A HIGH YIELDING, REPRODUCIBLE SYNTHESIS OF TRIMETHYLSILYLKETENE
ABSTRACT A two-step sequence for the preparation of trimethylsilylketene, from chloroacetaldehyde diethyl acetal via ethoxyacetylene, has been modified and optimized.
Reaction of Silylketenes with Carbanions : Simple Preparation of α-Silylketones Using Organocerium Reagents
Preparation of α-silylketones 1 by the reaction of three kinds of silylketenes 3a-c with various organometallic reagents 4 was studied. Although the use of n-BuLi, MeMgBr, Me2CuLi, Et3Al, and Et2Zn resulted in complicated reactions, organocerium reagents 4 (M=CeCl2) added selectively to the carbonyl carbon of 3 to generate enolate anions A, which were treated with aqueous NH4Cl or alkyl halides 5 to give 1. Seventeen α-silylketones 1a-q were prepared in 31-99% yields from three components, 3, alkyl- or arylcerium reagents 4, and proton or alkyl halides 5. This method was applied to a regiocontrolled preparation of two isomeric α-silylketones 1r, s.
The synthesis and some structural features of 2-Methyl-1,3-cyclobutanedione
The synthesis of 2-methyl-1,3-cyclobutanedione and its chemical transformations are reported. Physical data suggest that it exists in solution and the solid state as the enol. The characteristic acid strength can be accounted for by the carbonyl dipole interaction with the acid-base centre. Homoallylic coupling is shown to occur in the N.M.R. spectrum and is suggested to be general for similar systems.