Palladium-Catalyzed Synthesis of 3-Substituted Indoles from 2-Iodoaniline and Aldehydes

摘要

It is known that many indole containing compounds exhibit a wide spectrum of pharmacological and biological activities.Thus,besides conventional named routes,homogeneous transition metal-catalyzed synthetic methods have also been developed as alternative methods for the construction of indole framework because of the wide availability of substrates.We have also reported on ruthenium-catalyzed synthesis of indoles via an alkanol group transfer from alkanolamines to anilines(amine exchange reaction)and ring-opening of epoxides by anilines.In connection with this report,palladium-catalyzed direct or step-by-step annulation of 2-haloanilines with carbonyl compounds such as ketones,1,3-diketones and alpha-keto esters also give access to a variety of indoles.However,in contrast to the annulation with such carbonyl compounds,there is no precedent on the similar annulation of 2-haloanilines with aldehydes leading to indoles.Under these circumstances,herein we report on palladium-catalyzed synthesis of 3-substituted indoles from 2-iodoaniline and aldehydes.