A new class of C<sub>1</sub>-symmetric monosulfoximine ligands for enantioselective hetero Diels–Alder reactions
作者:Carsten Bolm、Marinella Verrucci、Oliver Simic、Pier Giorgio Cozzi、Gerhard Raabe、Hiroaki Okamura
DOI:10.1039/b309556h
日期:——
Quinoline-based C1-symmetricsulfoximines have been used as chiral ligands in copper-catalyzedasymmetric hetero Diels-Alder reactions leading to cycloadducts with up to 96% ee.
Highly Enantioselective Hetero-Diels−Alder Reactions Catalyzed by a <i>C</i><sub>2</sub>-Symmetric Bis(sulfoximine) Copper(II) Complex
作者:Carsten Bolm、Oliver Simić
DOI:10.1021/ja004261k
日期:2001.4.1
inevitably are achiral in the original salen structures. 8 Tests in sulfide oxidations with cumyl hydroperoxide as oxidant and the oxovanadium(IV) complex of ( S,S)-1 as catalyst proved successful, giving sulfoxides in high yields, although as racemates. We now synthesized related bis(sulfoximine) ( S,S-2 and were pleased to note that its copper complex showed both high activity and enantioselectivity
The carbonyl-Diels-Alder reaction catalyzed by bismuth (III) chloride
作者:Hélène Robert、Bernard Garrigues、Jacques Dubac
DOI:10.1016/s0040-4039(97)10791-2
日期:1998.3
In presence of bismuth (III) chloride, a carbonylated electrophile (ethyl mesoxalate or glyoxylate) and usual diene led selectively (65 to 100%) the hetero carbonyl-Diels-Alder reaction with the ene reaction product. BiCl3 exhibits strong catalytic activity and, compared with previous literature, reacts under mild conditions.
A group of chiral [(salen)Cr(III)] + BF 4 - complexes, with enhanced steric hindrance in 3,3'-positions of salicylidene moiety, has been synthesized and applied for the oxo-Diels-Alder reaction of alkyl glyoxylates with cyclohexa-1,3-diene. A readilyaccessiblecomplex that bears bulky adamanthyl substituents revealed its potential, leading to the cycloadducts with excellent selectivity (up to endolexo
The zinc(II)-catalysed hetero-DielsâAlder reaction
of the conjugated dienes 2,3-dimethylbuta-1,3-diene and
cyclohexa-1,3-diene with ethyl glyoxylate has been studied in the
presence of different C2-symmetric bisoxazolines.
The zinc(II)-catalysed reaction of 2,3-dimethylbuta-1,3-diene
with ethyl glyoxylate gives both the hetero-DielsâAlder and ene
products, the former being the major product with an enantiomeric excess
up to 87%. The hetero-DielsâAlderâ¶ene ratio is relatively
independent of the catalytic system and the solvent and is in the range
1â¶0.5â1â¶0.8. For the zinc(II)-catalysed
reaction of cyclohexa-1,3-diene with ethyl glyoxylate, the
hetero-DielsâAlder product is formed in up to 84% isolated yield
and with an enantiomeric excess up to 65%. The enantiomeric excess for
this reaction is very dependent on the solvent, with MeNO2
generally lowering the enantiomeric excess compared with
CH2Cl2. Based on the absolute stereochemistry of
the hetero-DielsâAlder products and semi-empirical calculations on
different bisoxazolineâzinc(II)âethyl glyoxylate
intermediates the mechanism for the reaction is discussed.