Unlocking the N2selectivity of benzotriazoles: Regiodivergent and highly selective coupling of benzotriazoles with allenes

Article abstract of DOI:10.1002/anie.201403682

The rhodium-catalyzed, highly N²- and N¹-selective coupling of benzotriazoles with allenes is reported. The exceptionally high N² and N¹ selectivities were achieved by using a rhodium(I)/DPEphos and rhodium(I)/JoSPOphos catalyst, respectively. This method permits the atom-economic synthesis of valuable branched N²- and N¹-allylated benzotriazole derivatives and allows for preliminary studies of their reactivity.

Full text of DOI:10.1002/anie.201403682

.
Angewandte
Communications
DOI: 10.1002/anie.201403682
Heterocycles Very Important Paper
Unlocking the N2 Selectivity of Benzotriazoles: Regiodivergent and
Highly Selective Coupling of Benzotriazoles with Allenes**
Kun Xu, Niels Thieme, and Bernhard Breit*
Abstract: The rhodium-catalyzed, highly N2- and N1-selective
coupling of benzotriazoles with allenes is reported. The
exceptionally high N2 and N1 selectivities were achieved by
using a rhodium(I)/DPEphos and rhodium(I)/JoSPOphos
catalyst, respectively. This method permits the atom-economic
synthesis of valuable branched N2- and N1-allylated benzo-
triazole derivatives and allows for preliminary studies of their
reactivity.
often the dominant product.[4–6] The aromaticity of the
benzenoid tautomer (A) was estimated to be 9.5 kcalmolÀ1
greater than that of the quinoid-like tautomer (A’), which
renders the N2-selective substitution of benzotriazole a very
challenging process.[3a] Although substantial efforts have been
made to solve this problem, only a poor N2 selectivity for
benzotriazoles was achieved (Scheme 2).[7] In our studies of
the rhodium-catalyzed atom-economic[8] addition of pronu-
cleophiles to allenes and alkynes[9,10] as an alternative to
allylic substitution,[11] we assumed that a suitable phosphine-
modified rhodium(I) catalyst may distinguish the energy
difference between the N2 and N1 intermediates in the
catalytic cycle, which may result in N2 and N1 alkylation.
Herein we report an unprecedented N2- and N1-selective
coupling of benzotriazoles with allenes, which allows for
regiodivergent allylation with high levels of selectivity
(Scheme 2).
B
enzotriazoles and their derivatives have been widely used
in organic synthesis, materials science, biological research,
and medicinal chemistry.[1] N-Alkyl-substituted benzotria-
zoles possess a broad spectrum of biological activities[2a–f]
including anti-inflammatory,[2b] antifungal,[2d] antibacterial,[2e]
and analgesic properties[2f] (Scheme 1). Unfortunately, the
The initial experiments were performed with benzotria-
zole and cyclohexylallene in the presence of [{Rh(cod)Cl}2]
(1.0 mmol%) and dppf (3 mmol%) in 1,2-dichloroethane
(DCE) at 808C. To our delight, the reaction gave a 93% yield
of the product as determined by NMR spectroscopy, although
the selectivity was still low (Table 1, entry 1). The feasibility
of benzotriazole as a pronucleophile encouraged us to screen
achiral bidentate diphosphine ligands with different bite
angles. However, most of the ligands only resulted in poor
selectivities (Table 1, entries 2 and 3) or traces of product.[12]
We were pleased to observe that high N1 selectivity was
obtained using DPPPent, although the yield was low (Table 1,
entry 4). To our delight, a 90% yield of the isolated N2
product (2a) was obtained using DPEphos.[12] Further opti-
mization led to a lower catalyst loading and an allene ratio
with a high selectivity of N2 relative to its isomers (N2/Nx =
94:6) and without a detrimental effect on the reactivity
(Table 1, entry 5). The corresponding regiocomplementary N1
Scheme 1. Examples of biologically active N-alkylated benzotriazoles.
difficulty in achieving the N-selective, particularly N2-selec-
tive, alkylation of benzotriazoles has limited their application.
In this regard, efficient synthetic methods for the N-selective
alkylation of benzotriazoles are highly desirable.
