Simple Synthesis of Multi-Halogen Pyrazino[1,2- a]indole-1,8(2 H,5 aH)-diones.

A concise and efficient one-pot synthesis of multi-halogen pyrazino[1,2- a]indole-1,8(2 H,5 aH)-dione ( MHPID) derivatives by the reaction of an enamino ester with multi-halogen benzoquinone derivatives is described. MHPIDs 3a-3d were obtained with good yields (78-83%) by refluxing enamino esters 1a and 1b and tetrahalogen-1,4-benzoquinones 2a and 2b for 24 h without the use of catalysts. Compounds 3e-3p were also obtained with excellent yields (69-92%) via the reaction of the phenyl-substituted enamino esters 1c-1h with tetrahalogen-1,4-benzoquinones 2a and 2b in CH3CN catalyzed by Cs2CO3. These two protocols are efficient and effective for the synthesis of MHPIDs. [ABSTRACT FROM AUTHOR]