Oxovanadium(V)-Catalyzed Direct Amination of Allyl Alcohols

Article abstract of DOI:10.1002/cctc.201801841

Direct amination of allyl alcohols is regarded as one of reliable methods to synthesize allyl amines in one step because water is only by-product. Oxovanadium(V) compound with triphenyl siloxide ligands was demonstrated to serve as an efficient catalyst in the direct amination of allyl alcohols. The catalytic direct amination reaction could be performed with both aromatic and aliphatic amines. This catalytic system induced selective direct amination in the case of the unsymmetrically substituted allyl alcohols. Furthermore, gram-scale direct amination reaction was successfully achieved.

Full text of DOI:10.1002/cctc.201801841

Accepted Article
Title: Oxovanadium(V)-Catalyzed Direct Amination of Allyl Alcohols
Authors: Takashi Sakuramoto, Toshikazu Hirao, Mamoru Tobisu, and
Toshiyuki Moriuchi
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10.1002/cctc.201801841
ChemCatChem
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Oxovanadium(V)-Catalyzed Direct Amination of Allyl Alcohols
Takashi Sakuramoto,[a] Toshikazu Hirao,[a,b] Mamoru Tobisu[a] and Toshiyuki Moriuchi *[a,c]
Dedication ((optional))
Abstract: Direct amination of allyl alcohols is regarded as one of
reliable methods to synthesize allyl amines in one step because water
is only by-product. Oxovanadium(V) compound with triphenyl siloxide
ligands was demonstrated to serve as an efficient catalyst in the direct
amination of allyl alcohols. The catalytic direct amination reaction
could be performed with both aromatic and aliphatic amines. This
catalytic system induced selective direct amination in the case of the
unsymmetrically substituted allyl alcohols. Furthermore, gram-scale
direct amination reaction was successfully achieved.
activation of amines by oxovanadium(V) compounds is
considered to be a convenient strategy for catalytic transformation
of amines. Direct amination of allyl alcohols has been
demonstrated by using in situ-generated (imido)titanium
compounds through [3,3]-sigmatropic rearrangement.[10] This
process, however, requires a stoichiometric amount of titanium
compounds and excess amount of amines. To the best of our
knowledge, oxovanadium(V) compounds have never been
utilized as a catalyst for direct amination of allyl alcohols. From
these points of view, we embarked upon the development of a
catalytic direct amination system from allyl alcohols by utilizing
oxovanadium(V) catalyst.
Introduction
We were interested in checking whether oxovanadium(V)
compound could serve as a catalyst in catalytic direct amination
of allyl alcohols. The reaction of p-anisidine (1a) with 1,3-
diphenylprop-2-en-1-ol (2a) in the presence of VO(OSiPh3)3 (10
mol%) as a catalyst and MS3A as a dehydrating reagent at 100 °C
was found to afford the corresponding allyl amine 3aa in 70% yield
(Table 1, entry 1). In this reaction, E-chalcone, the oxidized allyl
alcohol 2a, was not observed. The catalytic direct amination was
successfully performed even at 50 °C to give 3aa in a good yield
(entry 2). Reducing the temperature to 25 °C resulted in a lower
yield, and the allyl alcohol 1a and amine 2a remained unreacted
(entry 3). The amount of the catalyst loading could be reduced to
Allyl amines are synthetically useful substructures for
various nitrogen-containing compounds and building blocks of
biologically active compounds.[1] Allyl alcohols are regarded as
one of the important starting materials because allyl alcohols are
supplied in bulk and obtained cheaply. In the general method for
the synthesis of allyl amines from allyl alcohols, however, hydroxy
groups of allyl alcohols are converted to leaving groups such as
halides, phosphates, carboxylates and carbonates in the first
step.[2] Through this process, two steps are necessary to
synthesize allyl amines and undesired by-products are produced.
Recently, direct amination of allyl alcohols has attracted much
attention as one of reliable methods for the synthesis of allyl
amines because water is only by-product.[3,4] Generally, direct
amination of allyl alcohols has been performed by using precious
transition metal catalysts.[3a,3c,5] Only some non-precious metal
catalysts have been reported for direct amination of allyl
alcohols.[6] Development of an environmentally benign and cost
effective catalytic direct amination system is desirable.
