Synthesis and characterization of bis-cyclopropanated 1,3,5-tricarbonyl compounds. A combined synthetic, spectroscopic and theoretical study.

Bis-cyclopropanated 1,3,5-tricarbonyl compounds were prepared by a sequence of Claisen condensations and cyclopropanations. The optimization of the conditions proved to be very important to suppress retro-Claisen reactions. The conformation of these molecules was studied by experimental and computational methods. The syn/syn;syn/syn conformation is present for all derivatives. It is exclusively present in the case of the derivative containing a phenyl group located at the terminal carbon atom. In most cases, equilibria with other conformers are found.

2,2-Dichloro-1,3-bis(trimethylsilyl)-1,3-diaza-2-silacyclopentane.

In the title compound, C(8)H(22)Cl(2)N(2)Si(3), the central Si atom is tetrahedrally coordinated by two Cl and two N atoms in a molecule that has crystallographically imposed C(2) symmetry. Comparison is made with the isomorphous structure having titanium instead of silicon at the central position in the diazacyclopentane ring [Tinkler, Deeth, Duncalf & McCamley (1996). Chem. Commun. pp. 2623-2624].