synthesizing the target molecules. The perfect chemoselectivity between aromatic and aliphatic aldehydes is difficult to achieve by the previous methods. The aromatic aldehyde-selective nucleophilic addition in the presence of aliphatic aldehydes was newly accomplished. Namely, the aromatic aldehyde-selective nucleophilic addition using arenes and allyl silanes proceeded in the presence of trialkylsilyl
porphyrin-catalyzed allylation of aldehydes with allyltrimethylsilanes is developed. The formation of the aldehyde–cobalt porphyrin complex, the key intermediate for the addition of allylsilanes, is confirmed by theoretical studies and synchrotron-based X-ray absorption fine-structure measurements. Facile dissociation of the product by allylation from the cobalt complex regenerates the active complex with
Chlorotrimethylsilane combined with acetonitrile has characteristically promoted allylation of carbonyl compounds by diallyldibutyltin to produce a variety of homoallyl silyl ether in good yields, while the addition of HMPA or LiCl disturbed the allylation.
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.
Mesoporous aluminosilicate-catalyzed allylation of aldehydes with allylsilanes
Mesoporous aluminosilicate (Al-MCM-41) was found to catalyze the allylation of both aromatic and aliphatic aldehydes with allylsilanes although amorphous silica-alumina or mesoporous silicates (MCM-41, SBA-15) Could not catalyze the reaction under the same reaction conditions. The solid acid catalyst Al-MCM-41 could be reused three times without significant loss of activity. (C) 2009 Elsevier Ltd. All rights reserved.