Thermolysis of 1, 2, 3, 6-Tetrahydro-1, 2-diphenyl-1, 2-diphosphorin 1, 2-Disulfide

Abstract

Thermolysis of trans- and cis-1, 2, 3, 6-tetrahydro-1, 2-diphenyl-1, 2-diphosphorin 1, 2-disulfides [ 8 b] was carried out in the presence of 2, 3-diphenyl-1, 3-butadiene. [ 7 a] to give trans1, 2, 3, 6-tetrahydro-1, 2, 4, 5 -tetrapheny1-1, 2-diphosphorin 1, 2 -disulficie, [8 a], 3, 6-dihydro-2, 4, 5-triphenyl-2 H-1, 2-thiaphosphorin 2-sulfide [9 a]; and 1, 3, 4 -tripheny1-1-phospholene 1-su lfide [110a ] in 0-12, 8-26, and 0-7% yields, respectively. In the, cas of reaction of cis-[8 b]the isomerization to trans-[8 b] was also observed., A possible mechanism is proposed as follows: [8 b] undergoes the retro-Diels-Alder reaction to give J, 2-dipheny1-1, 2-diphosphene 1, 2-disulfide [4 a], which is trapped directly with [7 a] to afford [8 a], or dissociates to phenylphosphinothioylidene [6 a], which is trapped with [7 a], to give [9 a]and/or [10 a]