared and tested in asymmetric transfer hydrogenation of ketones using Ru3(CO)12 as a metal source. Alcohols were formed in up to 93% ee in the best cases, and good results were obtained with ortho-haloarylketones. [Copyright &y& Elsevier]

Abstract: Two room temperature liquid salts containing molybdenum(VI), [BMIM]2[MoO2(NCS)4] (1) and [DMIM]2[MoO2(NCS)4] (2), were immobilized on ionic liquid-modified silica leading to materials which showed notable catalytic activity for the reduction of sulfoxides into sulfides with triphenylphosphine (PPh3). The molybdenum liquid salts immobilized on the supported ionic liquid phase could be reused at least for three catalytic cycles without significant loss of activity. [Copyright &y& Elsevier]

Abstract: Herein, conditions for the fast and effective reduction of aromatic nitro groups bound to hydrophobic polystyrene-based Wang and Ring resins utilizing sodium dithionite in dichloromethane–water under PTC conditions are reported. Tetrabutylammonium hydrogen sulfate (TBAHS) was found to be an effective phase-transfer catalyst for this reaction. This method allows for the reduction of nitro groups to amino groups under mild conditions with complete conversion and is tolerant of other functional groups. This method is a superior alternative to tin(II) chloride-based reduction, which is known for its shortcomings. [Copyright &y& Elsevier]

Abstract: The first asymmetric reduction of ketimines with catecholborane employing an enantiopure N-triflyl phosphoramide as the organocatalyst has been developed. Five mole% of the catalyst provides the corresponding secondary amines in very good to almost quantitative yields and good enantioselectivities up to 86:14 e.r. under mild reaction conditions. [Copyright &y& Elsevier]

Abstract: Treatment of a range of trisubstituted β,γ-unsaturated esters with 2equiv of (−)-monoisopinocampheylborane results in hydroboration of their alkene functionalities and reduction of their ester groups to afford chiral 1,3-diols containing two new vicinal β,γ-(anti)-stereocentres in 67–85% enantiomeric excess. [Copyright &y& Elsevier]

Abstract: A simple and efficient method for the synthesis of alcohols from the corresponding carboxylic acids is described. Activation of carboxylic acid with 1-propanephosphonic acid cyclic anhydride (T3P) and subsequent reduction using NaBH4 yield the alcohol in excellent yields with good purity. Reduction of several alkyl/aryl carboxylic acids and Nα-protected amino acids/peptide acids as well as Nβ-protected amino acids was successfully carried out to obtain corresponding alcohols in good yields. All the products were fully characterized by 1H NMR and mass spectral analyses. The procedure is mild, simple and the isolation of the products is easy. [Copyright &y& Elsevier]

Abstract: Classically, 2,1-benzisoxazoles (anthranils) are prepared from 2-nitroacylbenzenes by a reductive heterocyclization reaction with Sn or SnCl2 concentrated HCl. Acid sensitive functionalities are expected to be incompatible with these conditions; milder approaches to the synthesis of 2,1-benzisoxazoles would be welcomed. We demonstrate that SnCl2·2H2O in a 1:1 mixture of EtOAc/MeOH is capable of mediating the tandem reduction–heterocyclization of a variety of 2-nitroacylbenzenes to their corresponding 2,1-benzisoxazoles in good to excellent yields under essentially neutral conditions. Importantly, several commonly used acid–labile protecting groups, including Boc carbamate, tert-butyl ether, and tert-butyl ester, proved orthogonal to these reaction conditions. [Copyright &y& Elsevier]

Abstract: The formation of alkoxy substituted di(pyridin-2-yl)amines and N-arylpyridin-2-ylamines by nitro group reduction is described. Unexpected substitution of ortho with the amino at C-6 was observed during the reduction using SnCl2·2H2O in different alcohols. The influence of the nature of the atom at the 3- and 5-positions of nitro-substituted di(pyridin-2-yl)amines and N-arylpyridin-2-ylamines was investigated. [Copyright &y& Elsevier]