N-Selective control over 1,2,3-triazoles, especially benzo-
triazoles, is a challenging topic in organic synthesis because of
the equilibrium between N1 (N3) and N2 tautomers.[3] In
comparison with non-benzo-1,2,3-triazoles, the N2 selectivity
of benzotriazoles is more difficult to achieve as a result of the
decreased aromaticity of the N2 tautomer.[3] In general,
a
mixture of N1- and N2-substituted benzotriazoles is
obtained, although the N1-substituted benzotriazole is most
[*] K. Xu, N. Thieme, Prof. Dr. B. Breit
Institut fꢀr Organische Chemie, Albert-Ludwigs-Universitꢁt Freiburg
Albertstrasse 21, 79104 Freiburg im Breisgau (Germany)
E-mail: bernhard.breit@chemie.uni-freiburg.de
[**] This work was supported by the DFG, the International Research
Training Group “Catalysts and Catalytic Reactions for Organic
Synthesis” (IRTG 1038), the Fonds der Chemischen Industrie, and
the Krupp Foundation. We thank Umicore, BASF, and Wacker for
generous gifts of chemicals.
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/anie.201403682.
Scheme 2. N-Selective substitution of benzotriazoles.
7268
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2014, 53, 7268 –7271

Angewandte
Chemie
Table 1: Ligand controlled N2- and N1-selective coupling of benzotriazole
with cyclohexylallene.
Entry[a,b,c]
Ligand
Yield/[%][d]
N1/N2[e]
1[a]
2[a]
3[a]
4[a]
5[b]
6[c]
dppf
dppp
dppb
DPPPent
DPEphos
JoSPOphos L
93
95
94
31
39:61
66:34
71:29
93:7
(90)[f]
(83)[f]
6:94[g]
98:2[h]
[a] Conditions: [{Rh(cod)Cl}2] (1.0 mol%), ligand (3.0 mol%), benzo-
triazole (0.25 mmol), cyclohexylallene (0.3 mmol), DCE (1.0 mL).
[b] Conditions: [{Rh(cod)Cl}2] (1.0 mol%), DPEphos (3.0 mol%), ben-
zotriazole (0.5 mmol), cyclohexylallene (0.6 mmol), DCE (1.25 mL).
[c] Conditions: [{Rh(cod)Cl}2] (2.0 mol%), JoSPOphos L (8.0 mol%),
benzotriazole (0.4 mmol), cyclohexylallene (0.6 mmol), DCE (2.0 mL).
[d] Yield of the N1 and N2 products in the crude reaction mixture as
Scheme 3. Scope of the rhodium-catalyzed N2-selective coupling of
benzotriazoles with allenes. [a] The yield is that of the isolated product.
[b] The ratio of N2 and its isomers (N2/Nx) was determined by GC-MS
analysis of the crude reaction mixture. [c] Conditions: [{Rh(cod)Cl}2]
(2.5 mol%), DPEphos (10 mol%), allene (1.5 equiv). [d] Determined
by 1H NMR spectroscopy after purification. Phth=phthaloyl,
TBS=tert-butylsilyl.
1
determined by H NMR spectroscopy and using 1,3,5-trimethoxyben-
zene as an internal standard. [e] Determined by GC-MS of the crude
reaction mixture. [f] Yield is that of the isolated product. [g] The GC-MS
ratio is N2/Nx (Nx: isomers of 2a). [h] The GC-MS ratio is N1/Nx (Nx:
isomers of 1a). cod=1,5-cyclooctadiene, Cy=cyclohexyl, dppb=1,4-
bis(diphenylphosphino)butane, dppf=1,1’-bis(diphenylphosphino)fer-
rocene, dppp=1,3-bis(diphenylphosphino)propane.
product (1a) was obtained, after intensive optimization,[12] in
83% yield and 98:2 (N1/Nx) selectivity by using JoSPOphos
L[13a] (Table 1, entry 6). Control experiments indicated that
both a rhodium precursor and ligand are necessary for the
coupling reactions.[12]
With the optimized conditions in hand, we then inves-
tigated the scope of the addition of different benzotriazoles
with allenes.[13b] A broad range of benzotriazole derivatives
were suitable substrates for the synthesis of N2-allylated
products with good to excellent yields and high selectivities
(Scheme 3). Both symmetrically (2a,b) and asymmetrically
(2c–g) substituted benzotriazole derivatives were smoothly
coupled with cyclohexylallene to give branched and N2-
allylated products, although a higher catalyst and allene
loading were needed in some cases (2e, 2g–I, and 2l).
