A convenient synthesis of chiral amino acid derived 3,4-dihydro-2 H-benzo[ b][1,4]thiazines and antibiotic levofloxacin

Abstract

A series of 3,4-dihydro- 2H-benzo[ b][1,4]thiazine derivatives 8a– g were synthesized via- a copper-catalyzed intramolecular N-aryl amination reaction on substituted 2-(2-bromophenylthio)-ethanamines which were synthesized by the nucleophilic substitution reaction of 2-bromobenzenethiol with Boc-protected amino alcohol derivatives. This strategy provides a short and an efficient entry to ( S)-3-methyl-1,4-benzoxazine 12, an advanced synthetic intermediate for the synthesis of levofloxacin.