A Planar-Chiral Phosphino(alkenyl) ferrocene for Suzuki-Miyaura C-C Coupling Reactions

作者：Schaarschmidt Dieter; Grumbt Martin; Hildebrandt Alexander; Lang Heinrich^*

来源：European Journal of Organic Chemistry, 2014, 2014(30): 6676-6685.

DOI：10.1002/ejoc.201402861

• Sandwich complexes
• Homogeneous catalysis
• Asymmetric catalysis
• C-C Coupling
• Palladium

Planar-chiral phosphinoferrocene [Fe((5)-C5H3-1-PPh2-2-(E)-CH=CHPh)((5)-C5H5)] (4) was applied in the presence of palladium in Suzuki-Miyaura couplings for the synthesis of sterically congested biaryls. The catalytic activity arises from homogeneous palladium phosphine complexes, of which the potential pre-catalyst [Pd(4)(2)Cl-2] was characterized structurally. The catalytic system is excellently suited for the synthesis of tri-ortho-substituted biaryls under mild conditions (0.1 mol-%, 50-100 degrees C), whereas its application towards the synthesis of tetra-ortho-substituted biaryls is quite limited. Comparing the performance of the reaction with 4 as catalyst and a range of substrates with differing ortho substituents suggests that transmetalation is rate determining. Complex (S-p)-4 was used in atropselective couplings, wherein enantioenrichments of up to 36% were achieved. The stereoselectivity depends to some extent on the steric properties of the boronic acids; however, slight changes at the aryl halides influence the enantioselectivity.

• 出版日期2014-10