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Paper | Regular issue | Vol 51, No. 8, 1999, pp.1849-1854
Published online, 1st January, 1970
DOI: 10.3987/COM-99-8560
Synthesis and Structure of Norbornane/ene-fused Thiouracils and Thiazino[3,2-a]pyrimidinones

Géza Stájer,* Angela E. Szabó, and Pál Sohár

*Institute of Pharmaceutical Chemistry, albert szent-györgyi Medical University,POB 121, H-6701 Szeged, Eötvös u. 6, Hungary

Abstract

Ethyl diexo-3-aminobicyclo[2.2.1]heptane- and -hept-5-ene-2-carboxy-lates (1a,b) and the diendo derivatives were transformed with thiophosgene to the isothiocyanates (2a,b and 3a,b) and then cyclized to the norbornane/ene-condensed 2-thioxopyrimidin-4-ones (4a,b and 5a,b). On heating, the norbornene compounds (4b and 5b) furnished thiouracil (6) via cyclopentadiene elimination. With dimethyl acetylenedicarboxylate, the thioxopyrimidinones (4a,b) and (5a,b) form angularly-fused [1,3]thiazino[3,2-a]pyrimidinones (7a,b and 8a,b). On heating, 7b decomposes to give 3-methyl-2,3-dihydro-2-thioxo-4(1H)-pyrimidi-none (9) in a retro Diels-Alder process by methyl migration and splitting-off of cyclopentadiene. The structures were elucidated by IR and NMR spectroscopies, with DNOE, DEPT and 2D-HSC techniques.