Ligand survey results in identification of PNP pincer complexes of iridium as long-lived and chemoselective catalysts for dehydrogenative borylation of terminal alkynes
作者:Chun-I Lee、Jessica C. DeMott、Christopher J. Pell、Alyson Christopher、Jia Zhou、Nattamai Bhuvanesh、Oleg V. Ozerov
DOI:10.1039/c5sc02161h
日期:——
Following the report on the successful use of SiNN pincercomplexes of iridium as catalysts for dehydrogenative borylation of terminal alkynes (DHBTA) to alkynylboronates, this work examined a wide variety of related pincerligands in the supporting role in DHBTA. The ligand selection included both new and previously reported ligands and was developed to explore systematic changes to the SiNN framework
继关于成功使用铱的 SiNN 钳形配合物作为末端炔烃 (DHBTA) 脱氢硼化为炔基硼酸盐的催化剂的报告之后,这项工作研究了各种相关钳形配体在 DHBTA 中的支持作用。配体选择包括新的和以前报道的配体,旨在探索 SiNN 框架(8-(2-二异丙基甲硅烷基苯基)氨基喹啉)的系统变化。令人惊讶的是,只有二芳基氨基/双(膦) PNP 系统显示出任何 DHBTA 反应性。筛选中使用的特定 PNP 配体(带有两个二异丙基膦基侧供体)显示 DHBTA 活性低于 SiNN。然而,利用 PNP 系统提供的配体优化机会,通过磷取代的变化导致发现了一种催化剂,其活性、寿命和范围远远超过了原始 SiNN 原型。在模型 PNP 系统中制备了几种 Ir 配合物,并作为催化循环中的潜在中间体进行了评估。其中,(PNP)Ir 二硼基络合物和硼基亚乙烯基络合物显示出催化能力较差,因此可能不是催化循环的一部分。
A General and Regioselective Synthesis of 5-Trifluoromethyl-pyrazoles
作者:Robert S. Foster、Harald Jakobi、Joseph P. A. Harrity
DOI:10.1021/ol3021918
日期:2012.9.21
Two synthetic approaches to 4-trifluoromethylsydnones, a novel class of these mesoionic reagents, are reported. These compounds undergo regioselective alkyne cycloaddition reactions, thereby providing a generalapproach to 5-trifluoromethylpyrazoles. This method has been employed in a short formal synthesis of the herbicide fluazolate.
Synthesis of 4-Fluoromethylsydnones and their Participation in Alkyne Cycloaddition Reactions
作者:Robert S. Foster、Harry Adams、Harald Jakobi、Joseph P. A. Harrity
DOI:10.1021/jo400381a
日期:2013.4.19
We report the synthesis and some structural studies of 4-trifluoromethyl, 4-difluoromethyl-, and 4-monofluoromethylsydnones. All but the latter compounds are stable and represent effective precursors to a range of pyrazoles after cycloadditionreactions with alkynes. The cycloadditions are generally highly regioselective and provide 5-fluoromethylpyrazole products, although we have observed that Bn-substituted
Chemo- and diastereoselective tandem dual oxidation of B(pin)-substituted allylic alcohols: synthesis of B(pin)-substituted epoxy alcohols, 2-keto-anti-1,3-diols and dihydroxy-tetrahydrofuran-3-ones
作者:Nusrah Hussain、Mahmud M. Hussain、Patrick J. Carroll、Patrick J. Walsh
DOI:10.1039/c3sc51616d
日期:——
B(pin)-substituted epoxy alcohols (55–96% yield, dr > 20 : 1). In the case of B(pin)-substituted bis-allylic alcohols, highly substituted bis-epoxy alcohols with five contiguous stereocenters were obtained (dr > 20 : 1). Furthermore, the difference in reactivity between allylicalcohols and 2-B(pin)-substituted allylicalcohols towards epoxidation enabled the selective oxidation of the allylicalcohol in the presence
Generation and Tandem Reactions of 1-Alkenyl-1,1-Heterobimetallics: Practical and Versatile Reagents for Organic Synthesis
作者:Hongmei Li、Patrick J. Carroll、Patrick J. Walsh
DOI:10.1021/ja077664u
日期:2008.3.1
A practical and straightforward method for generation of versatile 1-alkenyl-1,1-heterobimetallic intermediates and their application to construction of functionalized building blocks are disclosed. Beginning with readily available air-stable 1-alkynyl-1-boronate esters, hydroboration with dicyclohexylborane generates 1-alkenyl-1,1-diboro species. In situ transmetallation with dialkylzinc reagents