Trifluoroethanol Promoted Castagnoli-Cushman Cycloadditions of Imines with Homophthalic Anhydride.

Lactams are essential compounds in medicinal chemistry and key intermediates in the synthesis of natural products. The Castagnoli-Cushman reaction (CCR) of homophthalic anhydride with imines is an exciting method for accessing cyclic densely substituted lactam products. Most CCRs need to be catalyzed or heated. Herein, we report a new, efficient, metal and catalyst-free CCR for the synthesis of poly-substituted 3,4-lactams utilizing the unique properties of trifluoroethanol (TFE). This procedure provides high-speed and smooth access to a broad range of densely substituted 3,4-lactams in good yields and a 100% atom-economical fashion.