Hydrides copper, conjugate reduction

Lithium butyldimethylzincate, 221 Lithium sec-butyldimethylzincate, 221 Organolithium reagents, 94 Organotitanium reagents, 213 Palladium(II) chloride, 234 Titanium(III) chloride-Diisobutylalu-minum hydride, 303 Tributyltin chloride, 315 Tributyl(trimethylsilyl)tin, 212 3-Trimethylsilyl-l, 2-butadiene, 305 Zinc-copper couple, 348 Intramolecular conjugate additions Alkylaluminum halides, 5 Potassium t-butoxide, 252 Tetrabutylammonium fluoride, 11 Titanium(IV) chloride, 304 Zirconium(IV) propoxide, 352 Miscellaneous reactions 2-(Phenylseleno)acrylonitrile, 244 9-(Phenylseleno)-9-borabicyclo[3.3.1]-nonane, 245 Quina alkaloids, 264 Tributyltin hydride, 316 Conjugate reduction (see Reduction reactions)... 

S)-BINAP-, JOSIPHOS-, or (i ,S)-PPF-P(t-Bu)2-ligated copper hydride catalyzes conjugate reduction of o ,j8-unsaturated nitriles (319-321), dinitriles (322), ni-troalkenes (323,324), and sulfones (325,326) with phenylsilane or PMHS. 

Copper hydride species, notably Stryker s reagent [Ph3PCuH]6, are capable of promoting the conjugate reduction of a,( >-unsalurated carbonyl compounds [42], Taking advantage of this trustworthy method, Chiu et al. demonstrated in 1998 an intramolecular reductive aldol reaction in the synthesis of novel terpenoid pseudolaric acids isolated from Chinese folk medicine (Scheme 28) [43]. Two equivalents of [Ph3PCuH]6 enabled cycli-zation of keto-enone 104 to provide the bicyclic diastereomers 105 (66%) and 106 (16%). The reaction also was applied to the transformation of 107... 

Conjugate reduction.1 This stable copper(I) hydride cluster can effect conjugate hydride addition to a,p-unsaturated carbonyl compounds, with apparent utilization of all six hydride equivalents per cluster. No 1,2-reduction of carbonyl groups or reduction of isolated double bonds is observed. Undesirable side reactions such as aldol condensation can be suppressed by addition of water. Reactions in the presence of chlorotrimethylsilane result in silyl enol ethers. The reduction is stereoselective, resulting in hydride delivery to the less-hindered face of the substrate. 

Conjugate reduction of enones. a./ -Unsaturated ketones and aldehydes undergo 1,4-reduction in generally high yield with I equivalent of lithium aluminum hydride in the presence of 10 mole % of Cul and 1 equivalent of HMPT at -78°. The active agent presumably is LiHCuI. Cul can be replaced by mesitylcoppcr and copper(I) t-butoxide. 

Regmselective conjugate reduction and reductive silylation o o.p-unsaturated ketones, esters, and aldehydes usmg a stable copper (I) hydride cluster ((Ph3P)CuH]e... 

The stable, well-characterized copper(I) hydride cluster [(PPh3)CuH]6 is a useful reagent for conjugate reduction of a,p-unsaturated carbonyl compounds. o This hydride donor is chemically compatible with chlorotrimethylsilane, allowing formation of silyl enol ethers via a reductive silation process (Scheme 53). 

In order to explain this DKR, it was proposed that a copper enolate intermediate was formed on asymmetric conjugate reduction of the enone. Subsequent a-bond metathesis with silane yielded the silyl enol ether and regenerated the copper hydride catalyst. Under basic conditions, a rapid... 

Mechanistic insight highlighted the in situ formation of the hydride species via o-bond metathesis between [Cu(0 Bu)(IPr)] and the silane, followed by conjugate reduction leading to the formation of a copper enolate intermediate (Scheme 8.8). However, when an alcohol is introduced in the process, protonation of copper acetal occurs leading to the product and the alkoxide copper complex. 

Conjugate reduction of a,/8-unsaturated nitriles has long been a synthetic problem owing to over-reduction therefore new methodology is welcome. Copper hydride, formed from cuprous bromide, Vitride, and butan-2-ol in THF effectively converts the bis-nitrile (1) into the desired reduction product (Scheme 2). ... 

INVERSE ELECTRON-DEMAND DIELS-ALDER CYCLOADDITION OF A KETENE DITHIOACETAL. COPPER HYDRIDE-PROMOTED REDUCTION OF A CONJUGATED ENONE. 9-DITHIOLANOBICYCLO[3.2.2]NON-6-EN-2-ONE FROM TROPONE... 

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