Reaction between isocyanides and dialkyl acetylenedicarboxylates in the presence of strong CH-acids: one-pot synthesis of highly functionalized annulated 4 H-pyrans

Abstract

The highly reactive 1:1 adduct, produced from the reaction between dialkyl acetylenedicarboxylates and alkyl isocyanides, was trapped by strong cyclic CH-acids such as 4-hydroxy-6-methyl-2 H-pyran-2-one or 4-hydroxycoumarin to yield dialkyl 2-(alkylamino)-5-oxo-4 H,5 H-pyrano[3,2- c]chromene-3,4-dicarboxylates or dialkyl 7-methyl-2-(alkylamino)-5-oxo-4 H,5 H-pyrano[4,3- b]pyran-3,4-dicarboxylates in good yields at room temperature.