Steric Hindrance-Driven Access to 3,4,7-Trihydro-1,2-oxaphosphepine 2‑Oxides from Vinyloxiranes and Phosphoryl Diazomethanes

Various 3,4,7-trihydro-1,2-oxaphosphepine 2-oxides are synthesized in satisfactory to excellent yields from 2-aryl-2-vinyloxiranes and in situ-generated phosphenes from phosphoryl diazomethanes via the phosphene-induced and steric hindrance-driven ring expansion of vinyloxiranes. The reaction is an unprecedented synthetic strategy for 1,2-oxaphosphepine 2-oxide derivatives, featuring ring expansion of readily available starting materials, a fast reaction rate, high atom economy, no catalyst, and separable diastereomers.