Treatment of 1,3-di­(t-butyldimethylsilyl)-1,3-disilabicyclo­[1.1.0]­butane 1a with excess lithium in THF provided 1,3-dilithio-1,3-disilabicyclo[1.1.0]­butane 2 via reductive cleavage of the exocyclic Si–Si bonds at the bridgehead silicon atoms. In the single crystals obtained by recrystallization in the presence of 1,2-dimethoxyethane (DME), 2 exists as a solvent-separated ion pair, and its anionic part forms an aggregate that contains three lithium atoms sandwiched by two 1,3-disilabicyclo[1.1.0]­butan-1,3-diide units. Treatment of 2 with chlorotri­isopropylsilane provided triisopropylsilyl-substituted 1,3-disilabicyclo[1.1.0]­butane 1b. The structural characteristics of 1b are close to that of the short-bond isomer, which is consistent with previous theoretical predictions concerning the steric effects of the bridgehead substituents on the structure of silabicyclo[1.1.0]­butane.

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Die Thiazolon‐Derivate (I) gehen beim Erhitzen in Xylol in die Thioharnstoffe (II) (80% Ausbeute) über.