Cu(I)-catalyzed allylic amination of olefins

Article abstract of DOI:10.1016/S0040-4039(02)02441-3

The copper(I) complex [Cu(CH₃CN)₄]PF₆ catalyzes the allylic amination of alkenes by aryl hydroxylamine in fair to moderate yields. Unsymmetrical alkenes react with high regioselectivity with N-functionalization occuring at

Full text of DOI:10.1016/S0040-4039(02)02441-3

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 43 (2002) 9505–9508
Cu(I)-catalyzed allylic amination of olefins
a
a
b
a,
Gregg A. Hogan, August A. Gallo, Kenneth M. Nicholas and Radhey S. Srivastava *
a
Department of Chemistry, University of Louisiana at Lafayette, Lafayette, LA 70504, USA
b
Department of Chemistry and Biochemistry, University of Oklahoma, Norman, OK 73019, USA
Received 24 October 2002; accepted 30 October 2002
Abstract—The copper(I) complex [Cu(CH CN) ]PF catalyzes the allylic amination of alkenes by aryl hydroxylamine in fair to
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moderate yields. Unsymmetrical alkenes react with high regioselectivity with N-functionalization occuring at the less substituted
vinylic carbon. Trapping experiments indicate that free PhNO is not an intermediate in these reactions. © 2002 Elsevier Science
Ltd. All rights reserved.
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1. Introduction
amines. The ene reactions of azo-, nitroso- and N-
7
sulfinylcarbamate derivatives display high regioselec-
The hunt for new, selective chemical procedures for the
direct conversion of petroleum-derived hydrocarbons to
functionalized organic compounds is a major thrust of
research in both industry and academia. Transition
metal-promoted allylic amination of alkenes and alky-
nes offers an attractive route to functionalized amines
tivity with double bond migration, but require
additional NꢀN or NꢀO reduction steps to produce
allyl amines.
We and others have investigated the metal-catalyzed
allylic amination of olefins. At the outset,
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via CꢀN bond formation. While several important
molybdenum and iron -catalyzed aminations of olefins
by aryl hydroxylamines were developed. These reac-
tions proceed regioselectively with N-functionalization
at the less substituted olefinic carbon (Eq. (1)). Subse-
quently, metal-promoted allylic aminations of olefins
using the more readily available nitroarenes as aminat-
ing agents, carbon monoxide as reductant, and
1
processes for the oxidation of hydrocarbons exist, the
direct production of organonitrogen compounds from
hydrocarbons remains a desirable goal due to the com-
mercial potential of such processes. Contrary to signifi-
cantly
investigated
areas
of
homogeneous
metal-catalyzed olefin oxygenation, corresponding
metal-promoted nitrogenation reactions are remarkably
few and typically add nitrogen to the CꢀC unsatura-
tion. The stoichiometric formation of allyl amine from
an olefin has been reported with Group 16 imido
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Ru (CO )/diimine or [Cp(*)Fe(CO)2]2 as catalysts
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were discovered (Eq. (2)). These reactions require more
strenuous reaction conditions (150–200°C, 25–50 atm),
but the iron-catalyzed reactions also display high ene-
reaction type regioselectivity.
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compounds (R%N=X=NR%; X=S, Se ) as aminating
agents. This reaction displays moderate regioselectivity
for retention of the double bond position, proceeding
via an ene reaction followed by [2,3]-sigmatropic rear-
rangement. Sharpless reported the stoichiometric
Just recently, we discovered that photo-assisted, iron-
catalyzed allylic aminations using nitroarenes proceed
quite smoothly under much milder conditions, allowing
the reaction to be carried out in conventional
imido-transfer reactions of molybdooxaziridine com-
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12
plexes [MoL (h -RNO)] with alkenes, producing allyl
glassware.
n
(1)
*
0
Corresponding author. E-mail: rss1805@louisiana.edu
040-4039/02/$ - see front matter © 2002 Elsevier Science Ltd. All rights reserved.
