内酯直接氢解为羧酸(即不接触羰基的C烷氧基-O键的氢解)通常是困难的,因为当前使用布朗斯台德酸作为催化剂的策略通常需要苛刻的条件,例如高温和高温H 2压力。在此,我们报告了已开发的无溶剂催化转化方法,其中W(OTf)6被认为可以促进氢解过程。该策略可以在特别温和的条件下(例如,反应温度<150°C和1 atm H 2的条件下)有效地将内酯氢化为羧酸),并显示出较宽的基材范围。另外,该催化方案可以进一步应用于作为可再生聚合物的聚羟基链烷酸酯的氢解成相应的直链羧酸。随后进行了广泛的机理研究,密度泛函理论计算揭示了一种反应模式,包括在W(OTf)6的帮助下C═O键的完全裂解催化剂。此外,通过电喷雾电离质谱已成功检测到该机理中产生的关键中间体,即具有OTf部分的moiety。通过与布朗斯台德酸催化体系的比较,研究证实了OTf部分的存在可以显着降低与重排和消除过程相关的障碍。同时,重点放在阴离子发挥
Blue light-promoted photolysis of aryldiazoacetates
作者:Igor D. Jurberg、Huw M. L. Davies
DOI:10.1039/c8sc01165f
日期:——
Aryldiazoacetates can undergo photolysis under blue light irradiation (460–490 nm) at room temperature and under air in the presence of numerous trapping agents, such as styrene, carboxylic acids, amines, alkanes and arenes, thus providing a straighforward and general platform for their mild functionalization.
Carbon–carbon bond-forming reactions of α-carbonyl carbocations: exploration of a reversed-polarity equivalent of enolate chemistry
作者:Ping-Shan Lai、Joshua A. Dubland、Mohammed G. Sarwar、Michael G. Chudzinski、Mark S. Taylor
DOI:10.1016/j.tet.2011.07.065
日期:2011.9
Carbon–carbon bond-forming reactions of putative α-carbonyl carbocation intermediates generated by Lewis acid- or silver-promoted ionizations of toluenesulfonate or halide leaving groups are described. This under-exploited mode of reactivity represents an ‘umpolung’ of conventional enolate chemistry, and enables C–C bond construction in both intra- and intermolecular contexts. Attempts to develop diastereoselective
Isothiourea-Mediated Stereoselective <i>C</i>-Acylation of Silyl Ketene Acetals
作者:Philip A. Woods、Louis C. Morrill、Tomas Lebl、Alexandra M. Z. Slawin、Ryan A. Bragg、Andrew D. Smith
DOI:10.1021/ol1008747
日期:2010.6.4
Isothiourea DHPB promotes the diastereoselective C-acylation of silylketeneacetals with anhydrides or benzoyl fluoride, giving 3-acyl-3-aryl or 3-acyl-3-alkylfuranones in excellent yields and stereoselectivities (up to 99:1 dr).
Isothiourea-Catalysed Asymmetric C-Acylation of Silyl Ketene Acetals
作者:Philip A. Woods、Louis C. Morrill、Ryan A. Bragg、Andrew D. Smith
DOI:10.1002/chem.201100995
日期:2011.9.19
Screening of a range of chiral isothioureas and acyl donors to promote the asymmetric C‐acylation of silylketeneacetals indicates that C(2)‐aryl‐dihydropyrimidobenzothiazole‐derived isothioureas and propionic anhydride give optimal reactivity and enantioselectivity in this process. Under optimised conditions 3‐acyl‐3‐aryl or 3‐acyl‐3‐alkylfuranones are prepared in good yields and moderate to excellent