Conjugate reduction-allylic alkylation reactions

Scheme 3.3 Domino conjugate reduction-allylic alkylation reaction catalysed by a combination of copper catalysis and chiral palladium catalysis.

The classification is unaffected by allylic, vinylic, or acetylenic unsaturation appearing in both starting material and product, or by increases or decreases in the length of carbon chains for example, the reactions f-BuOH f-BuCOOH, PhCHgOH - PhCOOH, and PhCH=CHCH20H -PhCH=CHCOOH would all be considered as preparations of carboxylic acids from alcohols. Conjugate reduction and alkylation of unsaturated... 

Unfortunately, in 3-alkyl-substituted piperidine IV-oxides there is generally little discrimination between the ring a-carbon centers, and mixtures of regioisomeric products are obtained. When a double bond is present in the starting TZ-oxide, however, this functionality will direct the Polonovski reaction towards elimination of one of the allylic hydrogens. Thus, the (Z)-ethylidene product (18) is obtained from (16) after reduction of the conjugated iminium ion intermediate (17 equation S). ... 

Nevertheless, it must be pointed out that the formation of such transient species has never been spectroscopically observed. Native CDs are effective inverse phase-transfer catalysts for the deoxygenation of allylic alcohols, epoxydation,or oxidation " of olefins, reduction of a,/ -unsaturated acids,a-keto ester,conjugated dienes,or aryl alkyl ketones.Interestingly, chemically modified CDs like the partially 0-methylated CDs show a better catalytic activity than native CDs in numerous reactions such as the Wacker oxidation,hydrogenation of aldehydes,Suzuki cross-coupling reaction, hydroformylation, " or hydrocarboxylation of olefins. Methylated /3-CDs were also used successfully to perform substrate-selective reactions in a two-phase system. 

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