Rapid synthesis of polysubstituted phenanthridines from simple aliphatic/aromatic nitriles and iodo arenes: Via Pd(ii) catalyzed domino C-C/C-C/C-N bond formation

Article abstract of DOI:10.1039/c8cc03556c

An efficient and straightforward method has been developed for the synthesis of polysubstituted phenanthridines from simple aryl iodides and alkyl/aryl nitriles via the palladium-catalyzed nucleophilic addition of aryl iodides to nitriles followed by casc

Full text of DOI:10.1039/c8cc03556c

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Rapid Synthesis of Polysubstituted Phenanthridines from Simple
Aliphatic/Aromatic Nitriles and Iodo Arenes via Pd(II) Catalyzed
Domino C-C/C-C/C-N Bonds Formation
978
Received 00th January 20xx,
Accepted 00th January 20xx
Yogesh Jaiswal, Yogesh Kumar, Jagannath Pal, Ranga Subramanian and Amit
Kumar*
DOI: 10.1039/x0xx00000x
www.rsc.org/
An efficient and straightforward method has been developed for
the synthesis of polysubstituted phenanthridines from simple aryl
iodides and alkyl/aryl nitriles via the palladium-catalyzed
nucleophilic addition of aryl iodides to nitriles followed by cascade
formation of C-C and C-N bonds viz in-situ generated imine
directed sequential two fold C-H activation.
O
O
O
O
H3CO
H3CO
N
HO
N
OCH3
Decarine
Nortidiene
O
O
O
O
N
O
N
N
Carbon-carbon and carbon-nitrogen bonds are ubiquitously
present in most of the natural and synthetic made organic
molecules, particularly in heterocyclic frameworks. The
constructions of these bonds are arguably the most
challenging and important aspect for organic chemists. Hence,
the designing of catalytic strategies for multiple bonds (C-C/C-
C/C-N) formation in a one-pot manner viz domino approach
using an inexpensive substrate with the simple catalytic
H3CO
O
O
O
OCH3
Norchelerythrine
Trispheridine
Norsanguinarine
Figure 1. Bio-active compounds containing a phenanthridine core.
construction of important heterocyclic molecules from readily
available starting materials.10 We envisioned that the rapid
synthesis of biologically relevant phenanthridine derivatives
could be achieved in a one-pot manner from aryl iodides and
alkyl/aryl nitriles viz palladium catalyzed nucleophilic addition
of aryl iodides to nitriles, which would eventually generate
imine in-situ followed by cascade formation of C-C and C-N
bonds via imine directed sequential two fold C-H activation
(Scheme 1). To the best of our knowledge, this is the first
report in describing the synthesis of polysubstituted
phenanthridines involving the Pd-catalyzed insertion of nitrile
with dual C-H functionalization.
system is
a highly desirable and continuous effort in
contemporary organic synthesis.1,2 Functionalized heterocyclic
compounds, for instance, substituted phenanthridines are the
key structural motif that found in many natural products and
biologically relevant compounds (Figure 1).3,4 As
a
consequence of their diverse applications, several classical5
and new synthetic methods such as radical mediated
reaction,6 metal catalyzed cross coupling7 and photochemical
approaches8 have been developed for the synthesis of
phenanthridine motifs. Although a number of protocols are
available for their preparation, a majority of the strategy relies
on radical mediated chemical or photochemical reactions,
which essentially requires pre-functionalized starting
materials. Therefore, decreasing the overall efficacy of the
developed methods and not satisfying the green and
sustainability aspect of chemistry.
