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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]

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]

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]

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]

Abstract: A simple synthesis of 3-iodothiophenes was demonstrated using a wide range of ( Z )-thioenynes. The key step in the iodocyclofunctionalization was the selective reduction of the triple bond in ( Z )-thioenynes by the addition of iodine as an electrophilic agent. The 3-iodothiophenes were obtained in good to excellent yields of 61–92%. The 3-iodothiophenes were used as substrates in Sonogashira cross-coupling reactions to obtain thiophene acetylenes. [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 concise and high-yielding protocol for the synthesis of 5,6-dihydrophenanthridines is disclosed. The key feature includes a sequential reduction-cyclization reaction of N-acylcarbamates via N,O-acetal TMS ethers as a stable N-acyliminium ion precursor. [Copyright &y& Elsevier]

Abstract: The total synthesis of Resolvin D1, a potent endogenous anti-inflammatory lipid mediator derived from docosahexaenoic acid, has been achieved. The chiral hydroxy-groups at C7, C8 and C17 were obtained via a chiral pool strategy from 2-deoxy-d-ribose. Wittig reactions followed by a modified Pd0/CuI Sonogashira coupling and Zn(Cu/Ag) cis-reduction completed the total synthesis of Resolvin D1. [Copyright &y& Elsevier]

Abstract: A convenient in situ method is described for reductive removal of the amino group in position 1 of the anthraquinone (AQ) moiety. The reaction proceeds smoothly within a few minutes yielding novel AQ derivatives in excellent yields. Diazonium salt formation is followed by reduction with zinc in ethanol. The method has been applied to a variety of 1-amino-AQ derivatives. It allows access to a large library of new AQ derivatives which possess potential as pharmacological tools for studying purinergic signaling, and as potential drugs, for example, for the treatment of cancer and cardiovascular diseases. [Copyright &y& Elsevier]

Abstract: Solid supported palladium(0) (SS-Pd) catalyzed highly chemoselective reduction of nitroarenes to the corresponding anilines was accomplished under a milder reaction condition. This catalyst showed high compatibility with various reducing agents (NaBH4, Et3SiH, and NH2NH2·H2O) and a large number of reducible functional groups such as sulfonamide, amides, carboxylic acid, ester, alcohol, halide, hetero cycle, nitrile, alkene, carbonyl, O-benzyl, and N-benzyl were tolerated. Most of the reactions were clean and high yielding. The SS-Pd catalyst could be recycled up to seven runs without significant loss of activity. [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 reductive coupling of 1,3-dimethyluracil with benzophenone by Zn–TiCl4 in THF gave unusual two-to-one adduct and its further reduced product. The reductive coupling of 1,3-dimethyl-5-fluorouracil with benzophenone by Zn–TiCl4 also gave two-to-one adduct. 1,3-Dimethylthymine was, however, completely inert under the same conditions. [Copyright &y& Elsevier]

Abstract: The synthesis of 2-(arylaminomethyl)phenylboronic acid via an amination–reduction reaction has been investigated within a model system comprising 2-formylphenylboronic acid and N-ethylaniline. Adoption of the appropriate reaction conditions influences the reactivity of 2-formylphenylboronic acid, enabling efficient synthesis of so-far unobtainable 2-(arylaminomethyl)phenylboronic compounds. The first crystal structure of the aromatic amine derivative has been determined and described. [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: Secondary amides undergo in situ silyl imidate formation mediated by TMSOTf and an amine base, followed by addition to acetal acceptors to provide N-acyl-N,O-acetals in good yields. An analogous, high-yielding reaction is observed with 2-mercaptothiazoline as the silyl imidate precursor. Competing reduction of the acetal to the corresponding methyl ether via transfer hydrogenation can be circumvented by the replacement of CY2NMe with 2,6-lutidine under otherwise identical reaction conditions. [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: A library of benzimidazoles, benzoxazoles, and benzothiazoles was efficiently synthesized by condensation of o-phenylenediamine, o-aminophenol, and o-aminothiophenol respectively with aromatic aldehydes in the presence of catalytic amounts of Animal Bone Meal (ABM) and Lewis acids doped ABMs. Reactions were conducted under reflux conditions in air. The remarkable features of this new protocol are high conversion, short reaction times, and cleaner reaction profiles, straightforward procedure, and reduction in catalyst toxicity. [Copyright &y& Elsevier]

