Homologous SNV Reaction: Synthesis of l-Methyl-4-[4′-phenylsulfonyl-1′,3′-butadienyl]pyridinium Iodide and Its Reactivity with Thiol Groups Giving Rise to the Chromophoric Thioether

Abstract

Thioether 4-[(1' E,3' E)-4'-phenylsulfanyl-l',3'-butadienyl]pyridine 8 and sulfone 4-(4'-phenylsulfonyll',3'-butadienyl)pyridine 14 were prepared by re ac tion of the car ban ions de rived from al lyl ic thioether or al lyl ic sulfone with isonicotinaldehyde. The re ac tion with the sulfonyl car ban ion oc curred at the α po si tion and on heat ing the alcolate gave the dienic sulfone 14 . The cor re spond ing pyridinium io dide 10 and 15 were pre pared by re ac tion with methyl io dide, re spec tively, on pyridine deri vates 8 and 14 . The dienic pyridinium thioether 10 showed a long wave length ab sorp tion band cen tered at 420 nm. The re ac tion of dienic pyridiniu m sulfone 15 with thiophenol gave the dienic pyridinium thioether 10 by a nucleophilic vinylic sub sti tu tion. The re ac tion of sulfone 15 with glutathione was of sec ond or der and the rate con stant was 8.5 M -1 s -1 at 30 °C and pH 7, about 500 times smaller than the rate con stant ob served with ( E)- 1-methyl-4-(2-methylsulfonyl-l- ethenyl) pyridiniu m io dide 1. The dienic pyridinium thioether 10 was a neg a tive solvatochrome.