Rhodium-Catalyzed Selective C(sp2)-H Activation/Annulation of tert- butyl benzoyloxycarbamates with 1,3-Diynes: A one Step Access to Alkynylated Isocoumarins and Bis-Isocoumarins

We report here a Rh(III) catalysed regio- and stereo-selective synthesis of alkynylated and bis-iso- coumarin from 1,3-dialkyne. Exclusive one-pot formation of 3,3-bis-isocoumarin isomer has been achieved by elim- inating several other possibilities. This is the first example of transition metal catalyzed synthesis of alkynylated and bis-isocoumarin scaffold. The protocol is compatible with a wide range of functional groups affording good to excel- lent yields. Several mechanistic investigations including deuterium labeling experiment and kinetic isotope effect study have been carried out.