PII: S0040-4039(02)02441-3

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G. A. Hogan et al. / Tetrahedron Letters 43 (2002) 9505–9508
(2)
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Seeking new, more efficient metal-catalyzed aminations
with hydroxylamines, we were investigating Cu-pro-
moted reactions when a report by Lau and co-workers
disclosed allylic aminations with PhNHOH catalyzed
amines upon deprotection/alkylation.
The yields,
reactivity and chemoselectivity features of this reaction
are comparable to the Mo-, Fe- and Cu(II) -cata-
lyzed reactions.
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by various, mostly Cu(II) salts. A redox-recycle mech-
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9d
anism similar to that of Mo- and FePc -systems
involving the intermediacy of free PhNO was proposed.
We describe herein our studies of the copper(I)-cata-
lyzed allylic amination of alkenes using phenyl hydroxy-
lamine as a nitrogen-fragment donor. Trapping experi-
ments indicate that neither free nitrosobenzene nor
phenyl nitrene are intermediates in these reactions.
As we mentioned earlier, recent studies indicate that
amination of olefins catalyzed by hydrated cop-
per(II)chloride proceeds via free PhNO as the active
aminating agent. To probe whether this was also the
case for the reactions catalyzed by 1, we employed the
hetero-Diels–Alder reaction of nitrosobenzene, with
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2,3-dimethylbutadiene as a trapping test for PhNO.
The effective Diels–Alder trapping of PhNO by 2,3-
dimethylbutadiene at 100°C in the presence of a-
methylstyrene in dioxane (solvent) was first established
2
. Results and discussion
(
Eq. (4)). When the amination reaction of a-methyl-
Screening of a series of copper complexes revealed that
Cu(CH CN) ]PF , (1), has the best catalytic properties,
with phenyhydroxylamine as aminating agent. Addition
styrene by phenyl hydroxylamine catalyzed by 1 (10
mol% 1) was carried out in the presence of 2,3-
dimethylbutadiene (1:2, 100°C, dioxane), allyl amines
derived from the alkene (major) and diene (minor) and
a trace of 3,4-dimethyl-N-phenylpyrrole were formed;
the Diels–Alder adduct (trapping product from PhNO)
was not detected (Eq. (4)). Moreover, in a separate
experiment the D–A adduct was shown to be stable
under the catalytic conditions employed (DA-adduct, 1
(1:1) and excess AMS, 100°C, 5 h). To test for the
possible intermediacy of phenyl nitrene, we heated the
dioxane solution of o-(hydroxylamino)-biphenyl in the
[
3
4
6
of phenyl hydroxylamines to a dioxane solution (80–
1
00°C) with an excess of olefin and 10 mol% 1 produces
the corresponding N-aryl-N-allylamines in fair to mod-
erate yield accompanied by small quantities of azobenz-
ene and azoxybenzene (Eq. (3)).
Complex 1 was also employed as a catalyst to survey
the scope and selectivity of the amination with a repre-
sentative set of olefins. The important features of this
reaction include: (1) trisubstituted and 1,1-disubstituted
alkenes produce the highest yields; (2) unsymmetrical
alkenes react to produce the allyl amine derived from
double bond transposition, and (3) generally only single
isomers are produced. Features 1 and 2 are typical of
17
presence of 1; no carbazole, the product of nitrene
CꢀH insertion, was detected.
These results argue against the intermediacy of free
PhNO or phenyl nitrene in the aminations catalyzed by
1, and suggest that they may proceed via a coordinated
organonitrogen species. The differing trapping results
from the aminations catalyzed by CuCl ·2H O and
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ene-reactions.