Economical oxovanadium(V) compounds have Lewis acidity and
oxophilicity.[7] Oxovanadium(V) compounds have been reported
to serve as catalysts for isomerization of allyl alcohols via [3,3]-
sigmatropic rearrangement.[8] We have already developed the
one-step synthetic method of imidovanadium(V) compounds by
the reaction of oxovanadium(V) compounds with amines.[9] The
Table 1. The oxovanadium-catalyzed allyl amine formation from p-anisidine
(1a) and 1,3-diphenylprop-2-en-1-ol (2a).[a]
Entry
VO(OSiPh3)3
[mol%]
Temp.
[°C]
t
NMR yield
[%]
[h]
1
10
10
10
5
100
50
25
50
50
50
50
6
70
2
6
69
[a]
Department of Applied Chemistry, Graduate School of Engineering
Osaka University
3
24
24
24
24
24
12
Yamada-oka, Suita, Osaka 565-0871 (Japan)
Fax: (+81) 6-6879-7415
E-mail: moriuchi@chem.eng.osaka-u.ac.jp
hirao@chem.eng.osaka-u.ac.jp
4
85
5[b]
6[c]
7
5
30
[b]
[c]
Present address: The Institute of Scientific and Industrial Research
Osaka University
Mihoga-oka, Ibaraki, Osaka 567-0047 (Japan)
Present address: Division of Molecular Materials Science, Graduate
School of Science
5
66
0
trace
[a] Reaction conditions: 0.20 mmol of p-anisidine (1a) and 1,3-diphenylprop-
2-en-1-ol (2a), VO(OSiPh3)3, 0.2 g MS3A, 2.0 mL toluene, under nitrogen
atmosphere. [b] The reaction was perfoemed without MS3A. [c] 5 mol% of
VO(OiPr)3 was used instead of VO(OSiPh3)3.
Osaka City University
3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585 (Japan)
E-mail: moriuchi@sci.osaka-cu.ac.jp
Supporting information for this article is available on the WWW
underhttp://dx.doi.org/
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10.1002/cctc.201801841
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COMMUNICATION
5 mol% to afford the desired amination product in 85% yield
although a longer reaction time was required (entry 4). In this
catalytic direct amination, MS3A was found to play a key role as
dehydrating reagent to remove generated water (entry 5). Utilizing
VO(OiPr)3 as a catalyst instead of VO(OSiPh3)3 lead to the
decrease in the yield (entry 6). The amination reaction did not
proceed in the absence of VO(OSiPh3)3, revealing the efficiency
of the oxovanadium(V) catalyst for direct amination of allyl
alcohols (entry 7).
To explore the validity of this catalytic system, the substrate
scope of amines in the direct amination reaction was examined
by using 1,3-diphenylprop-2-en-1-ol (2a) as allyl alcohol under the
optimized reaction conditions (Table 2). In the case of p-
substituted aniline derivatives 1a-e with either electron-rich or
electron-deficient substituents, the direct amination reaction
proceeded well to give the corresponding allyl amines 3aa-ea in
good yields. For example, this oxovanadium(V)-catalyzed direct
amination system could be applied to the catalytic amination with
4-bromoaniline (1c), in which the obtained product can be utilized
for further transformation using Br group. The direct amination
reaction with o-substituted aniline such as o-nitroaniline 1f
underwent smoothly and the corresponding allyl amine 3fa was
obtained in an excellent yield. However, hexylamine (1g), an
aliphatic amine, did not show the reactivity to the allyl alcohol 1a
under the similar reaction conditions to aniline derivatives.
However, this problem was easily solved by examining the
reaction conditions. Eventually, by performing the reaction with 10
mol% of VO(OSiPh3)3 and 1.0 g of MS3A at 100 °C, the catalytic
direct amination with aliphatic amines could be driven to produce
the desired allyl amines. The optimized conditions were applied
to the reaction of aliphatic amines in the direct amination as
outlined in Table 3. The catalytic direct amination reaction with
various aliphatic amines proceeded in good yields. Even in the
case of a bulky amine such as 1-adamantylamine (1j), the desired
[a,b]
Table 3
RNH2
1
2a
Substrate scope in the amination of 1,3-diphenylprop-2-en-1-ol ( ).
VO(OSiPh3)3 10 mol%
R
OH
Ph
MS3A 1.0 g
NH
Ph
+
toluene, N2, 100 C, 24 h
Ph
Ph
2a
3ga la
-
Ph
Ph
NH
Ph
Ph
NH
Ph
NH
Ph
Ph
Ph
3ga
: 85%
3ha
3ia
: 85%
: 69%
Ph
N
Ph
Ph
NH
N
Ph
Ph
Ph
Ph
Ph
Ph
3ja
: 88%
3ka
3la
: 56%
: 69%
O
N
N
Ts
NH
Ph
N
Ph
Ph
Ph
Ph
[c]
3ma
: 79%
3na
: 59%
3oa
: 35%
2a
[a] Reaction conditions: 0.20 mmol of amines and 1,3-diphenylprop-2-en-1-ol ( ), 10
mol% of VO(OSiPh3)3, 1.0 g MS3A, 2.0 mL toluene, under a nitrogen atmosphere. [b]
The yield was determined by 1H NMR. [c] 300 mol% of p-toluenesulfonamide was used.
