Efficient Preparation of TMSCCl2Br and Its Use in Dichlorocyclopropanation of Electron-Deficient Alkenes

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• 作者：Dr. Darren S. Lee ; Dr. Mar&#237 ; a Jesú ; s Durá ; n-Peñ ; a ; Dr. Laurence Burroughs and Prof. Dr. Simon Woodward
• 刊名：Chemistry - A European Journal
• 出版年：2016
• 出版时间：May 23, 2016
• 年：2016
• 卷：22
• 期：22
• 页码：7609-7616
• 全文大小：1340K
• ISSN：1521-3765

文摘

The reaction of excess TMSCl and LiCCl<sub>2sub>Br at low temperature is a technically simple high yield route to TMSCCl<sub>2sub>Br. The latter is a stable source of the dichlorobromomethide carbanion, which undergoes 1,4-addition with cyclic nitroalkenes and (E)-fumarates leading to dichlorocyclopropanes after bromide expulsion. For nitrostyrenes the reaction arrests at the 1,4-addition product. Low temperature NMR spectroscopy studies and DFT calculations suggest the formation of an “ate” species [(nitronate)SiFMe<sub>3sub>]<sup>&minus;sup> which, upon boil-off of TMSF at 10&ndash;20&thinsp;°C, yields the cyclopropane. DFT calculations also support the experimental differences between fluoride and acetate as promotors.