Rhodium(III)-catalyzed intermolecular direct amination of aromatic C-H bonds with N-chloroamines

Article abstract of DOI:10.1021/ol203046n

A Rh(III)-catalyzed direct aromatic C-H amination is achieved using N-chloroamines as a reagent. Furthermore, we also developed a one-pot amination protocol involving in situ chlorination of the secondary amines. The catalytic amination operates at mild conditions with excellent functional group tolerance and regioselectivity.

Full text of DOI:10.1021/ol203046n

ORGANIC
LETTERS
2012
Vol. 14, No. 1
272–275
Rhodium(III)-Catalyzed Intermolecular
Direct Amination of Aromatic CꢀH Bonds
with N-Chloroamines
Ka-Ho Ng, Zhongyuan Zhou, and Wing-Yiu Yu*
State Key Laboratory for Chirosciences and The Open Laboratory for Chirotechnology
of the Institute of Molecular Technology for Drug Discovery and Synthesis, Department
of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University,
Hung Hom, Hong Kong
*bcwyyu@inet.polyu.edu.hk
Received November 11, 2011
ABSTRACT
A Rh(III)-catalyzed direct aromatic CꢀH amination is achieved using N-chloroamines as a reagent. Furthermore, we also developed a one-pot
amination protocol involving in situ chlorination of the secondary amines. The catalytic amination operates at mild conditions with excellent
functional group tolerance and regioselectivity.
Catalytic aromatic CꢀN bond formation1 via CꢀH bond
activation is an attractive strategy for preparing amino
compounds which are commonly found in pharmaceuticals
as well as agrochemical and functional materials. Without
requiring prefunctionalized arenes, the CꢀH bond amina-
tion approach should improve synthetic efficiency and atom
economy.2 Recent advances have been achieved for some
transition metal catalyzed CꢀH activation/CꢀC bond for-
mation reactions that exhibit remarkable site selectivity and
general substrate scope applications.3 In contrast, catalytic
direct CꢀN bond formation remains a formidable chal-
lenge, and catalytic systems that operate at mild conditions
with a wide substrate scope are rare.
Among others,4 Pd-catalyzed direct amidation of arene
CꢀH bonds has been extensively investigated. Major
developments have been made in the intramolecular direct
(4) For recent selected examples of Cu-catalyzed intermolecular
CꢀH bond amination reactions, see: (a) John, A.; Nicholas, K. M.
J. Org. Chem. 2011, 76, 4158. (b) Matsuda, N.; Hirano, K.; Satoh, T.;
Miura, M. Org. Lett. 2011, 13, 2860. (c) Guo, S.; Qian, B.; Xie, Y.; Xia,
C.; Huang, H. Org. Lett. 2011, 13, 522. (d) Miyasaka, M.; Hirano, K.;
Satoh, T.; Kowalczyk, R.; Bolm, C.; Miura, M. Org. Lett. 2011, 13, 359.
(e) Kawano, T.; Hirano, K.; Satoh, T.; Miura, M. J. Am. Chem. Soc.
2010, 132, 6900. (f) Wang, Q.; Schreiber, S. L. Org. Lett. 2009, 11, 5178.
(g) Monguchi, D.; Fujiwara, T.; Furukawa, H.; Mori, A. Org. Lett.
2009, 11, 1607. Several examples of intermolecular CꢀH amination
reactions catalyzed by other metals (e.g., Co, Ag, Fe) or metal-free
amination reactions were also reported: (h) Wert, S.; Kodama, S.;
Studer, A. Angew. Chem., Int. Ed. 2011, 50, 11511. (i) Wang, J.; Hou,
J.-T.; Wen, J.; Zhang, J.; Yu, X.-Q. Chem. Commun 2011, 47, 3652.
