Vilsmeyer-Haack reactions

YZ1367). On treatment of 6-/ -chlorophenyl-3-methyl-5-nitroso-imi-dazo[2,l-6]thiazole with dilute hydrochloric acid in dioxane at rt a ring transformation occurs [92JCS(CC)1394], Vilsmeyer-Haack reaction of 3-methy -6-phenylimidazo[2,l-6]thiazole (70, R = = H, R = Me, R" =... 

In a synthesis utilizing the Vilsmeyer-Haack reaction, the following reactions are carried out ... 

Several of these // -disubstituted [ C]formamides have demonstrated utility in C-[ " C]formylations of electron-rich aromatic and heteroaromatic substrates via the Vilsmeyer-Haack reaction °. In the presence of POCI3, Cl2(0)P0P(0)Cl2, (COCl)2 or (CF3S02)20 they can C-formylate benzene and naphthalene derivatives that possess an electron-releasing substituent (0-alkyl, S-alkyl, A -dialkyl) as well as anthracene, pyrrole. 

This synthetic strategy, however, leads in general to a mixture of isomers differing in the position of the -alkyl groups in certain thiophene rings. Thus e.g. alkyl-substituted 1,4-diketone 116 is cyclized with L.R. to terthiophene 117. On one hand this is bis-acylated to terthiophene 118 which is further converted into the bis-Mamiich base 120. On the other hand, terthiophene 117 is formylated under Vilsmeyer-Haack conditions to the terthiophene carbaldehyde 119. Both compounds are subjected to a Stetter reaction yielding the bis-1,4-diketone 121 which is cyclized by L.R. to the undecamer 122 [Eq. (50)]. 

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