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 2H-chromenes from C1-substituted glucal. The key step of our synthetic methodology was C-H activation in propylene carbonate solvent followed by 6π-electrocyclization aromatization in ethylene glycol as greener substitutes to toxic aprotic solvents, to obtain 2H-chromenes in a stepwise manner. The application of the developed methodology was further explored with the synthesis of a small library of substituted 2H-chromenes in good yields.

-Glycopyranosyl aldehydes: emerging chiral synthons in organic synthesis.

Herein, we have summarized the vast array of synthetic processes that have been developed for the synthesis of -glycopyranosyl aldehydes and diverse -glycoconjugates derived from them by covering the literature reported from 1979 to 2023. Notwithstanding its challenging chemistry, -glycosides are considered stable pharmacophores and are used as important bioactive molecules. The discussed synthetic methodologies to access -glycopyranosyl aldehydes take advantage of seven key intermediates, allene, thiazole, dithiane, cyanide, alkene, and nitromethane.