Abstract: Palladium catalyzed simple and efficient protocol for reductive carbonylation of aryl and heteroaryl compounds has been developed. The formylation of aryl and heteroaryl iodides takes place in the presence of Pd(acac)2/dppm catalyst at 10bar pressure of synthetic gas to give the desired aromatic and heteroaromatic aldehydes in good to excellent yields. Easy work-up, stability of the catalyst, low catalyst loading and less reaction time are the advantages of this method. [Copyright &y& Elsevier]

Abstract: Regioselective titanium alkoxide-mediated reductive cross-coupling reactions of allylic alcohols with vinylsilanes and imines have previously been demonstrated to proceed with allylic transposition by formal metallo-[3,3]-rearrangement [thought to proceed by a sequence of: (1) directed carbometalation, and (2) syn-elimination]. While many examples have been described that support this reaction path, a collection of substrates have recently been identified that react by way of an alternative pathway, delivering a concise convergent route to coupled products bearing a quaternary center. [Copyright &y& Elsevier]

Abstract: A diversity generative approach to bioactive and structurally complex natural products paecilomycine A–C, involving an intramolecular Pauson–Khand reaction as a key step is delineated. [Copyright &y& Elsevier]

Abstract: Stereoselective synthesis of two distinctive pyranone skeletons diospongin A and cryptofolione has been described based on an asymmetric aldol reaction starting from Chan’s diene. The synthetic strategy involves the enantioselective Mukaiyama aldol, diastereoselective reduction of δ-hydroxy-β-keto ester, a tandem sequence of deprotection, and intramolecular oxa-Michael reaction to obtain diospongin A and an asymmetric allylation and lactone formation using ring-closing metathesis reaction to obtain cryptofolione. [Copyright &y& Elsevier]

Abstract: The first examples of highly selective deprotection of silyl ethers by DIBALH are reported. Its selectivity enabled us to remove a primary TBS group and a primary TBDPS group in the presence of a secondary TES group. [ABSTRACT FROM AUTHOR]

Abstract: This work reports the catalytic activity of the oxo-complexes HReO4, MoO2(acac)2, WO2Cl2, and VO(acac)2 in the reduction of sulfoxides with PhSiH3 or HBcat. The results obtained showed that the catalyst systems PhSiH3/HReO4 (5mol%) and HBcat/HReO4 (5mol%) are highly efficient for the deoxygenation of sulfoxides. The complex MoO2(acac)2 was also efficient, but the reactions required more time and heating. Finally, the complexes WO2Cl2 and VO(acac)2 showed a moderate activity. [Copyright &y& Elsevier]

Abstract: Reaction of N-alkyl-N-arylsulfonyl-2-halo-propionamides with pentamethyldiethylenetriamine and either CuBr or CuCl leads to 2-aryl propionamides via initial radical generation, 1,4-aryl migration with loss of SO2 and reduction of the intermediate amidyl radical in 40–99% yields. [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: The unusual facial stereoselection in the hydride reduction of the Danishefsky pyranones (2,3,5,6-tetrahydro-4-pyranones) with L-Selectride (Li-sec-Bu3BH) has been explained based on the exterior frontier orbital extension model (the EFOE model). [Copyright &y& Elsevier]

Abstract: The reactions of 9-fluorenylidenemalononitrile (FDCN) and 1,1-diphenyl-2,2-dicyanoethylene (DPCN) with Hantzsch ester (HEH), N-methyl Hantzsch ester (Me-HEH), and 1-benzyl-1,4-dihydronicotinamide (BNAH) in oxygen-saturated acetonitrile have been studied. The aerobic reactions with HEH give solely reduction products. However, reactions with Me-HEH and BNAH not only result in reduction products, but also give varying amounts of oxidation products. The amount of oxidation product appears to be related to the electronic character and bulkiness of reactants. We propose that all these reactions follow a general mechanism of concerted electron-hydrogen atom transfer mechanism. If the electron-transfer complex is very tight, only ‘concerted hydride transfer reaction’ occurs. However, if the electron-transfer complex is not so tight, oxygen can capture the radicaloid intermediate to result in oxidation products. [Copyright &y& Elsevier]

