Palladium-catalyzed Allylic Amination Via Carbon-carbon Bond Cleavage And Chiral-at-metal Complex Catalyzed Asymmetric Cyclopropanation

In this dissertation transition-metal-catalyzed allylic amination of homoallylic alcohols via selective cleavage of carbon-carbon bond and catalytic asymmetric cyclopropanation of ?,?-unsaturated carbonyl compounds with bromomalonates in presence of chiral-at-metal complex were developed.Section I:This section disclosed a palladium(II)-catalyzed transformation involving selective C-C bond cleavage of tertiary homoallylic alcohols and sequential amination with amines as nucleophiles in the presence of stoichiometric amount of water as additive.By investigation of the catalysts,ligands,bases and solvents,the corresponding allylic amines were obtained in good to excellent yield(up to 98%).The mechanistic studies demonstrated that the hydroxyl group of the homoallyl alcohol would serve as a directing group to coordinate witth Pd(?),and the subsequent retro-allylation via a six-membered cyclic transition state would generate the desired?-allyl Pd intermediate.With a proper phosphine ligand,nucleophilic substitution reaction of ?-allyl Pd intermediate with a variety of amines would generate the corresponding products.Substrate investigation demonstrated that various functionalities were tolerated in our optimal reaction conditions.Aromatic amines with either electron-donating or electron-withdrawing groups on the aromatic rings delivered the corresponding products in good to excellent yields,while primary amines exhibited no reactivity in optimal reaction conditions.Section II:This section describes an unprecedented catalytic asymmetric cascade transformation including Michael-addition/intramolecular nucleophilic substitution reaction of ?,?-unsaturated carbonyl compound with bromomalonates by using chiral-at-rhodium(?)-complex as catalyst.After optimization of the reaction conditions on catalysts,bases,solvents and temperature,the corresponding cyclopropane derivatives were obtained with excellent enantioselectivity(up to 99%ee)and diastereoselectivity(dr>50:1).It is worthy to note that:(1)In the presence of chiral-at-iridium(?)complex as catalyst,the reaction did not occur which,demonstrates the vital role of the rhodium metal;(2)The reactivity and enantioselectivity are highly dependent on the solvents used.The relatively low reaction rates and enantioselectivity were achieved by using non-polar solvents such as toluene;(3)?,?-unsaturated acyl compounds with aryl substitution at the ?-positionwere well tolerated under the optimized reaction conditions to afford desired products in excellent yields.However,substrates with alkyl substitution showed relatively low reactivity to the reaction.