Synthesis of phosphaisocoumarins via iodocyclization.

4-Iodophosphaisocoumarins can be prepared in good yield and with high regioselectivity under mild conditions by the reaction of o-(1-alkynyl)phenylphosphonates with I(2) or ICl. The present reaction represents the first example of a phosphonate iodocyclization onto a C-C triple bond. The resulting iodides can be further elaborated using palladium-catalyzed coupling reactions.