First enantioselective reductive amination of α-fluoroenones

From α-fluoroenones 2, a synthesis of (E) ketone oxime O-alkyl ethers 5 is reported with good to excellent yields. Then the first enantioselective reduction of these ketimines, via oxazaborolidine, is described with moderate to good enantiomeric excesses, leading to valuable chiral fluoroallylic amines 1.     

Synthesis of a perfluoroalkyl-substituted α-diimine by Sm-mediated reductive coupling

Samarium iodide mediates the reductive coupling of imidoyl iodide 1 to the corresponding enediamine 2, which is oxidized by manganese dioxide to an N,N′-diaryl-α-diimine 3. Single-crystal X-ray diffraction analysis shows that 2 crystallizes in the E,E-geometry, with a substantial nonplanarity of the NC-CN moiety, allowing a π-stacking interaction between the N-aryl rings. Unlike its 2,3-dimethyl analogue, 3 resists formation of chelates with palladium(II) or platinum(II).     

The reductive cyclization of 8,8′-bisbromomethyl-1,1′-binaphthyl

Reductive cyclization of the title compound to the corresponding dinaphthocycloöctatriene is a facile process. The dinaphthocycloöctatriene does not undergo ring inversion on the NMR time scale, even at elevated temperatures.     

Synthesis of lactate derivatives via reductive radical addition to α-oxyacrylates

Lactate derivatives are important synthetic precursors to a variety of pharmaceutical products. Previously reported methods to prepare lactates require multiple steps or have limited scopes. Herein, we report a Ni-catalyzed reductive addition of a variety of alkyl iodides to α-oxyacrylates to afford substituted lactates. Exploring the scope of radical acceptors reveals that electron-deficient alkenes, ranging from cyclohexenone to para-caboxystyrene, undergo efficient coupling with alkyl iodides. This method represents an alternative strategy access lactate derivatives.     

A novel reductive ring-opening reaction of isoxazolidine to form functionalized 1,3-aminoalcohol

Reductive cleavage of the N-O bond of isoxazolidine ring with catalytic hydrogenation over Raney nickel was described. Bicyclic isoxazolidines could be effectively converted into the corresponding 1,3-amino-alcohol possessing a sultone or sultam moiety with high conversion and yield when the hydrogenation was catalyzed by freshly prepared Raney nickel under a pressure of 40 psi in the presence of triethylamine.     

A Synthesis of β-necrodol via a palladium catalyzed reductive enyne cyclization

The Pd catalyzed reductive enyne cyclization provides an approach to control 1,3- diastereoselectivity and thereby provides a five step synthesis of β-necrodol, a key substituent of the defensive secretion of the red-lined carrion beetle.     

Selectively reductive cleavage of the protected taxol side chain with sodium borohydride

During the course of our studies on the taxol chemistry,we have ever tried thereductive cleavage of the acotyl group at 20-C in compound 1a~(1,2) with the hydroxylgroup assistance at 4-C by sodium borohydride. However, the major product 2a~2(27%)still had the acetyl group at 20-C and the signal for the 10-C proton at 6.61 ppm(s)was shifted to 6.31 ppm(d, J=3.79 Hz). A new doublet signal at 3.62 ppm(d, J=3.80     

Azo-pyrene–based fluorescent sensor of reductive cleavage of isomeric azo functional group

In this study we investigated the reductive azo cleavage of an azo compound presenting a pyrene fluorophore (Azo-py). Because of dramatic changes in its fluorescence, Azo-py could be used as a monitoring system for the reductive azo cleavage. Electron transfer from the pyrene unit to the azo moiety induced fluorescence quenching; this quenched fluorescence was recovered after the reductive azo cleavage. IR and NMR spectroscopy were used to study the various structural states. The rate of reductive cleavage of the azo compound, determined through fluorescence monitoring, depended on its structural state: the cleavage of trans-Azo-py was much faster than that of the cis-Azo-py. Furthermore, the Azo-py fluorophore was highly sensitive to the presence of zinc, but not other metal compounds, and the pH.     

Palladium-catalyzed reductive Heck reaction of α,β-unsaturated alkenes and cycloalkyl iodides

The palladium catalyzed reductive Heck reactions of unactivated cycloalkyl iodides with α,β-unsaturated alkenes have been developed. A number of hydrocycloalkylated alkenes were obtained in reasonable yields under the optimized conditions. The obvious advantage of this approach is that the hydride source was provided by Et₃N and no other reductant or base was required in the reaction.     

Selective formation of unsymmetric ureas by selenium-catalyzed oxidative–reductive carbonylation with CO

A series of unsymmetric ureas containing substituted groups have been synthesized via selenium-catalyzed selective oxidative–reductive carbonylation of amines and nitro compounds with CO instead of phosgene in one-pot reaction. These catalytic reactions are important from both synthetic and industrial points of view, because not only the reactions can be proceeded with high selectivity of higher than 99% towards desired unsymmetric ureas, but also there exists a phase-transfer process of the selenium catalyst in the reaction, so that the after-treatment of the catalysts and products from the reaction systems can be easily separated by simple phase separation.     

