- A new selenium catalyzed synthesis of S-Alkyl carbonothioates from alcohols, carbon monoxide, sulfur and alkyl halides
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Selenium showed excellent catalytic activity for carbonothiolation of alcohols with carbon monoxide and sulfur under mild conditions. S-Alkyl carbonothioates were synthesized in good yields from various alcohols, carbon monoxide, elemental sulfur, and alk
- Mizuno, Takumi,Nishiguchi, Ikuzo,Hirashima, Tsuneaki,Ogawa, Akiya,Kambe, Nobuaki,Sonoda, Noboru
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p. 4773 - 4776
(2007/10/02)
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- Uncatalyzed and General Acid Catalyzed Decomposition of Alkyl Xanthates and Monothiocarbonates in Aqueous Solutions
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The decomposition of potassium alkyl xanthates and alkyl monothiocarbonates follows the rate law kobbsd = kH3O++> + kHA + kH2O in aqueos buffer solutions.The Broested coefficient βlg for the kH2O terms is -1.1 for the monothiocarbonates and -1.3 for the xanthates.These results complement the value of -1.1 observed for the alkyl monocarbonates and have been interpreted as late transition states in the decomposition direction.The reactions are also subject to general acid catalysis with α values of 0.9 +/- 0.2 and 0.8 +/- 0.1 for ethyl and methoxyethyl xanthates; α values for the monothiocarbonates are 0.58 +/- 0.05 and 0.57 +/- 0.01 for the methyl and methoxyethyl compounds, respectively.Solvent kinetic isotope effects (kD3O+/kH3O+) for ethyl and methoxyethyl xanthates are 2.53 and 2.12, respectevely; for ethyl, methyl, and methoxyethyl monothiocarbonate they are 1.95, 1.94, and 1.91, respectevely.The high Broensted value for ethyl xanthate and the resultant uncertainly in its numerical value coupled with the high inverse solvent isotope effect place this reaction on the borderline between a specific acid catalyzed mechanism and a concerted mechanism.The latter is favored because the value for kH3O+ is larger than that predicted for the protonation of the alcohol oxygen of the xanthates and monothiocarbonates; further, the formation of such protonated species is estimated to be sufficiently unfavorable as to require a breakdown step faster than a molecular vibration to account for the observed rates.Acetic acid does not catalyze the kH3O+ term for ethyl xanthate at very low pH; the small amount of catalysis at higher pH must therefore be true general acid catalysis and not a solvent effect.Broensted βlg values for the acid-catalyzed decompositions of the xanthates and monothiocarbonates are small.These results have been interpreted in terms of concerted general acid catalysis where little change in charge occurs on the leaving group oxygen in going from the starting material to the transition state.
- Millican, Robert J.,Angelopoulos, Maria,Bose, Anita,Riegel, Bram,Robinson, Darlyne,et al.
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p. 3622 - 3630
(2007/10/02)
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- A General Strategy for Elaboration of the Dithiocarbonyl Functionality, -(C=O)SS-: Application to the Synthesis of Bis(chlorocarbonyl)disulfane and Related Derivatives of Thiocarbonic Acids
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A variety of sulfenyl chlorides have been reacted with a variety of alkoxythiocarbonyl compounds to give adducts which then lose (spontaneously, or upon thermolysis, or in the presence of Lewis acid catalyst) the alkyl chloride to provide an assortment of dithiocarbonyl compounds in good to excellent yields.The preparations of bis(chlorocarbonyl)disulfane (1), ((trichloromethyl)dithio)carbonyl chloride (2), ((alkoxycarbonyl)dithio)carbonyl chlorides (3 and 4), and (((alkylthio)carbonyl)dithio)carbonyl chlorides (5 and 6) by this methodology were optimized; some of the (alkoxydichloromethyl)disulfanyl adducts, e.g., ROCCl2SS(C=O)Cl (10) and ROCCl2SS(C=O)OR'(54), were reasonable stable and could be isolated.All new compounds were characterized by analytical data, 1H and 13C NMR, IR, UV, and mass spectrometry, and high-yield derivatizations with alcohols or N-methylaniline.The reaction with N-methylaniline was also adapted to a rapid, convenient, and precise analytical-scale assay of mixtures of compounds containing acid chloride and/or sulfenyl chloride functionalities.The kinetics, mechanism, and stereochemistry of the dithiocarbonyl synthesis are discussed.
- Barany, George,Schroll, Alayne L.,Mott, Andrew W.,Halsrud, David A.
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p. 4750 - 4761
(2007/10/02)
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