Synthesis of 2-thio derivatives of 4-phenyl-9H-pyrimido[4,5-b]indole

The reaction of 3-benzylidene-2-ethoxyindolenine tetrafluoroborate with thiourea gives a mixture of 4-phenylpyrimido[4,5-b]indole-2(1H)-thione, its 3,4-dihydro derivative, and the corresponding disulfide, the product ratio depending on the reaction conditions. A number of transformations of the resulting compounds, in particular, those giving 2-alkylthio pyrimidoindole derivatives are described. Dedicated to the memory of Academician V. A. Koptyug on the occasion of the 75th anniversary of his birth. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1032–1037, June, 2006.