Catalytic Intramolecular Wittig Reaction Based on a Phosphine/Phosphine Oxide Catalytic Cycle for the Synthesis of Heterocycles

Abstract

The catalytic intramolecular Wittig reactions of carbonyl‐containing bromides are reported. The R 3 PO byproducts participate in the catalytic cycle; therefore, the Wittig reaction can be accomplished with only a catalytic amount of organophosphorus reagent. The reaction has also been applied to the efficient and selective synthesis of isoquinolin‐1(2 H )‐ones, indoles, 2,3‐dihydro‐1 H ‐2‐benzazepin‐1‐ones, benzofurans, and 1,2‐dihydroquinolines with a catalytic amount of phosphine oxide (0.1 equiv.) and a tetramethyldisiloxane/titanium isopropoxide [TMDS/Ti(O i Pr) 4 ] reductant system (yields: 35–88 %).