Palladium homoenolates catalysts

The reaction of zinc homoenolate 9 with acid chlorides in ethereal solvents containing 2 equiv of HMPA rapidly produces 4-ketoesters in high yield Eq. (44) [33]. A palladium catalyst [40] (or less effectively a copper catalist) [28] accelerates the reaction. This is in contrast to the cyclopropane formation in a nonpolar solvent see (Eq. 22 above). 

Alkoxy-l-siloxycyclopropane, e.g. 30, on treatment with zinc(II) chloride gives a stable zinc homoenolate, that can, for example, be reacted via an intermediate cuprate with enones to afford the Michael addition product.Addition of a palladium catalyst to the zinc species allows for arylation and for vinylation of the homoenolate in good yield. 

Substitution reactions of sp halides have been achieved with the aid of a palladium catalyst (Scheme 23). 14,19 variety of aryl bromides and iodides serve as electrophiles. Reactions with vinyl halides are stereospecific. Vinyl trifluoromethanesulfonates (triflates) also react rapidly with homoenolates. 

Zinc homoenolates (9) react rapidly with acid chlorides in ethereal solvents containing a dipolar aprotic solvent to give 1,4-keto esters in high yield (Scheme 23). 9 palladium catalyst (or, less effective, a copper catalyst) ° accelerates the reaction, in contrast to cyclopropane formation in halometh-ane solvents (see Section 1.14.3.1). 

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