THERMAL RACEMIZATION OF OPTICALLY ACTIVE AMINOSULFONIUM SALTS

Abstract

Optically active o-methoxyphenylphenylaminosulfonium salts were synthesized from optically active o-methoxyphenylphenyl-N-p-tosylsulfilimine. The rates of racemization of the salts have been meaured and found to follow first-order kinetics. The racemization proceeds through pyramidal inversion on the sulfur atom. The rate and the activation parameters determined for the racemization of o-methoxy-phenylphenyl-aminosulfonium perchlorate (1a) are 1.58 × 10⁻⁴ (sec⁻¹). ΔH ^≠ = 27 Kcal mol⁻¹. and ΔS ^≠ = 1 eu (75°C). respectively. These data show that the aminosulfonium salt racemizes 6–10 times faster than the corresponding sulfilimine.