Sumary:
The first representatives of a new ring system, the 2,3a,6a_triazaphenalenium quaternary salts are prepared by the cycloaddition of tetrahydro-4H-pyrido[1,2-alpyrimidin--4-ones containing an o-chloroenamine moiety with azomethines. Earlier we have reported2 that 6,7,8,9-tetrahydro-4H-pyrido[l,2-a]pyrimidin-$-ones (1) contain an active methylene group in position 9. Numerous electrophilic reactions have been accomplished on this site of the molecule, e.g. halogenation3, diazonium coupling4, acylation with isocyanates5 and reactive iminium chlorides6. From pharmacological considerations we aimed to bring about a new ring between the N-l and C-g atoms. For this purpose compounds 1, derived from 1 and phosgeneiminium-chloride6, proved to be convenient starting materials. Compounds 1 as amide chlorides generally are versatile starting materials for different reactions e.g. by loss of HCl they can smoothly be transformed into cl-chloroenamines 3 which are expected to take part in cycloaddition reactions. Similar cycloadditions of a-chloroenamines were thoroughly investigated by Viehe and his co-workers7 in the last decade. They observed the cycloadditions of simple a-chloroenamines with olefines. acetylenes, nitriles and azomethines. These results tempted us to accomplish similar cycloaddition reactions with heterocyclic enamines of type 3. We failed to carry out cyclisation reactions with C=C double bonds but our attempts were successful in the case of aldimines and ketimines. It has turned out that the cyclisation of a-chloroenamines 3 with the imines 4 takes place under mild conditions, at -room temperature in solvents such as CHC13 or MeCN. All of the cycloaddition products obtained in MeCN at 80°C are well-defined salt-like compounds of pale yellow colour, soluble in water and polar organic solvents. 3 C nmr Chemical shifts, JEOL FX-100 solvent=CDC13 G(TMS)=O ppm