Modular Synthesis of a New Class of Bis(amino-oxazoline) Using Palladium-Catalyzed Buchwald-Hartwig Amination Methodology
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- 作者：Simon Doherty ; Julian G. Knight ; Catherine H. Smyth ; Nicholas T. Sore ; Rakesh K. Rath ; William McFarlane ; Ross W. Harrington ; William Clegg
- 刊名：Organometallics
- 出版年：2006
- 出版时间：August 28, 2006
- 年：2006
- 卷：25
- 期：18
- 页码：4341 - 4350
- 全文大小：217K
- 年卷期：v.25,no.18(August 28, 2006)
- ISSN：1520-6041
文摘
The palladium-catalyzed Buchwald-Hartwig aryl amination between 2,2'-diaminobiphenyl and 2 equivof 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 selectivefor monoarylation, and the resulting products have been reacted in a second arylation to affordunsymmetrically substituted bis(amino-oxazolines). These new diamido/donors belong to the tropos classof ligand and exist as an equilibrium mixture of S,aS,S- and S,aR,S-diastereoisomers, which interconvertby rotation about the biaryl axis. Variable-temperature 1H NMR studies and line-shape analysis of simulated spectra gave 
H
and S 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], whichhas a highly unusual sawhorse geometry at copper with the two oxazolines occupying trans coordinationsites and two weak interactions to the nitrogen atoms of the secondary amino groups. 1H and 13C NMRspectra of this copper complex are entirely consistent with a single C2-symmetric diastereoisomer insolution that shows no sign of diastereointerconversion even after standing for one week.
H and S 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], whichhas a highly unusual sawhorse geometry at copper with the two oxazolines occupying trans coordinationsites and two weak interactions to the nitrogen atoms of the secondary amino groups. 1H and 13C NMRspectra of this copper complex are entirely consistent with a single C2-symmetric diastereoisomer insolution that shows no sign of diastereointerconversion even after standing for one week.