Highly Enantioselective Proton-Initiated Polycyclization of Polyenes
摘要:
This report describes the synthesis of a range of chiral polycyclic molecules (tricyclic to pentacyclic) from achiral polyene precursors by enantio-selective proton-initiated polycyclization promoted by the 11 complex of o,o'-dichloro-BINOL and SbCl5. Excellent yields (ca. 90% per ring formed) and enantioselectivety (20:1 to 50:1) were obtained. The process is practical as well as efficient, because the chiral ligand is both readily prepared from R,R- or S,S-BINOL and easily recovered from the reaction mixture by extraction.
A two-step mimic for direct, asymmetric bromonium- and chloronium-induced polyene cyclizations
作者:Scott A. Snyder、Daniel S. Treitler、Andreas Schall
DOI:10.1016/j.tet.2010.03.037
日期:2010.6
Although direct, asymmetric, halonium-induced cyclizations have proven difficult to achieve in the absence of enzymes, this report provides a two-step alternative based on reacting polyenes with chiral mercury(II) complexes to afford a number of polycyclic organomercurials that can be subsequently converted, with retention, into their corresponding chlorine, bromine, and iodine derivatives in good
Nucleophilic phosphite–ureacooperative high-turnover catalysts have been designed for the highly selectivebromocyclization of homogeranylarenes. The introduction of a urea moiety and bulky aryl groups in the catalyst inhibits decomposition of the catalyst and the generation of byproducts. Only 0.5 mol% of the catalyst successfully promotes the bromocyclization of 4-homogeranyltoluene to give the
Two Unprecedented Reactions of Nitrosyl Triflate: NO<sup>+</sup>-Induced Cationic Cascade Cyclization and C═C Oxidative Cleavage
作者:G. Sudhakar Reddy、E. J. Corey
DOI:10.1021/acs.orglett.3c00353
日期:2023.3.24
Nitrosyl triflate is shown to react with olefins in a CH2Cl2 solution by three different pathways depending on structure and reaction conditions: (1) cationic cyclization, (2) C═C cleavage, and (3) allylic nitrosation. Possible reaction pathways are described.