A cationic rhodium(I)/(R)-Segphos [(4,4'-bi-1,3-benzodioxole)-5,5'-diylbis(diphenylphosphine)] complex catalyzes the highly enantioselective [4 + 2] annulation of 2-alkynylbenzaldehydes with acyl phosphonates, leading to benzopyranones with a phosphonate-substituted quaternary carbon center in moderate to high yields with excellent ee's. The crystal structure of one of the products was detd. [on SciFinder(R)]