Palladium-catalyzed Dearomatization Reaction Versus Stille Coupling Reaction Of Benzylic Chlorides With Tributylallylstannane

The coupling reaction of organometallic reagents with organic electrophilic reagents(such as aromatic halides, alkyl halides, and acyl chlorides etc.) in the presence of catalytic amount of transition mental proceeded smoothly under mild reaction conditions with high selectivity and excellent yields. In the palladium-catalyzed cross-coupling reaction for the construction of carbon-carbon bonds, using ligands to control the regioselectivity of the reaction has not been reported. A novel ligand-controlled chemoselective palladium-catalyzed coupling reaction of diarylmethyl chlorides with tributylallylstannane was researched in this thesis.In this thesis, we found that, when triphenylphosphine was used as a ligand, the reactions of diarylmethyl chlorides with tributylallylstannane proceeded in the presence of Pd catalyst in acetone at room temperature to give the allylative dearomatization products in high yields, and the Stille-coupling products were not observed. The reactions proceeded under mild reaction conditions with various substrates, with high yields and high selectivity, and which could be applied to synthesis of bioactive compounds. All products were identified by IR, ¹H NMR, ¹³C NMR and HRMS.We also found that, when tricyclohexylphosphine was used as a ligand, the reactions of diarylmethyl chlorides with tributylallylstannane proceeded in the presence of Pd catalyst in acetone at room temperature to give the Stille-coupling products, and the allylative dearomatization products were not observed.In conclusion, the reaction pathways(dearomatization vs Stille coupling) can be controlled by using different ligands to control chemoselectivity of the coupling reaction of diarylmethyl chlorides with tributylallylstannane. When triphenylphosphine was used as a ligand, the allylative dearomatization of diarylmethyl chlorides occurred, exclusively; whereas the employ of tricyclohexylphosphine as a ligand instead of triphenylphosphine, only offered Stille coupling products of diarylmethyl chlorides.