Synthesis of 2-(3-acylselenoureido)benzonitriles and 2-(3-acylselenoureido)thiophene- 3-carbonitriles 5a-5f by addition of 2-aminonitriles 4a-4c to benzoyl- or 2,2-dimethyl- propanoylisoselenocyanate and their cycloaddition reactions are described. Structures of compounds 5a-5f were supported by CIMS, FTIR, 1H, 13C, 77Se and 15N NMR spectra. The parameters of 15N and 77Se nuclei were obtained from inverse 1H-X 2D HMBC and GSQMBC correlation experiments at natural abundance. Structure of compound 5b was confirmed by X-ray analysis. The geometry of 5b was optimized by ab initio RHF/DZVP quantum chemistry calculation. A very good correlation between the calculation and experimental data was found. The geometry of 5e was optimized by ab initio DFT/VWN/DZVP quantum chemistry calculation. It was found that title compounds 5a-5f do not undergo isomerization to acylisoselenoureas, in contrast to analogous ester derivatives. Fused 6-imino-6H-1,3- selenazinium salts (chlorides 6a-6f, hydrogensulfates 7a-7f and tetrafluoroborates 8a-8f) were prepared by an acid cyclization of 5a-5f. It was found that neutralization of 6a-6f, 7a-7f and 8a-8f led to their retrocyclization to 5a-5f. Selenoureas 5a-5f with equimolar amounts of methanolic potassium hydroxide afforded potassium salts 9a-9f. Only the salts 9b, 9c, 9e and 9f of the thiophene series were isolated. Their heating in methanol solution led to deacylation of isoselenoureas 10b and 10c. The in situ prepared compounds 9a and 9d cyclized and deacylated to 4-aminoquinazoline-2-selenole 11a under the same conditions. The compounds 5a-5f and 10a-10c cyclized to fused 4-aminopyrimidine-2-selenols 11a, 11b and 4-aminopyrimidine-2-selenone 12c by boiling in methanolic potassium hydroxide solution.
A THEORETICAL STUDY OF THE STEREOCHEMICAL COURSE OF THE ACID CYCLIZATION OF TWO 5-OXOGERMACREN- 6,12-OLIDES EPIMERIC IN C4