One-pot synthesis of triazolothiadiazepine 1,1-dioxide derivatives via copper-catalyzed tandem [3+2] cycloaddition/N-arylation

Article abstract of DOI:10.1002/adsc.201000465

A practical and efficient synthesis of triazolothiadiazepine-1,1-dioxide derivatives via copper-catalyzed [3+2]cycloaddition, followed by N-arylation is described. The method is also applicable to the synthesis of indoline- and thiophene-fused triazolothiadiazepine 1,1-dioxide derivatives.

Full text of DOI:10.1002/adsc.201000465

COMMUNICATIONS
DOI: 10.1002/adsc.201000465
One-Pot Synthesis of Triazolothiadiazepine 1,1-Dioxide
Derivatives via Copper-Catalyzed Tandem [3+2]
Cycloaddition/N-Arylation
Deepak Kumar Barange,a Yu-Chen Tu,a Veerababurao Kavala,a Chun-Wei Kuo,a
and Ching-Fa Yaoa,*
a
Department of Chemistry, National Taiwan Normal University, 88, Sec.4, Tingchow Road, Taipei, Taiwan 116, Republic of
China
Fax : (+886)-2-2932-4249; phone: (+886)-2-2930-9092; e-mail: cheyaocf@ntnu.edu.tw or cheyaocf@yahoo.com.tw
Received: June 15, 2010; Revised: September 28, 2010; Published online: January 4, 2011
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/adsc.201000465.
Abstract: A practical and efficient synthesis of tri-
A
derivatives
via
copper-catalyzed [3+2]cycloaddition, followed by
N-arylation is described. The method is also appli-
cable to the synthesis of indoline- and thiophene-
fused triazolothiadiazepine 1,1-dioxide derivatives.
Keywords: copper(I) iodide; fused triazoles; one-
pot porcess; sultams; triazolothiadiazepine 1,1-diox-
ides
The sultam moiety is a backbone scaffold of many
heterocyclic compounds of synthetic and pharmaceut-
ical importance.[1] Among the sultam derivatives, ben-
zothiadiazepine 1,1-oxides are a pivotal structural
entity and possess a remarkable range of biological
properties such as antiblastic, antitumor, apoptotic
and antihypertensive activities.[2] On the other hand,
the 1,2,3-triazole moiety has its own importance in
synthetic, medicinal and materials chemistry.[3] Espe-
cially, fused triazole derivatives have gained much at-
tention due to their wide range of biological activi-
ties.[4] Hence, one can expect upon fusion of benzo-
Figure 1. Biologically active heterocycles containing
sultam moiety.
a
thiadiazepine 1,1-dioxides with 1,2,3-triazoles the the synthesis of a 1,2,3-triazole fused with benzothia-
products may display an interesting range of biologi- diazepine 1,1-oxides by using this strategy, has not yet
cal properties. Examples of a few bioactive molecules been reported.[6j] The Cu(I)-catalyzed 1,3-diploar cy-
consisting of sultam and triazole rings can be seen in cloaddition is frequently employed for the synthesis
the Figure 1.
of 1,2,3-triazoles.[5] Moreover, Cu(I) salts are known
À
A number of approaches are available for the syn- to be efficient catalysts for the formation of C N
thesis of 1,2,3-triazoles[3,5] as well as benzothiadiaze- bonds.[7] It is noteworthy that they also play a vital
pine 1,1-oxide derivatives.[2] In addition, the synthesis role in the construction of certain types of bioactive
of several fused triazoles has been reported in the lit- N-heterocycles through the formation of multiple
erature.[6a–i] However, to the best of our knowledge, bonds.[8] We wish to report herein on a one-pot strat-
Adv. Synth. Catal. 2011, 353, 41 – 48
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
41

