Silaheterocyclen IX. Darstellung und Charakterisierung von 2,4-Dineopentyl-1,3-disilacyclobutanen

Abstract

The E/Z-isomers of 2,4-dineopentyl-1,3-disilacyclobutanes (R 1R 1SiCHCH 2 tBu) 2 are obtained in good yields from the reaction of diorganovinylchlorosilanes R 1R 2Si(Cl)CHCH 2 with Li tBu in non-polar solvents. This synthetic route becomes less attractive as the number of chlorosubstituents at the vinylsilane increases: Thus, tetrachloro-2,4-dineopentyl-1,3-disilacyclobutane ( 2) cannot be prepared from Cl 3SiCHCH 2 ( 1) and Li tBu in a preparative scale. Addition of a twice-molar amount of NEt 3 to the mixture of 1/Li tBu results in the formation of this basic disilacyclobutane as the sole reaction product in nearly quantitative yield. Evidently the bis-donor stabilized neopentylsilene (Et 3N) 2 · Cl 2SiCHCH 2 tBu (δ), whose reactivity is comparable to that of diorganoneopentylsilenes R 2SiCHCH 2 tBu (R = Me,Ph), is responsible for this clean reaction. These experimental findings are in good agreement with the cycloaddition behaviour of δ. Careful refunctionalization of the tetrakis[bis(diethylamino)]substituted disilacyclobutane 6 with gaseous HCl at low temperature is an alternative route to 2, which can be transformed into the H-, F- and organo-substituted derivatives by substitution reactions. However, the preparation of disilacyclobutanes of the type R 1R 1 SiCH(CH 2 tBu)SiR 2R 2C H-(CH 2 tBu) by selective replacement of the chloroatoms failed. These compounds can be obtained from the reaction of the corresponding vinylchlorosilanes with Li tBu in the presence of NEt 3 at the Lewis base in good yields.