Halogen (2d), free amino (2 f), and hydroxy (2g) groups were
well tolerated. To our delight, a pyridine-conjugated triazole
was also allylated with high N2 selectivity (2e). A range of
terminal allenes was readily prepared in one or two steps from
commercially available starting materials.[12] Allenes bearing
protected alcohols (2i and 2l) and phthalimide (2j) were
compatible. 1,1-Disubstituted allenes (2k,l) were also suitable
substrates, and furnished useful quaternary carbon centers.
Symmetric benzotriazole derivatives and different allenes
were tested in the rhodium-catalyzed N1-selective coupling
reactions. The regiocomplementary branched N1-allylated
products were obtained in high yields and high N1 selectivities
(Scheme 4, 1a–g).[13c]
Scheme 4. Scope of the rhodium-catalyzed N1-selective coupling of
benzotriazoles with allenes. [a] The yield is that of the isolated product.
[b] The ratio of N1 and its isomers (N1/Nx) was determined by GC-MS
analysis of the crude reaction mixture. [c] Determined by H NMR
spectroscopy after purification.
1
To explore the reactivity of the “less-aromatic” N2-
allylated benzotriazoles (Scheme 5), 2a and 2e were sub-
jected to hydrogenation with Pd/C under H2 (1 atm) at room
temperature. The conjugated benzene and pyridine ring were
completely hydrogenated under these mild conditions in 99%
(3a) and 73% (3b) yield, respectively. Different substituents
on the benzene ring of N2-allylated benzotriazoles (2c and 2 f)
also allowed the synthesis of the corresponding hydrogenated
products (3c,d), which are difficult to prepare by other
methods.[14a] Ozonolysis of 2a followed by reductive work up
with NaBH4 led to 4a in 89% yield.[14b] Furthermore, the
Angew. Chem. Int. Ed. 2014, 53, 7268 –7271
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org 7269

.
Angewandte
Communications
Scheme 5. Transformations of N2-allylated benzotriazoles. a): Pd/C
(10 mol%), H2 (1 atm), MeOH, RT, 16 h; 3a (product of 2a), 99%
yield; 3b (2e), 73% yield. b): Pd/C (10 mol%), H2 (30 atm), EtOH,
608C, 16 h; 3c (2c), 99% yield; 3d (2 f), 80% yield. c): O3, MeOH,
À788C; then NaBH4 (product of 2a). d) [{Rh(cod)acac] (0.68 mol%),
6-DPPon (3.4 mol%), H2/CO (1:1, 1 atm), THF, RT, 24 h, linear/
branched=87:13. e): 9-BBN (2.0 equiv), THF, RT, 16 h; then H2O2,
NaOH, EtOH, RT, 3 h. acac=acetylacetonate, 9-BBN=9-borabicyclo-
[3.3.1]nonane
Scheme 7. Proposed mechanism for the rhodium-catalyzed N1- and
N2-selective coupling of benzotriazoles with allenes.
(C or C’),[15e–g] which could generate the desired branched N-
allylic benzotriazoles on reductive elimination.[16] The N se-
lectivity is dictated by the energy difference between the two
catalytic cycles: the N2-selective product is formed via A-B-C,
and the N1-selective product is produced via A’-B’-C’.
However, the origin of why the two bidentate ligands favor
one pathway over the other remains unclear at this moment,
and must be addressed in future studies.
allylic double bond can be easily modified to other useful
functional groups (4b,c).
To study the possible mechanism (Scheme 6), isotopic-
labeling experiments were conducted with [D]benzotriazole
and cyclohexylallene under optimized conditions. Deuterium
incorporation was only observed at the internal position of
To conclude, we have developed the first highly N2-
selective coupling of benzotriazoles with allenes by using
a rhodium/DPEphos catalyst system. The regiocomplemen-
tary N1 allylation was also achieved in high yields and high
selectivities by using a rhodium/JoSPOphos ligand. A broad
range of new N2- and N1-allylated benzotriazoles was
prepared in an atom-economic manner. This method may
extend the application of alkyl-substituted benzotriazoles.
