(57) A process for the preparation of 3-substituted thiophenes which involves cyclisation
of a novel intermediate, avoids the use of previously employed expensive starting
materials. The thiophenes are useful for the preparation of penicillins and cephalosporins.
The process is for the preparation of a thiophene of formula (I):
where R1 represents a carboxylic acid group, or an ester or amide thereof or a nitrile group;
R2 represents a group suitable for use as an α-substituent in the side-chain of a penicillin
or cephalosporin; which comprises treating a compound of formula (II):
wherein X represents halogen or optionally functionalised hydroxyl, Y represents halogen,
hydroxyl, or alkoxy; with a source of nucleophilic sulphur under basic conditions.
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