Diastereoselective allylation of α-ketoamides bearing camphor N-tosylpyrazolidinone auxiliary: efficient synthesis of highly optically active two stereoisomers

Complementary allylation conditions were developed for the synthesis of both diastereomers of tertiary homoallylic alcohols. Treatment of camphor N-tosylpyrazolidinone derived α-ketoamides with allyltributylstannane afforded both the individual homoallylic alcohols in high optical purity (up to 98% de) when the reaction was carried out in the presence of Sn(OTf)2 and PdCl2, respectively. The stereochemical outcome and reversal of stereoselectivity in the reaction are proposed based on 13C NMR and FTIR studies.