Mechanistic investigations and asymmetric variants are
currently underway and will be reported in due course.
Received: March 25, 2014
Published online: May 23, 2014
Scheme 6. Mechanistic investigations. a) Scope of the N1-selective
coupling, 32% yield. b) Optimized conditions for N2-selective cou-
pling, 78% yield. c) Cyclohexylallene (1.2 equiv), À408C to room
temperature.
Keywords: allenes · allylic compounds · benzotriazoles ·
heterocyles · homogeneous catalysis
.
[1] a) J. A. Joule, K. Mills, Heterocyclic Chemistry, Wiley, West
Sussex, 2010, Chap. 32 – 33; b) S. Rachwal in Comprehensive
Heterocyclic Chemistry III, Vol. 5 (Eds.: A. R. Katritzky, C. A.
Ramsden, E. F. V. Scriven, R. J. K. Taylor), Elsevier Science &
Technology, Oxford, 2008, pp. 1 – 209; reviews on the application
of non-benzo-1,2,3-triazoles: c) L. J. Macpherson, A. E. Dubin,
M. J. Evans, F. Marr, P. G. Schultz, B. F. Cravatt, A. Patapoutian,
Nature 2007, 445, 541 – 545; d) J. E. Moses, A. D. Moorhouse,
Chem. Soc. Rev. 2007, 36, 1249 – 1262; e) D. Fournier, R.
Hoogenboom, U. S. Schubert, Chem. Soc. Rev. 2007, 36, 1369 –
1380; f) L. S. Wong, F. Khan, J. Micklefield, Chem. Rev. 2009,
109, 4025 – 4053; g) F. Amblard, J. H. Cho, R. F. Schinazi, Chem.
Rev. 2009, 109, 4207 – 4220; h) J. C. Jewett, C. R. Bertozzi, Chem.
Soc. Rev. 2010, 39, 1272 – 1279; i) P. L. Golas, K. Matyjaszewski,
Chem. Soc. Rev. 2010, 39, 1338 – 1354; j) A. H. El-Sagheer, T.
Brown, Chem. Soc. Rev. 2010, 39, 1388 – 1405.
the alkene.[12] The stoichiometric reaction of benzotriazole
with [{Rh(cod)Cl}2] and DPEphos in CDCl3 was monitored
1
by NMR spectroscopy.[12] The H NMR spectrum (263 K) of
the reaction after five minutes reaction at room temperature
showed a major rhodium hydride species at d = À14.17 ppm
(1JRh-H = 14.0 Hz), which indicates the oxidative addition of
the N H bond of benzotriazole to the rhodium center.[15a] The
À
subsequent addition of cyclohexylallene to the mixture at
À408C led to immediate consumption (a few seconds) of the
Rh-H species, which suggests hydrometalation of Rh-H to
cyclohexylallene.[15b–d] Warming the mixture to room temper-
ature led to the formation of the coupling product 2a in 83%
yield (N2/Nx > 99:1).[12]
[2] Examples of biologically active N-alkyl-substituted benzotria-
zoles: a) G. Scapin, S. B. Patel, J. W. Becker, Q. Wang, C.
Desponts, D. Waddleton, K. Skorey, W. Cromlish, C. Bayly, M.
Therien, J. Y. Gauthier, C. S. Li, C. K. Lau, C. Ramachandran,
B. P. Kennedy, E. Asante-Appiah, Biochemistry 2003, 42, 11451 –
11459; b) K. M. Dawood, H. Abdel-Gawad, E. A. Rageb, M.
On the basis of the labeling experiments, the following
mechanism can be proposed (Scheme 7). Oxidative addition
of the tautomers (A or A’) of benzotriazole to RhI generates
a RhIII complex (B or B’).[15a] Hydrometalation of the less-
substituted double bond could generate a s-allyl-Rh complex
7270 www.angewandte.org
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2014, 53, 7268 –7271

Angewandte
Chemie
Ellithey, H. A. Mohamed, Bioorg. Med. Chem. 2006, 14, 3672 –
Jꢃkel, B. Plietker, J. Am. Chem. Soc. 2003, 125, 4438 – 4439;
3680; c) M. H. Paluchowska, R. Bugno, S. Charakchieva-Minol,
d) S. S. Kinderman, R. Gelder, J. H. Maarseveen, H. E. Schoe-
maker, H. Hiemstra, F. P. J. T. Rutjes, J. Am. Chem. Soc. 2004,
126, 4100 – 4101; e) N. Nishina, Y. Yamamoto, Angew. Chem.
