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Tandem β‐Boration/Arylation of α,β‐Unsaturated Carbonyl Compounds by Using a Single Palladium Complex To Catalyse Both Steps
Author(s) -
Bonet Amadeu,
Gulyás Henrik,
Koshevoy Igor O.,
Estevan Francisco,
Sanaú Mercedes,
Úbeda M. Angeles,
Fernández Elena
Publication year - 2010
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200903095
Subject(s) - chemistry , medicinal chemistry , carboxylate , palladium , ligand (biochemistry) , acetonitrile , moiety , phosphine , toluene , aryl , coupling reaction , catalysis , stereochemistry , organic chemistry , alkyl , biochemistry , receptor
Diphenyl(3‐methyl‐2‐indolyl)phosphine (C 9 H 8 NPPh 2 , 1 ) gives stable dimeric palladium(II) complexes that contain the phosphine in P,N‐bridging coordination mode. On treating 1 with [Pd(O 2 CCH 3 ) 2 ], the new complexes [Pd(μ‐C 9 H 7 NPPh 2 )(NCCH 3 )] 2 ( 2 ) or [Pd(μ‐C 9 H 7 NPPh 2 )(μ‐O 2 CCH 3 )] 2 ( 3 ) were isolated, depending on the solvent used, acetonitrile or toluene, respectively. Further reaction of 3 with the ammonium salt of 1 led to the substitution of one carboxylate ligand to afford [Pd(μ‐C 9 H 7 NPPh 2 ) 3 (μ‐O 2 CCH 3 )] ( 4 ), in which the bimetallic unit is bonded by three C 9 H 7 NPPh 2 − moieties and one carboxylate group. Using this methodology, [Pd 2 (μ‐C 6 H 4 PPh 2 ) 2 (μ‐C 9 H 7 NPPh 2 )(μ‐O 2 CCX 3 )] (X=H ( 7 ); X=F ( 8 )) were synthesised from the ortho ‐metalated compounds [Pd(C 6 H 4 PPh 2 )(μ‐O 2 CCX 3 )] 2 (X=H ( 5 ); X=F ( 6 )). Complexes 3 , 4 , 7 , and 8 have been found to be active in the catalytic β‐boration of α,β‐unsaturated esters and ketones under mild reaction conditions. Hindrance of the carbonyl moiety has an influence on the reaction rate, but quantitative conversion was achieved in many cases. More remarkably, when aryl bromides were added to the reaction media, complex 7 induced a highly successful consecutive β‐boration/cross‐coupling reaction with dimethyl acrylamide as the substrate (99 % conversion, 89 % isolated yield).