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Aldehyde‐Assisted Hydrogen Transfer during the Formation of Hydride–Iridafurans from Alkynes and Aldehydes
Author(s) -
Posadas Cristina M.,
Rendón Nuria,
LópezSerrano Joaquín,
Hernández Yohar A.,
Álvarez Eleuterio,
Paneque Margarita,
Poveda Manuel L.
Publication year - 2013
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.201202794
Subject(s) - chemistry , medicinal chemistry , hydride , metallacycle , aldehyde , aryl , ligand (biochemistry) , dimethyl acetylenedicarboxylate , alkyl , alkoxide , ethylene , reagent , trigonal bipyramidal molecular geometry , stereochemistry , hydrogen , organic chemistry , molecule , x ray crystallography , catalysis , biochemistry , physics , receptor , diffraction , cycloaddition , optics
The bis(ethylene) Ir I complex [Tp Me 2Ir(C 2 H 4 ) 2 ] ( 1 ; Tp Me 2=hydrotris(3,5‐dimethylpyrazolyl)borate) reacts with two equivalents of aromatic or aliphatic aldehydes in the presence of one equivalent of dimethyl acetylenedicarboxylate (DMAD) with ultimate formation of hydride iridafurans of the formula [Tp Me 2I r(H){C(R 1 )C(R 2 )C(R 3 )O }] (R 1 =R 2 =CO 2 Me; R 3 =alkyl, aryl; 3 ). Several intermediates have been observed in the course of the reaction. It is proposed that the key step of metallacycle formation is a CC coupling process in the undetected Ir I species [Tp Me 2Ir{η 1 ‐ O ‐R 3 C(O)H}(DMAD)] ( A ) to give the trigonal‐bipyramidal 16 e − Ir III intermediates [Tp Me 2I r{C(CO 2 Me)C(CO 2 Me)C(R 3 )(H)O }] ( C ), which have been trapped by NCMe to afford the adducts 11 (R 3 =Ar). If a second aldehyde acts as the trapping reagent for these species, this ligand acts as a shuttle in transfering a hydrogen atom from the γ‐ to the α‐carbon atom of the iridacycle through the formation of an alkoxide group. Methyl propiolate (MP) can be used instead of DMAD to regioselectively afford the related iridafurans. These reactions have also been studied by DFT calculations.