2006, 118, 3392 – 3395; Angew. Chem. Int. Ed. 2006, 45, 3314 –
3317; f) R. L. Lalonde, B. D. Sherry, E. J. Kang, F. D. Toste, J.
Am. Chem. Soc. 2007, 129, 2452 – 2453; g) I. S. Kim, M. J.
Krische, Org. Lett. 2008, 10, 513 – 515; h) T. Kawamoto, S.
Hirabayashi, X. Guo, T. Nishimura, T. Hayashi, Chem. Commun.
2009, 3528 – 3530; i) S. B. Han, I. S. Kim, H. Han, M. J. Krische, J.
Am. Chem. Soc. 2009, 131, 6916 – 6917; j) J. Moran, A. Preetz,
R. A. Mesch, M. J. Krische, Nat. Chem. 2011, 3, 287 – 290; k) P.
Koschker, A. Lumbroso, B. Breit, J. Am. Chem. Soc. 2011, 133,
20746 – 20749; l) K. L. Butler, M. Tragni, R. A. Widenhoefer,
Angew. Chem. 2012, 124, 5265 – 5268; Angew. Chem. Int. Ed.
2012, 51, 5175 – 5178; m) A. Lumbroso, N. Abermil, B. Breit,
Chem. Sci. 2012, 3, 789 – 793; n) M. L. Cooke, K. Xu, B. Breit,
Angew. Chem. 2012, 124, 11034 – 11037; Angew. Chem. Int. Ed.
2012, 51, 10876 – 10879; o) K. Xu, N. Thieme, B. Breit, Angew.
Chem. 2014, 126, 2194 – 2197; Angew. Chem. Int. Ed. 2014, 53,
2162 – 2165; p) C. Li, B. Breit, J. Am. Chem. Soc. 2014, 136, 862 –
865.
´
A. J. Bojarski, E. Tatarczynska, E. Chojnacka-Wꢀjcik, Arch.
Pharm. Chem. Life Sci. 2006, 339, 498 – 506; d) Z. Rezaei, S.
Khabnadideh, K. Pakshir, Z. Hossaini, F. Amiri, E. Assadpour,
Eur. J. Med. Chem. 2009, 44, 3064 – 3067; e) M. Cano, A.
Palomer, A. Guglietta, (Ferrer Internacional, S.A.), WO
2010000704 (A1), 2010; f) C. Park, K. Min, Y. Shin, Y. Shin, H.
Yoon, W. Kim, E. Ryu, C. Chung, H. Kim, (Sk Biopharmaceut-
icals Co. Ltd.), US 20100311789 (A1), 2010.
[3] Theoretical studies on benzotriazoles: a) F. Tomꢁs, J. M.
Abboud, J. Laynez, R. Notario, L. Santos, S. O. Nilsson, J.
Catalꢁn, R. M. Claramunt, J. Elguero, J. Am. Chem. Soc. 1989,
111, 7348 – 7353; b) A. R. Katritzky, K. Yannakopoulou, J. Org.
Chem. 1990, 55, 5683 – 5687; c) J. Catalꢁn, P. Pꢂrez, Chem. Phys.
´
Lett. 2005, 404, 304 – 308; d) J. Poznanski, A. Najda, M. Bretner,
D. Shugar, J. Phys. Chem. A 2007, 111, 6501 – 6509.
[4] Synthesis of N1-substituted non-benzo-1,2,3-triazoles: a) V. V.
Rostovtsev, L. G. Green, V. V. Fokin, K. B. Sharpless, Angew.
Chem. 2002, 114, 2708 – 2711; Angew. Chem. Int. Ed. 2002, 41,
2596 – 2599; b) L. Zhang, X. Chen, P. Xue, H. H. Y. Sun, I. D.
Williams, K. B. Sharpless, V. V. Fokin, G. Jia, J. Am. Chem. Soc.
2005, 127, 15998 – 15999; c) J. Kalisiak, K. B. Sharpless, V. V.
Fokin, Org. Lett. 2008, 10, 3171 – 3174.
