Modular Synthesis of a New Class of Bis(amino-oxazoline) Using Palladium-Catalyzed Buchwald−Hartwig Amination Methodology

Abstract

The palladium-catalyzed Buchwald−Hartwig aryl amination between 2,2‘-diaminobiphenyl and 2 equiv of 2-(2‘-bromophenyl)oxazoline has been used to prepare a new class of tetradentate bis(amino-oxazoline). The reaction between 2,2‘-diaminobiphenyl and 1 equiv of 2-(2‘-bromophenyl)oxazoline is highly selective for monoarylation, and the resulting products have been reacted in a second arylation to afford unsymmetrically substituted bis(amino-oxazolines). These new diamido/donors belong to the tropos class of ligand and exist as an equilibrium mixture of S,aS,S- and S,aR,S-diastereoisomers, which interconvert by rotation about the biaryl axis. Variable-temperature 1H NMR studies and line-shape analysis of simulated spectra gave ΔH ⧧ and ΔS ⧧ values of 51.5−57 kJ mol-1 and −25.9 to −57.0 J mol-1 K-1, respectively, for diastereointerconversion. Interestingly, reaction of one of the symmetrical bis(amino-oxazoline) with [Cu(MeCN)4][PF6] results in dynamic resolution to afford diastereopure (S,aS,S)-[Cu(L)][PF6], which has a highly unusual sawhorse geometry at copper with the two oxazolines occupying trans coordination sites and two weak interactions to the nitrogen atoms of the secondary amino groups. 1H and 13C NMR spectra of this copper complex are entirely consistent with a single C 2-symmetric diastereoisomer in solution that shows no sign of diastereointerconversion even after standing for one week.

Development of bis(arylimino)acenaphthene (BIAN) copper complexes as visible light harvesters for potential photovoltaic applications

“…[64][65][66][67][68][69] Out of these instances, one consists of a distorted octahedral Cu(I), 68 two possess trigonal monopyramidal Cu centers with long axial bonds, 65,67 while the remaining two have been described as distorted square planar or sawhorse geometries. 64,66 In particular, the bis(amino-oxazoline) Cu(I) complex reported by Doherty et al has exceptionally long Cu-N bonds of 2.640(5) and 2.838(5) Å, which have been aptly considered as weak interactions between the Cu and aniline ligands. 66 Since the sum of the van der Waals radii of Cu(I) and N is 2.90 Å, 4 joins a class of rare Cu(I) complexes containing weak Cu-N interactions.…”

“…64,66 In particular, the bis(amino-oxazoline) Cu(I) complex reported by Doherty et al has exceptionally long Cu-N bonds of 2.640(5) and 2.838(5) Å, which have been aptly considered as weak interactions between the Cu and aniline ligands. 66 Since the sum of the van der Waals radii of Cu(I) and N is 2.90 Å, 4 joins a class of rare Cu(I) complexes containing weak Cu-N interactions. 66 The pendant o-iodoaryl rings appear to be almost perpendicular to the acenaphthene ring, and the dihedral angles among the two contiguous aryl rings varied between 71.2(3) and 89.7(4)°.…”

“…66 Since the sum of the van der Waals radii of Cu(I) and N is 2.90 Å, 4 joins a class of rare Cu(I) complexes containing weak Cu-N interactions. 66 The pendant o-iodoaryl rings appear to be almost perpendicular to the acenaphthene ring, and the dihedral angles among the two contiguous aryl rings varied between 71.2(3) and 89.7(4)°. This is unlike most of the known homoleptic Cu(I) Ar-BIAN complexes.…”

Density Functional Theoretical Study on the Mechanism of Alcoholysis of Acylpalladium(II) Complexes

“…The other mechanism commences with reversible formation of intermediate I1 followed by inner-sphere attack of the alkoxide ligand (OCH 3 ) at the carbon atom of the palladium-bound carbonyl group (reductive elimination via a Meisenheimer intermediate I2 or insertion pathway) [17][18][19][20]. The Suzuki [21][22][23][24][25][26], Heck [27][28][29][30][31][32], Stille [33][34][35][36] and Buchwald-Hartwig [20,[37][38][39] couplings are modern methods in organic synthesis. The award of the 2010 Nobel Prize was due to the very high importance of such methods.…”

Synthesis, Structural Studies, and Catalytic Application of Palladium Complexes Containing Anilido‐Oxazolinate Ligands

“…Anilido‐oxazolinates ( V ), which originate from IV through the replacement of the imine group with the isoelectronic oxazolinate group, have received less attention 5. Metal complexes bearing I – V as ancillary ligands have been studied and have demonstrated excellent catalytic activities in hydrogenation,1c hydrosilylation,1d hydroamination,1e cyclization,1f oxidation,2l,4b cross‐coupling,2f,5c–5e cycloalkene oxide/CO 2 copolymerization,1g,4c,5a olefin polymerization, [1h–1l,3e,4d–4i] and ring‐opening polymerization of cyclic esters. [1m–1o,4j–4m,5g–5i] Recently, some palladium complexes bearing I , [1j,1k,1u–1z] II ,2a–2g III ,3b,3c IV ,4a,4g and V 5c–5f have been synthesized and fully characterized.…”