Thiophenes 1.3- oxathiolium salts

Oxathiolium salts, anhydro-5-hydroxy-thiophene synthesis from, 4, 899... 

A very promising new route to substituted thiophens has recently been developed by Hartmann. The reaction of 2-aryl-1,3-oxathiolium salts such as (33) with malononitrile in the presence of base yields 3-amino-4-cyanothiophens (34), with ethyl malonate or ethyl cyanoacetate 3-hydroxy-thiophens (34a), and finally with nitromethane 3-nitrothiophens (34b). The... 

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