(j) Gu, L.; Neo, B. S.; Zhang, Y. Org. Lett. 2011, 13, 1872. (k) Kim, H. J.;
Kim, J.; Cho, S. H.; Chang, S. J. Am. Chem. Soc. 2011, 133, 16382. (l) Kim,
J. Y.; Cho, S. H.; Joseph, J.; Chang, S. Angew. Chem., Int. Ed. 2010, 49,
9899. (m) Cho, S. H.; Kim, J. Y.; Lee, S. Y.; Chang, S. Angew. Chem., Int.
Ed. 2009, 48, 9127.
(5) (a) Tan, Y.; Hartwig, J. F. J. Am. Chem. Soc. 2010, 132, 3676.
(b) Li, J.-J.; Mei, T.-S.; Yu, J.-Q. Angew. Chem., Int. Ed. 2008, 47, 6452.
(c) Tsang, W. C. P.; Zheng, N.; Buchwald, S. L. J. Am. Chem. Soc. 2005,
127, 14560. For the intramolecular amidation involving the proposed
Pd(IV) intermediates, see: (d) Mei, T.-S.; Wang, X.; Yu, J.-Q. J. Am.
Chem. Soc. 2009, 131, 10806. (e) Jordan-Hore, J. A.; Johansson,
C. C. C.; Gulias, M.; Beck, E. M.; Gaunt, M. J. J. Am. Chem. Soc.
2008, 130, 16184. (f) Wasa, M.; Yu, J.-Q. J. Am. Chem. Soc. 2008, 130,
14058.
(1) For reviews on direct amination/amidation of (hetero)aryl
(pseudo)halides, see: (a) Hartwig, J. F. Acc. Chem. Res. 2008, 41, 1534.
(b) Surry, D. S.; Buchwald, S. L. Angew. Chem., Int. Ed. 2008, 47, 6338.
(c) Wolfe, J. P.; Wagaw, S.; Marcoux, J.-F.; Buchwald, S. L. Acc. Chem.
Res. 1998, 31, 805.
(2) For reviews on direct CꢀH bond amination/amidation, see:
(a) Armstrong, A.; Collins, J. C. Angew. Chem., Int. Ed. 2010, 49, 2286.
(b) Collet, F.; Dodd, R. H.; Dauban, P. Chem. Commun. 2009,5061. (c) Muller,
P.; Fruit, C. Chem. Rev. 2003, 103, 2905.
(3) For reviews on recent advances of transition metal catalyzed
CꢀH activation/CꢀC bond formation, see: (a) Yeung, C. S.; Dong,
V. M. Chem. Rev. 2011, 111, 1215. (b) Lyons, T. W.; Sanford, M. S.
Chem. Rev. 2010, 110, 1147. (c) Chen, X.; Engle, K. M.; Wang, D.-H.;
Yu, J.-Q. Angew. Chem., Int. Ed. 2009, 48, 5094. (d) Alberico, D.; Scott,
M. E.; Lautens, M. Chem. Rev. 2007, 107, 174.
r
10.1021/ol203046n
Published on Web 12/13/2011
2011 American Chemical Society

CꢀN bond formation with amide as coupling partners,5
and a highly reactive PdIV intermediate was proposed.5dꢀf
Not long ago, we described the Pd-catalyzed intermolecu-
lar arene CꢀH amidation via nitrene intermediates.6 De-
spite these efforts, the direct CꢀN bond formation is
largely limited to amides as a coupling partner.7 A recent
breakthrough has been achieved by Yu et al. on the Pd-
catalyzed oxidative CꢀH amination with alkylamines.7a
Yet, the majority of the Pd-mediated CꢀN bond forma-
tion would require forceful conditions (e.g., high tempera-
ture or reactivity reagents), posing serious limitations to
the substrate scope and practicality.
