Cuprate addition, stereoelectronics

The common starting material 32, derived from known lactam 31 [25], was treated with divinyl lithium cuprate to afford the adduct 33 as a single isomer. The stereoselectivity of this addition reaction can be explained by A(l 3) strain and stereoelectronic effect[26] the same as our recent investigations. On the other hand, deprotection of the TBDPS... 

These results can be explained in terms of an interplay of stereoelectronic and steric factors. Steric factors are evidently more important in the reaction of bulky cuprate clusters than in the Sakurai reaction. Thus stereoelectronic factors predominate in the allylsilane reaction. Similar effects are observed in conjugate additions to substituted cyclohepten-ones. 

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