Allylic geminal dicarboxylates

Allylic geminal dicarboxylates 285 are prepared by Pd-catalyzed reaction of propargyl acetate 284 with AcOH [104], Two products 287 and 288 are obtained from gem-allylic compounds 286, and 288 is an allylic ester and undergoes the second allylation. Several applications to asymmetric syntheses have been reported [48]. Reaction of 289 with dimethyl methylmalonate afforded 290 with 95% ee. 

In addition to cyclic allylic substrates, malonate nucleophiles have been used in reactions with both symmetrical" and unsymmetrical" acyclic systems, and with geminal dicarboxylates. Malonates and Meldrum s acid have also been used as nucleophiles in the desymmetrization of meso diesters. 

The only examples of this class of substrates, that have been studied, are geminal dicarboxylates 44 which are readily prepared from aldehydes [44,45]. Enantioselective displacement of one of the enantiotopic carboxylate groups by the chiral catalyst leads to the chiral allyl complex 45 (Scheme 18). This intermediate which is of the same type as 18 (Scheme 12) has been shown to undergo regioselective nucleophihc addition at the acetoxy-bearing terminus with inversion of configuration (see Sect. 9.5). 

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