Ru3(CO)12-catalyzed reaction of 1,6-diynes, carbon monoxide, and water via the reductive coupling of carbon monoxide

Article abstract of DOI:10.1021/acs.orglett.0c02349

We report the ruthenium-catalyzed cyclization of 1,6-diynes with two molecules of carbon monoxide and water to give a variety of catechols. This reaction likely proceeds through the intermediacy of the water-gas shift reaction to generate an yne- diol-typ

Full text of DOI:10.1021/acs.orglett.0c02349

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Letter
Ru3(CO)12-Catalyzed Reaction of 1,6-Diynes, Carbon Monoxide, and
Water via the Reductive Coupling of Carbon Monoxide
Cathleen M. Crudden,* Yuuki Maekawa, Joshua J. Clarke, Tomohide Ida, Yoshiya Fukumoto,
Naoto Chatani,* and Shinji Murai*
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ABSTRACT: We report the ruthenium-catalyzed cyclization of
1,6-diynes with two molecules of carbon monoxide and water to
give a variety of catechols. This reaction likely proceeds through the
intermediacy of the water−gas shift reaction to generate an yne−
diol-type intermediate followed by a [4 + 2] cycloaddition with 1,6-
diynes. The reaction requires no external reductants or hydride
sources and provides a novel and valuable method for the synthesis
of a variety of catechols.
he water−gas shift (WGS) reaction is a crucial industrial
with a second molecule of CO gives dioxyacetylene IV.5 This
species can be trapped by cycloaddition with diynes 1,6
yielding monosilylated catechols 2-Si (Scheme 1B). We
speculated that this reaction might be carried out under
WGS conditions if metal dihydride I could be considered a
surrogate for II.
The use of metal catalysts to affect the cycloaddition of
alkynes and diynes with a variety of partners, including other
alkynes, alkenes, carbon dioxide, and nitriles, has become a
topic of intense interest.7 However, the synthesis of catechols
through this type of cycloaddition has not been reported, even
though early transition metals have been shown to affect the
reductive coupling of CO to yield disiloxyethylenes under
stoichiometric conditions.8 Other examples where two
molecules of CO are incorporated result in the preparation
of 1,4-benzoquinones or 1,4-hydroquinones and thus do not
proceed through the intermediacy of dihydroxyethyne.9
Interestingly, despite their well-documented use in metathesis
reactions and stoichiometric organometallic chemistry,10a,b
metal carbyne species are scarcely invoked in catalytic
transformations.10c,d
T
process for the production of high purity hydrogen gas
from carbon monoxide (CO) and water. Metal dihydrides (I)
are key intermediates (Scheme 1A).1 The WGS reaction has
Scheme 1. Water−Gas Shift Reaction for the Synthesis of
Catechols from 1,6-Diynes
Herein, we report a novel, scalable synthesis of catechols
through the intermediacy of a WGS reaction, where water is
employed as the source of hydrogen, via metal carbynes as
likely intermediates (Scheme 1C).
To optimize the reaction, we began with substrate 1a, which
is predisposed toward cyclization because of the Thorpe−
been also applied in hydrogenation reactions as well as catalytic
reactions for the regeneration of active catalytic species;2
however, its use in organic synthesis remains underdeveloped.
Our group previously reported that 1,6-diynes react with
carbon monoxide and hydrosilane in the presence of simple Ru
catalysts to provide catechol derivatives (Scheme 1B).3 This
reaction is proposed to proceed via a unique 1,3-shift of the
silyl group in complex II to the oxygen atom of a coordinated
CO.4 Reaction of the resulting silyloxycarbyne complex III
Received: July 14, 2020
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Ingold effect introduced by the geminal ester substituents.
Reaction between 1a and carbon monoxide was carried out in
a stainless steel autoclave employing 50 atm of CO and a polar
solvent to which several equivalents of water was added.
Ru3(CO)12 was employed as the catalyst at 2 mol % loading
and the reaction carried out at 140 °C for 20 h. Under these
conditions, the desired product (2a) was isolated after
trituration in 81% yield (Table 1, entry 1).
