DOI: 10.1002/cctc.201600165
Communications
Palladium-Catalyzed Carbonylative Synthesis of Aryl
Formates under Mild Conditions
Li-Bing Jiang,[a] Rui Li,[a] Hao-Peng Li,[a] Xinxin Qi,[a] and Xiao-Feng Wu*[a, b]
Aryl formates have been extensively applied as CO sources in
CO-free carbonylation reactions. However, there are no catalyt-
ic synthetic procedures for their preparation. In this manu-
script, we developed a convenient palladium-catalyzed proce-
dure for the synthesis of aryl formates. Good yields were
achieved under mild reaction conditions with formic acid as
the formyl source.
obtained at room temperature. Remarkably, this is the first cat-
alytic procedure for the synthesis of aryl formates.
Initially, we chose naphthalen-2-ol as the model substrate so
that we could establish our catalytic system. With formic acid
as the solvent and by using acetic anhydride (Ac2O) and
sodium acetate (NaOAc) as the additives at room temperature
under a nitrogen atmosphere, various phosphine ligands were
tested (Table 1). To our delight, desired naphthalen-2-yl for-
Transition-metal-catalyzed carbonylative coupling reactions
have experienced impressive progress during the last few dec-
ades.[1] Numerous novel carbonylation procedures have been
developed. Taking advantage of using carbon monoxide as
one of the cheapest and most abundant C1 sources, many car-
bonylative procedures have been industrialized. However, the
high toxicity, flammability, and non-odiferous character of CO
have limited its application at the laboratory scale. This limita-
tion has also been recognized by chemists, and much effort
has been devoted to solving this challenge. Hence, various CO-
gas free methodologies have been developed during the last
few years.[2] CO surrogates including Mo(CO)6,[3] formamides,[4]
(CH2O)n,[5] formic acid,[6] aryl formates[7] and so forth[8] have
been explored for the in situ generation of CO for carbonyla-
tion reactions. Additionally, two-chamber systems with the
ex situ generation of CO for carbonylation reactions have also
been developed.[9]
Table 1. Optimization of the Pd-catalyzed synthesis of aryl formates.[a]
Entry
Ligand[b]
Conversion [%]
Yield[c] [%]
1
2
3
4
5
6
7
8
Ph3P
Bu(Ad)2P
Cy3P
60
49
35
30
46
31
40
48
36
50
30
28
20
85
100
100
42[d]
39[d]
30[d]
27[d]
32[d]
29
34
27
27
40
22
16
18
54[e]
71[f]
84[g]
(o-tolyl)3P
XPhos
dppb
dppe
dppp
dpppe
BINAP
Xantphos
dppf
9
10
11
12
13
14
15
16
DPEphos
–
–
Concerning aryl formates, they can be applied as a source of
either CO or formate in carbonylation reactions, such as in the
alkoxycarbonylation of aryl halides to produce aryl benzoates
and in the hydroesterification of alkenes.[10] Although the appli-
cation of aryl formates has been extensively explored, their
preparation is still based on traditional organic synthesis, that
is, a two-step procedure involving reaction of formic acid with
acetic anhydride at 608C to produce acetic formic anhydride
followed by reaction of acetic formic anhydride with phenols
at room temperature to give the aryl formate derivatives.
Herein, we wish to report our new results on the palladium-
catalyzed carbonylative synthesis of aryl formates. With formic
acid as the formyl source, good yields of aryl formates can be
–
[a] Reactions conditions: naphthalen-2-ol (1 mmol), Pd(OAc)2 (3 mol%),
ligand (4 mol%), NaOAc (5 mol%), Ac2O (10 equiv.), HCOOH (4 mL), 12 h,
RT, N2. [b] Ad=1-adamantyl, Cy=cyclohexyl, XPhos=2-dicyclohexylphos-
phino-2’,4’,6’-triisopropylbiphenyl, dppb=1,4-bis(diphenylphosphino)bu-
tane, dppe=1,2-bis(diphenylphosphino)ethane, dppp=1,3-bis(diphenyl-
phosphino)propane,
BINAP=2,2’-bis(diphenylphosphino)-1,1’-binaphthyl, Xantphos= 9,9-di-
methyl-4,5-bis(diphenylphosphino)xanthene, dppf=1,1’-bis(diphenyl-
dpppe=1,5-bis(diphenylphosphino)pentane,
phosphino)ferrocene, DPEphos=bis[2-(diphenylphosphino)phenyl] ether.
[c] GC yields determined by using dodecane as an internal standard.
[d] Ligand (6 mol%). [e] Pd(PPh3)4 (2 mol%). [f] Pd(PPh3)4 (2 mol%), NaOAc
(0.5 equiv.); yield of isolated product. [g] Pd(PPh3)4 (2 mol%), NaOAc
(1.0 equiv.); yield of isolated product.
[a] L.-B. Jiang, R. Li, H.-P. Li, Dr. X. Qi, Prof. Dr. X.-F. Wu
Department of Chemistry
mate was produced in 42% yield by using Ph3P as the ligand
(Table 1, entry 1). With more basic or sterically hindered li-
gands, the yields decreased (Table 1, entries 2–5). Various bi-
dentate phosphine ligands were then checked. However, no
better yields were achieved, and the simplest Ph3P ligand
proved to be the best ligand (Table 1, entries 6–13). Then, the
commercially available pre-prepared tetrakis(triphenylphos-
Zhejiang Sci-Tech University
Xiasha Campus, Hangzhou 310018 (P.R. China)
[b] Prof. Dr. X.-F. Wu
Leibniz-Institut für Katalyse e.V. an der Universität Rostock
Albert-Einstein-Strasse 29a, 18059 Rostock (Germany)
Supporting Information for this article can be found under http://
ChemCatChem 2016, 8, 1788 – 1791
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