Cyclizations under Vilsmeier conditions

Interestingly, o-cyanomethoxybenzonitrile (26) gives a Thorpe-Ziegler type of cyclization under Vilsmeier conditions (DMF/POCl3), that is without the addition of a base. Further cyclization of the assumed 3-amino-2-cyanobenzofuran 27 with the Vilsmeier reagent afforded benzofuro-[3,2-d]pyrimidine (28) in poor yield, (91JHC263) (Scheme 7). 

Cyclic enamines and imines, 6, 147 Cyclic hydroxamic acids, 10, 199 Cyclic peroxides. 8, 165 Cyclizations under Vilsmeier Conditions, 31, 207... 

Meth-Cohn, O., Tamowski, B. Cyclizations under Vilsmeier conditions./Adv. Heterocycl. Chem. 1982,31,207-236. 

Useful reviews on redox transformations of thiophen derivatives (179 references), on the stereochemistry of carbonyl derivatives of five-membered heterocycles (257 references), on synthetic approaches to dihydrothiophens (135 references), and on biosteric thiophens" have been published. Aspects of thiophen chemistry have been treated in reviews on the synthesis of heterocycles by thermal [2 + 2] cycloaddition reactions of acetylenes and on aspects and perspectives of organic heterocyclic chemistry. A review comparing the chemistry of thieno[2,3-h]- and thieno [3,2-i ]-thiophen with that of benzo[ft] thiophen and quinoline has been published. In Advances in Heterocyclic Chemistry, the development of benzo[6] thiophen from 1968 to 1980 and of selenophen from 1970 to 1980 was presented. Other aspects of thiophen chemistry are treated in chapters on Dewar Heterocycles," on Cyclizations under Vilsmeier Conditions, on Polyfluoroheteroaromatic Compounds, and on Reactions of Benzyne with Heterocyclic Compounds. " Several dissertations treating various aspects of thiophen chemistry have appeared. " ... 

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