A new dehydrogenative [4 + 1] annulation between para-quinone methides (p-QMs) and iodonium ylides for the synthesis of 2,3-dihydrobenzofurans

A new dehydrogenative [4 + 1] annulation of para-quinone methides (p-QMs) with acyclic and cyclic phenyl iodonium ylides has been established, delivering a variety of functionalized 2,3-dihydrobenzofurans with the retention of the quinone methide unit in generally good yields. The reaction pathway involves 1,6-nucleophilic addition, nucleophilic substitution and oxidation under mild metal-free and convenient conditions, and provides a practical access to construct benzofuran frameworks.