Deepak Kumar Barange et al.
COMMUNICATIONS
Table 1. Effect of base in presence of CuI, TMSN3 in DMF.
Scheme 1. One-pot strategy for the synthesis of 7.
egy for the synthesis of a 1,2,3-triazole fused with
benzothiadiazepine 1,1-oxides 7 (Scheme 1).
We initially examined various reaction conditions
using 6a as a model precursor. Unfortunately, our ini-
tial results, which involved the reaction of sodium
azide as well as tosyl azide in the presence of an inor-
ganic or organic base with copper(I) catalyst failed to
yield the desired product. However, a trace amount
of the desired product was detected using the proce-
dure of Yamamoto et al.[9] employing TMSN3. A
series of bases was screened in an attempt to improve
the product yield. A slight improvement in product
yield was observed when inorganic bases (t-BuOK,
NaOMe, K2CO3 and Cs2CO3) were used and an or-
ganic base (Et3N) gave a slightly better yield than the
inorganic bases. On the other hand, the yield of the
desired product was further increased when Hunigꢁs
base (DIPEA) was used in the reaction. The results
of these experiments are summarized in Table 1.
[a]
All reactions were carried out on a 0.5-mmol scale.
Isolated yields.
[b]
Table 2. Effect of solvent in the presence of 30 mol% CuI,
and TMSN3.
We next increased the amount of catalyst loading
to 20 mol%. Under these conditions, the conversion
was increased to 80% for a 12 h reaction period.
However, the use of 30 mol% of CuI resulted in a
considerable acceleration of the reaction. No signifi-
cant improvement was observed when an additional
amount of catalyst was used. Moreover, the use of
other Cu(I) salts, such as CuBr and CuCl were less ef-
ficient for the reaction but did afford the products
albeit in low yield. Furthermore, the effect of solvent
on the reaction was examined for a range of solvents.
Non-polar solvents were ineffective and no product
was detected. A poor yield was obtained when
DMSO was used as a solvent, and DMF was found to
be the best solvent for the reaction (Table 2).
After optimizing the reaction conditions, we further
pursued the scope of the reaction with respect to
[a]
other
2-iodo-N,4-disubstituted-N-(prop-2-ynyl)ben-
All reactions were carried out on 0.5-mmol scale.
Isolated yields.
Substrate decomposed.
[b]
ACHTUNGTRENNUNGzenesulfonamide derivatives.
[c]
The present protocol could be successfully applied
to the in situ [3+2]cycloaddition/N-arylation of vari-
ous 2-iodo-N,4-disubstituted-N-(prop-2-ynyl)-benzene-
ACHTUNGTRENNUNGsulfonamide derivatives and the results are summar-
ized in Table 3. As shown in Table 3, the formation of course of the reaction (Table 3, entries 1–3). The sub-
a cyclized product was efficient in most cases, afford- stituent on the nitrogen, however, had a considerable
ing the corresponding triazolobenzothiadiazepine 1,1- effect on the reaction. The product yields were drasti-
dioxide derivatives in moderate to good yields. The cally decreased when the N-methyl group was re-
functional group on benzene in the o-iodobenzenesul- placed with an N-ethyl group or an N-butyl group
fonamide derivatives had no significant effect on the (Table 3, entries 4 and 5). This one-pot cyclization re-
42
asc.wiley-vch.de
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2011, 353, 41 – 48

One-Pot Synthesis of Triazolothiadiazepine 1,1-Dioxide Derivatives
Table 3. One-pot synthesis of triazolobenzothiadiazepine 1,1-dioxide from 2-iodo-
N,4-disubstituted-N-(prop-2-ynyl)-benzenesulfonamides.
[a]
All reactions were carried out on a 1-mmol scale.
Isolated yields.
[b]
action of N-methyl derivatives proceeds much faster over, the 2-bromo-N-substituted-N-(prop-2-ynyl)ben-
than reactions using N-ethyl and N-butyl derivatives.
zenesulfonamides, derived from the amine, which con-
Using the optimized reaction conditions we next tain an electron-releasing group also afforded the cor-
examined various 2-bromo-N-substituted-N-(prop-2- responding products (Table 4, entries 4 and 5).
ynyl)benzenesulfonamide derivatives. As summarized
Indoline is an important motif that is found in
in Table 4, a number of 2-bromo-N-substituted-N- many natural products and pharmaceuticals. Hence,
(prop-2-ynyl)benzenesulfonamide derivatives were we attempted to incorporate an indoline motif into
used in the present reaction conditions and triazolo- the cycloaddition precursor. The precursor (15) was
benzothiadiazepine 1,1-dioxide derivatives were iso- prepared in 5 steps by following known literature pro-
lated in moderate to good yields. Despite the compa- cedures.[11] Using the present reaction conditions, the
rable yields of the products, reactions using bromo precursor (15) was converted into the corresponding
precursors required a slightly longer time for comple- indoline-fused 1,2,3-triazolobenzothiadiazepine 1,1-
tion than those of iodo precursors. This may be due oxide (16) in moderate yield (Scheme 2).
to differences in the reactivities of iodide and bro-
The diversity of the present methodology was
mide groups. Unlike the reactions of iodo precursors, additionally demonstrated by the synthesis of thio-
the substituent on the nitrogen had no effect on the phene-fused 1,2,3-triazolothiadiazepine 1,1-oxides
reaction in the case of the bromo compounds. More- (Scheme 3). It is known that the thiophene-fused
Adv. Synth. Catal. 2011, 353, 41 – 48
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
43

