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 β‐boryl β,γ‐unsaturated aldehydes in good to high yields. Furthermore, the silaformylation of allenes was achieved with a formate ester and PhMe 2 Si−B(pin) as the silicon source.