Table 2. Reaction of Terminal Alkynes with CO and H2O in
the Presence of Ru3(CO)12
a
Table 1. Optimization of Reaction Conditions for
Cycloaddition of 1,6-Diyne 1a
entry
catalyst
H2O (equiv)
solvent
yield (%)
1
2
3
Ru3(CO)12
Ru3(CO)12
Ru3(CO)12
Ru3(CO)12
Ru3(CO)12
Fe3(CO)12
Os3(CO)12
Ru3(CO)12
Ru3(CO)12
Ru3(CO)12
Ru3(CO)12
Ru3(CO)12
4
5
2
4
4
4
4
4
4
4
4
4
1,4-dioxane
1,4-dioxane
1,4-dioxane
1,4-dioxane
1,4-dioxane
1,4-dioxane
1,4-dioxane
CH3CN
THF
CH2Cl2
toluene
CH3OH
81
70
51
61
24
0
a
4
5
b
6
7
8
9
10
11
12
0
79
81
46
38
51
a
b
CO pressure: 30 bar. Reaction temperature:120 °C.
Using larger or smaller amounts of water gave decreased
yields of product 2a (70% yield for 15 mmol of H2O and 51%
yield for 6 mmol of H2O, entries 2 and 3). Decreasing the CO
pressure also led to lower product yields (30 atm of CO gave
61% yield) as did lower temperatures (24% yield at 120 °C)
(entries 4 and 5). Using Fe3(CO)12 or Os3(CO)12 as the
catalyst in place of Ru3(CO)12 gave no reaction (entries 6 and
7). The reaction was tolerant to other solvents such as CH3CN
(79%) and THF (81%); however, lower yields were obtained
in CH2Cl2 (46%), toluene (38%), and CH3OH (51%) (entries
8−12).
These optimized conditions (Table 1, entry 1) were then
applied to a variety of diyne substrates (Table 2). Gratifyingly,
the cycloaddition reaction did not require geminal substitution
on the diyne, with the simple 1,6-heptadiyne (1b) reacting to
give catechol 2b in 59% yield. Oxygen or nitrogen substitution
in the tether as in 1c and 1d were well tolerated as was the
ketone in 1e, yielding catechols 2c−2e. However, 1,7-
heptadiyne (1f), which would yield the tetrahydronaphthalene
structure, gave a complex mixture of products as did the related
ether 1g, illustrating the importance of the fused 5/6 ring.
Internal alkynes could also be employed as shown in Table
3. Diynes bearing a single substituent at the acetylenic
terminus (methyl, 1h, or phenyl, 1j) gave adducts 2h and 2j
in good yields, although terminal ethyl ester-substituted diyne
1i reacted with much lower efficiency. Disubstituted diynes 1k
and 1l reacted smoothly to afford the corresponding
hexasubstituted catechols 2k and 2l; however, diphenyl
derivative 1m gave none of the desired product.
a
Yields reported for isolated products.
instructive. Instead of the desired catechol, cyclopentadie-
neone−Ru complex 3m was isolated. This species results from
incorporation of a single molecule of carbon monoxide in a
well-precedented [2 + 2 + 1] cycloaddition, with Ru(CO)3
binding to the cyclopentadieneone unit.11 This compound was
isolated in 89% yield relative to the added ruthenium catalyst
(Scheme 2), and its structure was confirmed spectroscopically
and by X-ray crystallography (Figure 1). The observation of
compound 3m suggests that the [2 + 2 + 1] cycloaddition
reaction is less sensitive to steric constraints than the desired
[2 + 2 + 2] and that, once formed, these adducts can serve as
catalyst sinks halting further transformations. Previous studies
of Ru-catalyzed cycloadditions of diynes have documented the
observation of related compounds, especially with sterically
hindered diynes.12
The catechol synthesis was also attempted employing alkyne
1n, which contains a terminal nitrile, since a successful
cycloaddition would yield a pyridone product. Unfortunately,
conditions were not found to affect pyridone synthesis,
although product 2n was observed in small amounts along
with other unidentified products (Scheme 3). Since catechol
Although identifiable byproducts were rarely observed, a
side product from the reaction of diphenyl diyne 1m was
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Table 3. Reaction of Internal Alkynes with CO and H2O in
a
the Presence of Ru3(CO)12
Figure 1. Single-crystal X-ray structure of compound 3m (Ru, green;
C, gray; O, red). Thermal elipsoids are shown at 50% probability.
Selected bond lengths (Å) and angles [degs]: avg Ru−C(C≡O)
1.936(2); avg C−O(C≡O) = 1.130(2); avg C(C≡O)−Ru−C(C≡O)
94.86(7).