R2
R2
I
C-C/C-N
C-C
R1 CN
R2
+
R2
R1
NH
R1
N
Scheme 1: Working Hypothesis
Nitriles represent an important class of organic molecules
which have been extensively utilized for the synthesis of
nitrogen-containing heterocyclic frameworks11 and have a
broad range of applications in polymer chemistry and
pharmaceutical industry owing to their diverse variations.12
Transition metal- catalyzed nucleophilic addition on nitriles
was elegantly demonstrated by Larock et al. for the synthesis
of acyclic aryl ketone products.13 Since then, a remarkable
advance in this field has been achieved. In 2013, Hsieh and co-
With this understanding and our research interest in the
development of a new synthetic methodology for the
Department of Chemistry, Indian Institute of Technology Patna, Bihta 801106,
Bihar, India
*E-mail: amitkt@iitp.ac.in or amitktiitk@gmail.com
Electronic Supplementary Information (ESI) available: [details of any
supplementary information available should be included here]. See
DOI: 10.1039/x0xx00000x
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workers reported a method for the synthesis of fluorenones standard conditions to afford the corresponding products in
from aryl iodides and aryl nitriles under palladium catalyzed moderate to good yields (3r-u, 45-62%). It is worthy to note
conditions with limited substrate scope.14 Considering these that in case of short-chain aliphatic nitriles 1r-1u, further
facts and for validating our hypothesis, we began our arylation occurred at the 4th position of the phenanthridine
investigation by selecting 2-phenylacetonitrile 1a and ring and providing 4/6- substituted phenanthridine derivatives
phenyliodide 2a as model substrates. In a general procedure, in low yields (3rr-uu, 15-20%).
1a and 2a were treated with Pd(OAc)2 (10 mol%), AgBF4 (3.0
Table 1. Scope of Aliphatic Nitriles for the Synthesis of
equiv.) and TFA (20 mol%) in toluene at 130 oC for 48 h
afforded the phenanthridine 3a, in 17% yield. However, the
outcome of this results was quite opposite from the previously
described method.14 We further optimized the reaction for this
particular substrate by carrying out extensive screening of
solvent, oxidant, ligand, time and temperature to obtain the
optimum yield (for detailed optimization studies, see
Supporting Information, Table S1-S5). After judicious
optimization, we concluded that reaction of 1a with
iodobenzene 2a in presence of Pd(OAc)2 (10 mol%), AgBF4 (3.0
equiv.), JohnPhos (20 mol%), in DCE at 130 oC for 48 h afforded
the product 3a in 80% yield (Scheme 2). Surprisingly, under the
optimized reaction conditions, there was no evidence of α-
arylation, which was some concern due to the presence of
active C-H bond adjacent to nitrile group.15
Phenanthridiene Derivativesa
Scheme 2. Synthesis of phananthridiene from 1a and 2a
Having obtained optimal reaction conditions, we set out to
explore the scope of this unique approach with different
aliphatic nitriles with respect to iodobenzene and the results
are listed in Table 1. Initially, aryl-acetonitriles 1a-e bearing
electron donating groups at different positions (ortho, meta,
and para) were tested under optimized reaction conditions
and furnished the desired product 3a-e in good yields(53-80%).
Furthermore, when moderate electron withdrawing groups
such as bromine, chlorine, fluorine were introduced at para-
position of an aryl ring, expected products 3f-h also procured
in moderate to good yields (45-60%).
aReaction Conditions: 1 (0.25 mmol), 2a (0.75 mmol), Pd(OAc)2 (10 mol%), AgBF4
(0.75 mmol), JohnPhos (20 mol%) in 2.5 mL of DCE at 130 oC for 48 h. b72 h.
