Pivotal Synthesis of Tetrasubstituted Epoxides from Ketones and α‐Halo B/Si Ylides with Understanding of the Activation Modes

The epoxidation of ketones with α‐monohalo borylsilylmethane reagents renders tetrasubstituted epoxides, opening a new reactive pathway by supression of Boron‐Wittig or Peterson olefination pathways. This method enables the preparation of novel 1,1,2,2‐tetrasubstituted borosilylepoxides with intrinsic control of the diastereoselectivity. A mechanism, based on density functional theory calculations, has been postulated analyzing the role of the α‐iodo B, Si‐ylide in the cyclization pathway. Complementarily, enolates generated from ketones can also interact with the α‐monohalo diborylsilylmethane reagents to acceed the 1,1,2,2‐tetrasubstituted borosilylepoxides. The versatility of these entities has been demonstrated through postfunctionalization reactions.