Eine neue Methode zur Darstellung von Silaheterocyclen durch Cycloaddition im System Heterobutadien/HSiCl3/NR3

A New Method for the Generation of Silaheterocycles via 4 + 1]-Cycloaddition Reaction in the System Heterobutadiene/HSiCl₃/NR₃ The reaction of trichlorosilane with tert. amines provides the anion SiCl₃^– (Benkeser type system). This system can be used as a simple accessible SiCl₂ synthon in certain cases. Thus 4 + 1]-cycloadditions of diazabutadienes in the system HSiCl₃/NR₃ lead to silacyclopentene derivatives. The reaction of 1,3-diaza-1,3-dienes with equimolar amounts of DBU and HSiCl₃ in THF gives the 1,4-diazasila-cyclopentene (CF₃)₂C–N=C(Ph)–N(^tBu)–SiCl₂ ( 2 a ) derivative only in one case 6], whereas in other cases hydrosilylation products are obtained. In (CF₃)₂CH–N=C(Ph)–N(^tBu)–SiCl₂F ( 3 a ), which is obtained from ( 2 a ) with wet toluene, the amidinate is bidentate and thus coordinating in a chelating fashion to the five-coordinate silicon atom. 1,4-diaza-1,3-dienes (DAD) give the 4 + 1]-cycloaddition products in all cases. Product distribution and yield are strongly influenced by the substituents, the nature of the solvent and the reaction conditions. All compounds have been characterized by NMR and mass spectroscopy. In five cases, the results of crystal structure determinations by X- ray diffraction are reported.