ANALOGS OF NEUROEFFECTORS .V. NEIGHBORING-GROUP EFFECTS IN REACTIONS OF ESTERS THIOLESTERS AND SELENOLESTERS . HYDROLYSIS AND AMINOLYSIS OF BENZOYLCHOLINE BENZOYLTHIOLCHOLINE BENZOYLSELENOLCHOLINE AND OF THEIR DIMETHYLAMINO ANALOGS
ANALOGS OF NEUROEFFECTORS .V. NEIGHBORING-GROUP EFFECTS IN REACTIONS OF ESTERS THIOLESTERS AND SELENOLESTERS . HYDROLYSIS AND AMINOLYSIS OF BENZOYLCHOLINE BENZOYLTHIOLCHOLINE BENZOYLSELENOLCHOLINE AND OF THEIR DIMETHYLAMINO ANALOGS
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DOI：
10.1021/jo01339a069
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发表时间：
1966-01-01
影响因子：
3.6
通讯作者：
MAUTNER, HG
中科院分区：
文献类型：
--
作者：
CHU, SH;MAUTNER, HG
为了获得邻基效应在异源酯、硫酯和硒酸酯反应中的相对重要性，研究了2-二甲氨基乙基苯甲酸酯、2-二甲氨基乙基硫酰苯甲酸酯、2-二甲氨基乙基硒酰苯甲酸酯、苯甲酰胆碱、苯甲酰硫酰胆碱和苯甲酰硒酰胆碱的氨解和水解。从酯到硫酯再到硒酸酯，氨解速率急剧增加。叔代和季代类似物与-丁胺的反应速率基本相同。三种胆碱异构物的水解速率相当相似，反应活性顺序为硒酸酯>酯>硫酯。在pH值低于8时，硒酸酯和硫酸酯（在较小程度上）与磷酸盐相互作用的能力变得具有动力学意义。对于叔氨基化合物，pH值与对数Aobed的关系得到s形曲线，由此可以推导出二甲基铵基团的解离常数。在pH值低于11的条件下，二甲氨基的苯基辅助能加速所有高于胆碱类似物的叔氨基化合物的反应速率；硫酯和硒酸酯的这种效应比酯的更为明显。亲核催化而非一般的酸特异性碱催化似乎参与其中，正如观察到的，水解的相对顺序，硒酸酯比硫酸酯比酯快，是以前注意到的氨水解，不同于通常注意到的这类异构物的水解。当pH值高于11时，叔氨基化合物的水解速度比它们的第四类似物慢。
To obtain information about the relative importance of neighboring-group effects in thereactions of isologous esters, thiolesters, and selenolesters, a study of the aminolysis and hydrolysis of2-dimethylaminoethyl benzoate, 2-dimethylaminoethyl thiolbenzoate, 2-dimethylaminoethyl selenolbenzoate, benzoyl choline, benzoyl thiol-choline, and benzoyl selenolcholine was carried out. Aminolysis rates increased sharply from ester to thiolester to selenolester. Tertiary and quaternary analogs reacted with-butylamine at essentiallyidentical rates. The three choline isologs underwent hydrolysis at rather similar rates, the order of reactivity being selenolester> ester> thiolester. Below a pH of 8 the ability of the selenolester and, to a lesser extent, of the thiolester to interact with phosphatebecame kinetically significant. For the tertiary amino compounds, plots of pH against log Aobed yielded sigmoid curves from which the dissociationconstants of the dimethylammonium groups could be derived. Anchimeric assistance by the dimethylamino group accelerated the reaction rates of all the tertiary amino compounds above those of the choline analogs below a pH of 11; this effect was more pronounced for the thiolester and selenolester than for the ester. Nucleophilic catalysis rather than general acid-specific base catalysis appears to be involved as suggested by the observation that the relative order of hydrolysis, selenolester faster than thiolester faster than ester, is that previouslynoted for theaminolysis and different from that nor-mally noted for the hydrolysis of such isologs. At pH values above 11, the tertiary amino compounds underwent hydrolysis more slowly than their quaternary analogs.