Unexpected disproportionation of 4,4′-dialkylamino substituted diaryl selenides and tellurides

Abstract

The unsymmetrical diaryl selenides 1a and b disproportionate under acidic conditions, to produce the corresponding symmetrical analogues. Similarly, the aminosubstituted compounds 2b–d and 2k react with 2a to establish an equilibrium mixture with high selectivity. Diaryl tellurides 5a and b also exchange aryl groups, whereas aminosubstituted diaryl sulfides are stable under the reaction conditions. The process, which involves carbon-selenium/tellurium bond cleavage, may involve a free radical mechanism.