Efficient syntheses of O - and N -alkylated products of 1,2,3,4-tetrahydrobenzo[ c ][2,7]naphthyrin-5(6 H )-one are presented. The O -alkylated analogues were synthesized through a reduction-cyclization cascade and a selective O-alkylation reaction; whereas the N -alkylated analogues were obtained through a key Buchwald coupling. [ABSTRACT FROM AUTHOR]

Abstract: The reduction of aromatic imines prepared from (S)-Ile-(S)-Ile-OMe, (S)-Val-(S)-Val-OMe, and (S)-Val-(S)-Val-(S)-Val-OMe with Zn–MsOH in THF gave C 2-symmetric (R,R)-diamines in high yields and stereoselectivities. [Copyright &y& Elsevier]

Abstract: The combination of highly stereoselective vinyllithium addition and hydroboration–protonation of the resulting allylic alcohol permits the preparation of the completely protected C1–C12 fragment 2 of the novel macrocyclic cytotoxic agent tedanolide 1. [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: An unusual aromatisation of the dihydropyrimidine fragment in 6-nitro-7-substituted-4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidines has first been found to occur in parallel with reduction of the nitro group using a number of reducing agents. [Copyright &y& Elsevier]

Abstract: A series of bicyclic sulfonamides, 14–17, was prepared by thermal, intramolecular Diels–Alder cycloaddition. The ratio of exo:endo-diastereoisomers formed following this process was found to be dependent on the substitution pattern of the dienophile. Styryl substituted sulfonamides preferentially formed the corresponding exo-adducts, whereas vinyl substituted sulfonamides preferentially gave the endo-adducts. These adducts were treated under dissolved metal reduction conditions and it was found that compounds possessing an N-benzyl substituent underwent preferential debenzylation and resisted further reduction. The complementary N-isobutyl functionalised materials only underwent the double reduction when a phenyl substituent was present. [Copyright &y& Elsevier]

Abstract: Salinosporamide A (NPI-0052, 1), a highly potent 20S proteasome inhibitor, has been prepared from its ketone precursor (2) by asymmetric enzymatic reduction. The yields are quantitative with complete stereoselective conversion to the desired product, with no evidence for the undesired diastereomer. This process should lead to new synthetic strategies for the total synthesis of 1. [Copyright &y& Elsevier]

Abstract: A stereoselective route for the synthesis of the C31–C39 fragment of (+)-phorboxazoles is described. The route features Birch reduction, ozonolysis and acid-catalysed cyclisation of enantiopure precursors as key transformations to give the tetrahydropyran ring, starting from m-anisaldehyde as a masked β-keto ester to obtain the pyran skeleton of compound 1. [Copyright &y& Elsevier]

Abstract: A direct asymmetric reductive Manich-type reaction that allows for the formation of three contiguous stereocenters with high chemo-, diastereo-, and enantioselectivity is presented. [Copyright &y& Elsevier]

Abstract: With the aid of proposals from a computer program for synthesis design, a new method of synthesizing azaspiranes has been developed. In this method, one starts with a suitable benzoic acid ester, which is subjected to Birch reduction. Then the anionic intermediate is alkylated with 1,2-dibromoethane. The product is subsequently reacted with an amine to give a spiro lactam. [Copyright &y& Elsevier]

Abstract: The Birch reduction–dialkylation reaction has been studied with different aromatic carboxylic acids and primary and secondary bromides. From these results it can be concluded that it is a reasonably general reaction. However, we found important exceptions with the primary bromides: allyl bromide, β-phenethyl bromide, and 5-bromo-2-methyl-2-pentene. The unusual behavior of allyl bromide is briefly discussed. [Copyright &y& Elsevier]

Abstract: A new simple and efficient methodology for reductive sulfur extrusion from 2,1,3-benzothiadiazole compounds has been developed using NaBH4 in the presence of catalytic amounts of CoCl2·6H2O (1mol%). This method is an efficient alternative for the generation of various 1,4-disubstituted-2,3-diaminobenzene derivatives from 4,7-disubstituted-2,1,3-benzothiadiazoles. The diamines can be easily converted into 4,7-disubstituted-quinoxaline compounds by simple reaction with glyoxal–sodium bisulfite. [Copyright &y& Elsevier]

