Triethylamine-Promoted Henry Reaction/Elimination of HNO2/Cyclization Sequence of Functionalized Nitroalkanes and 2-Oxoaldehydes: Diversity-Oriented Synthesis of Oxacycles

The triethylamine-promoted cascadeHenry reaction/eliminationofHNO(2)/cyclization reaction of 2-oxoaldehydes with nitroalkanesbearing various remote functionalities is described. Both chiral andachiral nitroalkanes were applicable to this protocol, leading toa variety of oxacycles, such as chromenes, chromanes, cyclic hemiacetals,and polycyclic acetals. An unexpected regioselective photooxygenationoccurred without sensitizer during derivatization to convert a deriveddiene product into a dioxetane by reaction with singlet oxygen, whichprovided chromen-2-one and benzaldehyde after fragmentation.

Automated summary

This study presents the triethylamine-promoted cascade Henry reaction/elimination of HNO(2)/cyclization reaction of 2-oxoaldehydes with nitroalkanes bearing various remote functionalities. Both chiral and achiral nitroalkanes were found to be suitable for this protocol, resulting in the formation of a variety of oxacycles, including chromenes, chromanes, cyclic hemiacetals, and polycyclic acetals. Unexpected regioselective photooxygenation occurred during derivatization without a sensitizer, converting the derived diene product into a dioxetane through reaction with singlet oxygen, ultimately yielding chromen-2-one and benzaldehyde after fragmentation.