SYNTHESIS OF A-LAMBDA(4)-THIA-1,6-DISELENA-3,4-DIAZAPENTALENES, 1,6,6A-LAMBDA(4)-TRISELENA-3,4-DIAZAPENTALENES, 6A-LAMBDA(4)-THIA-1,3,4,6-TETRAAZAPENTALENES, AND 6A-LAMBDA(4)-SELENA-1,3,4,6-TETRAAZAPENTALENES FROM CYCLIC THIOUREAS AND SELENOUREAS

Imidazolidine-2-thione (7a) and the corresponding 2-selone (7b), hexah ydropyrimidine-2-thione (7c) and 2-selone (7d), and hexahydro-1H-1,3-d iazepine-2-thione (7e) and 2-selone (7f) reacted with 2,4-dinitrobenzy l chloride to give the 2-(2,4-dinitrobenzylthio) and 2-(2,4-dinitroben zylseleno) 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-dinitrobenzylselsn o)-4,5-dihydroimidazole (9a) and (9b), and2-(2,4-dinitrobenzylthio)- a nd ,4-dinitrobenzylseleno)-1,4,5,6-tetrahydropyrimide (9c) and (9d), a nd 2-(2,4-dinitrobenzylthio)- and obenzylseleno)-4,5,6,7-tetrahydro-1H -1,3-diazepine (9e) and (9f). The bases (9a)-(9f) reacted with isosele nocyanates with elimination of 2,4-dinitrotoluene and concomitant addi tion of two molecules of the isoselenocyanate to give 1,6,6a lambda 4- triheterapentalenes of two structural type, depending on the size of t he heteroring in the bases (9a)-(9f). The imidazoles (9a) and (9b) gav e 6a lambda 4-thia-1,6-diselena-3,4-diazapentalenes (10a)-(10j) and 1, 6,6a lambda 4-triselena-3,4-diazapentalenes (11a)-(11h), respectively. The sulfur-containing bases (9c) and (9e) gave 6a lambda 4-thia-1,3,4 ,6-tetraazapentalenes (12a)-(12j) and (14a)-(14d), respectively, and t he selenium-containing bases (9d) and (9f) gave 6a lambda 4-selena-1,3 ,4,6-tetraazapentalenes (13a)-(13j) and (15a)-(15d). Heteroatom-hetero atom covalent bond energies have been estimated for representative mem bers of the series (10)-(14) by using the Huggins equation and experim entally determined bond lengths. (C) 1997 John Wiley & Sons, Inc.