[10] Selected examples of the coupling of pronucleophiles with
alkynes for the synthesis of allylic products: a) Y. Yamamoto, M.
Al-Masum, N. Asao, J. Am. Chem. Soc. 1994, 116, 6019 – 6020;
b) M. Al-Masum, Y. Yamamoto, J. Am. Chem. Soc. 1998, 120,
3809 – 3810; c) L. M. Lutete, I. Kadota, Y. Yamamoto, J. Am.
Chem. Soc. 2004, 126, 1622 – 1623; d) A. Lumbroso, P. Koschker,
N. R. Vautravers, B. Breit, J. Am. Chem. Soc. 2011, 133, 2386 –
2389.
[11] Reviews on transition-metal-catalyzed allylic alkylation:
a) B. M. Trost, D. L. V. Vranken, Chem. Rev. 1996, 96, 395 –
422; b) B. M. Trost, M. L. Crawley, Chem. Rev. 2003, 103,
2921 – 2943; c) Z. Lu, S. Ma, Angew. Chem. 2008, 120, 264 – 303;
Angew. Chem. Int. Ed. 2008, 47, 258 – 297.
[5] a) A. R. Katritzky, J. Wu, W. Kuzmierkiewicz, S. Rachwal,
Liebigs Ann. Chem. 1994, 1 – 5; b) A. R. Katritzky, I. B. Pusch-
mann, C. V. Stevens, A. P. Wells, J. Chem. Soc. Perkin Trans. 2
1995, 1645 – 1649; c) P. Sanna, A. Carta, G. Paglietti, J. Hetero-
cycl. Chem. 1997, 34, 97 – 106; d) S. H. Mashraqui, S. Kumar,
C. D. Mudaliar, Bull. Chem. Soc. Jpn. 2001, 74, 2133 – 2138; e) H.
Lee, J. Won, M. Kim, S. Park, K. Jung, B. R. Kim, S. Lee, Y.
Yoon, J. Org. Chem. 2009, 74, 5675 – 5678; f) W. Liu, D. Zhang, S.
Zheng, Y. Yue, D. Liu, X. Zhao, Eur. J. Org. Chem. 2011, 6288 –
6293; g) W. Yan, T. Liao, O. Tuguldur, C. Zhong, J. L. Petersen,
X. Shi, Chem. Asian J. 2011, 6, 2720 – 2724; h) M. Zhang, X. Guo,
S. Zheng, X. Zhao, Tetrahedron Lett. 2012, 53, 6995 – 6998.
[6] N1-selective substitution of benzotriazoles: a) A. R. Katritzky, J.
Wu, Synthesis 1994, 597 – 600; b) H. Duan, W. Yan, S. Sengupta,
X. Shi, Bioorg. Med. Chem. Lett. 2009, 19, 3899 – 3902; c) W.
Yan, Q. Wang, Y. Chen, J. L. Petersen, X. Shi, Org. Lett. 2010, 12,
3308 – 3311; d) W. Yan, X. Ye, K. Weise, J. L. Petersen, X. Shi,
Chem. Commun. 2012, 48, 3521 – 3523.
[12] See the Supporting Information for details.
[13] a) The JoSPOphos L ligand gives 46% ee, the corresponding
racemic ligand gives the same N1 selectivity; b) reactions of non-
benzo-conjugated triazoles under N2-selective coupling condi-
tions: 4-phenyl-1H-1,2,3-triazole (98% yield, N2/Nx = 93:7), 4-
(tert-butyl)-1H-1,2,3-triazole (68% yield, N2/Nx = 94:6), 1H-
1,2,3-triazole (77% yield, N2/Nx = 74:26), 1H-1,2,4-triazole
(98% yield, N1/Nx > 99:1); c) reaction of 1H-1,2,3-triazole
under N1-selective coupling conditions: 43% yield, N1/Nx =
49:51.
[14] a) D. E. Levy, M. S. Smyth, R. M. Scarborough, (Millennium
Pharmaceuticals, Inc., USA), US 20030153556 (A1), 2002;
b) A. R. Katritzky, R. Maimait, S. N. Denisenko, P. J. Steel,
N. G. Akhmedov, J. Org. Chem. 2001, 66, 5585 – 5589.
[15] Oxidative addition of N-H to rhodium: a) G. A. Ardizzoia, S.
