Furo benzothiophenes

Furo[3,2-fa]benzothiophenes (37) were synthesized in an analogous way (91JHC269) by smooth cyclization of the cyanomethyl ether 36 in the presence of K2C03/DMF. The starting 2-cyano-3-hydroxybenzothiophene 35 was obtained from methyl 2-thiohydroxybenzoate and chloroacetonitrile. Under Vilsmeier conditions (POCl3/DMF), the 2-cyano-3-cyanomethoxy-... 

Furo- and thieno- analogues (187 X = O, S) of PQQ have been prepared via the cyclization of a 6-amino-5-hydroxybenzofuran or benzothiophene with the dimethyl ester of 4-ketoglutaconic acid, followed by oxidation (HN03) of the triesters (186) to the ort/to-quinones (Scheme 26) <94HCA100>. 

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