We describe the development of efficient benzannulations of siloxy alkynes with pyridinium and isoquinolinium salts. Such reactions are successfully promoted by a stoichiometric amount of silver(I) benzolate under mild reaction conditions. This process proceeds via a formal inverse-electron demand Diels-Alder reaction, followed by fragmentation of the initially produced bicyclic adducts to deliver a range of synthetically useful phenols and naphthols.
A highly efficient palladium-catalyzed decarbonylative dehydration reaction of carboxylic acids is reported. This method transforms abundant and renewable even-numbered natural fatty acids into valuable and expensive odd-numbered alpha olefins. Additionally, the chemistry displays a high functional group tolerance. The process employs low loading of palladium catalyst and proceeds under solvent-free and relatively mild conditions.
Enantioenriched potassiumβ-trifluoroboratoamides have been synthesizedviaan asymmetric, copper-catalyzed 1,4-addition of tetrahydroxydiboron (BBA) and tetrakis(dimethylamino)diboron toα,β-unsaturated amides. These dibora reagents provide access to the desired organotrifluoroborates using effective and atom economical sources of boron. The copper-catalyzedβ-boration is extended toα,β-unsaturated ketones and esters. Desired potassium organotrifluoroborates are synthesized with yields up to 92% and enantiomeric ratios up to 98:2. The enantioenriched potassiumβ-trifluoroboratoamides are successfully cross-coupled with an array of aryl and heteroaryl chlorides in high yield with complete stereochemical fidelity as the transmetalation proceeds through an SE2 mechanismviaan open transition state.
A concise thiolation of C(sp3)–H bond of cycloalkaneswith diaryl disulfides in the presence of oxidant ofdi-tert-butylperoxide (DTBP) has been developed. This reactionwithout using any of metal catalyst, tolerates varieties of disulfides andcycloalkanes substrates, giving good to excellent chemical yields, whichprovides a useful approach to cycloalkyl aryl sulfides from unactivatedcycloalkanes.
Phosphine-catalyzed 3+2] and 4+3]annulation reactions of C,N-cyclic azomethine imines with allenoates have been developed to give a variety of pharmaceutically attractive tetrahydroisoquinoline derivatives in moderate to excellent yields. The two distinct reaction pathways, 3+2] and 4+3]cyclization, depend on the nature of the nucleophilic phosphine and the allenoate. Generally, for α-alkylallenoates, the reactions always proceed with 3 +2]cyclization as the major pathway no matter what phosphine was used; for α-ArCH2-substituted allenoates, the reaction pathway was controlled by the phosphine catalyst used.
The water-insoluble and water-soluble Nheterocyclic carbene (NHC)–amine palladium complexes, Ipr-Pd(deba)Cl and SO3-Ipr-Pd(deba)Cl, were synthesized. Both catalysts exhibit excellent activity in the phosphine-free double carbonylation of aryl iodides with amines to produce a-keto amides. Moreover, as the water-soluble catalyst exhibits significant compatibility in the aqueous phase with the activities of different Pd-NHC complexes, we conclude that the intramolecular amine ligand strongly affects the selectivity of the products in double carbonylation reaction and serves as an alternative of phosphine ligands.