enantioselective carbonyl-ene reaction of alkyl glyoxylates with various 1,1-disubstituted olefins, catalysed by chiral (salen)Cr(III)BF4 complexes, has been studied. We found that a chromiumcomplex bearing adamantyl substituents at the 3,3′-positions of the salicylidene moiety catalysed the reaction with much greater selectively than the classic Jacobsen-type catalyst. The reaction proceeded effectively
<i>C</i><sub>2</sub>-Symmetric Copper(II) Complexes as Chiral Lewis Acids. Enantioselective Catalysis of the Glyoxylate−Ene Reaction
作者:David A. Evans、Christopher S. Burgey、Nick A. Paras、Tomas Vojkovsky、Steven W. Tregay
DOI:10.1021/ja980549m
日期:1998.6.1
ene reaction with glyoxylate esters;3 however, due to the limiting reactivity of the catalyst-glyoxylate complex,4 only nucleophilic 1,1-disubstituted olefins may be employed. We have recently reported that bidentate bis(oxazolinyl) (box) Cu(II) complexes 1-3 are effective enantioselective catalysts in Diels-Alder5 and aldol reactions6 with substrates that can participate in catalyst chelation. In this
Stereoselective Assembly of a 1,3-Diene via Coupling between an Allenic Acetate and a (<i>B</i>)-Alkylborane: Synthetic Studies on Amphidinolide B1
作者:Amit K. Mandal、John S. Schneekloth,、Craig M. Crews
DOI:10.1021/ol051175m
日期:2005.8.1
has been described. The C16 stereochemistry was set by asymmetric allylic alkylation. C21 and C25 stereogenic centers were set by an enantioselective/diastereoselective double allylation reaction. The C9 configuration was set by an asymmetric heteroene reaction. A differentially substituted stereodefined 1,3-diene iodide was synthesized by iodide-mediated S(N)2' reaction. A novel stereoselective method
A Concise Synthesis of (<i>S</i>)-γ-Fluoroleucine Ethyl Ester
作者:Christian Nadeau、Francis Gosselin、Paul D. O’Shea、Ian W. Davies、Ralph P. Volante
DOI:10.1055/s-2005-923593
日期:——
We report herein a six-step, chromatography-free, through-process for the asymmetric synthesis of (S)-γ-fluoroleucine ethyl ester sulfate salt (6) that proceeds in 25% overall yield from inexpensive ethyl glyoxylate. This approach features a Ti/Zn-catalyzed glyoxylate-ene reaction-olefin hydrofluorination-amine alkylation as key steps.