Intramolecular "hydroiminiumation and -amidiniumation" of alkenes: A convenient, flexible, and scalable route to cyclic iminium and imidazolinium salts
Intramolecular "hydroiminiumation and -amidiniumation" of alkenes: A convenient, flexible, and scalable route to cyclic iminium and imidazolinium salts
复制标题
DOI：
10.1021/jo0703909
复制
发表时间：
2007-04-27
影响因子：
3.6
通讯作者：
Bertrand, Guy
中科院分区：
文献类型：
--
作者：
Jazzar, Rodolphe;Bourg, Jean-Baptiste;Bertrand, Guy
将化学计量的HCl加到烯醛二胺、-甲胺和-酰胺中，导致sp(2)-氮原子的质子化。由此得到的烯基铝盐、-甲酰胺盐和-酰胺盐可以被分离和充分表征，包括单晶X-射线衍射研究。这些盐的加热溶液通过氮-氢键在悬垂的碳-碳双键上的形式外加成清洁和区域选择性地诱导环闭合，提供相应的环状铝盐、二氢异喹啉盐和咪唑啉盐。特别值得注意的是，新的4，4-二取代咪唑盐可以通过这种合成路线获得。类似地，将光气加到烯基脲和烯基酰胺中，然后温和加热，分别干净地得到C-氯咪唑盐和环状C-氯亚胺盐。用四(三苯基膦)钯处理后者，可以制备第一个以环芳胺卡宾为配体的过渡金属络合物。氚标记实验表明，氢亚胺和-氨基转移反应的机理涉及到速率决定步骤中分子内质子向双键的转移。这种新的合成方法提供了各种N-杂环卡宾(NHC)和环烷基和芳基氨基卡宾(CAAC)的前体。
Addition of a stoichiometric amount of HCl to alkenylaldimines, -formamidines, and -amidines results in the protonation of the sp(2)-nitrogen atom. The resulting alkenylaldiminium, -formamidinium, and -amidinium salts can be isolated and fully characterized, including single-crystal X-ray diffraction studies. Heating solutions of these salts induces ring closure cleanly and regioselectively via formal "exo" addition of the nitrogen-hydrogen bond to the pendent carbon-carbon double bond, affording the corresponding cyclic aldiminium, dihydroisoquinolinium, and imidazolinium salts. Of special interest, novel 4,4-disubstituted imidazolinium salts are accessible via this synthetic route. Similarly, addition of phosgene to alkenyl ureas and alkenyl amides, followed by gentle heating, cleanly affords C-chloro imidazolinium, and cyclic C-chloro iminium salts, respectively. Treatment of the latter with tetrakis(triphenylphosphine)palladium allows for the preparation of the first transition-metal complex bearing a cyclic arylaminocarbene as ligand. Deuterium labeling experiments suggest that the mechanism of the hydroiminiumation and -amidiniumation reactions involves an intramolecular proton transfer to the double bond in the rate-determining step. This novel synthetic methodology gives access to a variety of N-heterocyclic carbene (NHC) and cyclic alkyl- and arylaminocarbene (CAAC) precursors.