Three-component reactions of aromatic aldehydes and two different nucleophiles and their leaving ability-determined downstream conversions of the products

Many three-component reactions of aro- matic aldehydes with activated methylene derivatives and an associated nucleophile have been developed by using l-proline as the catalyst. Nucleophiles, such as indoles, thiophenols, mercaptans, 2-methylfuran and benzenesulfinic acid, could be successfully used in the reactions while the activated methylene deriv- atives can be 1,3-cyclohexanedione, dimedone, 1,3- cyclopentanedione, 1-phenyl-3-methyl-5-pyrazolone, 4-hydroxycoumarin, 4,6-dihydroxy-2-mercaptopyri- midine, 4-hydroxy-1-methyl-2quinolone, 4-hydroxy- 6-methyl-2-pyrone and 2-hydroxy-1,4-naphthoqui- none. Investigation of the downstream utilization of the products from the above multicomponent reac- tions (MCRs) revealed that selective cleavages of carbon-carbon and carbon-heteroatom bonds in these molecules are indeed possible, which opens an avenue to access some new SN1-type reactions. Par- ticularly, when the MCR product of an aromatic al- dehyde, dimedone and thiophenol was treated with an acid catalyst in the presence of an appropriate nu- cleophile, cleavage of the carbon-sulfur bond oc- curred preferentially, thus providing many complex molecules that cannot be attained by other known methods.