Preparation of indolizine-3-carboxamides and indolizine-3-carbonitriles by 1, 3-dipolar cycloaddition of N-(cyanomethyl)pyridinium ylides to alkenes in the presence of tetrakispyridinecobalt(II) dichromate or manganese(IV) oxide

摘要

Two selective procedures for the synthesis of potentially important agrochemicals, indolizine-3-carboxamides (6) and indolizine-3-carbonitriles (7), were developed. In the presence of tetrakispyridinecobalt(II) dichromate (TPCD), compounds 6 are readily synthesized by a one-pot reaction sequence which consists of a 1, 3-dipolar cycloaddition of pyridinium N-ylides to alkenes, followed by an aromatization and a regiospecific hydration reaction. When MnO_2 instead of TPCD was used in the 1, 3-dipolar addition reaction, the nitrile group of the indolizine product was not hydrated and compounds 7 were obtained as final products. Both procedures utilize convenient conditions and inexpensive reagents, and give products in good to high yields.