Selective carbon-carbon bond formation based on organosilicon reagents: Origin and application

Abstract

Several new observations on the selective carbon-carbon bond forming reactions are described. Iodotrimethylsilane and trimethylsilyl triflate activate selectively the C-Cl bond rather than the C-0 bond of α-chloro ethers and catalyze the allylation with allylsilanes to give the corresponding homoallyl ethers effectively in good yield. This reaction was successfully applied to the preparation of C-allylated sugars. Thus methyl α-D-glucopyranoside, methyl α-D-mannopyranoside and, in particular, the corresponding α-D-glycopyranosyl chlorides readily undergo allylation with allylsilanes in a highly stereoselective mode. The electronic effects on the diastereoselection in the reaction of allylsilanes with benzaldehyde acetals are then described. Cycloaddition reactions of 1-alkoxy- 3-trimethylsilyl-l,3-butadienes with various dienophiles including heterodienophiles were found to proceed very smoothly in a perfectly regiospecific mode. N-(Trimethylsilylmeth-yl)aminomethyl ethers, readily prepared from (trimethylsilylmethyl)-amines, formaldehyde and an alcohol, react with electron deficient alkenes in the presence of iodosilane or silyl triflate in combination with cesium fluoride to give the corresponding pyrrolidine derivatives stereospecifically in excellent yield. 2-Dimethylaminomethyl-3-trimeth-ylsilylmethyl-l,3-butadiene reacts with a variety of dienophiles involving heterodienophiles to give cycloadducts which are converted readily to 1,2-dimethylenecyclohexanes after successive treatments with methyl iodide and cesium fluoride in acetonitrile. © 1985 IUPAC