Atom-efficient metal-catalyzed cross-coupling reaction of indium organometallics with organic electrophiles

The novel metal-catalyzed cross-coupling reaction of indium organometallics with organic electrophiles is described. Triorganoindium compounds (R3In) containing alkyl, vinyl, aryl, and alkynyl groups are efficiently prepared from the corresponding Lithium or magnesium organometallics by reaction with indium trichloride. The cross-coupling reaction of R3In with aryl halides and pseudohalides (iodide 2, bromide 5; and triflate 4), vinyl triflates, benzyl bromides, and acid chlorides proceeds under palladium catalysis in excellent yields and with high chemoselectivity. Indium organometallics also react with aryl chlorides as under nickel catalysis. In the cross-coupling reaction the triorganoindium compounds transfer; in a clear example of atom economy, all three of the organic groups attached to the metal, as shown by the necessity of using only 34 mol % of indium. The feasibility of using R3In in reactions with different electrophiles, along with the high yields and chemoselectivities obtained, reveals indium organometallics to be useful alternatives to other organometallics in cross-coupling reactions.