Other arylhydroxylamines are also
effective as aminating agents, including DNP-NHOH,
which provides access to secondary N-alkyl-allyl
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(3)
(4)

G. A. Hogan et al. / Tetrahedron Letters 43 (2002) 9505–9508
9507
9a,d
[
Cu(CH CN) ]PF indicate that different intermediates
pathways. We and others
have established the dra-
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are involved in the two processes. While both systems
likely involve Cu(I)/Cu(II) shuttling, the different lig-
and sets could be responsible for the differing reaction
matic influence of the coordinating ligands in the iron-
catalyzed aminations. Acetonitrile is a relatively weak
donor and likely more loosely bound to copper com-
Table 1. Allylic amination catalyzed by [Cu(CH CN) ]PF (1)
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G. A. Hogan et al. / Tetrahedron Letters 43 (2002) 9505–9508
pared to chloride ion. Thus, PhNO/PhNHOH could
coordinate at the vacant site created by the dissociation
of acetonitrile. The resulting complex (of PhNO or
azodioxide, ArN(O)N(O)Ar) could react with olefin with
transfer of PhNO to generate an allyl hydroxylamine
complex. Dissociation of the later and subsequent
deoxygenation by Cu(I) would afford allyl amine and
Cu(II), which in turn can react with PhNHOH to
regenerate the reactive intermediate. The slow deoxygena-
tion step seems to be responsible for the modest yields
of allyl amine.
References
1. (a) Parshall, G. W. Homogeneous Catalysis, Wiley, New
York, 1980; pp. 101–119; 129–135; 185–207; (b) Sheldon,
R. A.; Kochi, J. K. Metal-catalyzed Oxidations of Organic
Compounds; Academic Press: New York, 1981; pp. 271–
279.
2. (a) Sharpless, K. B.; Hori, T. J. Org. Chem. 1976, 41, 176;
(b) Kresze, G.; Braxmeier, H.; Munsterer, H. Org. Syn.
1987, 65, 159.
3
. (a) Sharpless, K. B.; Hori, T.; Truesdale, L. K.; Dietrich,
C. O. J. Am. Chem. Soc. 1976, 98, 269; (b) Bruncko, M.;
Khuong, T.-A. V.; Sharpless, K. B. Angew. Chem., Int. Ed.
Engl. 1996, 35, 454.
3. Summary
4. Liebeskind, L. S.; Sharpless, K. B.; Wilson, R. D.; Ibers,
J. A. J. Am. Chem. Soc. 1978, 100, 7061.
Complex 1 catalyzes the regioselective amination of
olefins using phenyl hydroxylamine as an aminating
agent. Although further insight into the mechanism of this
process is being sought, the absence of free nitrosobenzene
and nitrene argue in favor of an ‘on the metal’ reaction
pathway.
5. (a) Brimble, M. A.; Heathcock, C. H. J. Org. Chem. 1993,
58, 5261; (b) Brimble, M.; Heathcock, C. H.; Nobin, G.
N. Tetrahedron: Asymmetry 1996, 7, 2007; (c) Leblanc, Y.;
Zamboni, R.; Berstein, M. A. J. Org. Chem. 1991, 56, 1971.
6. (a) Keck, G. E.; Webb, R. R.; Yates, J. B. Tetrahedron 1981,
37, 4007;(b)Ensley, H. E.;Mahadevan, S. TetrahedronLett.
1
1
988, 3255; (c) Knight, G. T. J. Chem. Soc., Chem. Commun.
970, 1016; (d) Banks, R. E.; Haszeldine, R. N.; Miller, P.
J. Tetrahedron Lett. 1970, 11, 4417; (e) Seymour, C. A.;
Greene, F. D. J. Org. Chem. 1982, 47, 5226.
4. Experimental
7
8
. Whitesell, J. K.; Yaser, H. K. J. Am. Chem. Soc. 1991, 113,
1
8
General: The alkene in run 6 (Table 1), phenylhy-
3526.
1
9
20
droxylamine, 2,4-dinitrophenylhydroxylamine
and
were pre-
pared according to literature methods. Anhydrous
,4-dioxane (Aldrich), [Cu(CH CN) ]PF (Strem), and
. (a) Srivastava, A.; Ma, Y.; Pankayatselvan, R.; Dinges, W.;
Nicholas, K. M. J. Chem. Soc., Chem. Commun. 1992, 853;
2
1
2
,3,5,6-tetrafluorophenylhydroxylamine
(
b) Srivastava, R. S.; Nicholas, K. M. J. Org. Chem. 1994,
1
3
4
6
59, 5365.
all other reactants were obtained commercially. GC/
MS and MS spectra were obtained at 70 eV (EI). GC
analyses utilized a 3% column packed with 3% OV101.
