Project description:Pd(II)-catalyzed Fujiwara-Moritani reactions can be carried out without external acid at room temperature and in water as the only medium. A highly active cationic Pd(II) catalyst, [Pd(MeCN)(4)](BF(4))(2), easily activates aromatic C-H bonds to produce electron-rich cinnamates in good yields.
Project description:Intramolecular Pd-catalyzed alkene carboamination reactions of substituted 2-allyl-N-(2-bromobenzyl)anilines are described. The substrates for these reactions are generated in two steps from readily available 2-allylanilines and 2-bromobenzaldehyde derivatives. The transformations afford substituted tetrahydroindoloisoquinolines, an uncommon class of fused bicyclic heterocycles, in good yield. The mechanism of these transformations is described, and a model that accounts for the observed product stereochemistry is proposed.
Project description:The Pd-catalyzed amination of unprotected benzo-fused heterocycles is reported, which allows for greater flexibility and efficiency in the modification of this important class of molecules. The generality of these simple and efficient procedures is demonstrated through the synthesis of a wide variety of structural types.
Project description:N-heterocyclic carbenes (NHCs) catalyze a domino Michael addition/acylation reaction to form 3,4-dihydrocoumarins. The reaction proceeds through addition of the NHC to an aryloxyaldehyde followed by elimination of a phenoxide leaving group, generating an enol intermediate. This transient nucleophile generated in situ performs a 1,4-addition onto a conjugate acceptor, and the carbene catalyst is regenerated upon acylation of the phenoxide anion resulting in formation of 3,4-dihydrocoumarins.
Project description:Palladium-catalyzed alkene difunctionalization reactions between alkenes bearing tethered aryl or alkenyl triflates and enolate nucleophiles are described. The transformations form two C-C bonds, a ring, and up to two stereocenters, while producing substituted cyclopentane derivatives that contain appended carbonyl functionality. Products are formed with up to >20:1 diastereoselectivity, and formation of sterically congested bonds between quaternary carbon atoms is feasible.
Project description:A new method for the synthesis of 2-aminoimidazole products is described. The heterocyclic products are generated in good yields via Pd-catalyzed carboamination reactions of N-propargyl guanidines and aryl triflates. This methodology generates both a C-N and C-C bond during the annulation step and facilitates the rapid construction of 2-aminoimidazole products with different aryl groups. The utility of this methodology was demonstrated in the total synthesis of preclathridine A, preclathridine B, and dorimidazole B from a single intermediate.
Project description:The stereoselective synthesis of 2,4- and 2,5-disubstituted 1,3-oxazolidines is accomplished via Pd-catalyzed carboamination of O-vinyl-1,2-amino alcohol derivatives. The transformations generate cis-disubstituted products with good to excellent diastereoselectivity, and enantiomerically enriched substrates are converted without loss of optical purity. In addition to yielding synthetically useful products that are difficult to generate with existing methods, these transformations illustrate that electron-rich enol ethers are viable substrates for alkene carboamination processes.
Project description:Pd-catalyzed carboetherifications of 1-, 2-, or 3-substituted γ-hydroxy internal alkenes afford tetrahydrofuran products bearing three stereocenters in good yield with moderate to good stereoselectivity.
Project description:A new method for the construction of 2-substituted and 2,2-disubstituted chromans via Pd-catalyzed carboetherification reactions between aryl/alkenyl halides and 2-(but-3-en-1-yl)phenols is described. These reactions effect formation of a C-O bond and a C-C bond to afford the chroman products in good yield, and also provide stereoselective access to tricyclic chroman derivatives.
Project description:The Pd-catalyzed coupling of malonate nucleophiles with alkenes bearing tethered aryl or alkenyl triflates is described. These alkene difunctionalization reactions afford malonate-substituted cyclopentanes that contain fused aryl or cycloalkenyl rings. The transformations generate a five-membered ring, two C-C bonds, and provide products bearing up to three stereocenters with good chemical yield and generally high diastereoselectivity.