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A Planar‐Chiral Phosphino(alkenyl)ferrocene for Suzuki–Miyaura C–C Coupling Reactions
Author(s) -
Schaarschmidt Dieter,
Grumbt Martin,
Hildebrandt Alexander,
Lang Heinrich
Publication year - 2014
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201402861
Subject(s) - chemistry , transmetalation , steric effects , palladium , catalysis , ferrocene , phosphine , stereoselectivity , aryl , halide , aryl halide , medicinal chemistry , homogeneous catalysis , combinatorial chemistry , organic chemistry , alkyl , electrode , electrochemistry
Abstract Planar‐chiral phosphinoferrocene [Fe(η 5 ‐C 5 H 3 ‐1‐PPh 2 ‐2‐( E )‐CH=CHPh)(η 5 ‐C 5 H 5 )] ( 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 °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.