We have developed an efficient vinylogous Mukaiyamaaldolreaction of 2-(trimethylsilyloxy)furan with various aromatic aldehydes mediated by bismuth triflate in lowcatalystloading (1 mol %). The reaction proceeds rapidly and affords the corresponding 5-(hydroxy(aryl)methyl)furan-2(5H)-ones in high yields with good to very good diastereoselectivities (dr up to >98:2). Such selectivities, albeit previously
Brønsted acid precatalysts for the Mukaiyamaaldol type reactions of sterically hindered ketones. By using Tf2CHCH2CHTf2 in a range from 0.5 to 2.0 mol %, the vinylogous Mukaiyamaaldolreaction of α-substituted cyclohexanones with 2-silyloxyfurans smoothly proceeded to give the aldol products in excellent yield without the loss of diastereoselectivity. Under similar conditions, acyclic ketene silyl acetals
Introducing strong acids: The reaction of electron‐rich arenes with Tf2CHCH2CHTf2 (Tf=trifluoromethanesulfonyl; triflyl) smoothly gave 2,2‐bis(triflyl)ethylated arenes. This reaction provides a convenient methodology for the introduction of a Tf2CH group, which is known to be a strongly Brønsted acidicfunctionality, to organic compounds in a regioselective manner (see scheme). On the basis of this