Mesoporous aluminosilicate-catalyzed allylation of carbonyl compounds and acetals
摘要:
A mesoporous aluminosilicate (Al-MCM-41) was found to be an effective heterogeneous catalyst for the reaction of both carbonyl compounds and acetals with allylsilanes to afford the corresponding homoallyl silyl ethers and homoallyl alkyl ethers, respectively. Both the mesoporous structure and the presence of aluminum moiety were indispensable for the high catalytic activity of Al-MCM-41. Moreover, Al-MCM-41 could catalyze the reaction of acetals chemoselectively in the presence of the corresponding carbonyl compounds. The solid acid catalyst Al-MCM-41 could be recovered easily by filtration and could be reused three times without a significant loss of catalytic activity. (C) 2011 Elsevier Ltd. All rights reserved.
A catalytic amount of tris(p-bromophenyl)aminium hexachloroantimonate promoted the substitution reactions of dimethylacetals with various silylatednucleophiles through an electron transfer mechanism. Silyl compounds include silyl enol ether, ketene silyl acetal, and allylsilane. One methoxy group of the substrates was effectively substituted by nucleophiles to form carbon-carbon bonds.
In the presence of a catalytic amount of trityl perchlorate or diphenylboryl triflate, acetals react smoothly with allyltrimethylsilanes to give the corresponding homoallyl ethers in good yields with good regio- and stereoselectivities.
Catalytic amounts of triarylpyrylium saltsphotochemically and thermally promoted the substitution reactions of dimethyl acetals with silylated nucleophiles.