Reductive transpositions allylic alcohols

For reduction of allylic alcohols with double bond transposition, see page 229, Section 4. 

Allylphosphine oxides may be used to make allyl alcohols by the reductive removal of the Ph2PO group with LAH. The reaction involves transposition of the double bond (equation Li(Bu 0)3AlH breaks selectively the C—P phosphonate bond, and this reagent is chemoselective and can... 

Reactions of Enols and Enolate Anions.—Several methods are described for transposition of an oxo-function to the adjacent site. They involve formation of a suitable a-substituted derivative (hydroxymethylene ° or benzylidene ) and subsequent steps which transform the substituent into an isolated oxo-group. Condensations leading to both the 2-hydroxymethylene- and the 2-arylidene-3-oxo-steroids are described for 3-ketones of the 5jS-series, and also of the 5j8,9j5,10a-( retro ) series.Condensations of aromatic aldehydes at C-2 in the 5 -series are unusually slow enolisation towards C-4 is preferred, but steric compression between C-4 and C-6 in 5/3-compounds severely hinders the condensation reaction at C-4, allowing reaction at C-2 via the 2-enol. Reduction of a 21-hydroxymethylene-pregnan-20-one (337) with sodium borohydride afforded the homopregnanediol (338), although reduction of enolised P-dicarbonyl compounds frequently proceeds via elimination to give enones, and thence allylic alcohols. 

The Wharton reaction is the transformation of a,(3-epoxy ketones 1 by hydrazine to allylic alcohols 2. It is also known as the Wharton transposition, Wharton rearrangement, and Wharton reduction. 

Ni(U)-catalyzed Grignard reaction, furnishing allylic alcohols. Allylic ethers are also reactive when there is a phosphine group to coordinate Ni. Note that Grignard reagents which can act as hydride donors give products of reductive cleavage of the allylic ethers without transposition of the double bond. ... 

Reductive Transposition of Allylic Alcohols. Similar to the synthesis of allenes from propargylic alcohols, the Mitsunobu displacement of allylic alcohols with IPNBSH followed by hydrolysis, diazene formation, and sigmatropic loss of dinitrogen provides reductively transposed alkenes. This methodology has proven effective for the reductive transposition of a variety of allylic alcohols (eq 2). The overall transformation provides the desired olefin with high selectivity in the formation of the irans-alkene (eq 3). ... 

Full details have appeared of the deoxygenation of alcohols to alkanes by tripropylsilane reduction of their chloroformate esters (2,122). In a related procedure, alcohol selenocarbonates (69), prepared from the chloroformate esters, have been reduced to alkanes by tributyltin hydride. Both are believed to be radical-chain reactions. Primary allylic alcohols have been deoxygenated to terminal alkenes by the new stannylation-protodestannylation sequence shown in Scheme 32 the S-Sn exchange is another radical process. The intermediate allylstannanes may alternatively undergo a new oxidative destanny-lation as shown to give overall [l,3]-transposition of the allylic alcohol. ... 

Sodium acyloxyborohydride has been found to effect the reduction of aliphatic and aromatic nitriles to the corresponding amines any chloro, nitro, or aromatic substituents remain unaffected under the reaction conditions. Full details have appeared of the [3,3]sigmatropic rearrangement of trichloroacetamidic esters of allylic alcohols, which provides a superior method for the 1,3-transposition of amino (and hydroxy) functions (Scheme 2). 

Kumar and Dittmer have reported the synthesis of intermediates for the lactone moiety of mevinic acids using tellurium-induced nucleophilic reduction developed by their own group as the key step [122] (Scheme 75). Alcohol 331 was protected and converted into aldehyde 332, which upon Wittig reaction and reduction gave allylic alcohol 333. Sharpless epoxidation of 333 and tosylation of the primary alcohol afforded tosylate 334, which underwent the tellurium-induced transposition providing lactone 335 through spontaneous lactonization. However, in the case of the corresponding fcrf-butyl ester, there was no spontaneous lactonization observed. 

See also page 47, Section 93 and page 49, Section 9.4, for reduction of sulfur-containing derivatives of alcohols and phenols and page 229, Section 4, for reduction of allylic sulfonates and sulfones with double bond transposition. 

Scheme 12.6). Stereoselective reduction and chromatographic separation afforded diastereomerically pure derivative 32 in 94% ee. Removal of the silicon protecting group, followed by acetylation of the two secondary alcohols, set the stage for an elegant palladium-catalyzed allylic transposition that provided compound 33 with...

It is a reagent used for allylic transposition, de-bromination and reduction of alcohols in the presence of DEAD and PhsP. [Movassaghi et al. Angew Chem. IntEd Engl 45 5859 2006, Movassaghi Ahmad 7. Org. Chem. 72 1838 2007],... 

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