Deepak Kumar Barange et al.
COMMUNICATIONS
Table 4. One-pot synthesis of triazolobenzothiadiazepine-1,1-dioxides from 2-bromo-N-substitut-
ed-N-(prop-2-ynyl)benzenesulfonamides.
[a]
All reactions were carried on a 1-mmol scale.
Isolated yield.
[b]
sultam brinzolamide (3) has a potent antiepileptic ac- transmetallation with TMSN3, and then reductive
tivity.[12]
elimination to provide intermediate aryl azide I. Fur-
To propose a mechanism for this reaction, we con- thermore, this intermediate could serve for activation
sidered two literature reports, the first of which re- of the triple bond through a copper-coordinated inter-
ported on the direct catalytic transformation of aryl mediate to afford the cyclized compound 7a. The
and vinyl halides into azides, in the presence of Cu(I) second pathway goes via the generation of copper
or Cu(II).[13] The other study reports on the formation acetylide. The copper acetylide generated was reacted
of a 1,2,3-triazole from its corresponding N-methyl-N- with azide to furnish the six-membered copperACHTUNGTRENNUNG(III)
(prop-2-ynyl)benzenesulfonamide.[9] Based on these metallacycle intermediate. This six-membered inter-
two reports we envisage two mechanistic pathways mediate undergoes ring contraction to produce a five-
for the formation of 7a from 6a.
membered triazolyl-copper intermediate (IV). Proto-
Among them the first route involves the Cu(I)-oxi- nation of this intermediate by terminal alkyne or HI
dative addition to the aryl halide, followed by the generates the triazole compound (V), which will un-
44
asc.wiley-vch.de
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2011, 353, 41 – 48

One-Pot Synthesis of Triazolothiadiazepine 1,1-Dioxide Derivatives
Scheme 2. Synthesis of indoline-fused triazole sultams. Reagents and conditions: a) (CH3CO)2O, CH2Cl2, room temperature,
30 min, 79%; b) Br2, AcOH, room temperature, 10 min, 71%; c) ClSO3H, neat, 808C, 12 h, 35%; d) CH3NH2, Et3N, reflux,
2 h, 87%; e) propargyl bromide, K2CO3, acetone, reflux, 12 h, 81%; f) 30 mol% CuI, 2.5 equiv. TMSN3, 3 equiv. DIPEA,
DMF, 708C, 12 h, 40%. TMSN3 =trimethylsilyl azide, DIPEA=N,N-diisopropylethylamine (Hunigꢁs base).
Scheme 3. Synthesis of thiophene-fused 1,2,3-triazolo-thiadiazepine 1,1-oxides. Reagents and conditions: a) ClSO3H, À788C,
3 h, 82%; b) RNH2, CH2Cl2, room temperature; c) propargyl bromide, K2CO3, acetone, reflux; d) 30 mol% CuI, 2.5 equiv.
TMSN3, 3 equiv. DIPEA, DMF, 708C.
1
dergo N-arylation to afford 7a. (Scheme 4). The Cu(I) ized by H, 13C NMR and mass spectroscopic tech-
species catalyst regenerated during the process facili- niques which indicated the formation of triazole (V).
tates the progrees of the catalytic cycle. The structure
Although we could obtain the intermediate com-
of the representative compound 7a was confirmed un- pound (V), this cannot rule out the other possibility.
ambiguously by single crystal X-ray analysis as shown If we look into the literature, the copper-catalyzed
in Figure 2.[16]
azidination of aryl halides using NaN3 (Ma et al.)[13b]
In the proposed mechanisms, the crucial steps are is faster than the copper-catalyzed azide alkyne cyclo-
azidination (Path A) and copper-acetylide formation addition reported by Yamamoto et al.[9] using
(Path B). Hence, in order to verify which mechanism TMSN3.[9] Therefore, in order to compare the azidina-
is operative in this reaction, it is necessary to have in- tion and cycloaddition reactions, we carried out the
formation on the intermediate involved in the reac- reaction of N,4-dimethyl-N-(prop-2-ynyl)benzenesul-
tion.To determine this, we carried out the reaction in fonamide (22) and iodobenzene (23) under similar re-
the absence of base. To our delight, 30% of the ex- action conditions of the present protocol. Under the
pected cyclized product, triazolobenzothiadiazepine optmized reaction condition, we could isolate the N-
1,1-dioxide (7a) along with trace amounts of inter- [(1H-1,2,3-triazol-4-yl)methyl]-N,4 dimethylbenzene-
mediate was observed under the base-free condi- sulfonamide (24) as a sole product. There was no
tions.[15] The intermediate was isolated and character- trace amount of phenyl azide that could be isolated
Adv. Synth. Catal. 2011, 353, 41 – 48
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
45

