One-pot construction of dispirocyclohexanes via K2CO3-mediated desulfonylative Michael–Michael–aldol (2 + 2 + 2) annulation of sulfonyl 2-pyridyl flavanones and methylketones

Abstract

K₂CO₃-mediated one-pot tandem conversion from sulfonyl 2-pyridyl flavanones to dipyridyl dispirocyclohexanes with contiguous multiple stereogenic centers was accomplished in good yields via an intramolecular desulfonylative ring-contraction of sulfonyl 2-pyridyl flavanones followed by an intermolecular Michael–Michael–aldol (2 + 2 + 2) annulation of the resulting pyridyl aurone intermediate with methyl ketones under facile, open-vessel, inexpensive and environmentally friendly reaction conditions. A plausible mechanism is proposed and discussed herein. This protocol provides a highly effective ring-closure via three carbon–carbon (C–C) bond formation.