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

Abstract

AbstractThiophene and its derivatives with R = H, alkyl or −SCH3 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 = CH3S: substitution on S in the SCH3 group by butyllithium in THF/HMPT, abstraction of a CH3S proton by butyllithium in THF (without HMPT) and ring opening in strongly polar media with LiN(i‐Pr)2.