Premium
Solvent/Base Effects in the Selective Domino Synthesis of Phenanthridinones That Involves High‐Valent Palladium Species: Experimental and Theoretical Studies
Author(s) -
Donati Ludovic,
Leproux Pascale,
Prost Elise,
Michel Sylvie,
Tillequin François,
Gandon Vincent,
Porée FrançoisHugues
Publication year - 2011
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.201101354
Subject(s) - chemistry , palladium , catalysis , domino , solvent , dissociation (chemistry) , cascade reaction , catalytic cycle , selectivity , oxidative addition , combinatorial chemistry , solvent effects , medicinal chemistry , photochemistry , computational chemistry , organic chemistry
Abstract The domino reaction of o ‐bromobenzamides 1 a – m in the presence of K 2 CO 3 and the [PdCl 2 (PPh 3 ) 2 ] catalyst granted a selective access to phenanthridinones 2 or to the new 1‐carboxamide phenanthridinones 3 depending on the solvent, DMF or 1,4‐dioxane, respectively. Investigations of the reaction parameters provided the first example of a direct correlation between the base dissociation and the solvent polarity on the selectivity observed. Moreover, mechanistic studies (NMR spectroscopy and ESI‐MS monitoring) allowed us to characterize Pd II palladacycle 4 and biaryl species as common intermediates for these two domino processes. On that basis, C(sp 2 )C(sp 2 ) bond formation is envisaged by generation of a Pd IV complex after oxidative addition of 1 into Pd II palladacycle 4 , a rationale that is supported by DFT calculations. A general catalytic cycle is proposed to account for these observations.