Organocatalytic enantioselective synthesis of dihydronaphthofurans and dihydrobenzofurans: reaction development and insights into stereoselectivity

SUSAM Z. D., Ozcan B. D., Kurtkaya E., YILDIRIM E., TANYELİ C.

ORGANIC & BIOMOLECULAR CHEMISTRY, vol.20, no.44, pp.8725-8740, 2022 (SCI-Expanded) identifier identifier identifier

  • Publication Type: Article / Article
  • Volume: 20 Issue: 44
  • Publication Date: 2022
  • Doi Number: 10.1039/d2ob01571d
  • Journal Name: ORGANIC & BIOMOLECULAR CHEMISTRY
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Biotechnology Research Abstracts, CAB Abstracts, Chemical Abstracts Core, Chimica, Compendex, EMBASE, MEDLINE, Veterinary Science Database
  • Page Numbers: pp.8725-8740
  • Middle East Technical University Affiliated: Yes

Abstract

Squaramide/cinchona alkaloid-derived bifunctional organocatalysts are in high demand in asymmetric transformations. Bifunctional quinine-derived sterically encumbered squaramide (H-bond donor) organocatalysts were used to catalyze the asymmetric Friedel-Crafts/S(N)2 type domino reaction of (Z)-alpha-bromonitroalkenes and alpha/beta-naphthols and phenol derivatives to generate enantiomerically enriched dihydronaphthofuran (DHN) and dihydrobenzofuran (DHB) derivatives, respectively. The target adducts were obtained in up to >99% ee under mild conditions with a relatively low catalyst loading (5 mol%) compared to the methods known in the literature. In addition, density functional theory (DFT) calculations were performed to establish a possible outcome, explaining the origin of the stereoselectivity. It was discovered that pi-stacked interactions for the trans-conformation in the Friedel-Crafts step are 0.79 kcal mol(-1) more stable than the cis-conformation.