Syntheses of 2,5-bis(4-methyl-2-thienyl)tbiophene 3 and 2,5-bis(4-methyl-2-thienyl)pyrrole 4 are described. The key step involves Stetter reaction between 4-methyl-2-thiophenecarboxaldehyde and divinyl sulfone. Cydizaton of the resulting 1,4-bis-(4-methyl-2-thienyl)-1,4-butanedione 2 with Lawesson's reagent gives 2,5-bis(4-methyl-2-thienyl)thiophene 3. whereas condensation with ammonium acetate provides the 2,5-bis(4-methyl-2-thienyl)pyrrole 4. 5&9
The intramolecular Diels‐Alder reactions of the furans 3, 11a and 11b produced indanone 6 and tetralones 14a and 14b respectively, presumably via the corresponding allenyl ethers 4, 12a and 12b and the intramolecular cycloadducts 5, 13a and 13b.
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