Base‐induced deprotonation and ring opening of thiophene and some of its derivatives

Abstract

Abstract Thiophene and its derivatives with R = H, alkyl or −SCH 3 group in the 2‐ and 5‐positions (1 and 4) undergo the following types of reaction with strong bases, depending upon the nature of the base and the solvent or solvent mixture: if R = H or alkyl: abstraction of the 2‐ and 5‐proton in relatively apolar media and ring opening to enynethiolates in strongly polar media (HMPT); if R = CH 3 S: substitution on S in the SCH 3 group by butyllithium in THF/HMPT, abstraction of a CH 3 S proton by butyllithium in THF (without HMPT) and ring opening in strongly polar media with LiN( i ‐Pr) 2 .