MECHANISM AND STEREOCHEMICAL CONSIDERATIONS IN REACTION OF SOME ARYLSERINE DERIVATIVES WITH THIONYL CHLORIDE

The reaction of esters of N-acylphenyl- and p-nitrophenylserinates with thionyl chloride has been studied by nmr. The erythro isomers rapidly cyclize to trans-oxazolines which open (more slowly) to erythro-β-chloro-β-arylalaninates. (threo-Phenylserinates give threo-β-chloro derivatives without the intervention of oxazolines, while the threo-p-nitrophenyl analogs slowly form cis-oxazolines which do not open under the same conditions. Reasons for the different mechanisms based on both steric and electronic factors are offered. Hydrolytic studies help reconcile present results with some prior reports which, by themselves, seem inconsistent. © 1969, American Chemical Society. All rights reserved.