Synthesis of 8-membered trifluoromethyl benzoxazocines via a Pd-catalyzed ring-expansion reaction of trifluoromethyl benzoxazinones with 2-methylidenetrimethylene carbonate and mechanistic investigations

We report a Pd-catalyzed ring-expansion reaction of trifluoromethyl benzoxazinones with 2-methylidenetrimethylene carbonate. This method exhibits high efficiency and broad functional group tolerance, which leads to the rapid assembly of a series of valuable 8-membered trifluoromethyl benzoxazocines with good yields in a simple manner. The synthetic utility of the approach is demonstrated by the facile transformation of product. Finally, the reaction mechanism was investigated by density functional theory (DFT) calculations, suggesting that the carbonyl group has a greater influence on the site-selectivity than the trifluoromethyl group in the decarboxylative ring re-construction process of benzoxazinones.