Asymmetric iodolactonization of gamma- and delta-unsaturated carboxylic acids has been explored in the presence of six different chiral organocatalysts 5-8. The catalyst 6b was found to facilitate the cyclization of 5-arylhex-5-enoic acids 1 to the corresponding iodolactones 2 with up to 96% ee. By this protocol, unsaturated carboxylic acids are converted enantioselectively to synthetically useful delta-lactones in high yields using commercially available NIS. Apparently, both hydrogen bonding and aryl/aryl interactions are important for efficient stereodifferentiation.
A productive alliance: In an enantioselective organocatalytic bromolactonization of 5‐substituted hex‐5‐enoic acids (see scheme), it appears that the formation of an ion pair through interaction of the trisimidazoline catalyst 1 with the substrate both creates a chiral environment and promotes the cyclization by activating the carboxylic acid. DBDMH=1,3‐dibromo‐5,5‐dimethylhydantoin.
A method for conducting enantioselectivebromolactonizationreactions of trisubstituted alkenoic acids, using the C3‐symmetric trisimidazoline 1 and 1,3‐dibromo‐5,5‐dimethyl hydantoin as a bromine source, has been developed. The process generates chiral δ‐lactones that contain a quaternary carbon. The results of studies probing geometrically different olefins show that (Z)‐olefins rather than (E)‐olefins
Predicting Highly Enantioselective Catalysts Using Tunable Fragment Descriptors**
作者:Nobuya Tsuji、Pavel Sidorov、Chendan Zhu、Yuuya Nagata、Timur Gimadiev、Alexandre Varnek、Benjamin List
DOI:10.1002/anie.202218659
日期:2023.3.6
Fast and robust predictive models using flexible 2D fragmentdescriptors, particularly suited for asymmetric catalysis, are described. From training data with only moderate selectivities, highlyenantioselectivecatalysts were predicted and validated, enabling a catalytic asymmetric construction of 2,2-disubstituted tetrahydropyrans.