A novel and convenient preparation for steroidal 1,3-oxathiolane-2-thiones (cis cyclic dithiocarbonates) at room temperature in high yields has been reported by the reaction of steroidal 5α,6α-epoxides with CS2 in THF using lithiumbromide as catalyst <1997TL5705> (Equation (15)).
The cis products were obtained selectively as the sole products. The reactions of various oxiranes with CS2 under the same reaction conditions have also been examined <1995JOC473>. The desired dithiocarbonates were obtained regioselectively in high yields, and the formation of the regioisomeric trithiocarbonates and episulfides was suppressed (Equation (16)).
The selectivity and yield of the reactions were strongly reduced when other alkali halides were applied as catalysts <1995JOC473>. Using this method, 4-arylspiro[1,3-oxathiophene-2-thione]-5-tetral-1-one was prepared <2001MI365>.
A facile, one-pot synthesis of a number of insecticidal thiophosphoryl xanthates was performed using the mild base 1,8-diaza[5,4,0]bicycloundeca-7-ene in the DBU-catalyzed sequential reaction of various alcohols ROH (R = allyl, i-Bu, n-Bu, s-Bu, 2-Ph-ethyl, furfuryl; all in excess) with CS2 and diethoxyphosphoryl chloride <2001SL625> (Equation (17)).
The catalyst in this reaction is mild and can be removed from the reaction mixture simply by washing with water.
Another mild, chemoselective, and efficient protocol for the thiocarbonylation of alcohols and the thiocarbamation of amines has been reported using CS2 and alkyl halides in the presence of caesium carbonate and tetrabutylammonium iodide (TBAI) <2001TL2055> (Scheme 20).
For the syntheses of various arylseleno- and aryltellurothionoformates (PhOC(S)SeAr and PhOC(S)TeAr, respectively), commercially available phenyl chlorothionoformate was reacted with (Me3Si)3SiSeAr and (Me3Si)3SiTeAr, respectively, and 4 mol.% of tetrakis(triphenylphosphine)palladium. Yields were excellent, 86–96% after chromatography, and the products were identified unequivocally by 125Te and 77Se NMR <1998JOC5713>.
Aliphatic gem-dibromide compounds can be produced from a copper(II) bromide-promoted oxidation of hydrazones <1997T557>. The hydrazones are easily prepared from the corresponding aldehyde or ketone with hydrazine hydrate in the presence of 4 Å molecular sieves.
Treatment of hydrazones with copper(II) bromide–lithium t-butoxide in THF produces gem-dibromides in moderate yields (Equations (107) and (108)). A variation of this method simply consists of using copper(II) bromide–triethylamine in methanol (Equations (109) and (110)). This procedure proved to be practical and more efficient than the copper(II) bromidesingle bondlithium t-butoxide oxidative system. Analogously, the use of copper(II) chloride leads to gem-dichloro compounds.
