Synthesis of 3-acyl-5,6-dihydro-1,4-oxathiines through ring expansion of thiiranes

Synthesis of 3-acyl-5,6-dihydro-1,4-oxathiines has been achieved via reactions of thiiranes and α-diazo-β-1,3-dicarbonyl compounds under microwave and copper sulfate-assisted conditions. The current method provides a direct and simple strategy in efficient preparation of 3-acyl-1,4-oxathiines from readily available thiiranes and trans-3-acyl-5,6-dihydro-1,4-oxathiines as stereospecific products for 1,2-disubstituted cis-thiiranes. The reaction mechanism was also proposed.