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Efficient Preparation of TMSCCl 2 Br and Its Use in Dichlorocyclopropanation of Electron‐Deficient Alkenes
Author(s) -
Lee Darren S.,
DuránPeña María Jesús,
Burroughs Laurence,
Woodward Simon
Publication year - 2016
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201600607
Subject(s) - carbanion , nitronate , cyclopropane , chemistry , yield (engineering) , bromide , fluoride , medicinal chemistry , nuclear magnetic resonance spectroscopy , computational chemistry , organic chemistry , photochemistry , inorganic chemistry , materials science , ring (chemistry) , alkyl , nitro , metallurgy
The reaction of excess TMSCl and LiCCl 2 Br at low temperature is a technically simple high yield route to TMSCCl 2 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 3 ] − which, upon boil‐off of TMSF at 10–20 °C, yields the cyclopropane. DFT calculations also support the experimental differences between fluoride and acetate as promotors.