Ultrasound-Facilitated Direct meta-C-H Functionalization of Arenes: A Time-Economical Strategy under Ambient Temperature with Improved Yield and Selectivity.

The horizon of ultrasound-assistance has been expanded to palladium-catalyzed distal C-H functionalization of arenes. Compared to thermal conditions, operationally simple ultrasound mediated distal C-H functionalization occurred with a shorter reaction time and enhanced reactivity of reactants to give superior yields with improved selectivity both in terms of meta:others and mono:di. A wide variety of meta-functionalizations such as olefination, alkylation, acetoxylation, allylation and cyanation were successfully carried out under ambient temperature.