Mechanistic features of isomerizing alkoxycarbonylation of methyl oleate
Type
ArticleAuthors
Roesle, PhilippDürr, Christoph J.
Möller, Heiko Maa
Cavallo, Luigi

Caporaso, Lucia

Mecking, Stefan
KAUST Department
Biological and Environmental Sciences and Engineering (BESE) DivisionChemical Science Program
KAUST Catalysis Center (KCC)
Physical Science and Engineering (PSE) Division
Date
2012-10-16Online Publication Date
2012-10-16Print Publication Date
2012-10-24Permanent link to this record
http://hdl.handle.net/10754/562374
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Show full item recordAbstract
The weakly coordinated triflate complex [(P̂P)Pd(OTf)] +(OTf)- (1) (P̂P = 1,3-bis(di-tert- butylphosphino)propane) is a suitable reactive precursor for mechanistic studies of the isomerizing alkoxcarbonylation of methyl oleate. Addition of CH 3OH or CD3OD to 1 forms the hydride species [(P ̂P)PdH(CH3OH)]+(OTf)- (2-CH3OH) or the deuteride [(P̂P)PdD(CD 3OD)]+(OTf)- (2D-CD3OD), respectively. Further reaction with pyridine cleanly affords the stable and isolable hydride [(P̂P)PdH(pyridine)]+(OTf) - (2-pyr). This complex yields the hydride fragment free of methanol by abstraction of pyridine with BF3OEt2, and thus provides an entry to mechanistic observations including intermediates reactive toward methanol. Exposure of methyl oleate (100 equiv) to 2D-CD 3OD resulted in rapid isomerization to the thermodynamic isomer distribution, 94.3% of internal olefins, 5.5% of α,β-unsaturated ester and <0.2% of terminal olefin. Reaction of 2-pyr/BF3OEt 2 with a stoichiometric amount of 1-13C-labeled 1-octene at -80 °C yields a 50:50 mixture of the linear alkyls [(P ̂P)Pd13CH2(CH2) 6CH3]+ and [(P̂P)PdCH 2(CH2)6 13CH3] + (4a and 4b). Further reaction with 13CO yields the linear acyls [(P̂P)Pd13C(=O)12/13CH 2(CH2)6 12/13CH3(L)] + (5-L; L = solvent or 13CO). Reaction of 2-pyr/BF 3·OEt2 with a stoichiometric amount of methyl oleate at -80 °C also resulted in fast isomerization to form a linear alkyl species [(P̂P)PdCH2(CH2) 16C(=O)OCH3]+ (6) and a branched alkyl stabilized by coordination of the ester carbonyl group as a four membered chelate [(P̂P)PdCH{(CH2)15CH 3}C(=O)OCH3]+ (7). Addition of carbon monoxide (2.5 equiv) at -80 °C resulted in insertion to form the linear acyl carbonyl [(P̂P)PdC(=O)(CH2)17C(=O)OCH 3(CO)]+ (8-CO) and the five-membered chelate [(P ̂P)PdC(=O)CH{(CH2)15CH3}C(=O) OCH3]+ (9). Exposure of 8-CO and 9 to 13CO at -50 °C results in gradual incorporation of the 13C label. Reversibility of 7 + CO ⇄ 9 is also evidenced by ΔG = -2.9 kcal mol-1 and ΔG† = 12.5 kcal mol-1 from DFT studies. Addition of methanol at -80 °C results in methanolysis of 8-L (L = solvent) to form the linear diester, 1,19-dimethylnonadecandioate, whereas 9 does not react and no branched diester is observed. DFT yields a barrier for methanolysis of ΔG† = 29.7 kcal mol -1 for the linear (8) vs ΔG† = 37.7 kcal mol-1 for the branched species (9). © 2012 American Chemical Society.Citation
Roesle, P., Dürr, C. J., Möller, H. M., Cavallo, L., Caporaso, L., & Mecking, S. (2012). Mechanistic Features of Isomerizing Alkoxycarbonylation of Methyl Oleate. Journal of the American Chemical Society, 134(42), 17696–17703. doi:10.1021/ja307411pSponsors
P.R. gratefully acknowledges support from the Carl-Zeiss-Foundation by a graduate fellowship. S.M. is indebted to the Fonds der Chemischen Industrie.Publisher
American Chemical Society (ACS)PubMed ID
23072478Relations
Is Supplemented By:- [Dataset]
Roesle, P., Durr, C. J., Moller, H. M., Cavallo, L., Caporaso, L., & Mecking, S. (2013). CCDC 893845: Experimental Crystal Structure Determination [Data set]. Cambridge Crystallographic Data Centre. https://doi.org/10.5517/ccz03qs. DOI: 10.5517/ccz03qs HANDLE: 10754/624731
ae974a485f413a2113503eed53cd6c53
10.1021/ja307411p
Scopus Count
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