Enantioselective Acyl Migration Reactions of Furanyl Carbonates with Chiral DMAP Derivatives.

We developed an efficient enantioselective acyl migration reaction of furanyl carbonates to construct all-carbon quaternary stereogenic centers. In some cases, the reactions required only 0.05 mol % (minimum 500 ppm order) of catalyst and showed a high TOF value (3,640 h-1). Multigram-scale reactions (10 grams) also proceeded with high enantioselectivity (>99:1 er) in quantitative yield. The catalyst was robust and easily recovered in 98% yield, and could be recycled in the same reaction without a loss of catalytic activity or enantioselectivity. A wide range of functional groups could be tolerated (15 examples, >98% yield, up to >99:1 er), and a variety of optically active 3,3'-disubstituted benzofuranone derivatives, which are useful intermediates for the synthesis of natural products and pharmaceuticals, were efficiently obtained. Control experiments on the catalyst structure (e.g., catalyst 1a vs 1a' and 1a'') and computational calculations revealed that both the catalytic activity and enantioselectivity should be enhanced by hydrogen bonding between a catalyst and a substrate. Moreover, this system was applied to the challenging γ-selective acyl migration reaction of furanyl carbonates with high γ-selectivity and high enantioselectivity (α:γ = 10:90, 95:5 er) .