oa South African Journal of Chemistry - Synthesis of indoles : tetrahydropyrazino[1, 2-a]indole-1, 4-dione and pyrazino[1, 2-a]indole-6, 13-diones from piperazine-2, 5-diones
The readily available piperazine-2, 5-dione has been used to prepare both 1:1 (1-3), with stereotopic methylene protons; and 2:1 (4-6) arylmethylenepiperazine-2, 5-diones in above average yields. The halo-derivatives, 1, 4 and 5 were cyclized to pyrazino[1, 2-a]indoles, 7-9, using copper bronze. Indole compounds 7 and 9 were further treated, separately, with lithium aluminium hydride, sodium borohydride, lithium hydroxide monohydrate and butyl lithium to yield 2-substituted indoles 10-13.
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