Interactions of 3‐Acylisocoumarins with Ethane‐1,2‐diamines: A Simple Route to 3,4‐Dihydro‐6 H ‐pyrazino[1,2‐ b ]isoquinolin‐6‐ones and Their Hydrogenated Derivatives

The recyclization of isocoumarins under the N ‐nucleophile action is a well‐known route to different isoquinolones. But addition of functional groups in such substrates can provide more complicated nitrogen‐containing heterocycles. In this study, the easy formation of 3,4‐dihydro‐6 H ‐pyrazino[1,2‐ b ]isoquinolin‐6‐one system via the interaction of 3‐acylisocoumarins and ethane‐1,2‐diamines is demonstrated. As the acyl component of reaction, 3‐acetyl‐ and 3‐benzoylisocoumarins, 2,3‐dihydro‐1 H ‐benzo[ c ]chromene‐4,6‐dione, and heteroanalogs of 3‐acetylisocoumarin were successfully used; and the amino component was represented by ethane‐1,2‐diamine, some cyclic vicinal diamines, methyl 2,3‐diaminopropanoate, and N 1 ‐methylethane‐1,2‐diamine. The variation of substrates gave different structures with 3,4‐dihydro‐6 H ‐pyrazino[1,2‐ b ]isoquinolin‐6‐one core; and the number of products can grow extremely because of this core's aptitude to reduction. Thus, 1,2,3,4‐tetrahydro‐6 H ‐pyrazino[1,2‐ b ]isoquinolin‐6‐ones, 1,2,3,4,11,11a‐hexahydro‐6 H ‐pyrazino[1,2‐ b ]isoquinolin‐6‐ones and 1,3,4,6,11,11a‐hexahydro‐2 H ‐pyrazino[1,2‐ b ]isoquinolines were synthetized by using various reduction methods for separate 3,4‐dihydro‐6 H ‐pyrazino[1,2‐ b ]isoquinolin‐6‐ones.