Palladium-catalyzed Cross-coupling Reaction Of Organoaluminum Reagents And Propargyl Ester Or Alkynyl Bromides

Allenes and 1,2-disubstituted acetylenes derivatives are widely found in natural products and bioactive compounds.They also have important application value in the fields of materials science and biopharmaceutical.Therefore,the synthesis of allenes and 1,2-disubstituted acetylenes compounds has become a hot field of organic synthetic chemistry,and has attracted a great amount of attention.On the basis of previous research work,this dissertation efforts were focuses on the synthesis of allenes and 1,2-disubstituted acetylenes compounds by the cross-coupling reaction of organoaluminium reagents and propargyl acetates or alkynyl bromide catalyzed by metal palladium.This thesis mainly consists of the following two parts:Part Ⅰ:S_N2’substitution reactions between organoaluminum reagent and propargyl acetates catalyzed by palladium was study.Effects of catalysts,ligands,solvents,lading of catalyst,the amounts and type of organoaluminum reagents,ratios of ligand to metal,reaction temperature and reaction times were studied.The results showed that the S_N2’substitution reaction of organoaluminum（0.4 mmol）with propargyl acetates（0.5 mmol）mediated by PdCl₂（dppf）（1 mol%）at 60^oC in THF without ligand could produce multi-substituted allenes in moderate to good yields（up to 98%）and high selectivities（up to 99%）.Part Ⅱ:A Highly efficient route for the synthesis of 1,2-disubstituted acetylene derivatives cross-couplings of alkynyl halides with（hetero）aryl aluminium reagents under mild conditions by palladium catalyzed was developed.Several factors affecting the reaction were discussed,and the results showed the cross-coupling of organoaluminum（0.8 mmol）with alkynyl halides（0.5 mmol）mediated by 1 mol%Pd（PPh₃）₄/2 mol%DPPE in THF could give corresponding cross-coupling products with good to excellent isolated yields（up to 99%）.The aryls bearing electron-donating or electron-withdrawing groups in either arylalkynylhalides or arylaluminum substrates gave cross-coupling products good yields.This process was simple and easily performed,which provides an efficient method for the synthesis of 1,2-disubstituted acetylenes derivatives.On the basis of the experimental results,a possible catalytic cycle has been proposed.The structures of all products were confirmed by HRMS and ¹H(¹³C)NMR data.