Transition-metal-free approaches to 2,3-diarylated indenones from 2-alkynylbenzaldehydes and phenols with tunable selectivity.

The first transition-metal-free regioselective synthesis of 2,3-diarylindenones via tandem annulation of 2-alkynylbenzaldehydes with phenols is described. Two different modes of reaction controlled by electronic effects and temperature furnished either "non-rearranged" or "rearranged" indenones in high selectivity.