Angewandte
Communications
Chemie
Hydroformylation Hot Paper
Rhodium-Complex-Catalyzed Hydroformylation of Olefins with CO2
and Hydrosilane
Xinyi Ren, Zhiyao Zheng, Lei Zhang, Zheng Wang, Chungu Xia,* and Kuiling Ding*
Abstract: A rhodium-catalyzed one-pot hydroformylation of
olefins with CO , hydrosilane, and H has been developed that
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affords the aldehydes in good chemoselectivities at low catalyst
loading. Mechanistic studies indicate that the transformation is
likely to proceed through a tandem sequence of poly(methyl-
hydrosiloxane) (PMHS) mediated CO reduction to CO and
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a conventional rhodium-catalyzed hydroformylation with CO/
H . The hydrosilylane-mediated reduction of CO in prefer-
ence to aldehydes was found to be crucial for the selective
formation of aldehydes under the reaction conditions.
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Scheme 1. Transition-metal-catalyzed carbonylation of olefins with CO2.
O
ver the past decades, the catalytic reduction of CO has
by reductive transformation of olefins in the presence of CO2
(Scheme 1d). Presumably, the hydrogenation propensity of
ruthenium catalysts or the high temperatures used in the
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been extensively explored to generate energy-rich small
molecules such as formic acid, carbon monoxide, methanol,
[
1,2]
[9]
and methane.
Several innovative methods for reductive
rhodium-catalyzed reverse water gas shift (RWGS) process
transformations of CO have also recently emerged, which
in these studies have precluded the isolation of these valuable
aldehydes.
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combine CO2 reduction with CÀC, CÀN, or CÀO bond
[10]
formation and significantly broaden the range of chemicals
As part of our ongoing studies on CO transformations,
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[3]
[11]
accessible from CO2. Of particular interest in this vein is the
we sought to develop a catalytic alkene hydroformylation
use of CO as a surrogate for highly toxic and flammable CO,
with CO as the CO surrogate. As hydrosilanes have been
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[12]
which is currently produced from fossil fuels and used in
used as viable reductants for CO2 transformations,
we
[4]
a myriad of industrial carbonylation processes. The efficient
began the study with 1-hexene (1a) as the substrate and
reduction of CO to CO and the subsequent valorization of
poly(methylhydrosiloxane) (PMHS, M = 1900) as the reduc-
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W
the CO thus obtained would be of great value in sustainable
tant under 25 bar of H /CO (4:1). A quick survey of reaction
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chemistry but the deoxygenative cleavage of the O=CO bond
is difficult owing to its high bond strength (532 kJmol ).
conditions indicated that Lewis basic N-methylpyrrolidone
(NMP) was the optimal solvent for the reaction whereas only
the isomerization/hydrogenation products were observed for
the reactions in toluene and THF (see the Supporting
Information). Gratifyingly, at 1008C with KF as the additive
À1 [5]
Several catalytic transformations involving the use of CO for
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carbonylative alkene functionalization have emerged
recently, providing elegant approaches to useful chemicals
[6]
[7]
[8]
such as carboxylic acids, esters, and alcohols (Sche-
me 1a–c). It is noteworthy that aldehydes, despite their
fundamental importance in chemical industry and organic
synthesis, represent a missing link and have not been obtained
and Rh(acac)(CO) /PPh3 as the catalyst, 1a was fully
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converted within 12 h to afford the aldehydes 2a and 2a’ in
54% yield with a 78:22 linear to branched ratio (l/b), along
with significant amounts of isomerized alkenes (Iso, 24%)
and the hydrogenation product (H, 3%; Table 1, entry 1). In
contrast, the reaction was very sluggish in the absence of any
phosphine ligands (entry 2), indicating a critical ligand
acceleration effect. Whereas diphosphine L2 and BINOL-
derived bis(phosphoramidite) L3 only led to modest yields of
the desired aldehydes (entries 3 and 4), the reactions with
bis(phosphoramidite)s L4 and L5, which bear a fused spi-
robisindane backbone, gave aldehydes 2a/2a’ in good yields
and high regioselectivity for the linear product (entries 5 and
[*] X. Ren, Prof. Dr. C. Xia
State Key Laboratory of Oxo Synthesis and Selective Oxidation
Lanzhou Institute of Chemical Physics
Chinese Academy of Sciences
18 Tianshui Middle Road, Lanzhou 730000 (P.R. China)
E-mail: cgxia@lzb.ac.cn
X. Ren, Dr. Z. Zheng, Dr. L. Zhang, Dr. Z. Wang, Prof. Dr. K. Ding
State Key Laboratory of Organometallic Chemistry
Shanghai Institute of Organic Chemistry
6
). L5 turned out to be optimal in terms of both catalytic
Chinese Academy of Sciences
activity and chemo/regioselectivity, and was thus used in our
further studies. The use of other hydrosilanes, for example,
PhSiH , Ph SiH , or PhMe SiH, afforded less satisfactory
345 Lingling Road, Shanghai 200032 (P.R. China)
E-mail: kding@mail.sioc.ac.cn
3
2
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Prof. Dr. K. Ding
results (entries 7–9). No aldehyde was observed in the
absence of PMHS (entry 10), indicating that the hydrosilane
is essential for the transformation. Interestingly, the reaction
University of Chinese Academy of Sciences
Beijing 100049 (P.R. China)
also proceeded in the absence of H , albeit in a largely
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Angew. Chem. Int. Ed. 2016, 55, 1 – 5
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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