Deepak Kumar Barange et al.
COMMUNICATIONS
Scheme 4. Plausible mechanism for the formation of 7a.
Scheme 5. Reaction of N,4-dimethyl-N-(prop-2-ynyl)ben-
AHCTUNGTREGzNNNU enesulfonamide and iodobenzene under optimized condi-
tions.
mation. This method has been applied to the synthesis
of indoline- and thiophene-fused triazole sultams,
which are synthetically valuable as novel heterocycles.
Biological studies of these compounds are currently
underway.
Figure 2. X-ray crystal structure of 5,9-dimethyl-4,5-
dihydrobenzo[f][1,2,3]triazolo[5,1-d][1,2,5]thiadiazepine 1,1-
dioxide (7a) (ORTEP view).[16]
N
N
ACHTUNGTRENNUNG
from the reaction mixture (Scheme 5). A recent
report of Chen et al. has also shown the triazole prod-
uct as an intermediate in a similar tandem process.[14]
Based on these facts we predict that Path B is reason-
able mechanistic route for the formation of 7a.
Experimental Section
General Procedure for Preparation of 5,9-Dimethyl-4,5-
dihydrobenzo[f]ACHTUNGTNER[NNUG 1,2,3]triazoloACHTNURTGEG[NNUN 5,1-d]ACHTNUGRTEN[NUGN 1,2,5]thiadiazepine
In conclusion, we report on a practical and efficient 1,1-Dioxides
synthesis of triazole-fused sultams via copper cata-
lyzed [3+2]cycloaddition followed by C N bond for-
To a stirred solution of the N-propargylated benzenesul-
ACHTUNGTRENUNfNG onamide (1 mmol) in DMF (3 mL), copper iodide
À
46
asc.wiley-vch.de
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2011, 353, 41 – 48

