Synthesis of allenes by palladium-catalyzed SN2′ reaction of indium organometallics with propargylic esters.

Allenes have been efficiently prepared by the reaction of propargylic esters (benzoates, acetates, carbonates) with triorganoindium compounds (R₃In) under palladium catalysis, via an S_N2’ rearrangement. The reaction proceeds smoothly at room temperature with a variety of aryl-, alkenyl-, and alkynylindium reagents. The yields obtained are high and the regioselectivity is complete both in the case of terminal and nonterminal propargylic esters.