Table 1. Reaction Optimizationa,b
additive
(equiv)
base
temp
yield
(%)
entry
1c
(equiv)
solvent
THF
(°C)
AgSbF6
(1.2)
ꢀ
ꢀ
80
80
80
<5
Recently, Rh(III)-catalyzed oxidative arene CꢀH func-
tionalizations leading to CꢀC bond formation are attracting
growing attention.8 With a directing group (e.g., CO2H,
NHAc, pyridyl, imine), the Rh(III) catalyst would undergo
ortho-CꢀH bond metalation to form an aryl-Rh(III)
complex.8oꢀq The aryl-Rh(III) has been shown to cross-
couple with alkynes,8kꢀn aldehydes8h,i/imines,8eꢀg and even
CO2.8j Inspired by these findings, herein we report the Rh-
(III)-catalyzed direct arene CꢀH amination with N-chloro-
amines under mild conditions. Our investigation focuses on
arylketone oximes as substrates since oximes are known to
direct electrophilic CꢀH metalation.3b,6b,6e,6g,6i Further-
more, the oxime group can be easily removed to recover
the carbonyl group for further structural transformations.
Stimulated by our earlier finding that [Rh(COD)Cl]2
would catalyze the coupling reaction of arylboronate,
R-aryldiazoactates, and N-chloromorpholine to form an
R-aminoacetate,6c we hypothesized that N-chloroamines
could be viable reagents for direct CꢀH amination.4e,9
First, acetophenone N-methyloxime (1a) was treated with
[Cp*RhCl2]2 (2.5 mol %), N-chloromorpholine (2a), and
AgSbF6 (1.2 equiv) in THF at 80 °C for 2 h, producing 3aa
in <5% yield (Table 1, entry 1). We were aware that
carboxylate would be needed for the Rh(III)-mediated
CꢀH activation; however, poor 3aa formation was ob-
served with AgOAc and CsOAc as additives (entries 2;3).
After several trials, a combination of AgSbF6 (1.5 equiv)
and CsOAc (1.5 equiv) was found to give 3aa in 38% yield
(entry 4). The molecular structure of 3aa, isolated as a
hydrochloride salt, has been established by X-ray crystallo-
graphy.10 It is noteworthy that no 3aa formation was
observed in the absence of [Cp*RhCl2]2 (entry 5). In this
2c
3c
AgOAc
(1.2)
THF
THF
<5
0
ꢀ
CsOAc
(1.2)
4c
AgSbF6
AgSbF6
AgSbF6
AgSbF6
AgSbF6
AgSbF6
AgSbF6
AgSbF6
AgSbF6
AgSbF6
AgSbF6
AgSbF6
AgSbF6
AgPF6
CsOAc
CsOAc
CsOAc
CsOAc
CsOAc
CsOAc
CsOAc
CsOAc
CsOAc
CsOAc
CsOAc
KOAc
THF
80
80
80
40
40
40
40
40
40
40
40
40
40
40
40
40
40
(38%)d
0
5c,e
6f
THF
THF
0
7g
8
THF
<5
(72)d
<5
<5
15
12
0
THF
9
dioxane
t-AmyOH
DMF
DCE
10
11
12
13
14
15
16
17
18
19
20
toluene
MeCN
THF
8
43
40
64
21
40
<5
Cs2CO3
CsOAc
CsOAc
CsOAc
CsOAc
THF
THF
AgBF4
THF
AgOTf
THF
AgSbF6
(0.3)
THF
21h
22i
AgSbF6
CsOAc
(0.3)
THF
THF
THF
40
40
40
(85)d
(81)d
61
AgSbF6
AgSbF6
CsOAc
(0.3)
23j,k
CsOAc
(0.3)
a Conditions: 1a (0.2 mmol), 2a (1.2 equiv), [Cp*RhCl2]2 (2.5 mol %),
solvent (1 mL), 2 h. b Yields determined by 1H NMR. c 2a (1.5 equiv).
d Isolated yields in parentheses. e No [Cp*RhCl2]2. f Morpholine
(1.5 equiv) was used. g N-Benzoyloxymorpholine (1.5 equiv) was used.
h Reaction time=1h. i [Cp*RhCl2]2 (1mol%). j [Cp*RhCl2]2 (0.5mol%).
k Reaction time = 3 h.
work, N-benzoyloxymorpholine was found to be an in-
effective reagent, and only a trace amount of 3aa was
formed under the Rh(III)-catalysis (entry 6). As expected,
morpholine, instead of the N-chloro derivative, failed to
yield any 3aa formation (entry 7).
