Reisinger Ales, Koch Rainer, Bernhardt Paul V, Wentrup Curt
Department of Chemistry, School of Molecular and Microbial Sciences, The University of Queensland, Brisbane, Qld 4072, Australia.
Org Biomol Chem. 2004 Apr 21;2(8):1227-38. doi: 10.1039/b317099c. Epub 2004 Mar 18.
Tetrazolo[1,5-a]pyridines/2-azidopyridines 1 undergo photochemical nitrogen elimination and ring expansion to 1,3-diazacyclohepta-1,2,4,6-tetraenes 3, which react with alcohols to afford 2-alkoxy-1H-1,3-diazepines 4 (5), with secondary amines to 2-dialkylamino-5H-1,3-diazepines 16, sometimes via isolable 2-dialkylamino-1H-1,3-diazepines 15, and with water to 1,3-diazepin-2-ones 19. The latter are also obtained by elimination of isobutene or propene from 2-tert-butoxy- or 2-isopropoxy-1H-1,3-diazepines 4 or 5. 1,3-Diazepin-2-one 22B and 1,3-diazepin-4-one 24 were obtained from hydrolysis of the corresponding 4-chlorodiazepines. Diazepinones 19 undergo photochemical ring closure to diazabicycloheptenones 25 in high yields. The 2-alkoxy-1H-1,3-diazepines 4 and 5 interconvert by rapid proton exchange between positions N1 and N3. The free energies of activation for the proton exchange were measured by the Forsén-Hoffman method as DeltaG([double dagger])298= 16.2 +/- 0.6 kcal mol(-1) as an average for 4a-c in CD2Cl2, acetone-d6, and methanol-d4, and 14.1 +/- 0.6 kcal mol(-1) for in 4c acetone/D2O. The structures of 2-methoxy-5,6-bis(trifluoromethyl)-1H-1,3-diazepine 4k, 1,2-dihydro-4-diethylamino-5H-1,3-diazepin-2-one 22bB, and diazabicycloheptanone were 26 determined by X-ray crystallography. The former represents the first reported X-ray crystal structure of any monocyclic N-unsubstituted 1H-azepine.
四唑并[1,5 - a]吡啶/2 - 叠氮吡啶1进行光化学脱氮和扩环反应生成1,3 - 二氮杂环庚 - 1,2,4,6 - 四烯3，其与醇反应生成2 - 烷氧基 - 1H - 1,3 - 二氮杂卓4（5），与仲胺反应生成2 - 二烷基氨基 - 5H - 1,3 - 二氮杂卓16，有时经由可分离的2 - 二烷基氨基 - 1H - 1,3 - 二氮杂卓15，与水反应生成1,3 - 二氮杂卓 - 2 - 酮19。后者也可通过从2 - 叔丁氧基 - 或2 - 异丙氧基 - 1H - 1,3 - 二氮杂卓4或5中消除异丁烯或丙烯得到。1,3 - 二氮杂卓 - 2 - 酮22B和1,3 - 二氮杂卓 - 4 - 酮24是由相应的4 - 氯二氮杂卓水解得到的。二氮杂卓酮19进行光化学闭环反应以高收率生成二氮杂双环庚烯酮25。2 - 烷氧基 - 1H - 1,3 - 二氮杂卓4和5通过N1和N3位之间的快速质子交换相互转化。质子交换的活化自由能通过Forsén - Hoffman方法测定，在CD2Cl2、丙酮 - d6和甲醇 - d4中4a - c的平均值为ΔG([双匕首])298 = 16.2±0.6 kcal mol⁻¹，在4c的丙酮/D2O中为14.1±0.6 kcal mol⁻¹。2 - 甲氧基 - 5,6 - 双（三氟甲基） - 1H - 1,3 - 二氮杂卓4k、1,2 - 二氢 - 4 - 二乙氨基 - 5H - 1,3 - 二氮杂卓 - 2 - 酮22bB和二氮杂双环庚酮26的结构通过X射线晶体学确定。前者代表首次报道的任何单环N - 未取代氮杂卓的X射线晶体结构。
