Copper(II)/Tin(II) Reagent for Allylation, Propargylation, Alkylation, and Benzylation of Disulfides and Elemental Sulfur:  New Insight into the “Copper Effect”

Abstract

Organic bromides and iodides react with diorganodisulfides in the presence of stannous chloride and catalytic cupric halide, giving rise to corresponding unsymmetrical sulfides. Similar reactions but with elemental sulfur provide trisulfides and tetrasulfides. The reactions proceed by copper thiolate as principal reactive intermediate.

The Chemistry of Organic Polysulfanes R−Sn−R (n > 2)

“…In this way diallyltri-and -tetrasulfane as well as other polysulfanes have been synthesized at temperatures of between 20 and 70 °C. 61 Bromobenzene and other arylbromides react with elemental sulfur at 220-240 °C to give S 2 Br 2 and mixtures of polysulfanes, 62 but no separation of these products has been reported.…”

“…The reaction of alkylbromides and -iodides with elemental sulfur to give tri- and tetrasulfanes is promoted by a mixture of tin(II) chloride and copper(II) chloride in THF−DMSO (2:1 v/v). In this way diallyltri- and -tetrasulfane as well as other polysulfanes have been synthesized at temperatures of between 20 and 70 °C …”

A Review of Heterolytic Synthesis Methodologies for Organotri- and Organotetrasulfane Synthesis

“…Rather than start with the inorganic sulfide, substituting with sulfur and an inorganic hydroxide together with an alkyl halide is also known 12a-c in which it is safe to assume that the reaction proceeds via a polysulfide anion or dianion and hence suffers from the same limitations (hydrazine as a reductant may also be added to reduce S 8 to produce reactive polysulfide anions). 12b Similarly, one may start from sulfur with either sodium metal in an aprotic solvent like DME (Scheme 1, entry 1), 13 or a tin/copper promotor (Scheme 1, entry 2), 14 but, once again, reaction in each case with RX yields a range of polysulfanes. Interestingly, reaction of sulfur with acrylonitrile in DMF and ammonia yields a moderate yield (49%) of the trisulfane, which is claimed by the au-thors to proceed via conjugate addition of a sulfur radical anion (Scheme 1, entry 3).…”

Recent Advances in Organic Reactions Involving Elemental Sulfur

“…Allyl bromides and iodides 203 reacted with elemental sulfur in the presence of stannous chloride and a catalytic amount of cupric halide, leading to corresponding trisulfides 204 and tetrasulfides 205 (Scheme ). Copper thiolates were suggested as the principal reactive intermediates …”