[13121-76-1] · C36H66SSn2 · Bis(tricyclohexyltin) Sulfide-Boron Trichloride · (MW 768.36)
[10294-34-5] · BCl3 · Bis(tricyclohexyltin) Sulfide-Boron Trichloride · (MW 117.17)
(functions as a conveniently prepared in situ form of boron trisulfide; a powerful sulfurating agent for the conversion of carbonyl units into their corresponding thiono carbonyl analogs, e.g. thioaldehydes, thioketones, b-thiolactams, thiolactams;1 thiophenes;2 the analogous bis(tricyclohexyltin) selenide-boron trichloride reagent is useful for selenation of carbonyl compounds to selenoaldehydes and selenoketones1)
Physical Data: bis(tricyclohexyltin) sulfide: mp 130-132 °C; BCl3: mp -107 °C; bp 12.5 °C.
Solubility: bis(tricyclohexyltin) sulfide: insol water; highly sol nonpolar organic liquids; less sol alcohol. Boron trichloride: Lewis acid, partially dissolves in aprotic organic liquids.
Form Supplied in: bis(tricyclohexyltin) sulfide: solid >97% pure; boron trichloride: gas (lecture bottle) 99.95% pure; more conveniently as a 1.0 M solution in dichloromethane, heptane, hexanes, or p-xylene.
Preparative Method: bis(tricyclohexyltin) sulfide: prepared in quantitative yield by treating tricyclohexyltin chloride with Na2S.9H2O in refluxing ethanol (95%) for 2 h; recrystallization from CH2Cl2/MeOH affords pure material, mp 130-132 °C.1
Purification: bis(tricyclohexyltin) sulfide: by recrystallization.
Handling, Storage, and Precautions: bis(tricyclohexyltin) sulfide: irritant; stable solid. Boron trichloride (dichloromethane solution): corrosive; moisture sensitive; stored in nitrogen-filled pressure bottles kept cold in a refrigerator.
Treating the tin sulfide reagent with a dichloromethane (or other) solution of Boron Trichloride in anhydrous toluene, at reflux, produces a highly reactive in situ form of boron trisulfide (eq 1). A potent form of boron triselenide is similarly derived from the corresponding tin selenide reagent (eq 2). [Bis(tricyclohexyltin) selenide is prepared in quantitative yield by treating tricyclohexyltin chloride with Na2Se in anhydrous THF for 2 h. Recrystallization from CH2Cl2/MeOH affords pure material, mp 130-132 °C.]1 Other Group 14 organometallic sulfides1 have been used as the chalcogen source with comparable efficacy (eq 3) and variations of the technique continue to be developed.3-5
If the in situ form of boron trisulfide is prepared in the presence of carbonyl-containing substrates, the carbonyl units are converted into their corresponding thiono analogs (eq 4); esters and lactones, however, generally are not converted in the process.
The selenium analogs are similarly prepared, though isolation of the selenones, due to their inherent instability, is limited to hindered nonenolizable derivatives such as fenchone (eq 5).
With some diketones such as 1,4-diones, thiophenes are the products (eq 6).2 Though no mechanism is presented, a thione intermediate that enolizes, cylizes, and then dehydrates to the aromatic system might be possible.
Boston University, MA, USA