Nucleophilic addition of amines to silyl- and germyl-substituted thiophene1,1-dioxides

Nucleophilic addition of secondary amines to tert-butyl-, trimethylsilyl- a nd trimethylgermyl-2,5-disubstituted thiophene 1,1-dioxides has been studie d. It has been shown that the reactivity and reaction pathway depend strong ly on the thiophene 1,1-dioxide structure, the basicity of the amine and th e 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 organ ic solvents, 2,5-bis(trimethylsilyl)-, 2-trimethylsilyl-5-trimethylgermyl- and 2,5-bis(trimethylgermyl)thiophene 1,1-dioxides add one piperidine molec ule, the vinylsilane fragment being more active than the vinylgermane one. The corresponding reactions of thiophene 1,1-dioxides with morpholine and d iethylamine failed to occur. In water, the addition of morpholine and dieth ylamine (one molecule in each case) or dimethylamine and piperidine (two mo lecules in each case) was accompanied by concomitant demetallation. The mol ecular structure of 3-piperidino-5-trimethylgermyl-2,3-dihydrothiophene 1,1 -dioxide was confirmed by X-ray analysis.