CONFORMATIONS OF 4,5,6-TRIPHENYL-TETRAHYDRO-1,3-THIAZINE-2-THIONES AND THEIR N-ALKYL DERIVATIVES. UNUSUAL THIAZINETHIONE OR AZETIDINE FORMATION UPON REACTION OF 3-AMINO- AND 3-METHYLAMINO-1,2,3-TRIPHENYLPROPYL CHLORIDES WITH POTASSIUM ETHYLXANTHATE

Abstract

Reaction of 3-amino- or 3-methylamino-1,2,3-triphenylpropyl chlorides (6 or 7) with potassium ethylxanthate leads to 4.5.6-triphenyl-tetrahydro-,3-thiazine-2-thione 1 or 1-methyl-2,3,4-triphenylazetidine 8 depending on the N-substitution. Conformational distribution of all possible diastereoisomeric thiazinethiones 1 and their N-alkyl derivatives 2–5 is determined by means of ¹H NMR spectroscopy. Allylic strain caused by N- substituents in the trans,cis-isomers strongly shifts the equilibrium between conformations with a,a,e or e,e,a phenyl groups towards the conformer with an axial neighbouring Ph-4 group. Vicinal couplings data for the diastereoisomeric azetidine 8 show different ring geometry depending on the configuration.