Prototropy in the System -ClCH-N=N-; Cycloadditions of 1-Aza-2-azoniaallene Cations Derived from Aldehydes
作者:Yiping Guo、Quanrui Wang、Johannes C. Jochims
DOI:10.1055/s-1996-4189
日期:1996.2
1,3-Disubstituted 1-aza-2-azoniaallene salts 10 were obtained as reactive intermediates on oxidation of aldehyde hydrazones 7 with tert-butyl hypochlorite and treatment of the resulting (1-chloroalkyl)azo compounds 8 with a Lewis acid (SbCl5). The allenes 10 underwent cycloadditions to the multiple bonds of nitriles, acetylenes, and olefins affording the heterocyclic salts 12, which gave the free bases 12’ with aqueous NaOH. The critical point of this sequence lies in the prototropic rearrangement of 8 into the hydrazonyl chlorides 9, from which no heterocumulenes 10 could be obtained. However, further chlorination of 7c led to the (1,1-dichloropropyl)azo compound 13, which gave the chloro substituted allenium salt 14 on treatment with SbCl5. Cycloaddition of 14 to acetonitrile afforded the chloro substituted 1,2,4-triazolium salt 16. Conditions for slow rearrangements 8 → 9 were found for compounds 8 derived from primary or secondary alkanecarbaldehydes. However, for (1-chloroalkyl)azo compounds derived from benzaldehyde or pivaldehyde the prototropy 8 → 9 was too fast to permit preparation of heterocumulenes 10.
1,3-二取代的1-氮-2-氮杂烯盐10作为活性中间体,通过醛肼7在叔丁基次氯酸酯氧化下制得,并对生成的(1-氯烷基)偶氮化合物8用路易斯酸(SbCl5)处理.烯盐10经与腈、炔烃、或烯烃的复分解反应得到含氮盐12,用NaOH水溶液处理即得到自由碱12'.本反应历程的关键点在于8向肼叉基氯化物9的质子迁移,而从9不能得到含异氰化合物10.而7c的进一步氯化导致(1,1-二氯丙基)偶氮化合物13生成,用SbCl5处理得到氯取代的烯盐14,与乙腈的复分解反应得到氯取代的1,2,4-三氮唑盐16.在由伯或仲脂肪醛衍生的(1-氯烷基)偶氮化合物8中,发现了缓慢的8-9重排反应,但对于由苯甲醛或新戊醛衍生的(1-氯烷基)偶氮化合物8而言,8-9重排过快,无法制得含异氰化合物10.