Environmentally benign diastereoselective synthesis of granatane and tropane aldol derivatives
作者:Aneta Nodzewska、Agnieszka Bokina、Katarzyna Romanowska、Ryszard Lazny
DOI:10.1039/c4ra02834a
日期:——
Direct aldol reactions of tropinone and granatanone (pseudopelletierine) with aromatic aldehydes were promoted by the presence of water. The anti–syn-diastereoselectivity depended on the amount of water used or on the possibility of product precipitation from the reaction mixture. Some of the reactions showed excellent atom economy, a low E factor, and high diastereoselectivity (up to 98%). In several cases ‘seeding’ with the anti isomer, used to induce the deposition of solid products, improved the conversion (up to 1.8 times) and the anti–syn ratio (up to 98 : 2). The applicability of spontaneous direct aldol reactions in the presence of water was also extended to N-alkyl nortropanones or norgranatanones using an aqueous–organic medium. However, under these conditions only the exo,syn isomers of the N-substituted aldols were obtained. The syn-selectivity for the tropane- and granatane-related aldols is specific for water-promoted reactions and results from thermodynamic control.
水的存在促进了托品酮和石榴酮(伪派尔特利林)与芳香醛的直接 aldol 反应。反应的反对–顺代谢选择性取决于使用的水的量或反应混合物中产物沉淀的可能性。一些反应表现出优异的原子经济性、较低的 E 因素和高达 98% 的立体选择性。在几个案例中,使用反对异构体进行“引种”,以诱导固体产物的沉淀,提高了转化率(高达 1.8 倍)和反对–顺比(高达 98:2)。在水的存在下,自发直接 aldol 反应的适用性也扩展到了 N-烷基北托品酮或北石榴酮,采用水-有机介质。然而,在这些条件下,只获得了 N-取代的 aldol 的外,顺异构体。对于与托品和石榴相关的 aldol,顺选择性是水促进反应所特有的,源于热力学控制。