We next examined the generality and limitation of this tandem
approach for the synthesis of 6-aryl substituted
phenanthridines by employing arylnitriles
4 with aryliodides 2
as the coupling partner. To our delight, when arylnitriles 4a-g
containing the electron donating groups such as methyl,
methoxy, and 3,4-dioxy at various positions of the aromatic
ring were subjected under similar reaction conditions, the
desired products 5a-g isolated in a good yields (65-75%) with
control of regioselectivity. The ambiguity of structure was
eventually confirmed by the single-crystal X-ray diffraction
analysis of 5c (CCDC no. and other details, see SI)16 in addition
to the spectroscopic evidence. This high-level selectivity is an
attractive feature of this reaction. Fortunately, when the
reaction was carried out with 4 mmol of benzonitrile 4a under
standard reaction conditions, the desired phenanthridine 5a
was isolated in 56% yield along with some uncharacterized
compounds and starting materials (15%). Reaction condition is
also tolerant towards various halo functional groups at meta
and para positions in the aryl nitriles component (5h-k, 58-
66%). Remarkably, the presence of strong electron-
withdrawing group such as trifluoromethyl at the para position
did not hamper the overall efficiency of the product yield (5l,
72%). To further diversify the scope of this transformation,
another reaction partner, aryliodides containing either
Pleasingly, aryl nitriles carrying strong electron withdrawing
group on phenyl ring such as -NO2 and -CF3, afforded the
phenanthridine derivatives 3i-j in a reasonably good yields (61-
65%). Similarly, the presence of ester group at the para
position does not affect the overall outcome of the
transformation (3m, 61%) and there was no evidence of ortho-
arylated product formation, which was a primary concern as
ester group might act as a directing group. The reaction
condition is also tolerant with sterically hindered nitriles such
as diphenylacetonitrile 1o and α-methyl phenylacetonitrile 1p
to produce the corresponding phenanthridines (65-68%, 3o-p).
Similarly, phenylsulphonylacetonitirle was also compatible
under the optimized reaction condition, affording
sulfonylatedphenanthridine 3q albeit in moderate yield (50%),
which is otherwise difficult to synthesize in one step. Next,
linear chain aliphatic nitriles such as methyl, iso-butyl, propyl
and pentyl nitriles were reacted well with iodobenzene under
2 | J. Name., 2012, 00, 1-3
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electron-donating or electron withdrawing groups were also withdrawing groups such as ester and nitro groups. Of note,
tested under similar conditions. Aryiodide containing an moderate electron withdrawing group survived well under
electron donating group (2n-o) at para position reacted well to reaction conditions. Further, tri-substituted phenanthridine
afford desired product in good yields (5n-o, 60-73%). The derivatives were synthesized in good yield (5s-u, 55-70%).
reaction of meta-substituted aryl iodides 2p-q containing two In order to understand the mechanistic aspect of this
possible sites for C-H bond activation proceeded with high unprecedented transformation, some control experiments
regioselectivity to give the less-hindered regioisomeric were performed (Scheme 3). Based on the outcome of this
products (5p-q, 50-63%).
transformation, we believe that imine (in-situ generated)
might be the potential reaction intermediate.13,14 To confirm
Table 2. Scope of Arylnitriles with Aryliodide for the Synthesis of
our hypothesis imine
6 was treated with iodobenzene 2a
Phenanthridine Derivatives.a
under optimized conditions (Scheme 3a), and the desired
product 5a was isolated in 55% yield. These results justify our
hypothesis and in-situ generated pallada-imine species
eventually direct the sequential formation of C-C and C-N
bonds in a one-pot manner. Similarly, we proceeded the
reaction with a short period (12 h) and at a lower temperature
o
(80 C) and found that the desired product formed in meager
yield (Scheme 3b and c) and rest starting materials was
recovered.
Scheme 4. The catalytic cycle of phenanthridine synthesis.
aReaction Conditions:
4 (0.25 mmol), 2 (0.75 mmol), Pd(OAc)2 (10 mol%),
AgBF4 (0.75 mmol), JohnPhos (20 mol%) in 2.5 mL of DCE at 130 oC for 48 h.
b72 h. dReaction was carried out at 4.0 mmol scale.
Guided with these supporting evidence and literature
reports,17
a
plausible reaction mechanism of this
transformation is outlined in Scheme 4. First, aryl palladium
species intI is generated by oxidative addition with phenyl
iodide 2a. Subsequently, nitrile 4a coordinate with the vacant
site of Pd and further undergoes for halide exchange in the
presence of AgBF4 to form intermediate intII and followed by
intramolecular 1,3 migration of the aryl group from the Pd
center to carbon to form pallada-imine species intIII
.
