N-Heterocyclic Carbene-Catalyzed Hydroacylation of Unactivated Double Bonds
摘要:
An intramolecular N-heterocyclic carbene (NHC)-catalyzed hydroacylation of unactivated double bonds is reported. Systematic variation of the catalyst structure revealed an N-mesitylthiazolylidene annulated with a seven-membered ring to be especially reactive. This NHC enables a unique C-C bond-forming reaction to afford substituted chroman-4-ones in moderate to excellent yields, even ones containing all-carbon quaternary centers.
The Significance of Degenerate Processes to Enantioselective Olefin Metathesis Reactions Promoted by Stereogenic-at-Mo Complexes
作者:Simon J. Meek、Steven J. Malcolmson、Bo Li、Richard R. Schrock、Amir H. Hoveyda
DOI:10.1021/ja907805f
日期:2009.11.18
Only when sufficient amounts of ethylene are generated and inversion at Mo through degenerate processes occurs at a sufficiently rapid rate is high enantioselectivity achieved, irrespective of the stereochemical identity of the initiating alkylidene (Curtin-Hammett kinetics). With diastereomeric metal complexes that undergo rapid interconversion, stereomutation at the metal center becomes inconsequential
本研究提供了光谱和实验证据,证明简并复分解对这类新兴手性催化剂的有效性至关重要。公开了两种非对映体复合物的分离和 X 射线表征,以及对此类引发剂新亲烯在促进闭环复分解过程中表现出的反应性和对映选择性模式的检查。只有当产生足够量的乙烯并且通过简并过程在 Mo 处以足够快的速度发生反转时,才能实现高对映选择性,而与引发亚烷基的立体化学特性无关(Curtin-Hammett 动力学)。对于经历快速互变的非对映金属配合物,金属中心的立体突变变得无关紧要,
Total Synthesis of Stemaphylline<i>N</i>-Oxide and Related C9a-Epimeric Analogues
作者:Michael L. Schulte、Mark L. Turlington、Sharangdhar S. Phatak、Joel M. Harp、Shaun R. Stauffer、Craig W. Lindsley
DOI:10.1002/chem.201302669
日期:2013.9.2
Winning the relay: The first total synthesis of stemaphylline N-oxide has been completed utilizing a bistandem relay ring-closing-metathesis (RRCM) strategy, necessitated by the conformation of the requisite tetraene. This effort also gave unnatural 9a-epi-stemaphylline and 9a-epi-stemaphylline N-oxide.