Brenna, G. LaMonica, A. Maspero, N. Masciocchi, M. Moret,
Inorg. Chem. 2002, 41, 610 – 614; hydrometalation of Rh-H to
allene: b) K. Osakada, J. Choi, T. Koizumi, I. Yamaguchi, T.
Yamamoto, Organometallics 1995, 14, 4962 – 4965; c) J. Choi, K.
Osakada, T. Yamamoto, Organometallics 1998, 17, 3044 – 3050;
d) D. N. Tran, N. Cramer, Angew. Chem. 2013, 125, 10824 –
10828; Angew. Chem. Int. Ed. 2013, 52, 10630 – 10634; rhodium
d- and p-allyl complexes: e) J. Wolf, H. Werner, Organometallics
1987, 6, 1164 – 1169; f) P. A. Evans, J. D. Nelson, J. Am. Chem.
Soc. 1998, 120, 5581 – 5582; g) B. Wucher, M. Moser, S. A.
Schumacher, F. Rominger, D. Kunz, Angew. Chem. 2009, 121,
4481 – 4485; Angew. Chem. Int. Ed. 2009, 48, 4417 – 4421.
[16] SN2’-type reductive elimination: a) J. A. Keith, D. C. Behenna,
J. T. Mohr, S. Ma, S. C. Marinescu, J. Oxgaard, B. M. Stoltz,
W. A. Goddard, J. Am. Chem. Soc. 2007, 129, 11876 – 11877; b) J.
Chen, Q. Peng, B. Lei, X. Hou, Y. Wu, J. Am. Chem. Soc. 2011,
133, 14180 – 14183.
[7] N2-Selective substitution of non-benzo-1,2,3-triazoles and ben-
zotriazoles: Alkylation: a) S. Kamijo, T. Jin, Z. Hou, Y.
Yamamoto, J. Am. Chem. Soc. 2003, 125, 7786 – 7787; b) S.
Kamijo, T. Jin, Z. Hou, Y. Yamamoto, J. Org. Chem. 2004, 69,
2386 – 2393; c) Y. Chen, Y. Liu, J. L. Petersen, X. Shi, Chem.
Commun. 2008, 3254 – 3256; d) X. Wang, K. Sidhu, L. Zhang, S.
Campbell, N. Haddad, D. C. Reeves, D. Krishnamurthy, C. H.
Senanayake, Org. Lett. 2009, 11, 5490 – 5493; e) X. Wang, L.
Zhang, D. Krishnamurthy, C. H. Senanayake, P. Wipf, Org. Lett.
2010, 12, 4632 – 4635; f) E. M. Asadulina, M. A. Bastrakov,
A. M. Starosotnikov, V. V. Kachala, S. A. Shevelev, Russ.
Chem. Bull. Int. Ed. 2009, 58, 421 – 425; Arylation: g) Y. Liu,
W. Yan, Y. Chen, J. L. Petersen, X. Shi, Org. Lett. 2008, 10, 5389 –
5392; h) X. Wang, L. Zhang, H. Lee, N. Haddad, D. Krishna-
murthy, C. H. Senanayake, Org. Lett. 2009, 11, 5026 – 5028; i) S.
Ueda, M. Su, S. L. Buchwald, Angew. Chem. 2011, 123, 9106 –
9109; Angew. Chem. Int. Ed. 2011, 50, 8944 – 8947; j) S. Ueda, S.
Ali, B. P. Fors, S. L. Buchwald, J. Org. Chem. 2012, 77, 2543 –
2547; k) J. Wen, L. Zhu, Q. Bi, Z. Shen, X. Li, Z. Wang, Z. Chen,
Chem. Eur. J. 2014, 20, 974 – 978.
[8] B. M. Trost, Science 1991, 254, 1471 – 1477.
[9] Selected examples on the coupling of pronucleophiles with
allenes: a) R. Zimmer, C. U. Dinesh, E. Nandanan, F. A. Khan,
Chem. Rev. 2000, 100, 3067 – 3125; b) J. S. Johnson, R. G. Berg-
man, J. Am. Chem. Soc. 2001, 123, 2923 – 2924; c) B. M. Trost, C.
Angew. Chem. Int. Ed. 2014, 53, 7268 –7271
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
7271