Quinoxaline Derivatives in the Synthesis of Macrocycles

Quinoxalin-2,3(17f,470-dione 69, 2,3-dichloroquinoxalines 70, quinoxalin-2,3 (17f,4fl)-dithione 71, 2,3-dibromomettylquinoxalines 72, 4-[3-(4-hydroxyphenyl)-2-quinoxalinyl]phenol 73a, 4-[3-(4-mercaptophenyl)-2-quinoxalinyl]thiophenol 73b, 2,3-dipyrrolylquinoxalines 74 and 75b, 2,3 dicyanoquinoxaline 76a and its benzo[/]-76b and the dibenzo[/,/ ]-76c annulated derivatives as well as 6,7-dicyanoquinoxalines 77 were used among the numerous derivatives of quinoxaline as key compounds for designing of the quinoxaline macrocycles (Fig. 5.7). 

The processing of quinoxaline podands 87b, c with sodium hydride and the subsequent reaction with quinoxaline 70b in a dilute solution of THF leads to the macrocycles 90 with two quinoxaline fragments. In the case of n = 1, the yields are good and in the case of n = 2 they are moderate (Ahmad et al. 1996). 

Meanwhile, the use of the potassium salts of compounds 91 in the reaction with 2,3-dichloroquinoxaline 70a in the boiling DMF solution did not lead to the corresponding macrocycles 92. These reactions resulted in the formation of a,co-bis 

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The procedure for the synthesis of macrocycles 224a, b, i.e., the precursores of 218a, b is given in Scheme 5.51. The synthesis is based on the 3-chloroquinoxalin-2-ones. In this process, a 7-methoxy derivative has been obtained from 7-methoxyquinoxalin-2,3-dione 69b by the treatment with thionyl chloride in DMF. 3-Chloroquinoxaline-2-ones are transformed into quinoxaline... 

An original method of constructing new types of crown ether derivatives 40b, c, f is a combination of the above approaches to the synthesis of bis(imidazo[l,5-a] quinoxaline)s (Mamedov et al. 2009). However, from compounds 36b, c, f, these macrocycles are obtained in low yields. The yield of products 40 insignificantly increases when the reaction is carried out in the presence of alkali metal salts (LiC104, NaCl, KI) as template agents (Scheme 4.20) (Mamedov et al. 2009). 

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