Lewis-acid-catalysed dominoreaction involving a Friedel–Crafts alkylation of variously substituted phenols followed by a direct lactonization has been successfully developed (22 examples, yields up to 98 %). This protocol tolerates not only opposite electron demand substituents on the starting materials, but also drastic modifications of the alkylating agents, and gives direct access to the corresponding
tetrafluoroborate (BMIm-BF4) efficiently generates BF3 from BF4–. This Lewis acid, strongly bound to the ionicliquids, can be efficiently used in classical BF3-catalyzed reactions. We demonstrated the BF3/BMIm-BF4 reactivity in four reactions, namely, a domino Friedel–Crafts/lactonization of phenols, the Povarov reaction, the Friedel–Crafts benzylation of anisole, and the multicomponentsynthesis of tetrahydro-