Catalyst-free synthesis of 2,3-dihydrobenzofurans through [4+1] cycloaddition of ortho-hydroxyphenylsubstituted para-quinone methides and sulfur ylides.

An efficient [4+1] cycloaddition of ortho -hydroxyphenylsubstituted para- quinone methides and sulfur ylides was achieved under the catalyst-free condition. With this developed protocol, a series of trans -2,3-dihydrobenzofurans were obtained in excellent yields (up to 99%) with high diastereoselectivities (>20:1 dr). The usefulness of the protocol was also demonstrated by the versatile conversions of the 2,3-dihydrobenzofurans into other functionalized benzofurans. [ABSTRACT FROM AUTHOR]