Crown ethers based on bis(benzimidazol-2-yl)alkanes and 1,2-bis(benzimidazol-2-ylsulfanyl)ethane

Abstract

Dibenzimidazo crown ethers were synthesized by alkylation of α,ω-bis(benzimidazol-2-yl)alkanes and 1,2-bis(benzimidazol-2-ylsulfanyl)ethane with tri-and tetraethylene glycol bis(4-toluenesulfonates). The structure of 6,7,9,10,12,13,21,22-octahydro[1,14,6,9,4,11]dioxadithiadiazacyclohexadecino[4,5-a:11,10-a′]dibenzimidazole was studied by X-ray analysis.Demands in new multidentate ligands with specified properties determine persistent attention to the development of methods of preparation and studies on the structure of macroheterocycles with variable size of the ring and nature and number of donor centers, as well as of those possessing exocyclic coordination centers. In this connection, crown ethers containing a benzimidazole heteroring attract some interest. With a view to synthesize such macrocyclic compounds we used as starting materials a series of α,ω-bis(benzimidazol-2-yl)alkanes and 1,2-bis(benzimidazol-2-ylsulfanyl)ethane; their analogs are known as efficient ligands for coordination to copper(II) ions [1].The corresponding 15-, 16-, and 18-membered dibenzimidazo crown ethers Ia-Ic having two or three oxygen atoms in the macroring were synthesized by alkylation of bis(benzimidazol-2-yl)alkanes IIa and IIb with tri-and tetraethylene glycol bis(4-toluenesulfonates) in dimethylformamide (DMF) in the presence of potassium hydroxide under argon (Scheme 1). The yields of compounds Ia-Ic were 44-67%. Initial 1,2-bis(1H-benzimidazol-2-ylsulfanyl)ethane (IV) was prepared by alkylation of 2,3-dihydro-1H-benzimidazole-2-thione (III) with 1,2-dichloroethane in aqueous sodium hydroxide (Scheme 2). O TsO O OTs O O m m + n = 1, m = 1 (а); n = 1, m = 2 (b); n = 2, m = 1 (c). Scheme 1.

Synthesis and Crystal Structure of Novel Benzimidazole Cyclophanes

“…在结构设计合成 过程中, 通过改变连接链的结构 [12,13] 而赋予了环蕃不同 的性能使其用途也越来越广. 其常用的合成路线有三 种: (1)一步成环法: 双功能基烷基试剂和苯并咪唑类化 合物直接环化得到苯并咪唑环蕃; (2)分步成环法: 先由 双功能基烷基试剂和苯并咪唑类化合物反应形成双苯 并咪唑化合物, 而后苯并咪唑的另一个氮原子再与另一 双功能基烷基试剂直接季胺化成环, 得到苯并咪唑环 蕃; (3)在合成苯并咪唑环的同时合成苯并咪唑环蕃 [14] .…”