Isothiourea-Catalyzed Enantioselective Carboxy Group Transfer
作者:Caroline Joannesse、Craig P. Johnston、Carmen Concellón、Carmen Simal、Douglas Philp、Andrew D. Smith
DOI:10.1002/anie.200904333
日期:2009.11.9
Transferable skills: Enantiomerically pure isothioureas promote the O‐ to C‐carboxyl grouptransfer of oxazolyl carbonates with excellent levels of enantiocontrol (see scheme). The origin of the enantioselectivity of this process was probed mechanistically and rationalized computationally.
A pseudo-enantiomeric pair of optically switchable helicenes containing a catalytic 4-N-methylaminopyridine (MAP) bottom unit and a C2-symmetric, (10R,11R)-dimethoxymethyl-dibenzosuberane top template was synthesized. They underwent complementary photoswitching at 290 nm (P/M′, <1/>99) and 340 nm (P/M′, 91/9) and unidirectional thermo-rotation at 130 °C (P/M′, >99/<1). They were utilized to catalyze
合成了含有催化的4- N-甲基氨基吡啶(MAP)底部单元和C 2对称(10 R,11 R)-二甲氧基甲基-二苯并亚戊烷顶部模板的可光学转换的螺旋对映体的对映体对映体。他们在290 nm(P / M ',<1 /> 99)和340 nm(P / M ',91/9)处进行互补光开关,并在130°C(P / M ',> 99 / <1)。它们被用来催化O-对C的对映异构Steglich重排。-羧基内酯,形成两种对映体,分别具有高达91%ee(R)和94%ee(S)的对映体。
Catalytic enantioselective Steglich rearrangements using chiral N-heterocyclic carbenes
作者:Craig D. Campbell、Carmen Concellón、Andrew D. Smith
DOI:10.1016/j.tetasy.2011.04.001
日期:2011.4
The evaluation of a range of enantiomerically pure NHCs, prepared in situ from imidazolinium or triazolium salt precatalysts, to promote the catalytic enantioselective Steglich rearrangement of oxazolyl carbonates to their C-carboxyazlactones, is reported. Modest levels of enantioselectivity (up to 66% ee) are observed using oxazolidinone derived NHCs. (C) 2011 Elsevier Ltd. All rights reserved.