The mechanism of the Mitsunobu reaction. II. Dialkoxytriphenylphosphoranes

Abstract

³¹P n.m.r. studies indicate that, in the Mitsunobu reaction, alcohols (ROH) react with triphenyl- phosphine (Ph₃P) and dialkyl azodicarboxylates to produce phosphoranes of the type Ph³P(OR)₂. Mixtures of alcohols produce, in addition, mixed phosphoranes, Ph₃P(OR)(OR'). Phosphoranes of the type Ph₃P(OR)N(CO₂R?)NHCO₂R' are probably intermediates in these reactions but are not observed by ³¹P n.m.r.