Abstract: The reaction of Artemisinin with solvated electrons () generated by radiolytic methods led to the formation of acid 2 as the only detectable product. A possible mechanism leading to the formation of compound 2 is discussed. [Copyright &y& Elsevier]

Abstract: The convergent syntheses of two possible diastereomers of the C25–C40 subunit resident in (−)-caylobolide A have been accomplished. The key reaction featured a chemoselective Ru-catalyzed cross-metathesis between a fully elaborated type I and two functionalized type II α,β-unsaturated ketones. [Copyright &y& Elsevier]

Abstract: We have developed a new method to synthesize aziridines from their corresponding hydantoins in one step using an excess of Red-Al overnight in refluxing toluene. This allows direct access to N–H aziridines without the need for protecting group strategies. [Copyright &y& Elsevier]

Abstract: A simple and useful method for the reduction of primary amides into the corresponding amines using a polymethylhydrosiloxane (PMHS)–Ti(OiPr)4 reducing system is described. Aromatic as well as aliphatic primary amides are reduced in high selectivity and excellent yields. The reduction could proceed via dehydration of the primary amide group into the corresponding nitrile which is then reduced into the corresponding primary amine. [Copyright &y& Elsevier]

Abstract: An InBr3–Et3SiH reducing system was developed to selectively convert aliphatic ketones to a variety of secondary alcohols in moderate to good yields. An initial mixing of InBr3 and PhSiH3 was followed by the addition of aliphatic ketones and a solvent to afford the symmetrical ether derivatives. [Copyright &y& Elsevier]

Abstract: A ruthenium catalyst formed in situ by combining [Ru(p-cymene)Cl2]2 and an amino acid hydroxy-amide was found to catalyze efficiently the asymmetric reduction of aryl alkyl ketones under transfer hydrogenation conditions using ethanol as the hydrogen donor. The secondary alcohol products were obtained in moderate to good yields and with good to excellent enantioselectivity (up to 97% ee). [Copyright &y& Elsevier]

Abstract: A rapid, economic, and high yielding methodology has been developed for hydroacylation/reduction of activated ketones by using 1,3-bis(2,4,6-trimethylphenyl)imidazolium chloride as a catalyst in combination with triethylamine. The reaction proceeded at an ambient temperature via generating N-heterocyclic carbene in situ that interacted with the (hetero)aryl aldehyde employed. While the reduction of ketones takes place in MeOH, the hydroacylation process was found to be effective in THF for both electron rich and deficient aldehydes. [ABSTRACT FROM AUTHOR]

Abstract: A simple and efficient synthetic path for N-1 or N-2 alkyl-substituted 2-aminobenzenesulfonamides was developed based on regioselective reduction with NaBH3CN in different solvents. [Copyright &y& Elsevier]

Abstract: A protocol for the hydrodehalogenation of halogenated pyridines and quinolines by the sodium borohydride/N,N,N′,N′-tetramethylethylenediamine (NaBH4–TMEDA) system under palladium catalysts is reported. Catalytic amounts of [1,1′-bis(diphenylphosphino)ferrocene] dichloropalladium(II) in combination with NaBH4–TMEDA rapidly hydrodehalogenate chloro(bromo)-pyridines and -quinolines at room temperature in quantitative yields. Chemoselective reduction of 4,7-dichloroquinoline affords 7-chloroquinoline as the sole product in almost quantitative yield. Moreover, palladium(II) acetate-triphenylphosphine and NaBH4–TMEDA are able to reduce efficiently reactive bromo-pyridines and -quinolines. [Copyright &y& Elsevier]

Abstract: In this work, we report the first practical application of high-valent oxo-complexes for the reduction of alkenes to the corresponding alkanes. The catalytic system Ph(Me)2SiH/ReIO2(PPh3)2 (5mol%) proved to be very efficient for the reduction of mono- and disubstituted alkenes under solvent-free conditions. [Copyright &y& Elsevier]

