Amidine nitrosation.
Amidine nitrosation.
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脒亚硝化。
DOI：
10.1021/jo035884u
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发表时间：
2004
期刊：
影响因子：
--
通讯作者：
Yu,Hongbin
中科院分区：
文献类型：
--
作者：
Loeppky,RichardN;Yu,Hongbin
研究了9种无环仲、叔脒（Ph-NC（R1）NR 2 R3; R1= H，CH 3，Ph; R2，R3= H，Ph或（CH 3）2或C（CH 2）4）和几种N-酰基脒的酸性亚硝化化学。主要的亚硝化产物是来自氨基部分的酰胺和来自重氮苯离子的化合物，在几种情况下，重氮苯离子被独立地捕获用于定量。叔脒也产生亚硝胺，产率虽低，但很高。苯甲脒不反应，N-酰基脒水解的速度比亚硝化快得多。数据支持以下假设：反应通过亚氨基氮的亚硝化发生，然后加入H2O得到四面体中间体（α-羟基亚硝胺），其主要分解途径产生酰胺和重氮离子。在吡咯烷衍生的脒的情况下，约25%的分解导致胺部分的裂解，其亚硝化得到N-亚硝基吡咯烷。在25 °C下，在含有过量亚硝酸根的乙酸水溶液中，脒亚硝化的伪一级速率常数范围为（3 - 106）× 10-5s-1，而脒的碱度范围超过5 pKaunits。速率常数校正脒碱度表明吡咯烷衍生脒是最活跃的。苯甲脒亚硝化反应活性的缺乏归因于H_2O加到N-亚硝基脒离子上的速率非常慢和可逆的亚硝化。
The acidic nitrosation chemistry of nine acyclic secondary and tertiary amidines (Ph-NC(R1)NR2R3; R1= H, CH3, Ph; R2, R3= H, Ph or (CH3)2or C(CH2)4) and severalN-acylamidines was investigated. The principal nitrosation products were amides derived from the amino moiety and compounds derived from the benzenediazonium ion, which was independently trapped for quantitation in several cases. Tertiary amidines also produce nitrosamines in minor, but significant, yields. The benzamidines did not react, and theN-acylamidines hydrolyzed much more rapidly than they nitrosated. The data support the hypothesis that the reaction occurs by nitrosation on the imino nitrogen, followed by the addition of H2O to give a tetrahedral intermediate (α-hydroxynitrosamine) for which the main decomposition pathway generates an amide and a diazonium ion. In the case of the pyrrolidine-derived amidines, about 25% of the decomposition results in cleavage of the amine moiety, which nitrosates to giveN-nitrosopyrrolidine. Pseudo-first-order rate constants for amidine nitrosation in aqueous acetic acid with excess nitrite at 25 °C ranged from (3 to 106) × 10-5s-1, while the amidine basicity ranged over 5 pKaunits. Rate constants corrected for amidine basicity showed the pyrrolidine derived amidines to be most reactive. The lack of benzamidine nitrosative reactivity is attributed to a very slow rate of H2O additon to theN-nitrosoamidinium ion and reversible nitrosation.