摘要:
The BF3-promoted addition of (S)-allenylstannane (S)-6 to aldehyde 16 afforded a 68:32 mixture of diastereomeric homopropargylic alcohols 17 and 18 whereas MgBr2-promoted addition gave adduct 17 as the exclusive product. The (R)-allenylstannane (R)-6, on the other hand, yielded a 30:1 mixture of syn and anti alcohol adducts 19 and 20 with BF3.OEt2 and a 1:92 mixture favoring the anti adduct 20 under MgBr2 catalysis.