The copper(I)-catalysed coupling of Grignard reagents with 5-lithio-2,3-dihydrofuran and 6-lithio-3,4-dihydro-2H-pyran

The organocuprates derived from reaction of Grignard reagents with CuBr·Me2S react with 5-lithio-2,3-dihydrofuran and 6-lithio-3,4-dihydro-2H-pyran via a 1,2-metallate rearrangement to generate an alkenylmagnesium cuprate.