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ortho ‐(Dimesitylboryl)phenylphosphines: Positive Boryl Effect in the Palladium‐Catalyzed Suzuki–Miyaura Coupling of 2‐Chloropyridines
Author(s) -
Malacea Raluca,
Chahdoura Faouzi,
Devillard Marc,
Saffon Nathalie,
Gómez Montserrat,
Bourissou Didier
Publication year - 2013
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.201201100
Subject(s) - chemistry , phosphine , palladium , moiety , borane , catalysis , regioselectivity , frustrated lewis pair , medicinal chemistry , lewis acids and bases , stereochemistry , combinatorial chemistry , organic chemistry
Catalytic systems combining ortho ‐(dimesitylboryl)phenylphosphines and palladium precursors have been evaluated in the Suzuki–Miyaura couplings of chloro‐N‐heterocycles, in particular 2‐chloropyridines, with arylboronic acids. The Lewis basic character of the substrates does not interfere with the Lewis acidic site of the ligands, even for a substrate featuring free NH 2 groups. The influence of several reaction parameters has been studied and the ortho ‐dimesitylboryl moiety was actually found to substantially enhance the catalytic performance. The role of this group has been examined using preformed phosphine‐borane/Pd complexes and the formation of an original phosphine/η 4 ‐boratabutadiene complex has been identified as a possible deactivation pathway. Regioselective coupling of 2,6‐dichloro‐3‐nitropyridine with phosphine‐borane/Pd catalysts has also been explored, and sequential double cross‐couplings were found to give a direct and efficient access to unsymmetrical 2,6‐diarylpyridines.