Chemoselective Synthesis of <i>Z</i>
-Olefins through Rh-Catalyzed Formate-Mediated 1,6-Reduction
作者:Raphael Dada、Zhongyu Wei、Ruohua Gui、Rylan J. Lundgren
DOI:10.1002/anie.201800361
日期:2018.4.3
Z‐olefins are important functional units in synthetic chemistry; their preparation has thus received considerable attention. Many prevailing methods for cis‐olefination are complicated by the presence of multiple unsaturated units or electrophilic functional groups. In this study, Z‐olefins are delivered through selective reduction of activated dienes using formic acid. The reaction proceeds with high
Oxidative Prins and Prins/Friedel–Crafts cyclizations for the stereoselective synthesis of dioxabicycles and hexahydro-1H-benzo[f]isochromenes via the benzylic C–H activation
作者:B. V. Subba Reddy、Prashant Borkar、J. S. Yadav、P. Purushotham Reddy、A. C. Kunwar、B. Sridhar、René Grée
DOI:10.1039/c1ob06489d
日期:——
stereoselectivity. Aryl tethered homoallylbenzyl ethers such as benzyl ethers of (E)- and (Z)-6-arylhex-3-enyl alcohols undergo a tandem Prins/Friedel–Crafts cyclization in the presence of stoichiometric amounts of DDQ and SnCl4via the benzylic C–H bond activation to furnish the corresponding trans- and cis-fused hexahydro-1H-benzo[f]isochromenes in good yields with complete stereoselectivity.
(In)和(z)-hex-3-en-1,6-二醇和hept-3-en-1,7-二醇的1-苄醚在In( OTF)3通过顺序C-H键活化和分子内的环化的Prins,得到相应的反式-和顺-融合六氢-2- ħ -呋喃并[3,2- c ^ ]吡喃和octahydropyrano [4,3- b ]吡喃分别以良好的产率和优异的立体选择性。芳基束缚的高烯丙基苄基醚,例如(E)-和(Z)-6- arylhex -3-烯基醇经过串联普林斯/弗里德尔-克拉夫茨环化反应中的化学计量的量和DDQ的SnCl存在4经由苄基C-H键活化,以提供相应的反式-和顺式-融合六氢1 H-苯并[ f ]异色酮的收率高,具有完全的立体选择性。
Enantioselective Prins cyclization: BINOL-derived phosphoric acid and CuCl synergistic catalysis
作者:Claudia Lalli、Pierre van de Weghe
DOI:10.1039/c4cc02826k
日期:——
The first catalytic enantioselective Prins cyclization is disclosed. The reaction is catalyzed by the combination of a chiral BINOL-derived bis-phosphoric acid and CuCl. The process consists of a tandem Prins/Friedel-Crafts cyclization that affords the hexahydro-1H-benzo[f]isochromenes products with three new contiguous stereogenic centers in high yields, and good enantio- and excellent diastereoselectivities
Epoxidation of Peptidyl Olefin Isosteres. Stereochemical Induction Effect of Chiral Centers at Four Adjacent Cα Positions
作者:Nurit Perlman、Mordechai Livneh、Amnon Albeck
DOI:10.1016/s0040-4020(00)00036-3
日期:2000.3
Four tripeptidyl olefin isosteres were prepared, each of which contains a single chiral center derived from the bulky amino acid phenylalanine at positions corresponding to the P-2-P'(2) positions of a protease substrate. The effect of these chiral centers on the stereochemical outcome of mCPBA epoxidation of the olefin functionality was studied. A chiral center at P-2 or P'(2) position has no significant effect, and the P'(1) position exerts a small stereoselectivity. A chiral center at the P-1 position, on the other hand, has a profound chiral induction effect on the epoxidation reaction. (C) 2000 Elsevier Science Ltd. All rights reserved.
FeCl3-catalyzed tandem Prins and Friedel–Crafts cyclization: a highly diastereoselective route to polycyclic ring structures
作者:Arun K. Ghosh、Chad Keyes、Anne M. Veitschegger
DOI:10.1016/j.tetlet.2014.05.092
日期:2014.7
Catalytic FeCl3 in the presence of 4 A molecular sieves has been shown to effect highly diastereoselective tandem Prins and Friedel-Crafts cyclization of substituted (E/Z)-6-phenylhex-3-en-1-ol and a variety of aldehydes to provide a range of polycyclic compounds in good to excellent yields. The reaction of an enantioenriched alcohol with an aldehyde provided the cyclization product without loss of optical activity. Furthermore, a Lewis acid catalyzed ring opening resulted in functionalized tetralin derivatives with multiple chiral centers. Published by Elsevier Ltd.