Nucleophilic addition of amines to silyl- and germyl-substituted thiophene 1,1-dioxides

Nucleophilic addition of secondary amines to tert-butyl-, trimethylsilyl- and trimethylgermyl-2,5-disubstituted thiophene 1,1-dioxides has been studied. It has been shown that the reactivity and reaction pathway depend strongly on the thiophene 1,1-dioxide structure, the basicity of the amine and the nature of the solvent. Addition of amines to 2,5-bis(tert-butyl)thiophene 1,1-dioxide does not occur either in organic or in aqueous media. In organic solvents, 2,5-bis(trimethylsilyl)-, 2-trimethylsilyl-5-trimethylgermyl- and 2,5-bis(trimethylgermyl)thiophene 1,1-dioxides add one piperidine molecule, the vinylsilane fragment being more active than the vinylgermane one. The corresponding reactions of thiophene 1,1-dioxides with morpholine and diethylamine failed to occur. In water, the addition of morpholine and diethylamine (one molecule in each case) or dimethylamine and piperidine (two molecules in each case) was accompanied by concomitant demetallation. The molecular structure of 3-piperidino-5-trimethylgermyl-2,3-dihydrothiophene 1,1-dioxide was confirmed by X-ray analysis.