Synergistic silver/scandium catalytic spiroketalization of β-alkynyl ketones for the atom economical synthesis of skeletally diverse spirocyclic isochromenes

Cheng-Long Ji, Yao Pan, Fang-Zhou Geng, Wen-Juan Hao,* Shu-Jiang Tu,* Bo Jiang*

Two types of new synergistic silver/scandium catalytic spiroketalizations of β-alkynyl ketones have been achieved, delivering a variety of skeletally diverse spirocyclic isochromenes in generally good yields and good diastereoselectivity in an atom-economic manner. In the former, bimetallic catalytic [4+2] cycloaddition worked well to provide a series of 6,6-benzannulated spiroketals whereas the latter gave unprecedented nitrogen-containing 5,6-benzannulated spiroketals through catalytic [3+2] cycloaddition under mild conditions.

Org. Chem. Front. 2019, 6, 474–479