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10.1002/cctc.201801841
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allyl amine 3ja was obtained in 88% yield. Moreover, secondary
aliphatic amine 1k-1n underwent the direct amination reaction to
afford the corresponding allyl amine 3ka-3na. In the case of p-
toluenesulfonamide 1o, the corresponding allyl amine 3oa could
be also produced in 35% yield by using 300 mol% of 1o.
Our next experiments focused on clarifying the scope of a
variety of allyl alcohols using p-anisidine (1a) (Table 4). The
catalytic direct amination reaction of the allyl alcohol 2b
proceeded moderately. Starting from the allyl alcohol 2c, the allyl
amine 3ac was obtained in 68% yield by using of 150 mol% of 2c.
This direct amination reaction was also applicable to the α-
methylated allyl alcohol 2d to give the desired allyl amine 3ad in
77% yield. The catalytic direct amination reaction of 4-phenyl-3-
buten-2-ol (2e) at 80 °C led to the formation of the allyl amines
3ae and 3af in 31% and 14% yields, respectively, wherein
unreacted substrates remained. Thus, the reaction temperature
was elevated, and the allyl amine 3ae was obtained selectively in
78% yield by performing the reaction with 200 mol% of 2e at
100 °C. The catalytic direct amination reaction of 1-phenyl-2-
buten-1-ol (2f) at 80 °C was also demonstrated to afford both allyl
amines 3ae and 3af, wherein the allyl alcohol 2e was obtained in
51% yield and the allyl alcohol 2f was not recovered. The allyl
alcohol 2e appears to be generated via [3,3]-sigmatropic
rearrangement of 2f. In fact, as shown in scheme 1, allyl alcohol
2f was converted to 2e under the reaction conditions in the
absence of amine 1a. However, the allyl alcohol 2f was not
obtained by the isomerization of the allyl alcohol 2e. At 100 °C,
the catalytic direct amination reaction of 2f proceeded
regioselectively to give the allyl amine 3ae in 81% yield by using
200 mol% of 2f. The regioselective conversion to α-methyl
cinnamylamine from 2e or 2f has been also observed in other
catalytic systems.[5b,6d,6f] Isomerization reaction of the allyl amine
3af was demonstrated to generate the regioisomer 3ae in 37%
yield (Scheme 2), indicating that the generated allyl amine 3af has
the capability to be converted to the allyl amine 3ae under the
reaction conditions.
In conclusion, catalytic direct amination of allyl alcohols was
performed by utilizing oxovanadium(V) catalyst. This catalytic
system could be applied to the direct amination reaction with both
aromatic and aliphatic amines. The selective direct amination was
also achieved in the case of the unsymmetrically substituted allyl
alcohols. Furthermore, gram-scale direct amination reaction
underwent successfully. Studies on the reaction mechanism and
synthetic versatility, and application of this practical catalytic
system to other reactions are now in progress.
Acknowledgments
This work was partly supported by the ACT-C program (Grant
Number JPMJCR12Z3) of Japan Science and Technology
Agency (JST). Thanks are due to the Analytical Center, Graduate
School of Engineering, Osaka University.
Keywords: oxovanadium(V) catalyst • direct amination • allyl
alcohol • allyl amine
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Entry for the Table of Contents (Please choose one layout)
COMMUNICATION
Oxovanadium(V) Catalyst • Direct
Amination
Takashi Sakuramoto, Toshikazu Hirao,
Mamoru Tobisu and Toshiyuki Moriuchi*
Page No. – Page No.
Catalytic direct amination of allyl alcohols was demonstrated by utilizing
oxovanadium(V) compound with triphenyl siloxide ligands. This oxovanadium(V)-
catalyzed direct amination reaction could be performed with both aromatic and
aliphatic amines. The selective direct amination was also conducted in the case of
the unsymmetrically substituted allyl alcohols. Furthermore, gram-scale direct
amination reaction was successfully achieved.
Oxovanadium(V)-Catalyzed Direct
Amination of Allyl Alcohols
*one or two words that highlight the emphasis of the paper or the field of the study
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