Lewis Acid Promoted Tandem Hydroarylation/Rearrangement of 2,2‐dialkyl‐3‐arylchromenes: A Facile Route to Functionalized Dihydroindanes and Dihydrochromans

ABSTRACT

A simple and efficient single pot strategy for the synthesis of trans ‐4‐hydroxy‐1,1‐dimethyl‐2‐phenyl‐3‐aryl‐2,3‐dihydro‐1 H ‐indanes 6a–g has been developed through a Lewis acid promoted tandem hydroarylation‐rearrangement of 2,2‐dialkyl‐3‐arylchromenes. Under optimized conditions, activation of chromenes 3 and 5 promotes intermolecular hydroarylation in presence of electron rich arenes to initially generate trans ‐2,2‐dimethyl‐3,4‐diaryl‐3,4‐dihydrochroman intermediates 7a–e , which under specified conditions can subsequently undergo Lewis acid induced skeletal reorganization involving ring opening and carbocationic rearrangement, ultimately leading to ring contraction and formation of the stereodefined trans ‐diaryl‐2,3‐dihydro‐1 H ‐indane framework.