Silicon Acceleration of a Tandem Alkene Isomerization/Electrocyclic Ring-opening of 2‑Methyleneoxetanes to α,β-Unsaturated Methylketones

The first rearrangement of 2-methyleneoxetanes to α,β-unsaturated methylketones is reported. It is proposed that when these substrates are heated, the corresponding oxetenes are formed and subsequently undergo electrocyclic ring-opening to methyl vinylketones. In particular, α-silyl-α,β-unsaturated methylketones were isolated in moderate to high yields and with high stereoselectivities. Based on the proposed mechanism, density functional theory explains the differential kinetics and stereoselectivities among substrates