15 research outputs found
Stereoselective synthesis of the ABCD ring framework of azaspiracids
A stereoselective synthesis of the ABCD ring framework of azaspiracid-1 and azaspiracid-3 has been achieved using a tandem bis-spiroketalization protocol in the presence of a mild proton source from 1,4-diketone precursor. A tetrahydrofuran intermediate with the correct stereochemistry for the D ring of azaspiracids-1 and 3 was then taken through a linear sequence of reactions to afford the desired diketone precursor. The D-ring of azaspiracid-1 was then constructed by employing a Sharpless asymmetric dihydroxylation followed by etherification using a homoallyl derivative. The structure of the ABCD ring framework with four contiguous rings was established by extensive NMR analysis
Condensation of orthoacetates with aldehydes: a new strategy for the preparation of α,β-unsaturated esters
α,β-Unsaturated esters are formed in good yields when aldehydes are heated with orthoacetates in the presence of a catalytic amount of phenol
Wacker oxidation of terminal olefins in a mixture of [bmim][BF<SUB>4</SUB>] and water
A simple and efficient PdCl<SUB>2</SUB>/CuCl catalyzed oxidation of alkenes has been successfully developed using a mixture of water and the ionic liquid [bmim][BF<SUB>4</SUB>] as solvent. Starting from various types of terminal olefins, the corresponding ketones have been prepared under mild reaction conditions and obtained in good to excellent yields after a simple extraction with diethyl ether. Furthermore, it was possible to recycle and reuse the ionic liquid and the catalytic system
Solid phase synthesis of hydroxy benzothiazepinones through cyclative release under thermolysis
Hydroxy benzothiazepinones were synthesized by a simple procedure involving epoxidation of polymer bound cinnamic acids followed by nucleophilic opening of the resulting glycidic ester by o-aminothiophenol to afford the intermediate hydroxy anilino-esters which underwent cyclization cleavage on heating in DMF to release the product completely
Reaction of orthoesters with alcohols in the presence of acidic catalysts: A study
1686-1692Allylic and benzylic alcohols are converted
into corresponding unsymmetrical ethers when reacted with various orthoesters
in the presence of montmorillonite KSF at ambient temperature. A detailed study
has been undertaken to examine the mechanism and generality of these reactions
with regard to various acidic catalysts, which reveal interesting competitive
reactions mainly O-acetylation,
together with trace amount of dimerized product. The type of the side product
and their relative quantity depends upon the nature of the catalyst employed.
Furthermore, the low yields of the Claisen rearrangement product obtained from
allylic alcohols under heating is rationalized due to the formation of some of
these products