Boraformylation and Silaformylation of Allenes

The boraformylation of allenes with B-2(pin)(2) and a formate ester as boron and formyl source, respectively, proceeds in the presence of a copper catalyst. The reaction selectively affords the corresponding -boryl ,-unsaturated aldehydes in good to high yields. Furthermore, the silaformylation of allenes was achieved with a formate ester and PhMe2Si-B(pin) as the silicon source.