Trialkylamines undergo reaction with vinylenedisulfonium salts with substitution of a sulfonium group to give the salts ( I ) [l]. We have examined whether further exchange of an onium group can be achieved by reaction of ( J ) with a tertiary amine. Reaction of ( I a ) or (1 b ) with trimethylamine affords, however, an almost quantitative (NMR spectra) 1 : 1 mixture of (2) and ( 3 a ) or ( 3 b ) , respectively. Compound ( 3 a ) is crystalline, ( 3 h ) was obtained as a colorless oil which was analyzed as crystalline hexafluorophosphate.
B F~If the weakly acid solution of ( I a ) in deuterium oxide is adjusted to pH x 7.5 with dilute sodium deuterium oxide solution H/D exchange of one of the two olefinic protons can be observed NMR spectroscopically.
BFpThe monodeuteriated compound ( 4 ) was isolated. It yields compound ( 5 ) on reaction with trimethylamine in dimethoxyethane. The structure of ( 5 ) was deduced NMR spectroscopicallybycomparison with ( 3 a ) and with (3-substituted vinylammonium compounds ['] (Table 1). The structure of ( 4 ) was inferred from ( 5 ) . The reaction ( 1 a ) + ( 4 ) shows that sp2 bonded protons are more strongly acidified by sulfonium groups in the c ( position than by ammonium groups. The Table 1 . Yields and some physical data of the compounds prepared.selective deuteration of compounds having a structure analogous to ( 1 )['I, moreover, enabled unequivocal assignment of the CH=CH signals in the 'H-and 13C-NMR spectra ['].Strong nucleophiles substitute the ammonium group in (1) chemospecifically: reaction of ( Z b ) with ( 6 a ) or ( 6 b ) in methanol at 0°C yields the oily tetrafluoroborates (7a)c4I or ( 7 b ) , respectively. Reaction of (6c) with ( J b ) in water at room temperature yields (7c). The crude solutions of compounds ( 7 ) still contain < 5 % of the corresponding cis isomer (NMR spectra). Compounds ( 7 b ) and ( 7 c ) were obtained in sterically pure form as the crystalline 2,4,6-trinitrobenzenesulfonate and hexafluorophosphate, respectively.Vinylsulfonium salts are excellent Michael acceptors and productive building blocks inThe reaction sequence cis-vinylenedisulfonium salt + trans-(1 )['I + trans-( 7 ) constitutes a novel route to trans-substituted vinylsulfonium salts. The cis isomers of (7) are formed stereoselectively from cis-vinylenedisulfonium salts and ( 6 ) [ 3 .4b1. The method thus offers the possibility of synthesizing both isomeric vinylsulfonium salts from a readily accessible starting compound.Compound ( 7 ) and its cis isomer ['] are to our knowledge the first azidovinylsulfonium salts reported in the literature. The compounds are interesting water-soluble "vinyl azides"[61.
ProcedureA solution of trimethylamine (126 mg, 2.13 mmol) in anhydrous acetone (1.3 ml) was added to a stirred solution of ( 1 b ) (400mg, 1.06mmol) in acetone at room temperature. After 1 h the reaction mixture was concentrated to 7 ml and filtered free from precipitated ( 2 ) . The filtrate after removal of solvent and drying (0.01 torr) afforded 285 mg (98 %) ( 3 b ) as a c...