One-step synthesis of α-hydorxy acids via reductive double carbonylation of organic halides

Palladium-catalyzed carbonylation of organic halides with water in the presence of calcium hydroxide or lithium hydroxide in primary or secondary alcoholic solvents afforded α-hydroxy acids.     

Intramolecular reductive ketone-alkynoate coupling reaction promoted by (η2-propene)titanium

Intramolecular reductive coupling of cycloalkanones tethered to alkynoates in the presence of (η(2)-propene)titanium was successfully performed to provide hydroxy-esters in a diastereoselective manner. Subsequent lactonization afforded angularly fused unsaturated tricyclic lactones which represent relevant substructures of numerous bioactive compounds.     

Why a cathodic activation by silver interface? Facile reductive homocoupling of 1-iodoalkanes

Smooth silver electrodes were used for the cathodic one-electron cleavage of primary alkyl iodides, RI. It has been shown that the catalytic process making possible the reduction of RI species is based on pre-reacting alkyl iodides with silver. It is then proposed that the transient species formed (via electron transfer?) at the silver interface could be written as R–Ag⁺, I⁻. Arguments to support this proposal are presented. Such chemically modified interfaces showed a specific electrochemical behaviour in propylene carbonate (PC) in the presence of tetraalkylammonium ammonium salts. Experimental conditions for yielding specifically a one-electron step for RI species are discussed and the resulting homocoupling is evidenced.     

Dehydration of α-silylalcohols in the reductive conversion of esters and ketones into alkenes

The conversion of esters and ketones into easily dehydrated α-silylated alcohols, and protodesilylation of the resultant vinylsilanes, gives alkenes under relatively mild acidic conditions.     

The roughened silver–palladium cathode for electrocatalytic reductive dechlorination of 2,4-Dichlorophenoxyacetic acid

The roughened silver–palladium (Pd/Ag(r)) electrode was fabricated by a convenient metallic replacement reaction, and its electrocatalytic property towards reductive dechlorination of 2,4-Dichlorophenoxyacetic acid (2,4-D) in basic aqueous solution have been evaluated. Experimental evidence is presented that Pd/Ag(r) exhibited powerful electrocatalytic activity for dechlorination of 2,4-D. In addition, a new dechlorination mechanism of 2,4-D was proposed, in which the formation of adsorbed 2,4-D on Ag is a key step.     

Unexpected α,β-unsaturated products of reductive amination of the macrolide antibiotic josamycin

Reductive amination of the macrolide antibiotic josamycin with alkyl amines, using three different reducing agents: NaBH₃CN, NaBH₄ and NaBH(OAc)₃, yields surprisingly different major products which are identified as either Lewis complexes, aminoalkyl derivatives or α,β-unsaturated derivatives of josamycin by ¹H and ¹³C NMR, FT-IR and ESI MS methods.     

Consecutive intermolecular reductive hydroamination: cooperative transition-metal and chiral Brønsted acid catalysis

Enantiomerically pure chiral amines are of increasing importance and commercial value in the fine chemical, pharmaceutical, and agrochemical industries. Here, we describe the straightforward synthesis of chiral amines by combining the atom-economic and environmentally friendly hydroamination of alkynes with an enantioselective hydrogenation of in situ generated imines by using inexpensive hydrogen. By following this novel approach, a wide range of terminal alkynes can be reductively hydroaminated with primary amines including alkyl-, and arylalkynes as well as aryl and heteroaryl amines. Excellent yields and selectivities up to 94?%?ee and 96?% isolated yield were obtained.     

SmI2-induced reductive cross-coupling of carbonyl compounds with (α,β-unsaturated esters

Reductive cross-coupling of carbonyl compounds with(α,β-unsaturated esters by SmI₂ to ?-lactones was highly accelerated by the addition of hexamethylphosphoric triamide (HMPA).     

Racemic and asymmetric cobalt-catalysed reductive aldol couplings of α,β-unsaturated amides with ketones

In the presence of diethylzinc as a stoichiometric reductant, substoichiometric quantities of an appropriate cobalt source catalyse diastereoselective reductive aldol coupling reactions of α,β-unsaturated amides with ketones. The use of a readily available oxazolidine as a chiral auxiliary imparts high levels of asymmetric induction in these reactions.     

Copper-catalyzed reductive coupling of tosylhydrazones with amines: a convenient route to α-branched amines

A general procedure for the reductive coupling of N-tosylhydrazones with amines in the presence of Cu(acac)(2) and Cs(2)CO(3) has been developed. The protocol is very effective and chemoselective with various primary and secondary aliphatic amines, aminoalcohols as well as azole derivatives to give α-branched amines in good yields.