THE REACTIONS OF A 1-ALKENESULFENATE ANION WITH TMS-X REAGENTS - A VARIABLE-TEMPERATURE NMR-STUDY

Lithium (E)-1-hexenesulfenate (5a) was treated with a number of TMS-X (TMS = trimethylsilyl) reagents to afford N,N-bis(trimethylsilyl)-(E)- 1-hexenesulfenamide (7a) and (or) di((E)-1 hexenyl) disulfide (8), usu ally in low yield. The cleanest reactions, those from use of TMS-Cl (t o afford 7a) and TMS-CN (which yields 8) were analyzed by variable tem perature NMR. It was found that the low-temperature silylation reactio n using TMS-Cl affords 7a and thiosulfinate 12 as initial products. Wa rming the mixture coerces the decomposition of 12. Treatment of 5a wit h TMS-CN also yields thiosulfinate 12 which is reduced to disulfide 8 as the temperature warms, possibly by action of cyanide ion. Evidence is presented that allows a confident structural assignment of the tran sient thiosulfinate 12, and mechanisms are suggested for the formation of 12. The study also led to the NMR observation of(E)-1-hexenesulfen ate (5a).