Subsequently, in-situ generated pallada-imine species intIII
form a five-membered Pd complex intIV via an agostic C-H
interaction (TS-I). Then, species intIV undergoes oxidative
addition/reductive elimination to deliver the intermediate
intVI. Further, intermediate intVI form seven-membered
cyclometalated species intVII via ortho C-H bond activation
through base assisted concerted palladation/deprotonation
(TS-II). Finally, a reductive elimination leads to the desired
phenanthridine 5a and regenerate palladium which goes on to
Scheme 3. Control Experiments.
Importantly, we observed that electron-rich aryl iodides were
more reactive and gave better yields than those possessing
electron withdrawing groups. Moreover, the reaction was
unsuccessful with aryl iodides containing strong electron
the catalytic cycle
.
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11363; (e) A. M. Linsenmeier, C. M. William and S. Brase, J.
Org. Chem. 2011, 76, 9127 and references cited therein.
For selected references on metal-catalyzed the synthesis of
phenanthridine see (a) C. Zhang, T. Li, L. Wang and Y. Rao,
Org. Chem. Front. 2017, 4, 386; (b) J. Tang, P. Sivaguru, Y.
Ning, G. Zanoni and X. Bi, Org. Lett. 2017, 19, 4026; (c) K.
Singh, A. K. Singh, D. Singh, R. Singh and S. Sharma, Catal. Sci.
Technol. 2016, 6, 3723; (d) A. Borah and P. Gogoi, Eur. J.
Org. Chem. 2016, 2200; (e) W. Guo, S. Li, L. Tang, M. Li, L.
Wen and C. Chen, Org. Lett. 2015, 17, 1232; (f) L. Zhang, G.
Y. Ang and S. Chiba, Org. Lett, 2010, 12, 3682; (g) T. Gerfaud,
L. Neuville and J. Zhu, Angew. Chem., Int. Ed., 2009, 48, 572;
(h) D. A. Candito and M. Lautens, Angew. Chem. Int. Ed.
2009, 48, 6713 and references cited therein.
In summary, we have developed an efficient and
unprecedented route for the direct synthesis of valuable
phenanthridine derivatives from simple and readily available
starting materials. The overall reaction proceeds via palladium-
catalyzed nucleophilic addition reaction followed by cascade
formation of carbon-carbon (ortho-arylation) and carbon-
nitrogen bonds through sequential two fold C-H activation.
Some of the noteworthy features of the present study are: a)
use of commercial and nontoxic starting materials, b)
straightforward and practical reaction conditions, c) atom and
step economical, d) highly regioselective, d) cascade formation
of C-C/C-C and C-N bonds, e) broad substrate scope, and f)
gram scale synthesis. The developed synthetic methods hold
great potential and will stimulate further research in the
synthesis of diverse heterocycles.
7
8
(a) P. Natrajan, N. Kumar and M, Sharma, Org. Chem. Front.
2016, 3, 1265; (b) Z. Zhang, X. Tang and W. R. Dolbier Jr, Org.
Lett. 2015, 17, 4401; (c) H. Jiang, X. An, K. Tong, T. Zheng, Y.
Zhang and S. Yu, Angew. Chem. Int. Ed. 2015, 54, 4055; (d) L.
Gu, C. Jin, J. Liu, H. Dinga and B. Fana, Chem. Commun. 2014,
50, 4643; (e) T. Xiao, L. Li, G. Lin, Q. Wang, P. Zhang, Z.-W.
Mao and L. Zhou, Green Chem. 2014, 16, 2418; (f) H. Jiang, Y.
Cheng, R. Wang, M. Zheng, Y. Zhang and S. Yu, Angew.
Chem., Int. Ed. 2013, 52, 13289; (g) B. Zhang, C. Muck-
Lichtenfeld, C. G. Daniliuc and A. Studer, Angew. Chem. Int.
Ed. 2013, 52, 10792.