Abstract: Mg-promoted reduction of benzophenones in the presence of ethyl trifluoroacetate and trimethylchlorosilane in N-methyl-2-pyrrolidinone afforded the corresponding cross-coupling products, which were easily transformed into C-trifluoroacetylated compounds of benzophenones through desilylation by tetrabutylammonium fluoride. [Copyright &y& Elsevier]

Abstract: Syntheses of several (sulfonyl)methylphosphonate analogs of geranyl, neryl, and farnesyl diphosphates are described. Key steps include utilization of an (E)-selective Horner–Wadsworth–Emmons olefination which couples an aldehyde to the sulfone phosphonate moiety, and a selective reduction of the resulting dienyl sulfone phosphonate substrates. [Copyright &y& Elsevier]

Abstract: This work reports a novel method for the reduction of sulfoxides with silanes catalyzed by high valent oxo-rhenium(V) and (VII) complexes. The catalytic system PhSiH3/ReIO2(PPh3)2 (1mol%) proved to be highly efficient for the reduction of a wide range of sulfoxides in excellent yields under mild conditions. This novel methodology is also highly chemoselective, tolerating several functional groups such as –CHO, –CO2R, –Cl, –NO2, and double or triple bonds. [Copyright &y& Elsevier]

Abstract: A one-pot selective synthesis of 2-substituted C5-, C6-, and C7-nitro- or amino-indoles has been developed from 2-halonitroanilines. These two types of nitrogen-substituted indoles have been selectively obtained by only varying the solvent used in the tandem Sonogashira coupling/heteroannulation reaction. Moreover, from commercially available 2-bromo-4,6-dinitroaniline an unprecedented in situ selective reduction of one of the nitro groups has allowed the synthesis of new 7-amino-5-nitro-2-substituted indoles. [Copyright &y& Elsevier]

Abstract: A practical and efficient three-step sequence for the deamination of α-aminoesters is reported. This method is based on the NaBH4-mediated selective reduction of α-diazoesters to α-hydrazonoesters and has been successfully applied to the deamination of several representative α-aminoesters including some l-cysteine ethyl ester derivatives, key intermediates in the synthesis of a series of CysLT1 antagonists. [Copyright &y& Elsevier]

Abstract: A chemoselective and highly efficient hydrogenation of nitroarenes and deoxygenation of pyridine N-oxides using a cheap and environmentally friendly H2/MoO2Cl2 system has been developed [Copyright &y& Elsevier]

Abstract: Nickel(II) chloride/sodium borohydride combination was employed for the reduction of 4-hydrazinoquinoline derivatives to the corresponding anilines. This reductive protocol was efficiently applied for the reductive cleavage of monosubstituted hydrazines. We described herein the microwave-assisted synthesis of 4-hydrazinoquinolines, which furnished a high yielding and rapid two-step procedure for the synthesis, under mild conditions, of 4-aminoquinolines as antimalarial precursors. [Copyright &y& Elsevier]

Abstract: Diborane is readily generated in situ at 25°C in toluene using the Bu4NBH4/PhCH2Cl and Bu4NBH4/I2 reagent systems. The reagent prepared in this way is used for the reduction of carbonyl compounds and hydroboration–oxidation of olefins to obtain the corresponding alcohols in good yields. [Copyright &y& Elsevier]

Abstract: A rapid method for efficient reduction of nitroalkanes and α,β-unsaturated nitroalkenes using SmI2/H2O/amine has been developed. [Copyright &y& Elsevier]

Abstract: A facile and efficient reduction of aromatic and aliphatic acyl chlorides to their corresponding aldehydes in the presence of Sm(0)/Bu3P has been developed with broad scope. This method prevents over reduction of products, that is, the over-reduction of aldehydes to alcohols. [Copyright &y& Elsevier]

2-Aminopyrimidines were facilely reduced to 2-amino-dihydro- or 2-amino-tetrahydropyrimidines with triethylsilane and trifluroacetic acid in high yields. By controlling the equivalents of reducing reagents and temperature, selective reduction could also be achieved for some substrates. [Copyright &y& Elsevier]