(6) For Pd-catalyzed nitrene-mediated CꢀN formation, see: (a) Ng,
K.-H.; Chan, A. S. C.; Yu, W.-Y. J. Am. Chem. Soc. 2010, 132, 12862. (b)
Thu, H.-Y.; Yu, W.-Y.; Che, C.-M. J. Am. Chem. Soc. 2006, 128, 9048.
For Pd-catalyzed reactions involving carbenes and carboradicals, see:
(c) Tsoi, Y.-T.; Zhou, Z.; Yu, W.-Y. Org. Lett. 2011, 13, 5360. (d) Tsoi,
Y.-T.; Zhou, Z.; Chan, A. S. C.; Yu, W.-Y. Org. Lett. 2010, 12, 4506. (e)
Chan, C.-W.; Zhou, Z.; Chan, A. S. C.; Yu, W.-Y. Org. Lett. 2010, 12,
3926. (f) Chan, W.-W.; Yeung, S.-H.; Zhou, Z.; Chan, A. S. C.; Yu,
W.-Y. Org. Lett. 2010, 12, 604. (g) Yu, W.-Y.; Sit, W. N.; Zhou, Z.; Chan,
A. S. C. Org. Lett. 2009, 11, 3174. (h) Yu, W.-Y.; Tsoi, Y.-T.; Zhou, Z.;
Chan, A. S. C. Org. Lett. 2009, 11, 469. (i) Yu, W.-Y.; Sit, W. N.; Lai,
K.-M.; Zhou, Z.; Chan, A. S. C. J. Am. Chem. Soc. 2008, 130, 3304.
(7) For an example of Pd-catalyzed intermolecular CꢀH amination,
see: (a) Yoo, E. J.; Ma, S.; Mei, T.-S.; Chan, K. S. L.; Yu, J.-Q. J. Am.
Chem. Soc. 2011, 133, 7652. For other examples of Pd-catalyzed
intermolecular CꢀH amidation, see: (b) Sun, K.; Li, Y.; Xiong, T.;
Zhang, J.; Zhang, Q. J. Am. Chem. Soc. 2011, 133, 1694. (c) Xiao, B.;
Gong, T.-J.; Xu, J.; Liu, Z.-J.; Liu, L. J. Am. Chem. Soc. 2011, 133, 1466.
(d) Xiong, T.; Li, Y.; Lv, Y.; Zhang, Q. Chem. Commun. 2010, 46, 6831.
To optimize the amination protocol, we extensively screen-
ed various experimental parameters. When we performed the
amination reaction at 40 °C, 3aa was formed in 73% yield
(entry 8). The lower temperature probably slowed down the
self-decomposition of the N-chloromorpholine in the reac-
tion mixture. Among the solvents being tested, THF was
the solvent of choice (entries 9;14). Compared to CsOAc,
KOAc and Cs2CO3 are ineffective additives, whereas the silvꢀer
salts of some noncoordinating anions such as PF6ꢀ, BF4
,
OTfꢀ produced less satisfactory results (entries 15ꢀ19).
273
Org. Lett., Vol. 14, No. 1, 2012

loadings (1ꢀ0.5 mol %) with 3aa being obtained in
61ꢀ81% yield (entries 22ꢀ23).
Table 2. Substrate Scopea,b
Table 2 depicts the results of the substrate scope study
using 2a as a coupling partner. In general, functionalized
oximes can be transformed to their respective arylamines
3baꢀ3ga in 43ꢀ73% yields with excellent ortho-selectivity.
