Electrophilic aromatic substitution. Part IV. Protodesilylation of 3-trimethylsilylfuran: electrophilic substituent constants for furan and thiophen

Abstract

3-Trimethylsilylfuran has been synthesised and its rate of protodesilylation relative to that of trimethylsilylbenzene determined as 117 in aqueous methanol–perchloric acid at 50°. The electrophilic substituent constant for the 3-position of furan is established as –0·45 for this reaction. The complete set of σ⁺-values now available for furan and thiophen in protodesilylation agrees well with those recently obtained from a gas-phase reaction.