Abstract: The total synthesis of tarchonanthuslactone ( 1 ) has been achieved by two different routes. In the first approach, LiAlH4–LiI reduction and RCM protocols, and in the second approach, Wacker oxidation and LiAlH4–LiI reduction were used as key steps. [Copyright &y& Elsevier]

The one-pot reaction of aldehydes, triacetic acid lactone, and Hantzsch 1,4-dihydropyridine affords 3-alkyl pyrones via a reductive alkylation strategy. [ABSTRACT FROM AUTHOR]

The first example of a one-pot sequential Cope/Rauhut-Currier reaction is reported and used to make functionalized decalin structures with all-carbon quaternary stereocenters. The substrates for the new sequential reaction are generated through a six-step sequence including an enantioselective Birch reduction-allylation reaction which makes the overall process asymmetric. [ABSTRACT FROM AUTHOR]

Abstract: The reaction of RhCl(PPh3)3 with Et2Zn easily generated a rhodium–hydride complex (Rh−H) that added to α,β-unsaturated esters to form rhodium enolate complexes by formal 1,4-reduction. These rhodium enolates gave the corresponding Reformatsky-type reagents through transmetalation, and they reacted with various aldehydes and ketones to give reductive aldol-type products in good to excellent yields. [Copyright &y& Elsevier]

Abstract: An efficient and practiced procedure for the preparation of γ-oxo esters from the β-azidocyclopropane esters has been developed. Ph3P was proven to be a good promoter in THF/H2O, and 11 γ-oxo esters were prepared in 73–99% yields under mild and neutral conditions. [Copyright &y& Elsevier]

Abstract: β-Hydroxy ketones were synthesized in one-pot from β-diketones by reducing alkyl ketones chemoselectively by keeping aryl ketone intact. Initially, β-diketones were enolized using LiHMDS and later alkyl ketone was chemoselectively reduced efficiently by lithium aluminium hydride. This method produces β- hydroxyl ketones from the corresponding β-diketones in high yield. [Copyright &y& Elsevier]

Abstract: As an efficient catalyst for asymmetric transfer hydrogenation reaction (ATH reaction) of α,β-unsaturated ketones, Rh-Cp∗–TsDPEN (Cp∗ =1,2,3,4,5-pentamethylcyclopenta-1,3-diene, TsDPEN= N-(p-toluenesulfonyl)-1,2-diphenyl- ethylenediamine) shows high chemoselectivity on Ce:glyph name="dbnd" />C reduction. In our method, both Ce:glyph name="dbnd" />C bonds in a variety of chromenone derivatives were reduced efficiently in aqueous media, resulting in at least 98% ee and up to 99% yields in a convenient way without further purification. The product was a useful intermediate for deriving chiral chroman-4-amine, which was reported as an effective agent against hypotension and inflammatory pain by inhibiting human bradykinin B1 receptor. [Copyright &y& Elsevier]

Abstract: A diastereoselective, boron-mediated aldol process inspired by the natural product fostriecin is described. Using a tertiary α′-stereocenter as the induction element, aldol adducts are provided with high yields, good to excellent levels of diastereoselection, and broad substrate scope. An Evans–Tischencko reduction of the aldol adduct from cinnamaldehyde resulted in the C8–C11 stereotriad of ent-fostriecin. [Copyright &y& Elsevier]

Abstract: Ytterbium triflate was shown to be effective in promoting the reduction of substituted aromatic and aliphatic aldehydes and ketones using isopropanol as the solvent and the reducing agent. The whole process furnished the desired adducts in 22-98% yield. [Copyright &y& Elsevier]

Abstract: Reduction of nitriles to aldehydes with diisobutylaluminium hydride (DIBAL-H) is an important transformation in organic chemistry. But the use of this reaction is limited for the lack of reproducibility due to the instability of the intermediates formed. In the current article we disclose the improvement of the reaction applying continuous flow technology. [Copyright &y& Elsevier]

Abstract: The treatment of alkyl or aryl halides with an excess of tetrakis(pyridine)lithium tetrakis(N-dihydropyridyl)aluminate affords the corresponding 3-substituted-1,2,3,6-tetrahydropyridines in moderate to good yields via a tandem alkylation–reduction reaction. [Copyright &y& Elsevier]