While electron-neutral and -deficient arenes can be amin-
ated with the Rh(III)-catalyzed reaction, slightly lower
yields (ca. 50%) were obtained with electron-deficient
arenes. Nevertheless, the Rh(III)-catalyzed reaction exhi-
bits better tolerance to electron-withdrawing groups (Br,
CF3, CO2Et) than the Pd(II)-catalyzed intermolecular
amidations.6a Tolerance to the bromo and ester functions
is especially noteworthy since they are useful for subse-
quent cross-coupling reactions.
To scrutinize further the regioselectivity, the amination
reaction of meta-substituted oxime 1h occurred exclusively
to the more open CꢀH bond (3ha: 83%). Likewise, 1i
bearing two methyl substituents was converted to 3ia
selectively. However, the analogous reaction of the meta-
methoxy-substituted oximes 1j produced inseparable re-
gioisomeric products 3ja and 3ja0 in a ratio of 56:44 based
on NMR analysis. Assuming the aryl-Rh(III) complexes
as the intermediate, our findings are compatible with an
earlier report by Jones and co-workers that CꢀH rhoda-
tion by [Cp*RhCl2]2 occurred nonregioselectively with
meta-methoxy-substituted 2-arylpyridines.8o In this work,
other bicyclic oximes such as those containing tetralone
(1kꢀl) and chromalone (1m) scaffolds are effective sub-
strates for the direct amination reactions. Successful
amination of the naphthalene and 2H-1,4-bezoxazin-3(4H)-
one scaffolds have also been accomplished to afford 3na and
3oa in 53% and 87% yields. We found that N-methoxyben-
zamide can be aminated to give 3pa in 40% yield.
a Conditions: substrate (0.2 mmol), 2a (1.2 equiv), [Cp*RhCl2]2
(2.5 mol %), CsOAc (30 mol %), AgSbF6 (1.5 equiv), THF (1 mL),
40 °C, 1 h. b Isolated yields. c 2a was slowly added over 30 min. d Reaction
temperature = 60 °C. e THF (3 mL). f The regioisomeric ratio was
determined by NMR analysis. g CsOAc (1.5 equiv).
Employing a substoichiometric amount (30 mol %) of
AgSbF6 resulted in poor 3aa formation (<5%, entry 20).
Notably, the best result (3aa: 85%) was attained under the
conditions [Cp*RhCl2]2 (2.5 mol %), AgSbF6 (1.5 equiv),
and CsOAc (30 mol %) in THF at 40 °C (entry 21). Indeed,
the catalytic system remained operational at lower catalyst
Employing 1a as the substrate, the amination scope has
been further extended to other N-chloroamines (Table 3).
Table 3. Amine Scopea,b
(8) For reviews on the Rh-catalyzed CꢀH activation/CꢀC bond
formation, see: (a) Colby, D. A.; Bergman, R. G.; Ellman, J. A. Chem.
Rev. 2010, 110, 624. (b) Satoh, T.; Miura, M. Chem.;Eur. J. 2010, 16,
11212. For recent selected examples of the Rh-catalyzed aromatic CꢀH
bond functionalizations, see: (c) Patureau, F. W.; Besset, T.; Glorius, F.
Angew. Chem., Int. Ed. 2011, 50, 1064. (d) Rakshit, S.; Grohmann, C.;
Besset, T.; Glorius, F. J. Am. Chem. Soc. 2011, 133, 2350. (e) Hesp,
K. D.; Bergman, R. G.; Ellman, J. A. J. Am. Chem. Soc. 2011, 133,
11430. (f) Tsai, A. S.; Tauchert, M. E.; Bergman, R. G.; Ellman, J. A.
J. Am. Chem. Soc. 2011, 133, 1248. (g) Li, Y.; Li, B.-J.; Wang, W.-H.;
Huang, W.-P.; Zhang, X.-S.; Chen, K.; Shi, Z.-L. Angew. Chem., Int. Ed.
