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Volume 5, Issue 3 (Suppl)
Mod Chem Appl, an open access journal
ISSN: 2329-6798
Global Chemistry 2017
September 04-06, 2017
September 04-06, 2017 | London, UK
5
th
Global Chemistry Congress
Mod Chem Appl 2017, 5:3(Suppl)
DOI: 10.4172/2329-6798-C1-006
Selective hydroformylation of alkyl acrylates using [2,2′-bis(dipyrrolylphosphinooxy)-1,1′-(±)-
binaphthyl]/Rh catalyst: reversal of regioselectivity
Hua Chen, Xueli Zheng and Xiao Shu
Sichuan University, China
H
ydroformylation of alkyl acrylate could provide 1,3- and 1,4-bifunctional carbonyl compounds, which could transform
to malonic acids, 1,4-dicarboxylic acid, lactones, 2-methyl-1,3-propanediol and 1,4-butanediol. Nevertheless, acrylate
was regarded as a kind of less reactive substrate compared with general olefins, and the problem might lies in the formation of
thermodynamically stable five- or six-membered rings through the coordination of carbonyl group to the Rh center [1], hence
high temperature or high pressure was required. And the hydroformylation generally gave the branched aldehyde as the major
product [2]. Hence, it is highly desirable to seek an accessible ligand/Rh system that affords linear aldehyde as the major product
with high efficiency due to the wide application of 1,4-bifunctional compounds. Herein, a series of P-N ligands (Fig. 1) were
synthesized and applied to Rh-catalyzed hydroformylation of alkyl acrylate. Intriguingly, highly selective hydroformylation of
alkyl acrylate could be realized by an accessible ligand 2,2’-bis(dipyrrolylphosphinooxy)-1,1’-(±)-binaphthyl (ligand L1) with
the presence of Rh(acac)(CO)2, that is, elevating the temperature to 90 oC, this Rh system could preferentially afford the linear
aldehyde with 96.1% regioselectivity, and the TOF could reach up to 9000 h-1. More importantly, the regioselectivity could be
readily controlled just through altering the temperature or the pressure, for instance, a high selectivity (> 99%) to branched
aldehyde was obtained under 20oC and 2 MPa. In addition, L1/Rh system had benign substrate compatibility. These results
enable the L1/Rh system to be a potential candidate for selective hydroformylation of functionalized olefin. Deuterioformylation
was conducted to explore the mechanism of regioselectivity reversal, and the results established that the reversible rhodium
hydride addition to form the Rh-alkyl species might play a vital role on this reversal. The β-hydride elimination of branched
Rh-alkyl species was comparatively stronger than that of linear one under increased temperature, probably because that L1
could cause comparatively larger steric repulsion in branched Rh-alkyl species under high temperature, due to its bulky and
rigid binaphthyl backbone characteristics. In turn, the linear Rh-alkyl species progress to linear aldehyde was facilitated.
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