Synthesis of 6aλ4‐thia‐1,6‐diselena‐3,4‐diazapentalenes, 1,6,6aλ4‐triselena‐3,4‐diazapentalenes, 6aλ4‐thia‐1,3,4,6‐tetraazapentalenes, and 6aλ4‐Selena‐1,3,4,6‐tetraazapentalenes from cyclic thioureas and selenoureas

Abstract

Imidazolidine-2-thione (7a) and the corresponding 2-selone (7b), hexahydropyrimidine-2-thione (7c) and 2-selone (7d), and hexahydro-1H-1,3-diazepine-2-thione (7e) and 2-selone (7f) reacted with 2,4-dinitrobenzyl chloride to give the 2-(2,4-dinitrobenzylthio) and 2-(2,4-dinitrobenzylseleno) derivatives (8a)-(8f) of 4,5-dihydroimidazolium chloride, 1,4,5,6-tetrahydropyr-imidinium chloride, and 4,5,6,7-tetrahydro-1H-1,3-diazepinium chloride. Deprotonation of the chlorides (8a)-(8f) gave, respectively, 2-(2,4-dinitrobenzylthio)-and 2-(2,4-dinitrobenzylseleno)-4,5-dihydroimidazole (9a) and (9b), 2-(2,4-dinitrobenzylthio)- and 2-(2,4-dinitrobenzylseleno)-1,4,5,6-tetrahydropyrimidine (9c) and (9d), and 2-(2,4-dinitrobenzylthio)- and 2-(2,4-dinitrobenzylseleno)-4,5,6,7-tetrahydro-1H-1,3-diazepine (9e) and (9f). The bases (9a)-(9f) reacted with isoselenocyanates with elimination of 2,4-dinitrotoluene and concomitant addition of two molecules of the isoselenocyanate to give 1,6,6aλ4-triheterapentalenes of two structural types, depending on the size of the heteroring in the bases (9a)-(9f). The imidazoles (9a) and (9b) gave 6aλ4-thia-1,6-diselena-3,4-diazapentalenes (10a)-(10j) and 1,6,6aλ4-triselena-3,4-diazapentalenes (11a)-(11h), respectively. The sulfur-containing bases (9c) and (9e) gave 6aλ4-thia-1,3,4,6-tetraazapentalenes (12a)-(12j) and (14a)-(14d), respectively, and the selenium-containing bases (9d) and (9f) gave 6aλ4-selena-1,3,4,6-tetraazapentalenes (13a)-(13j) and (15a)-(15d). Heteroatom-heteroatom covalent bond energies have been estimated for representative members of the series (10)-(14) by using the Huggins equation and experimentally determined bond lengths. © 1997 John Wiley & Sons, Inc.