Atropo- and Diastereoselective Construction of Tetracyclic Biphenylazepinium Salts Derived from Aminoalcohols: Use as Catalysts in Enantioselective Asymmetric Epoxidation

Abstract

A range of new biphenylazepinium salt organocatalysts effective for asymmetric epoxidation has been developed incorporating an additional substituted oxazolidine ring, and providing improved enantiocontrol in alkene epoxidation over the parent structure. Starting from enantiomerically pure aminoalcohols, tetracyclic iminium salts were obtained as single diastereoisomers through an atroposelective oxazolidine formation.

Biocatalytic Routes to Enantiomerically Enriched Dibenz[c,e]azepines

“…Enantiomerically pure dibenz[ c , e ]azepines have previously been synthesised by employing chiral‐pool starting materials, chiral‐auxiliary methodologies, and chiral‐transition‐metal catalysis for synthetic routes identified by traditional disconnection strategies. To identify new and potentially more‐efficient routes to these compounds, we sought to apply the principles, while at the same time expand the scope, of biocatalytic retrosynthesis …”

Five-Membered Ring Systems With O and N Atoms

“…A series of bacterial type-II topoisomerase inhibitors with a spiropyrimidinetrione unit, upon addition of an N-linked oxazolidinone substituent, exhibited an increased activity against both Gram-positive and Gram-negative bacteria. Notably, the organocatalysts were produced as single diastereoisomers through an atroposelective oxazolidine formation (15JOC8036). Oxazolidines were also used to mask or to access amino acid derivatives.…”

Preparation of C 2-Symmetric Biaryl Bisiminium Salts and Their Use as Organocatalysts for Asymmetric Epoxidation

“…We have recently used a similar process to prepare tetracyclic oxazolidines. 24 Scheme 3 Reagents and conditions: i) HBr (24% in H 2 O), 100 °C, 40 min, 85%; ii) Br 2 (1.1 equiv), CCl 4 , reflux, 1 h, 60%; iii) 14 (1 equiv), EtOH, r.t., 16 h; then NaBPh 4 (1.1 equiv), EtOH, MeCN, r.t., 5 min, 70%.…”