Studies On The Palladium Catalyzed Cross Coupling Reactions With Sterically Bulky And Electron-rich Phosphines

The development of sterically bulky and electron-rich phosphine ligands has advanced the activation of inert C-Cl bonds greatly. Our group designed and synthesized a new type of dialkylphenyl monodentated phosphines. Some applications of these ligands on the activation of inert C-Cl activation reaction had been conducted by Dr. Lu. In my dissertation more applications of these ligands on the Pd-catalyzed cross-coupling reaction including the activation reaction of inert C-Cl bond will be presented. Besides, the synthesis of 3,4-bisalkylidenecyclobutenes from propargylic carbonates and allenylic boronates under Pd-catalysis will also be discussed.The whole dissertation can be divided into the following three parts:Part Ⅰ:Pd-catalyzed Suzuki coupling reaction of optically chloroalkylidene-β-lactones with LB-Phos as the ligandBy utilizing 2,4,6-trimethoxyphenyl dicyclohexylphophine (LB-Phos) developed in our group, a Pd-catalysed Suzuki coupling reaction of optically active (S,Z)-α-choroalkylidene-β-lactones has been conducted. Aryl and vinyl boronic acids may be coupled with optically active β-lactones affording corresponding optically active products highly selectively and efficiently. For the alkyl boronic acid, a mixture of toluene and water by 10:1 in volume as solvent is necessary. When the pre-prepared complex PdCl2(LB-Phos)2 was used, the coupling reaction of the heteroarmoamtic boronic acids also proceeded smoothly.Part II:Pd-catalyzed borylation reaction of aryl chlorides and cross-coupling of aryl chlorides with B2pin2.2.1 By utilizing 2,6-diisopropoxyphenyl dicyclohexylphophine (Gorlos-Phos) as the ligand, a Pd-catalyzed borylation reaction of aryl chlorides and heteroaryl chlorides with B2pin2 was presented. This catalyst system was efficient and compatible with sensitive functional groups such as -OH,-CO2H,-CHO,-NH2 and-CONH2. When bis(neophentyl glycolato)diboron was used instead of bis(pinacolato)diboron, highly sterically hindered substrate 2-chloro-m-xylene could be transformed into the corresponding borate. Finally, we demonstrated a 10 g-scale borylation reaction catalyzed by 0.1 mol% Pd (Pd/L= 1:4) within 40.0 hours.2.2 By utilizing Pd(OAc)2/Gorlos-Phos as the catalyst, we developed the direct cross-coupling reaction of aryl chlorides in presence of B2pin2 affording symmetrical and unsymmetrical biaryls efficiently. Respectable selectivity of unsymmetrical biaryl has been achieved by applying the electronic effect. Sensitive functional groups such as -CHO,-COMe and -CO2 Me are well compatiblePart Ⅲ:Pd-catalysed Suzuki coupling and cyclization reaction of propargyl carbonates with allenyl boronates3.1 We found that specific 3,4-bisalkylidene-cyclobutenes could be prepared in one pot by Pd(OAc)2/Gorlos-Phos-catalyzed homo-coupling reaction of propargylic carbonates in presence of B2pin2. It is found that ligand, solvent and the amount of H2O are all crucial for the selectivity of the reaction.3.2 A Pd/Gorlos-Phos-catalyzed tandem reaction including Suzuki coupling reaction of propargylic carbonates with allenylic boronates and electrocyclization affording unsymmetric 3,4-bisalkylidene-cyclobutene was developed.