Migration of alkyl group from O to S in the reaction of O, S-dialkyl dithiocarbonates with boron trifluoride etherate was studied to elucidate the reaction mechanism on the basis of results from kinetics, crossover reaction, and products formed. It was worthy of note that dialkyl methyl sulfonium fluoroborates were formed in a fairly good yield in reactions with O-alkyl S-methyl dithiocarbonates (alkyl=benzyl and cholesteryl) with boron trifiuoride etherate. Formation mechanism of these by-products was investigated and discussed.
研究了 O、S-二烷基二硫代碳酸酯与三氟化硼醚反应中烷基从 O 向 S 的迁移,并根据动力学、交叉反应和生成物的结果阐明了反应机理。值得注意的是,在 O-烷基 S-甲基二硫代碳酸酯(烷基=苄基和胆甾基)与三氟化硼醚酸盐的反应中,生成的二烷基甲基氟硼酸锍的产率相当高。对这些副产品的形成机理进行了研究和讨论。
Thione-Thiol Rearrangement of Xanthates Catalyzed by Pyridine N-Oxides. Remarkably Enhanced Reactivity of 4-Dialkylaminopyridine N-Oxides.
Pyridine N-oxides bearing electron-donating substituents (III) are efficient catalysts for rearrangement of O-alkyl S-methyl dithiocarbonates (xanthates) (I) to the corresponding S-alkyl S-methyl dithiocarbonates (dithiolcarbonates) (II). Of the catalysts tested, 4-piperidinopyridine N-oxide (IIIh) is the best from the viewpoints of catalytic activity and solubility in I. Heating of I in the presence of catalytic amounts (0.02-0.05 molar eq) of IIIh gave II together with the symmetric S, S-dialkyl and S, S-dimethyl dithiocarbonates in good yields. The catalytic behavior of donor-substituted pyridine N-oxides is discussed on the basis of kinetic and molecular orbital calculation data. The complete calculation of the perturbation equation on the initial stage of the reaction was consistent with the experimentally observed activity of the catalysts.
带有给电子取代基的吡啶N-氧化物(III)是O-烷基S-甲基二硫代碳酸酯(黄原酸酯)(I)重排成相应S-烷基S-甲基二硫代碳酸酯(二硫醇碳酸酯)(II)的有效催化剂。在所测试的催化剂中,从催化活性和在 I 中的溶解度的角度来看,4-哌啶吡啶 N-氧化物 (IIIh) 是最好的。在催化量(0.02-0.05 摩尔当量)的 IIIh 存在下加热 I,得到 II 以及对称的S,S-二烷基酯和S,S-二甲基二硫代碳酸酯的产率良好。基于动力学和分子轨道计算数据讨论了供体取代的吡啶氮氧化物的催化行为。反应初始阶段微扰方程的完整计算与实验观察到的催化剂活性一致。
Harano, Kazunobu; Shinohara, Ikuo; Sugimoto, Shin-ichiro, Chemical and pharmaceutical bulletin, 1989, vol. 37, # 3, p. 576 - 581