A Simple and Efficient Synthesis of Fused Benzo[b]thiophene Derivatives

Abstract

A new approach to the synthesis of fused benzothiophene derivatives was developed based on iodine-promoted photo-cyclization of 4,5-diarylsubstituted thiophenes obtained in three steps from commercially available compounds. Comparative analysis showed that photochemical cyclization is a more efficient method for the preparation of fused benzo[b]thiophene derivatives, compared to oxidative coupling 4,5-diarylsubstituted thiophenes in the presence of iron (III) chloride and palladium catalyzed intramolecular arylation. This approach provides an efficient synthesis of functionally substituted naphtho[2,1-b: 3,4-b ']dithiophenes, phenanthro[9,10-b] thiophenes, benzo[1,2-b: 3,4-b': 6 , 5-b '']trithiophenes, as well as new fused heterocycles containing a pyridine ring and / or a carbazole moiety

Synthesis, Photophysical, and (Spectro)Electrochemical Properties of New Benzo[1,2-c][1,2,5]thiadiazoles and Benzo[1,2-d][1,2,3]triazoles Fused with Two Thiazole Rings

“…Acylation of diamines 12 and 13 with acid halides generated in situ from oxalyl chloride and carboxylic acids 14a – 14e led to the formation of N , N′ -diamides 15a – 15e and 16a – 16e in 69–86% yields. Carboxylic acids 14a and 14b were purchased from Sigma-Aldrich, and compounds 14d and 14e were prepared according to the procedure. − For the synthesis of 3-(2-ethylhexyl)-[2,2′-bithiophene]-5-carboxylic acid 14c , we used a method previously developed by us based on the Fiesselmann reaction. − …”

Synthesis of 4,5-Disubstituted Methyl 1H-Pyrrole-2-carboxylates from 3-Chloroacrylaldehydes and Hippuric Acid

“…13 C NMR spectra were recorded in J-modulation (J-MOD) mode. 16,[35][36][37] 2a,b,d,e,i 16,[28][29][30] were synthesized according to the described procedures.…”

“…All chemicals were of analytical grade and purchased from Sigma-Aldrich Chemical Co. Compounds 1сe,h, 16,[35][36][37] 2a,b,d,e,i 16,[28][29][30] were synthesized according to the described procedures.…”

“…One of the widely used building blocks for the synthesis of five-membered heterocycles is 3-chloroacrylaldehydes 15 16 17 18 19 20 21 22 23 accessible by the Vilsmeier–Haack reaction. 24 They are used to prepare both thiophenes and pyrroles.…”

“…9 Despite the fact that many reviews and books [10][11][12][13] are devoted to the methods of preparation and properties of pyrrole and its derivatives, the development of new approaches to the synthesis of these heterocycles still remains an urgent task due to their high significance. 14 One of the widely used building blocks for the synthesis of five-membered heterocycles is 3-chloroacrylaldehydes [15][16][17][18][19][20][21][22][23] accessible by the Vilsmeier-Haack reaction. 24 They are used to prepare both thiophenes and pyrroles.…”