Synthesis of substituted 2H-Chromenes via Pd-catalyzed C–H activation and thermal cyclization.

A proficient approach has been developed for the synthesis of substituted 2 H -chromenes from C1-substituted glucal. The key step of our synthetic methodology was C–H activation in propylene carbonate solvent followed by 6 π- electrocyclization aromatization in ethylene glycol as greener substitutes to toxic aprotic solvents, to obtain 2 H -chromenes in a stepwise manner. The application of the developed methodology was further explored with the synthesis of a small library of substituted 2 H -chromenes in good yields. [Display omitted] • Synthesis of substituted 2 H -chromenes from d -mannose. • 6 π- electrocyclization aromatization in ethylene glycol. • Utilization of green solvents and gram-scale synthesis. [ABSTRACT FROM AUTHOR]