A Novel Method to Construct 2-Aminobenzofurans via [4 + 1] Cycloaddition Reaction of In Situ Generated Ortho -Quinone Methides with Isocyanides.

A new approach for the synthesis of 2-aminobenzofurans has been described via Sc(OTf) 3 mediated formal cycloaddition of isocyanides with the in situ generated ortho -quinone methides ( o -QMs) from o -hydroxybenzhydryl alcohol. Notably, as a class of readily available and highly active intermediates, o -QMs were first used in the construction of benzofurans. This [4 + 1] cycloaddition reaction provides a straightforward and efficient methodology for the construction of 2-aminobenzofurans scaffold in good yield (up to 93% yield) under mild conditions.