preparing (E)- and (Z)-stereodefined fully substituted enol tosylates is described. α-Substituted β-keto esters undergo (E)-selective enol tosylations using TsCl–Me2N(CH2)6NMe2 as the reagent (method A, 13 examples; 63–96%) and (Z)-selective enol tosylations using TsCl–TMEDA–LiCl as the reagent (method B, 13 examples; 62–99%). A plausible mechanism for the (E)- and (Z)-enol tosylation selectivity is proposed
N-Heterocyclic Carbene Catalyzed Umpolung of Michael Acceptors for Intermolecular Reactions
作者:Akkattu T. Biju、Mohan Padmanaban、Nathalie E. Wurz、Frank Glorius
DOI:10.1002/anie.201103555
日期:2011.8.29
leahciM! The N‐heterocyclic carbenecatalyzedumpolung of Michaelacceptors proceeds through the formation of a deoxy‐Breslow intermediate (see scheme; EWG=electron‐withdrawing group). This nucleophilic species can react with other Michaelacceptors in an intermolecular fashion, thereby resulting in the formation of homo‐ or heterodimeric olefins. This “Michaelumpolung” should become a valuable method
漏气!N杂环卡宾催化的Michael受体的化合物通过形成脱氧Breslow中间体进行(参见方案; EWG =吸电子基团)。这种亲核物质可以分子间方式与其他迈克尔受体反应,从而导致形成同二聚或异二聚烯烃。这种“ Michael umpolung”应该成为形成致密官能化烯烃的一种有价值的方法。
Decarboxylation and simultaneous reduction of silver(<scp>i</scp>) β-ketocarboxylates with three types of coordinations
β-ketocarboxylates were prepared by reaction of β-ketocarboxylic acids with silver nitrate in the presence of diethanolamine. The silver(I) β-ketocarboxylates decomposed over a narrow temperature range to form metallic silver, CO2, and the corresponding ketones. In addition, products derived from radical intermediates were detected by mass spectroscopic analysis for some silver(I) β-ketocarboxylates. Infrared
The beta-ketoesters of formula I are useful as precursors for organoleptic compounds, especially for flavors, fragrances and masking agents and antimicrobial compounds.
Electrooxidation of Malonate and Acetylacetate Derivatives in the Presence of Halide Ions
作者:Mitsuhiro Okimoto、Yukio Takahashi
DOI:10.1055/s-2002-34839
日期:——
β-Dicarbonyl compounds, such as dimethyl malonate derivatives and methyl acetoacetate derivatives, were electrooxidized in methanol in the presence of halogen ions to afford the corresponding dimethyl α-halomalonates and methyl α-halocarboxylates. Electrooxidation of bis(β-dimethoxycarbonyl) derivatives similarly afforded cyclic compounds and dihalides.