Reactions of bromine and lead tetra-acetate with 2-(substituted hydrazino)-5-phenyl-1,3,4-oxadiazoles: routes to 3-aryl-6-phenyl-1,2,4-triazolo[3,4-b][1,3,4]oxadiazoles
作者:R. N. Butler、T. M. Lambe、F. L. Scott
DOI:10.1039/p19720000269
日期:——
solvolysis products are also obtained. A second route to the new ring system with tribromodiazabutadienes has also been developed. The oxadiazole ring of the new 1,2,4-triazolo[3,4-b][1,3,4]oxadiazoles is labile to acid and base and a preferential ring interconversion pattern of oxadiazole to triazole has been noted. In the reaction of the 2-(substituted hydrazino)-5-phenyl-1,3,4-oxadiazoles with lead
2-(取代的肼基)-5-苯基-1,3,4-恶二唑在乙酸中与溴反应生成过溴化物或肼基溴化物,在乙酸钠的存在下。在苯中用三乙胺处理肼基溴化物或在水性溶剂中溶剂分解可导致环化成新的1,2,4-三唑并[3,4- b ]-[1,3,4]恶二唑环系统。环化涉及恶二唑环,它是亲核试剂,可攻击肼基溴化物中不稳定的碳-溴位点。在溶剂分解中,这种内部亲核攻击与溶剂分子对外部亲核的攻击竞争,并且还获得了直接的溶剂分解产物。还已经开发了使用三溴二氮杂丁二烯的新环系统的第二条路线。新型1,2,4-三唑[3,4-]的恶二唑环b ] [1,3,4]恶二唑对酸和碱不稳定,已发现恶二唑向三唑的优先环互变模式。在2-(取代的肼基)-5-苯基-1,3,4-恶二唑与四乙酸铅的反应中,在潜在的环化位点存在氧原子会抑制环化。相反,该反应涉及hydr的乙酰氧基化,并且最多仅给出痕量的1,2,4-三唑并[3,4- b ] [1,3,4]恶二唑。