Halogen Bond‐Catalyzed Povarov Reactions

Abstract

The use of a bidentate halogen bond donor to catalyse Povarov reactions of imines derived from aryl adehydes and anilines is reported. Dienophiles used in these reactions included 2,3-dihydrofuran, N-vinyl-2-pyrrolidone and N-Cbz-protected 2,3-dihydropyrrole. Very high isolated yields of the desired 1,2,3,4-tetrahydroquinoline products were obtained with low catalyst loadings (0.01 equivalents) and short reaction times (minutes to hours) at ambient temperature. Notably, the bis(benzimidazolium iodide)-based catalyst used in these reactions proved to be more efficient than analogous bromine and chlorine functionalized compounds, as well as a related monodentate benzimidizolium iodide. These observations are similar to what has been reported by others regarding halogen bond organocatalysis, and may prove useful in guiding catalyst design as the field moves forward.