Enantioselective (4+2) Annulation of Donor-Acceptor Cyclobutanes by N-Heterocyclic Carbene Catalysis
作者:Alison Levens、Adam Ametovski、David W. Lupton
DOI:10.1002/anie.201609330
日期:2016.12.23
Herein we report the enantioselective (4+2) annulation of donor–acceptor cyclobutanes and unsaturated acyl fluorides using N‐heterocycliccarbenecatalysis. The reaction allows a 3‐step synthesis of cyclohexyl β‐lactones (25 examples) in excellent chemical yield (most ≥90 %) and stereochemical integrity (all >20:1 d.r., most ≥97:3 e.r.). Mechanistic studies support ester enolate Claisen rearrangement
Asymmetric [3 + 2] annulations catalyzed by a planar-chiral derivative of DMAP
作者:Erhard Bappert、Peter Müller、Gregory C. Fu
DOI:10.1039/b603172b
日期:——
A planar-chiral DMAP derivative catalyzes an intriguing [3 + 2] annulation reaction of silylated indenes to produce diquinanes that bear three contiguous stereocenters (one quaternary and two tertiary).
<i>N</i>-<i>tert</i>-Butyl Triazolylidenes: Catalysts for the Enantioselective (3+2) Annulation of α,β-Unsaturated Acyl Azoliums
作者:Lisa Candish、Craig M. Forsyth、David W. Lupton
DOI:10.1002/anie.201304081
日期:2013.8.26
range of N‐tert‐butyl‐substituted triazolylidene N‐heterocyclic carbenes have been prepared. Of these, the morpholinone‐derived catalyst (1) proved best suited to the enantioselective synthesis of cyclopentanes from donor–acceptor cyclopropanes and α,β‐unsaturated acyl fluorides. The performance of this catalyst has been correlated to the electronic nature of the catalyst by 13C NMR analysis. M.S.=molecular
但(基)不徒劳:的范围ñ -叔已经制备丁基取代triazolylidene N-杂环卡宾。其中,吗啉酮衍生的催化剂(1)被证明最适合从供体-受体环丙烷和α,β-不饱和酰基氟对映体选择性合成环戊烷。通过13 C NMR分析,该催化剂的性能与催化剂的电子性质相关。MS =分子筛,TMS =三甲基甲硅烷基。
N-Heterocyclic Carbene-Catalyzed Ireland–Coates Claisen Rearrangement: Synthesis of Functionalized β-Lactones
作者:Lisa Candish、David W. Lupton
DOI:10.1021/ja310449k
日期:2013.1.9
The N-heterocyclic carbene (NHC)-catalyzed Claisen rearrangement of hybrid Ireland-Coates structures has been achieved, allowing the stereoselective synthesis of highly functionalized beta-lactones. The reaction proceeds with high diastereoselectivity (>20:1) and affords a diverse range of beta-lactone fused cyclopentanes. Mechanistic studies are detailed.
Enantioselective All-Carbon (4+2) Annulation by <i>N</i>-Heterocyclic Carbene Catalysis
作者:Lisa Candish、Alison Levens、David W. Lupton
DOI:10.1021/ja508542n
日期:2014.10.15
The enantioselective vinylogous Michael/aldol cascade is an underdeveloped approach to cyclohexenes. Herein we describe a highly enantioselective (most >= 98:2 er) and diastereoselective (all >= 15:1 dr) N-heterocyclic carbene catalyzed cycloisomerization of acyclic dienyl esters to cyclohexyl beta-lactones. Derivatizations avail cyclohexenes bearing four contiguous stereogenic centers, while mechanistic studies support olefin isomerization prior to cyclization.