2011, 50, 2115. (h) Park, J.; Park, E.; Kim, A.; Lee, Y.; Chi., K.-W.;
Kwak, J. H.; Jung, Y. H.; Kim, I. S. Org. Lett. 2011, 13, 4390. (i) Yang,
L.; Correia, C. A.; Li, C.-J. Adv. Synth. Catal. 2011, 353, 1269.
(j) Mizuno, H.; Takaya, J.; Iwasawa, N. J. Am. Chem. Soc. 2011, 133,
1251. (k) Too, P. C.; Chua, S. H.; Wong, S. H.; Chiba, S. J. Org. Chem.
2011, 76, 6159. (l) Hyster, T. K.; Rovis, T. J. Am. Chem. Soc. 2010, 132,
10565. (m) Stuart, D. R.; Alsabeh, P.; Kuhn, M.; Fagnou, K. J. Am.
Chem. Soc. 2010, 132, 18326. (n) Guimond, N.; Gouliaras, C.; Fagnou,
K. J. Am. Chem. Soc. 2010, 132, 6908. For more detailed studies of
cyclorhodated ArylꢀRh(III) complexes, see: (o) Li, L.; Brennessel,
W. W.; Jones, W. D. Organometallics 2009, 28, 3492. (p) Li, L.;
Brennessel, W. W.; Jones, W. D. J. Am. Chem. Soc. 2008, 130, 12414.
(q) Davies, D. L.; Al-Duaij, O.; Fawcett, J.; Giurdiello, M.; Hilton, S. T.;
Russell, D. R. Dalton Trans. 2003, 4132.
a Conditions: 1a (0.2 mmol), N-chloroamine (1.2 equiv), [Cp*RhCl2]2
(2.5 mol %), CsOAc (30 mol %), AgSbF6 (1.5 equiv), THF (1 mL), 40 °C,
d
2 h. b Isolated yields. c Reaction was carried out at rt for 15 h.
[Cp*RhCl2]2 (5 mol %). e N-Chloro-N-methylbutylamine (2f) was added
slowly over 30 min.
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Org. Lett., Vol. 14, No. 1, 2012

Analogous to 2a, the Rh-catalyzed coupling of N-chloropi-
peridine and 4-Boc-N-chloropiperazine gave 3ab (87%) and
3ac (63%) effectively. The analogous reaction of N-chlor-
oethyl nipecotate afforded 3ad in 53% yield. Yet, the reac-
tions of aliphatic N-chlorodialkylamines furnished the desired
products (e.g., 3ae and 3af) in moderate yields (35ꢀ44%).
Scheme 2. Proposed Mechanism
Scheme 1. One-Pot Direct Amination
Development of a one-pot direct amination protocol
without isolating the N-chloroamines would be attractive
for synthetic application. In this work, we prepared 2a by
treating morpholine with NCS in THF for 20 min in the
dark. Afterward, the mixture was added to the THF
solution containing 1a, [Cp*RhCl2]2, AgSbF6, and CsOAc
(Scheme 1), and 3aa was obtained in 80% yield. The one-
pot protocol can be applied to the couplings of piperidine
and N-Boc-piperazine. To illustrate the practicality of our
protocol, we demonstrated that the O-methyl oxime can
be easily removed by heating 3aa in 6 M HCl to afford
N-(2-acetylphenyl)morpholine in 89% yield. According to
the literature, 2-aminoacetophenones are useful scaffolds
in some medicinally active compounds.10,11
The catalytic amination reaction should involve initially
electrophilic metalation of the ortho-arene CꢀHbondofthe
oximes to afford an aryl-Rh(III) species (Scheme 2). The
Rh(III)-mediated CꢀH metalation should be reversible. In
this work, treating 1a-d5 with [Cp*RhCl2]2 (5 mol %),
AgSbF6 (1.5 equiv), and CsOAc (0.3 equiv) in MeOH at
40 °C for 20 min in the absence of haloamine led to a 47%
loss of ortho-deuteriums.10 This finding is comparable to the
previous results reported by Fagnou et al.8m,n By means of
competitive experiments with 1a and 1a-d5 as substrates, a
