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Unusual Control of Reaction Selectivity through a Subtle Change in the Ligand: Proof of Concept and Application in Pd‐Catalyzed C–P Bond Formation
Author(s) -
Ananikov Valentine P.,
Ivanova Julia V.,
Khemchyan Levon L.,
Beletskaya Irina P.
Publication year - 2012
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.201200342
Subject(s) - chemistry , catalysis , steric effects , ligand (biochemistry) , catalytic cycle , selectivity , electrospray ionization , combinatorial chemistry , metal , stereochemistry , computational chemistry , mass spectrometry , organic chemistry , chromatography , biochemistry , receptor
A new concept for the design of ligands for transition‐metal‐catalyzed reactions is described. It was shown that the steric effect of triarylphosphanes upon coordination to a metal center can be controlled by switching between unrestricted and restricted rotation modes. The ligands studied were intrinsically tuned to possess characteristic signals in the 1 H, 13 C, 31 P NMR and electrospray ionization mass spectrometry (ESI‐MS), thus allowing mechanistic studies to be easily carried out. The efficiency of the developed method was demonstrated in a study on the mechanistic pathways of Pd‐catalyzed hydrophosphorylation of alkynes. The catalytic cycle was explored step‐by‐step by using ESI‐MS and NMR methods. Several Pd species were detected under catalytic conditions and the nature of the intermediate metal complexes were evaluated. The process responsible for capturing the Pd catalyst in the inactive resting state and the routes leading to catalyst decomposition were identified and described. For the first time, the catalytic reaction mechanism of hydrophosphorylation of alkynes was revealed at a molecular level, which led to the design of a novel practical procedure for Pd‐mediated C–P bond formation. A new Pd/P[(MeO) n C 6 H 5– n ] 3 catalytic system was proposed with the outstanding ability to control reaction selectivity simply by adjusting the methoxy substituents in the phosphane ligand.