9. (a) Srivastava, R. S.; Nicholas, K. M. Tetrahedron Lett.
1994, 35, 8739; (b) Srivastava, R. S.; Khan, M. A.; Nicholas,
K. M. J. Am. Chem. Soc. 1996, 118, 3311; (c) Srivastava,
R. S.; Nicholas, K. M. J. Am. Chem. Soc. 1997, 119, 3302;
(d) Johannsen, M.; Jorgenson, K. A. J. Org. Chem. 1994,
59, 214; (e) Johannsen, M.; Jorgenson, K. A. J. Org. Chem.
1995, 60, 5979.
10. (a) Cenini, S.; Ragaini, F.; Tollari, S.; Paone, D. J. Am.
Chem. Soc. 1996, 118, 11964; (b) Ragaini, F.; Cenini, S.;
Tollari, S.; Tummolillo, G.; Beltrami, R. Organometallics
1999, 18, 928.
11. (a) Srivastava, R. S.; Nicholas, K. M. J. Chem. Soc., Chem.
Commun. 1998, 2705; (b) Kolel-Veetil, M.; Khan, M. A.;
Nicholas, K. M. Organometallics 2000, 19, 3754.
12. Srivastava, R. S.; Kolel-Veetil, M.; Nicholas, K. M.
Tetrahedron Lett. 2002, 43, 931.
Catalytic allylic amination of olefins: All reactions
were performed under dry argon. The general method
for the preparation of compound 4 is as described.
The olefin, a-methylstyrene (7 mmol) and 1 (0.15
mmol) were added to 1,4-dioxane (2 mL) and heated
to reflux (80–100°C). Phenylhydroxylamine (1.5
mmol) was dissolved in 1,4-dioxane (10 mL) and was
slowly added over a period of 5–6 h with a syringe
pump. The reaction mixture was then heated for two
additional hours. The metal-catalyst was precipitated
with hexane and filtered. The resulting solution was
concentrated by a rotary evaporator and dried under
vacuum. The crude mixture was purified by column
chromatography (silica gel) using dichloromethane–
petroleum ether (30:70) as the eluent. The compo-
nents of the mixture were analyzed by GC and
GC–MS using naphthalene as the internal standard.
Comparison with authentic samples prepared as
1
1
3. Ho, C.-M.; Lau, T.-C. New J. Chem. 2000, 24, 859.
4. (a) Oppolzer, W.; Snieckus, V. Angew. Chem., Int. Ed. Engl.
1
978, 17, 476; (b) Hoffman, H. M. R. Angew. Chem., Int.
Ed. Engl. 1969, 8, 556; (c) Snider, B. Acc. Chem. Res. 1980,
3, 426.
5. Singh, S.; Nicholas, K. M. Synth. Commun. 2001, 31, 3087.
1
1
9
16. Taylor, E. C.; Tseng, C.-P.; Rampal, J. B. J. Org. Chem.
described in the literature identified the allyl amines.
1982, 47, 552.
In a separate procedure, compounds 8 and 9 were
15
17. (a) Sundberg, R. J.; Brenner, M.; Suter, S. R.; Das, B. P.
Tetrahedron Lett. 1970, 2715; (b) Sundberg, R. J.; Heintzel-
men, R. W. J. Org. Chem. 1974, 39, 2546.
isolated and identified as described in the literature.
18. Campbell, M. M.; Sainsbury, M. Tetrahedron 1985, 23,
Acknowledgements
5637.
1
9. Kamm, O. Org. Synth. 1925, 4, 57.
We thank Professor R. D. Braun of the Department of
Chemistry, UL-Lafayette for helpful discussions.
20. Borche, W. Chem. Ber. 1923, 56, 1494.
21. Miller, A. O.; Furin, G. G. J. Fluorine Chem. 1987, 36, 247.