Highly diastereoselective addition of methyl 2-(N-benzylamino)-1-cyclohexenecarboxylate to chiral acrylates
摘要:
Conjugate addition reaction of achiral Methyl 2-(N-benzylamino)-1-cyclohexenecarboxylate 2 to chiral acrylates 4a, 4b, 4c led, after treatment of the primary adducts with sodium methoxyde, to alpha,alpha-disubstituted beta-keto ester 1 with high enantiomeric excesses.
with kinetically controlled generated lithium dienolate 6a to form chiral bicyclo[2.2.2]octanes 4 with modest d.e.. It was found, that the diastereoselection is improved, when the corresponding trimethylsilyl ether 6b reacts with chiral acrylates under Lewis acid catalysis. The absolute stereochemistry of these bicyclo[2.2.2]octanes was determined by X-ray analysis.
Asymmetric Synthesis of Optically Active 3-Cyclohexene-1-carboxylic Acid Utilizing Lactic Ester as a Chiral Auxiliary in the Diastereoselective Diels–Alder Reaction
The optically active 3-cyclohexene-1-carboxylic acid was synthesized through a TiCl4-catalyzed diastereoselectiveDiels–Alderreaction utilizing lactic acid ester as a chiralauxiliary, which can be removed by washing with H2O. The (S)- and (R)-isomers were both derivedfrom easily available ethyl l-lactate.
使用乳酸酯作为手性助剂,通过 TiCl 4催化的非对映选择性 Diels-Alder 反应合成光学活性的 3-环己烯-1-羧酸,可以通过 H 2 O洗涤去除。 ( R )-异构体均衍生自容易获得的L-乳酸乙酯。
Manickum, Thavrin; Ross, Gregory H. P., South African Journal of Chemistry, 1994, vol. 47, # 1, p. 1 - 16
作者:Manickum, Thavrin、Ross, Gregory H. P.
DOI:——
日期:——
Complex pyrrolidines via a tandem Michael reaction/1,3-dipolar cycloaddition sequence. A novel method for the generation of unsymmetrical azomethine ylides
作者:Philip Garner、Fariba Arya、Wen Bin Ho
DOI:10.1021/jo00289a005
日期:1990.1
An asymmetric route to the 5,6-dihydro-4H-1,3-thiazine skeleton via an asymmetric hetero diels-alder reaction
Magnesium bromide mediated hetero Diels-Alder cycloaddition of diene 1 (R(1) = Ph) to chiral N-acryloyl-2-oxazolidinone 4b leads to 5b as the sole adduct formed. Chiral auxiliary removal leads to enantiomerically pure 5,6-dihydro-4H-1,3-thiazine 3 (R(2) = Bn). The selectivity of the cycloaddition is reversed under thermal or high pressure activation. The predominant diastereomeric adduct 6b is isolated in pure form after flash chromatography.