=
=
Scheme 3. Reaction of Alkyne Bearing a Terminal Nitrile
reagents are at different oxidation states. As noted in the
introduction, the most reasonable suggestion for the observed
product is that metal hydrides are generated in situ via the
water gas shift reaction (Scheme 4).1 Isomerization of the
Scheme 4. Proposed Reaction Pathway
a
1
Yields reported for isolated products. H NMR yields are shown in
parentheses (1,3,5-trimethoxybenzene was used as an internal
b
standard). With 6 mol % of Ru3(CO)12.
proposed intermediate metal carbonyl dihydride via a 1,3-
metal hydride shift gives hydroxycarbyne metal complex 4. The
suggested 1,3-hydride shift (Scheme 4) is proposed on the
basis of precedent from related silyl systems4 and considerable
other literature describing the intermediacy of hydroxy
carbynes such as 4 as an alternative to the less stable formyl
tautomers.13 Reaction of this species with another molecule of
carbon monoxide would result in yne−-diol metal complex 6
via a metallacyclopropenone 5 in analogy with similar reactivity
seen in other metal complexes.5,14
Scheme 2. Reaction of Diphenyl Diyne
The feasibility of yne−diol complex 6 is supported by
reactions of related hydrosilanes performed in the absence of
the 1,6-diyne (Scheme 5).15 We previously reported that the
Rh-catalyzed reaction between CO and a hydrosilane gives
ene−diol 8, presumably derived from metal ene-silanol
derivative 7. The stereochemistry of the ene-silanol 8 was
shown to be cis, as expected for the mechanism shown.
2n was presumably produced by an unprecedented inter-
molecular cycloaddition, we also examined the reaction of
phenyl acetylene; however, none of the desired product was
observed from this alkyne.
From a mechanistic point of view, the use of water in place
of hydrosilane is somewhat remarkable since these two
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Notes
Scheme 5. Formation of Ene−Diol in the Absence of Diene
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We acknowledge the Natural Sciences and Engineering
Research Council of Canada (NSERC) and the Canada
Foundation for Innovation (CFI) for funding of the work from
this lab as described in this article. Y.M. is a recipient of a JSPS
postdoctoral fellowship. JSPS and NU are acknowledged for
funding of this research through the World Premier Interna-
tional Research Center Initiative (WPI) program. This work
was partially supported by a Grant in Aid for Specially
Promoted Research by MEXT (No. 17H06091).
In conclusion, we have developed a ruthenium-catalyzed
catechol synthesis from a variety of diynes utilizing the WGS
reaction to generate 1,2-hydroxyethyne from two molecules of
CO and water. Reactions proceeding via metal carbyne
complexes remain under represented in catalytic trans-
formations. In this context, it is noteworthy that formation
of a metal oxy−acetylene complex from a metal carbyne,
carbon monoxide, and hydrogen is a likely pathway for the
transformations described. Efforts to expand the synthetic
applicability of this unique reactive intermediate are in
progress.
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The Supporting Information is available free of charge at
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Experimental details and NMR spectra (PDF)
Accession Codes
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AUTHOR INFORMATION
Corresponding Authors
■
Shinji Murai − Nara Institute of Science and Technology, Ikoma,
Nara 630-0192, Japan; Email: murai@ad.naist.jp
Naoto Chatani − Department of Applied Chemistry, Faculty of
Engineering, Osaka University, Suita, Osaka 565-0871, Japan;
orcid.org/0000-0001-8330-7478; Email: chatani@
chem.eng.osaka-u.ac.jp
Cathleen M. Crudden − Department of Chemistry, Queen’s
University, Kingston, Ontario K7L 3N6, Canada; Institute of
Transformative Bio-Molecules (WPI-ITbM), Nagoya
University, Chikusa, Nagoya 464-8601, Japan; orcid.org/
0000-0003-2154-8107; Email: cruddenc@chem.queensu.ca
Authors
Yuuki Maekawa − Department of Chemistry, Queen’s
University, Kingston, Ontario K7L 3N6, Canada; Institute of
Transformative Bio-Molecules (WPI-ITbM), Nagoya
University, Chikusa, Nagoya 464-8601, Japan
Joshua J. Clarke − Department of Chemistry, Queen’s
University, Kingston, Ontario K7L 3N6, Canada
Tomohide Ida − Department of Applied Chemistry, Faculty of
Engineering, Osaka University, Suita, Osaka 565-0871, Japan
Yoshiya Fukumoto − Department of Applied Chemistry,
Faculty of Engineering, Osaka University, Suita, Osaka 565-
0871, Japan; orcid.org/0000-0003-1064-0354
Complete contact information is available at:
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