Crossing the threshold from accelerated substitution to elimination with a bifunctional macrocycle
作者:Jeremiah J. Gassensmith、Jung-Jae Lee、Bruce C. Noll、Bradley D. Smith
DOI:10.1039/b719658j
日期:——
binding amide residues can be N-alkylated at highly accelerated reaction rates to give quaternary ammonium products. This present study examines the reactivity with 1,2-disubstituted ethanes. Accelerated substitution is observed with 1,2-dichloroethane (5000 times faster than analogous control amines); whereas, accelerated elimination is the outcome with 3-halopropionitriles (10000 times faster than
Rapid Fixation of Methylene Chloride by a Macrocyclic Amine
作者:Jung-Jae Lee、Keith J. Stanger、Bruce C. Noll、Carlos Gonzalez、Manuel Marquez、Bradley D. Smith
DOI:10.1021/ja042208g
日期:2005.3.1
A simple macrocyclic amine is alkylated by methylene chloride to give a quaternary ammonium chloride salt. When methylene chloride is the solvent, the reaction exhibits pseudo-first-order kinetics, and the reaction half-life at 25.0 degrees C is 2.0 min. The reaction half-life for a structurally related, acyclicamine is approximately 50 000 times longer. Detailed calculations favor a mechanism where
简单的大环胺被二氯甲烷烷基化得到季铵氯化物盐。当二氯甲烷为溶剂时,反应呈现准一级动力学,25.0°C下的反应半衰期为2.0分钟。结构相关的无环胺的反应半衰期大约长 50 000 倍。详细的计算有利于其中二氯甲烷与大环缔合形成活化的预反应复合物的机制。大环氮随后以经典的 SN2 轨迹攻击二氯甲烷,尽管碳-氯键断裂,但氯离去基团并未与新形成的阳离子大环分离,因此产物是紧密结合的离子对。起始胺和产物盐的 X 射线晶体结构,