(a) H.-B. Zhao, Z.-J. Liu, J. Song and H.-C. Xu, Angew. Chem.
Int. Ed. 2017, 56, 12732; (b) M. Ramanathan and S.-T. Liu, J.
Org. Chem. 2015, 80, 5329; (c) J. Li, H. Wang, J. Sun, Y. Yangc
and L. Liu, Org. Biomol. Chem. 2014, 12, 7904; (d) I. Deb and
N. Yoshikai, Org. Lett. 2013, 15, 4254.
Authors
acknowledge
financial
support
by
CSIR
(02(0229)/15/EMR-II), New Delhi and Indian Institute of
Technology (IIT) Patna.
Conflicts of interest
9
The authors declare no conflict of interest.
Notes and references
1
(a) B. Zhang and A. Studer, Chem. Soc. Rev. 2015, 44, 3505;
(b) L.-M. Tumir, M. R. Stojkovic and I. Piantanidac, Beilstein J.
Org. Chem. 2014, 10, 2930; (c) A. V. Gulevich, A. S. Dudnik, N.
Chernyak and V. Gevorgyan, Chem. Rev. 2013, 113, 3084; (d)
G. Zeni, and R. C. Larock, Chem. Rev. 2006, 106, 4644.
10 (a) Y. Jaiswal, Y. Kumar and A. Kumar, J. Org. Chem. 2018,
83, 1223; (b) Y. Kumar, Y. Jaiswal, M. Shaw and A. Kumar,
Chem. Select. 2017, 2, 6143; (c) Y. Kumar, Y. Jaiswal and A.
Kumar, J. Org. Chem. 2016, 81, 12247; (d) Y. Kumar, M.
Shaw, R. Thakur and A. Kumar, J. Org. Chem. 2016, 81, 6617;
(e) Y. Jaiswal, Y. Kumar, R. Thakur, J. Pal, R. Subramanian
and A. Kumar, J. Org. Chem. 2016, 81, 12499.
2
(a) G. Saini, P. Kumar, G. S. Kumar, A. R. K. Mangadan, and
M. Kapur, Org. Lett. 2018, 20, 441; (b) P. Gandeepan and C.-
H. Cheng, Chem. Asian J. 2016, 11, 448; (c) Y. Hayashi, Chem.
Sci. 2016, 7, 866; (d) M. Gulías, and J. L. Mascareñas, Angew.
Chem. Int. Ed. 2016, 55, 11000; (e) Y. Segawa, T. Maekawa,
and K. Itami, Angew. Chem. Int. Ed. 2015, 54, 66.
11 (a) K. Hu, Q. Zhen, J. Gong, T. Cheng, L. Qi, Y. Shao, and
J.Chen, Org. Lett. 2018, 20, 3083; (b) M. Meng, L. Yang, K.
Cheng and C. Qi, J. Org. Chem. 2018, 83, 3275; (c) L. Qi, K.
Hu, S. Yu, J. Zhu, T. Cheng, X. Wang, J. Chen and H. Wu, Org.
Lett. 2017, 19, 218; (d) K. Hu, L. Qi, S. Yu, T. Cheng, X. Wang,
3
(a) T. Ishikawa, Med. Res. Rev, 2001, 21, 61; (b) T. Nakanishi,
and M. Suzuki, J. Nat. Prod. 1998, 61, 1263; (c) A. Cappelli,
M. Anzini, S. Vomero, L. Mannuni, F. Makovec, E. Doucet, M.
Hamon, G. Bruni, M. R. Romeo, M. C. Menziani, P. G.
Benedetti, and T. Langer, J. Med. Chem. 1998, 41, 728; (d) Y.
L. Janin, A. Croisy, J.-F. Riou, and E. Bisagni, J. Med. Chem.
1993, 36, 3686; (e) G. J. Atwell, B. C. Baguley, and W. A.
Denny, J. Med. Chem. 1988, 31, 774; (f) S. V. Kessar, Y. P.