primary kinetic isotope effect (kH/kD) = 2.7 was observed,
suggesting that the CꢀH bond cleavage is rate-limiting.12
The mechanism of the CꢀN bond coupling step remains
to be elucidated. In this work, treating the cyclorhodated
2-phenylpyridine (2PP) complex [Cp*RhCl(2-PP)] with 2a
(1.1 equiv) and AgSbF6 (2.2 equiv) at40°C for 3h afforded
the corresponding amination product in 52% yield.10 This
result suggested that the reaction is likely to go through the
cyclometalated aryl-Rh(III) complexes. A possible path-
way for the CꢀN bond coupling may involve prior co-
ordination of the N-chloroamine to the aryl-Rh(III) com-
plex. Migration of the aryl group to the nitrogen prompted
by the chloride abstraction with Agþ would result in the
CꢀN bond formation .13 Compatible with this notion, a
stoichiometric amount of Ag salt is needed for the amina-
tionreaction. Moreover, changing the halide leaving group
to benzoate is also detrimental to the reaction.
In summary, we developed a Rh(III)-catalyzed intermo-
lecular ortho-CꢀH amination of acetophenone O-methyl
oximes using N-chloroamines, and a one-pot protocol
using amines directly for the CꢀH amination is also
developed. The Rh-catalyzed reaction exhibits high func-
tional group tolerance, regioselectivity, and broad sub-
strate scope under relatively mild conditions. Mechanistic
studies and application of the Rh-catalyzed reaction to
other substrate classes will be reported in due course.
Acknowledgment. We thank the financial support from
the Hong Kong Research Grants Council (PolyU5017-
07P; SEG_PolyU01) and The Area of Excellence Scheme
(AoE/P-10-01) administeredby theHong KongUniversity
Grants Committee. K.H.N. thanks The Hong Kong Poly-
technic University for the award of the Postgraduate
Studentship.
Supporting Information Available. Experimental de-
tails, characterization data, and copies of 1H, 13C NMR
spectra of all new compounds. This material is available
free of charge via the Internet at http://pubs.acs.org.
(9) For a review on N-haloamines, see: (a) Kovacic, P.; Lowery,
M. K.; Field, K. W. Chem. Rev. 1970, 70, 639. For recent examples using
N-chloroamines as reagents, see: (b) Hatakeyama, T.; Yoshimoto, Y.;
Ghorai, S. K.; Nakamura, M. Org. Lett. 2010, 12, 1516. (c) Barker, T. J.;
Jarvo, E. R. J. Am. Chem. Soc. 2009, 131, 15598.
(12) Intermolecular primary KIE (kH/kD) values of 2.2ꢀ4.2 have
been reported for Rh-catalyzed ortho-CꢀH activation of arenes; for
examples, see refs 8e, 8m, and 8n.
(10) See Supporting Information for detailed experimental.
(11) (a) Tulp, M.; Bohlin, L. Trends Pharmacol. Sci. 2005, 26, 175.
(b) Bellamy, F. D.; Chazan, J. B.; Dodey, P.; Dutartre, P.; Ou, K.;
Pascal, M.; Robin, J. J. Med. Chem. 1991, 34, 1545.
(13) The analogous reaction of chloroamines with organoboranes
was proposed to occur via anionotropic migration of an alkyl group
from boron to nitrogen; see: Kabalka, G. W.; McCollum, G. W.; Kunda,
S. A. J. Org. Chem. 1984, 49, 1656.
Org. Lett., Vol. 14, No. 1, 2012
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