两种常见受保护形式的胺(氨基甲酸酯和磺酰胺)在 Ni 催化的 Suzuki 反应中作为导向基团的能力已被用于开发用于交叉偶联未活化烷基亲电子试剂的催化不对称方法。在市售镍配合物和手性配体存在下,外消旋仲溴化物和氯化物在室温下以良好的 ee 立体收敛过程中形成 CC 键。旨在阐明与 Ni(氨基甲酸酯和磺酰胺的氧)结合的位点的结构对映选择性研究导致发现,砜也可用作外消旋烷基卤化物的不对称 Suzuki 交叉偶联的有用导向基团。据我们所知,这项研究提供了在金属催化的不对称 CC 键形成反应中使用磺酰胺或砜作为有效导向基团的第一个例子。一项机理研究表明,金属转移发生时保留了立体化学,并且由此产生的 Ni-C 键在催化循环的后续阶段不会发生均裂。
Asymmetric Alkyl−Alkyl Cross-Couplings of Unactivated Secondary Alkyl Electrophiles: Stereoconvergent Suzuki Reactions of Racemic Acylated Halohydrins
作者:Nathan A. Owston、Gregory C. Fu
DOI:10.1021/ja105924f
日期:2010.9.1
A method for asymmetric alkyl-alkylSuzuki reactions of unactivatedsecondaryalkyl electrophiles, specifically, cross-couplings of racemic acylated halohydrins with alkylborane reagents, has been developed. A range of protected bromohydrins, as well as a protected chlorohydrin and a homologated bromohydrin, are coupled in good ee by a catalyst derived from commercially available components.
已开发出一种用于未活化仲烷基亲电试剂的不对称烷基-烷基 Suzuki 反应的方法,特别是外消旋酰化卤代醇与烷基硼烷试剂的交叉偶联。一系列受保护的溴醇,以及受保护的氯醇和同系溴醇,通过衍生自市售组分的催化剂以良好的 ee 偶联。
Stereoconvergent Amine-Directed Alkyl–Alkyl Suzuki Reactions of Unactivated Secondary Alkyl Chlorides
作者:Zhe Lu、Ashraf Wilsily、Gregory C. Fu
DOI:10.1021/ja203560q
日期:2011.6.1
A new family of stereoconvergent cross-couplings of unactivatedsecondaryalkyl electrophiles has been developed, specifically, arylamine-directed alkyl-alkylSuzuki reactions. This represents the first such investigation to be focused on the use of alkylchlorides as substrates. Structure-enantioselectivity studies are consistent with the nitrogen, not the aromatic ring, serving as the primary site
Synthesis of ketones from iodoalkenes, carbon monoxide and 9-alkyl-9-borabicyclo[3.3.1]nonane derivatives via a radical cyclization and palladium-catalysed carbonylative cross-coupling sequence
Under irradiation (tungsten lamp), the palladium-catalysed three-component cross-coupling reaction between iodoalkenes such as 6-iodo-1-hexene or their derivatives, carbon monoxide (1 atm) and 9-alkyl- or 9-aryl-9-BBN derivatives (9-BBN = 9-borabicyclo[3.3.1]nonane) produces unsymmetrical ketones in moderate to high yields; the oxidative addition of iodoalkenes to a palladium(0) complex proceeds via a radical process, thus allowing cyclization of the iodoalkenes to five-membered rings prior to the couplings with carbon monoxide and boron reagents.
Palladium-catalyzed inter- and intramolecular cross-coupling reactions of B-alkyl-9-borabicyclo[3.3.1]nonane derivatives with 1-halo-1-alkenes or haloarenes. Syntheses of functionalized alkenes, arenes, and cycloalkenes via a hydroboration-coupling sequence
Catalytic Asymmetric γ-Alkylation of Carbonyl Compounds via Stereoconvergent Suzuki Cross-Couplings
作者:Susan L. Zultanski、Gregory C. Fu
DOI:10.1021/ja2079515
日期:2011.10.5
With the aid of a chiral nickel catalyst, enantioselective gamma- (and delta-) alkylations of carbonyl compounds can be achieved through the coupling of gamma-haloamides with alkylboranes. In addition to primary alkyl nucleophiles, for the first time for an asymmetric cross-coupling of an unactivated alkyl electrophile, an arylmetal, a boronate ester, and a secondary (cyclopropyl) alkylmetal compound are shown to couple with significant enantioselectivity. A mechanistic study indicates that cleavage of the carbon-halogen bond of the electrophile is irreversible under the conditions for asymmetric carbon-carbon bond formation.