3,3‐Bis[alkylthio]‐phenylacrylaldehyde als Bausteine für Thiophene und Pyrazole

3,3‐Bis[alkylthio]‐2‐phenylacrylaldehydes as Building Sets for Thiophenes and Pyrazoles Alkylation of the dithiolate 2 either with methyliodide and α‐CH‐acid halogenated compounds R2CH2X or only with the latter reagent yields ketene S,S‐acetals 3. Base catalyzed cyclization of 3 leads to the thiophenes 4 Reaction of 3,3‐bis[methylthio]‐2‐phenylacrylaldehyde 3f with hydrazine affords a mixture of aldehydrazone 5 and aldazine 6. The pyrazole 7a is obtained by refluxing 5 in 1‐butanol. Mass spectra of the pyrazoles 7b, c and reaction of 3f with aniline prove the attack of a nucleophile on the formyl group in the first step.