Ring-fused aminal is an interesting structural skeleton in biologically active and pharmaceutically relevant compounds. A novel and efficient method for synthesizing benzosulfamidate-fused tetrahydroquinazolines is described. By employing the [4+2]-cycloaddition of 2-aminophenyl enones with cyclic N-sulfimines in the presence of DMAP as a base, the desired benzosulfamidate-fused tetrahydroquinazolines were obtained in good yields with high diastereoselectivities. Furthermore, an organocatalytic asymmetric [4+2]-cycloaddition was successfully achieved using a squaramide-based catalyst, enabling the enantioselective synthesis of chiral ring-fused tetrahydroquinazolines with high yields and enantio- as well as diastereoselectivities (up to 89 % yield, 94 % ee, and >30 : 1 dr).
Keywords: Asymmetric organocatalysis; Benzosulfamidate; Cyclic aminal; Tetrahydroquinazoline; [4+2]-Cycloaddition.
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