Access to Highly Strained Tricyclic Ketals Derived from Coumarins

J Org Chem. 2022 Mar 18;87(6):4476-4482. doi: 10.1021/acs.joc.2c00018. Epub 2022 Mar 8.

Abstract

Synthesis of highly strained fused substituted dihydrobenzopyran cyclopropyl lactones derived from coumarin carboxylates are reported. The substrate scope tolerates a variety of 6- and 8-substituents on the coumarin ring. Substitution at the 5- or 7-position is resistant to tricyclic lactone formation except with 7-methyl substitution. Benzamide-containing coumarins afford the tricyclic ketal. A plausible mechanism is proposed for the formation of the fused lactone: intramolecular rearrangement of trans cyclopropyl methyl ketones with phenolic acetate via the formation of a hemiacetal.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Coumarins*
  • Ethers
  • Lactones*

Substances

  • Coumarins
  • Ethers
  • Lactones