One-Pot Synthesis of Triazolothiadiazepine 1,1-Dioxide Derivatives
(30 mol%), azidotrimethylsilane (2.5 equiv.) and DIPEA
(3 equiv.) were added and the whole reaction mixture was
heated at 708C for 2–6 h under a nitrogen atmosphere.
After consumption of starting material, the mixture was
cooled to room temperature then methanol and ethyl ace-
tate were added, the inorganic solid that separated out was
filtered through a short celite pad. The filtrate was concen-
trated under reduced pressure. The residue was purified
with silica gel column chromatography to afford the cyclized
compound in moderate to good yields (40–82%).
P. Carato, B. Pfeiffer, P. Renard, S. Lꢂonce, A. Pierrꢂ,
P. Chavatte, P. Berthelot, J. Med. Chem. 2005, 48,
7363–7373; f) G. Marfe, C. D. Stefano, R. Silvestri, E.
Abruzzese, G. Catalano, L. D. Renzo, G. Filomeni, E.
Giorda, G. L. Regina, E. Morgante, M. R. Ciriolo,
M. A. Russo, S. Amadori, P. Sinibaldi-Salimei, BMC
Cancer 2007, 7, 207; g) O. Migliara, S. Petruso, V. Sprio,
J. Heterocycl. Chem. 2009, 16, 835–837; h) A. Rolfe,
G. H. Lushington, P. R. Hanson, Org. Biomol. Chem.
2010, 8, 2198–2203, and references cited therein.
[3] a) Chem. Soc. Rev. 2010, 39, 1221–1408; b) W.-Q. Fan,
A. R. Katritzky, in: Comprehensive Heterocyclic
Chemistry II, (Eds.: A. R. Katritzky, C. W. Rees,
E. F. V. Scriven), Elsevier Science, Oxford, 1996, Vol. 4,
pp 1–126; c) Y. L. Angell, K. Burgess, Chem. Soc. Rev.
2007, 36, 1674–1689, and references cited therein.
[4] a) A. Lauria, C. Patella, G. Dattolo, A. M. Almerico, J.
Med. Chem. 2008, 51, 2037–2046; b) A. Martinez, H.
Gutiꢂrrez-de-Terꢃn, J. Brea, E. Ravina, M. I. Loza,
M. I. Cadavid, F. Sanz, B. Vidal, V. Segarra, E. Sotelo,
Bioorg. Med. Chem. 2008, 16, 2103–2113; c) M. Nasr,
A. Nasr, Arch. Pharm. Pharm. Med. Chem. 2002, 335,
389–394; d) A. W. Thomas, Bioorg. Med. Chem. Lett.
2002, 12, 1881–1984.
[5] a) S. H. Kim, H. S. Choi, J. S. Kim, J. Lee, D. T. Quang,
J. S. Kim, Org. Lett. 2010, 12, 560–563; b) M. Meldal,
C. W. Tornøe, Chem. Rev. 2008, 108, 2952–3015;
c) V. D. Bock, H. Hiemstra, J. H. v. Maarseveen, Eur. J.
Org. Chem. 2006, 51–68; d) V. V. Rostovtsev, L. G.
Green, V. V. Fokin, B. K. Sharpless, Angew. Chem.
2002, 114, 2708–2711; Angew. Chem. Int. Ed. 2002, 41,
2596–2599, and references cited therein.
Physical and Spectral data of Representative
Compound (7a)
5,9-Dimethyl-4,5-dihydrobenzo[f]
[1,2,5]thiadiazepine 1,1-dioxide (7):[16] Yield: 80%; white
solid, mp 183–1848C; FT-IR (KBr): n=2930, 1346,
1160 cmÀ1 1H NMR (400 MHz, CDCl3): d=8.06 (s, 1H),
ACHTUGTNREN[UNG 1,2,3]triazoloACHTUNGTNER[NUGN 5,1-d]-
ACHTUNGTRENNUNG
;
7.95 (d, J=7.9 Hz, 1H), 7.76 (s, 1H), 7.42 (d, J=7.9 Hz,
1H), 4.40 (s, 2H), 2.86 (s, 3H), 2.55 (s, 3H); 13C NMR
(100 MHz, CDCl3): d=146.1, 134.0, 133.1, 132.7, 130.0,
128.8, 127.3, 125.5, 44.1, 38.0, 21.7; LR-MS (EI): m/z (rela-
tive intensity)=264 (M+,100), 171 (98), 118 (18), 68 (19);
HR-MS: m/z=264.0681, calcd. for C11H12N4O2S (M+):
264.0681.
Supporting Information
Experimental details, characterization, 1H and 13C NMR
spectra of products 1–36 are provided in the Supporting In-
formation.
[6] a) R. A. Brawn, M. Welzel, J. T. Lowe, J. S. Panek, Org.
Lett. 2010, 12, 336–339; b) V. S. Sudhir, N. Y. P. Kumar,
R. B. N. Baig, S. Chandrasekaran J. Org. Chem. 2009,
74, 7588–7591; c) C. Chowdhury, S. Mukherjee, B. Das,
B. Achari, J. Org. Chem. 2009, 74, 3612–3615; d) C.
Chowdhury, A. K. Sasmal, P. K. Dutta, Tetrahedron
Lett. 2009, 50, 2678–2681; e) M. Alajarin, J. Cabrera,
A. Pastor J. M. Villalgordo, Tetrahedron Lett. 2007, 48,
3495–3499; f) H. Yanai, T. Taguchi, Tetrahedron Lett.
2005, 46, 8639–8643; g) S. Hotha, R. I. Anegundi,
A. A. Natu, Tetrahedron Lett. 2005, 46, 4585–4588;
h) S. Rçper, M. H. Franz, R. Wartchow, H. M. R. Hoff-
mann, Org. Lett. 2003, 5, 2773–2776. i) During the
review process the synthesis of these kind of products
in different synthetic strategy appeared: C. S. Cham-
bers, N. Patel, K. Hemming Tetrahedron Lett. 2010, 51,
4859–4861.
[7] a) A. