Asymmetric Mn(III)-based radical synthesis of functionalized 2,3-dihydrofurans
摘要:
The oxidative radical addition of alkyl acetoacetates to p-methoxycinnamoyl oxazolidinones promoted by Mn(III) has been studied. It only gives trans-disubstituted 2,3-dihydrofurans, with d.r. ranging from 2:1 to 9:1, depending on the substituent of the chiral auxiliary. After chromatographic separation of the two diastereomers, the oxazolidinone can be removed to afford enantiopure dihydrofuranyl esters in good overall yield. (C) 2000 Elsevier Science Ltd. All rights reserved.
Diastereoselective Conjugate Addition of Cyanide to α,β-Unsaturated Oxazolidinones: Enantioselective Synthesis of <i>ent</i>-Pregabalin and Baclofen
作者:Alan Armstrong、Nicola Convine、Matthew Popkin
DOI:10.1055/s-2006-941584
日期:2006.6
Conjugate addition of cyanide to chiral α,β-unsaturated oxazolidinones catalyzed by samarium(III) isopropoxide proceeds with good diastereoselectivity. The addition products can be converted into the biologically active targets ent-pregabalin and baclofen.
Lewis acid catalyzed asymmetric halohydrin reactions of chiral α,β-unsaturated carboxylic acid derivatives with N-halosuccinimide (NXS) as the halogen source
Lewisacid catalyzed asymmetric halohydrin reactions—(halohydroxylation as well as halomethoxylation) of chiral α,β-unsaturated carboxylicacid derivatives were performed using N-halosuccinimide (NXS; X = Br, I) as the halogen source. Regio- and anti-selectivity of 100% and moderate to good diastereoselectivity with good yields were observed when Oppolzer’s sultam was used as the chiral auxiliary.
使用N-卤代琥珀酰亚胺(NXS; X = Br,I)作为卤素源,进行路易斯酸催化的手性α,β-不饱和羧酸衍生物的不对称卤代醇反应(卤代羟基化以及卤代甲氧基化)。当Oppolzer的sultam用作手性助剂时,观察到区域选择性和抗选择性为100%,中等至良好的非对映选择性,并具有良好的收率。路易斯酸中,Yb(OTf)3被发现是最好的催化剂。烯酰基和肉桂酰基底物顺利地进行了溴代醇反应,较富电子的肉桂酰基底物优选经历了碘代醇反应。但是,缺电子的肉桂酰基底物不响应此路易斯酸催化的NXS与卤代醇反应(X = Cl,Br,I)。
Silver(I)-promoted asymmetric halomethoxylation of chiral α,β-unsaturated carboxylic acid derivatives: enantioselective synthesis of N-protected syn-β-methoxy-α-amino acids
Asymmetric halomethoxylation of chiral α,β-unsaturated carboxylic acid derivatives was performed with halogens (Br2/I2) promoted by silver(I) salts with high regio- and anti-selectivity and moderate to good diastereoselectivity. Reagent controlled diastereoselectivity was observed for N-cinnamoyl-2-oxazolidinone substrates especially for cinnamoyl and electron-deficient cinnamoyl substrates, when Ag2O
手性α,β-不饱和羧酸衍生物的不对称卤甲氧基化反应,是由银(I)盐促进的卤素(Br 2 / I 2)具有较高的区域选择性和抗选择性,并且具有中等至良好的非对映选择性。当使用Ag 2 O代替AgNO 3作为促进剂时,对于N-肉桂酰基-2-恶唑烷酮底物,尤其是肉桂酰基和电子缺陷型肉桂酰基底物,观察到了试剂控制的非对映选择性。包含Oppolzer的sultam手性助剂的Enoyl底物独立于Ag(I)盐的抗衡离子。该方法用于N-保护的顺式的两种对映体的短合成-β-甲氧基苯基丙氨酸以及N和O保护的顺式-β-甲氧基酪氨酸,它们是具有生物活性的环肽和去污肽抗生素的不常见氨基酸成分。
Highly Regio- and Stereoselective Asymmetric Bromoazidation of Chiral α,β-Unsaturated Carboxylic Acid Derivatives: Scope and Limitations
Lewis acid catalyzed asymmetric bromoazidation of chiral α,β-unsaturated carboxylic acid derivatives was performed using N-bromosuccinimide (NBS) and trimethylsilyl azide (TMSN3) as the bromine and azide sources. Among the Lewis acids, Yb(OTf)3 was found to be the best catalyst. Regio- and anti-selectivity of 100% and moderate to good diastereoselectivity (up to 89:11) with good yields were obtained
halohydrin reaction of chiral N-enoyl-2-oxazolidinones 1 by halogen (Br2/I2) and water were efficiently carried out in aqueous organic solvent promoted by silver(I) with high anti- and regioselectivity and moderate to good diastereoselectivities. The alkenoyl, cinnamoyl and electron-deficient cinnamoyl substrates smoothly underwent bromohydrin reaction in aqueous acetone but no iodohydrin reaction, where
在卤素(Br 2 / I 2)和水(银)促进的有机溶剂中,手性N-烯丙基-2-恶唑烷酮1的卤代醇反应可以高效地进行,具有高的抗和区域选择性,并且具有中等至良好的非对映选择性。链烯酰基,肉桂酰基和缺电子的肉桂酰基底物在丙酮水溶液中顺利进行溴代醇反应,但没有碘代醇反应,其中富电子的肉桂酰基底物优选在丙酮水溶液中进行碘代醇反应,在THF水溶液中观察到中等的非对映选择性和非对映选择性增强。