New approach for the general synthesis of oxotetrahydroindoles via intramolecular cycloadditions of azomethine ylides with tethered alkynes

摘要

A new method for the synthesis of oxotetrahydroindoles has been achieved employing an intramolecular dipolar cycloaddition approach involving mesoionic species (munchnones) with electron-deficient alkynes. The methodology is quite general and convergent as shown by the synthesis of a variety of tri- and tetrasubstituted oxotetrahydroindoles 18,21,24,27,30, and 34. LiI-based ester cleavage in the presence of an electrophilic acetylenic ketone was critical for Formation of the requisite cycloaddition substrates.