Theoretical studies on the stereochemical course of 1,3-dipolar cycloaddition of azomethine ylides derived from indol-2,3-dione and thiazolidine-4-carboxylic acid

摘要

1,3-Dipolar cycloadditon of azomethine ylides with different dipolarophiles leads to the formation of novel heterocyclic spiro compounds having two or more chiral centers. The theoretical studies (HF/3-21G) on the 1,3-dipolar cycloaddition reaction between ethene and azomethine ylide A4 derived from isatin and thaizolidine-4-carboxylic acid, indicates that the energy barrier for this addition is about similar to8 kcal/mol higher than that in simplest azomethine ylide A1. HF/3-21G studies on a series of azomethine ylides A2 and A3 suggested that the increased barrier is mainly due to stabilization of azomethine ylides arising from aromatic indol nucleus. Semi-empirical studies indicate that the cycloaddition is streocontrolled as the transition states corresponding to only the stericlly allowed paths could be located on the potential energy surface. [References: 27]