Preparation of 1,10-Dimethyl-benzo[c]cinnolines by Photochemical Cyclodehydrogenation of Azobenzenes

Abstract

Photocyclodehydrogenation of methylated azobenzene derivatives to the corresponding benzo[c]cinnolines was utilized for the synthesis of a number of compounds featuring sterically hindered methyl groups with different degrees of sterical hindrance including close mutual methylmethyl interaction. Such compounds are of special theoretical interest in the context of intramolecular dynamics, spectroscopy, and quantum (tunneling) effects. Factors determining synthetic accessibility and product distribution are discussed.

Progress in the Synthesis of Cinnoline Derivatives

“…1963 年, Went 小组 [40a] 采用 AlCl 3 作为催化剂(Schroll 反 应), 在加热条件下得到了一系列噌啉聚环类化合物, 但由于 E 式构型的偶氮不发生反应, 因此收率普遍较 低. 随后, Müller 小组 [41] 采用光照条件发生[6π]环化反 应, 使得收率有了明显改善 (光照可以促使 E 式构型的 偶氮转化为 Z 式). 2013 年, Sharma 小组 [42] 同样采用光照 条件, 以 77%～86%的收率得到 10 个噌啉并环类化合 物, 这些化合物表现出与对照药吲哚美辛相当的抗炎活 性.…”