Gupta, P. Balakrishnan, K. K. Sawal, T. Mohammad, and M.
Dutt, J. Org. Chem., 1988, 53, 1708.
Z. Li, Y. Xia, J. Chen and H. Wua, Green Chem., 2017, 19
1740; (e) S. Yu, L. Qi, K. Hu, J. Gong, T. Cheng, Q. Wang, J.
,
Chen, and H. Wu, J. Org. Chem. 2017, 82, 3631; (f) J-C. Hsieh,
,
Y-C. Chen, A-Y. Cheng, and H.-C. Tseng, Org. Lett. 2012, 14
1282.
12 (a) Y. Kumar, Y. Jaiswal and A. Kumar, Eur. J. Org. Chem.
2018, 494; (b) V. V. Kouznetsov and C. E. P. Galvis,
Tetrahedron 2018, 74, 773; (c) V. Y. Kukushkin and A. J. L.
Pombeiro, Chem. Rev. 2002, 102, 1771; (d) D. Wohrle and G.
Knothe, J. Polym. Sci. A. 1988, 26, 2435 and references cited
there in.
13 (a) A. A. Pletnev and R. C. Larock, J. Org. Chem. 2002, 67,
9428; (b) R. C. Larock, Q. Tian and A. A. Pletnev, J. Am. Chem.
Soc. 1999, 121, 3238.
14 (b) J.-C. Wan, J.-M. Huang, Y.-H. Jhan and J.-C. Hsieh, Org.
Lett. 2013, 15, 2742.
15 M. Nambo, M. Yar, J. D. Smith and C. M. Crudden, Org. Lett.
2015, 17, 50.
16 For further details see the supporting information.
17 (a) Y.-F. Chen and J.-C. Hsieh, Org. Lett. 2014, 16, 4642; (b) D.
Takeda, K. Hirano, T. Satoh and M. Miura, Heterocycles
2012, 86, 1; (c) J. Peng, T. Chen, C. Chen and B. Li, J. Org.
Chem. 2011, 76, 9507; (d) M. Blanchot, D. A. Candito, F.
Larnaud and M. Lautens, Org. Lett, 2011, 13, 1486. (e) D. L.
Davies, S. M. A. Donald, and S. A. Macgregor, J. Am. Chem.
Soc. 2005, 127, 13754.
4
(a) T. C. Johnstone, S. M. Alexander, W. Lin and S. J. Lippard,
J. Am. Chem. Soc. 2014, 136, 116; (b) K. K. Schrader, F.
Avolio, A. Andolfi, A. Cimmino and A. Evidente, J. Agric. Food.
Chem. 2013, 61, 1179; (c) O. B. Abdel-Halim, T. Morikawa, S.
Ando, H. Matsuda and M. Yoshikawa, J. Nat. Prod. 2004, 67
,
1119; (d) T. Ishikawa, Med. Res. Rev. 2001, 21, 61; (e) S. D.
Phillips and R. N. Castle, J. Heterocyclic. Chem. 1981, 18, 223.
(a) L. Sripada, J. A. Teske and A. Deiters, Org. Biomol. Chem.
2008, 6, 263; (b) G. T. Morgan and L. P. Walls, J. Chem. Soc.
1931, 2447; (c) A. Pictet and A. Hubert, Ber. Dtsch. Chem.
Ges, 1896, 29, 1182.
(a) C. J. Evoniuk, G. dos P. Gomes, S. P. Hill, S. Fujita, K.
Hanson and I. V. Alabugina, J. Am. Chem. Soc. 2017, 139,
16210; (b) C. Pan, H. Zhang, J. Han, Y. Cheng, and C. Zhu,
Chem. Commun. 2015, 51, 3786; (c) S. Lu, Y. Gong and D.
Zhou, J. Org. Chem. 2015, 80, 9336; (d) M. Tobisu, K. Koh, T.
Furukawa and N. Chatani, Angew. Chem., Int. Ed, 2012, 51,
5
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