Iodination–Group-Transfer Reactions to Generate Trisubstituted Iodoalkenes with Regio- and Stereochemical Control
作者:Joseph A. Kaplan、Suzanne A. Blum
DOI:10.1021/acs.joc.3c01495
日期:2023.9.15
amines), yielding trisubstituted acyclic alkenes and an example acyclic tetrasubstituted alkene. X-ray crystallographic determination of reaction intermediates and products confirms that the initial electrophilic-cyclization step sets the stereo- and regiochemistry of the product. The products serve as synthetic building blocks by readily participating in downstream functionalization reactions, including
三取代烯烃的区域和立体合成仍然是一个重大的合成挑战。在此,开发了一种通过从碘化亲电环化机制中转移中间体来生产区域和立体定义的三取代碘烯烃的方法。具体来说,环化锍离子对中间体通过亲核碘化物开环转化为烯烃。或者,AgOTf 清除碘化物可防止开环,从而能够分离锍离子对中间体。离子对的分离能够获得互补的反应性,包括通过替代亲核体(即胺)开环,产生三取代的无环烯烃和示例无环四取代的烯烃。反应中间体和产物的 X 射线晶体学测定证实,最初的亲电环化步骤决定了产物的立体化学和区域化学。该产品可作为合成构件,轻松参与下游官能化反应,包括氧化、钯催化交叉偶联和亲核置换。
Mechanistic Insight from Lewis-Acid-Dependent Selectivity and Reversible Haloboration, as Harnessed for Boron-Based Electrophilic Cyclization Reactions
作者:Martin Stang、Robert J. Mycka、Suzanne A. Blum
DOI:10.1021/acs.joc.3c01653
日期:2023.11.3
access regio- and stereodefined cyclic sulfonium zwitterions via the slower but thermodynamically favored electrophilic cyclization pathway. Reversibility was noted by following the reaction by NMR spectroscopy, and by characterizing the kinetic and thermodynamic products by a combination of 2D NMR spectroscopy and single-crystal X-ray diffraction. The “mixed” reagent bromocatechol borane (BrBcat) displayed
Repurposing π Electrophilic Cyclization/Dealkylation for Group Transfer
作者:Joseph A. Kaplan、Adena Issaian、Martin Stang、David Gorial、Suzanne A. Blum
DOI:10.1002/anie.202112351
日期:2021.12
Hijacking electrophiliccyclization intermediates allows for a pathway to acyclic tri- and tetrasubstituted alkenes with predictable regio- and stereochemistry. Mechanistic studies indicate concerted thioboration of the alkyne precedes rate-determining ring opening and investigate the effects of ring-size and functional groups on reaction selectivity.