Uncatalyzed diastereoselective synthesis of alkyliminofurochromone-derived benzylmalononitriles via a three-component cascade reaction: competition between Diels-Alder cycloaddition and Michael addition

Diastereoselective Michael addition reactions of 3-(alkylamino)-9H-furo[3,4-b]chromen-9-one intermediate, produced from the [1 + 4] cycloaddition/tautomerization reaction between 3-formylchromones and alkyl isocyanide in dry CH₂Cl₂, with arylidene malononitrile were developed to afford a wide range of functionalized 2-((S)-((R,Z)-3-(alkylimino)-9-oxo-3,9-dihydro-1H-furo[3,4-b]chromen-1-yl)(aryl)methyl)malononitrile derivatives in good yields and excellent diastereoselectivities under mild conditions. Excellent diastereoselectivity has been achieved to yield products containing two stereogenic carbons and one stereogenic imine group. Two C-C and one C-O bonds were selectively formed to provide new alkylated iminofurochromones in good yields.