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Paper | Regular issue | Vol 48, No. 9, 1998, pp.1851-1866
Published online, 1st January, 1970
DOI: 10.3987/COM-98-8219
Nitrogen Bridgehead Compounds Part 90. An Efficient Versatile Synthesis of 1-Methyl-2-substituted 1,2,3,4-Tetrahydro-6H-pyrazino[2,1-b]quinazoline-3,6-diones

József Kökösi,* János Almási, Benjamin Podányi, Miklós Fehér, Zsolt Böcskei, Kálmán Simon, and István Hermecz*

*Institute for Pharmaceutical, Chemistry Semmelweis, University of Medicine, Högyes E. u. 9. 1092 Budapest, Hungary

Abstract

A versatile synthesis of 2-substituted 1-methyl- and 1,4-dimethyl-1,2,3,4-tetrahydro-6H-pyrazino[2,1-b]quinazoline-3,6-diones is presented, starting from 2-(1-bromoethyl)quinazolin-4(3H)-one. The key step of the reaction sequence is the diastereoselective cyclization of 2-{[1-(N-2-haloacyl-N-substituted amino]ethyl}quinazolin-4(3H)-ones. Usually 1,4-dimethyl derivatives are obtained as pure racemic cis-compounds (2-alkyl and 2-benzyl derivatives), or a mixture of diastereomers, containing the 4-methyl group in quasiaxial position.