Stereochemistry of 2-Amino-1-benzocycloalkanol Derivatives Reaction of 2-Acylamino-1-benzocycloalkanol with Thionyl Chloride or Concentrated Sulfuric Acid

Abstract

As a method for conversion of configuration in 2-amino-1-benzocycloalkanol (I) via oxazoline derivative (V), reaction of cis- and trans-2-acylamino-1-benzocycloalkanol (IVa-d) with thionyl chloride or concentrated sulfuric acid was examined. On treatment of IV with thionyl chloride, all of trans isomers (trans-IVa-d) afforded cis-Va-d in a high yield, cis isomers of five- and six-membered ring derivatives (cis-IVa-c) gave cis-Va-c and cis-chloride (cis-VIa-c), while cis-isomer of seven-membered ring (cis-IVd) gave rise to trans-Vd besides cis-Vd and VId. On the other hand, treatment of IV with cold concentrated sulfuric acid gave only cis-V regardless of ring size or conformation. Under the same reaction condition, isomerization of cis-Vd to trans-Vd was observed.