Reaction of benzoxasilocines with aromatic aldehydes: Synthesis of homopterocarpans

Abstract

Condensation of 2H-benzo[g][1,2]oxasilocines with aromatic aldehydes in the presence of boron trifluoride affords mixtures of cis/ trans 2-phenyl-3-vinylchromans with moderate yields. These can be transformed into homopterocarpans, a synthetic group of substances homologous to the natural isoflavonoid pterocarpans.

Synthesis of Pterocarpans

“…This was the first enantioselective total synthesis of (-)-cis-pterocarpin described in literature. The modified Sakurai-Hosomi can be applied to the condensation of 2H-benzo[g] [1,2]oxasilocines (123) with aromatic aldehydes in the presence of boron trifluoride, affording 2-phenyl-3vinylchromanes (124) in moderate yields [107]. The method is useful for the preparation of the skeleton of the non natural analogs of the pterocarpans, homopterocarpans (126) (scheme 40).…”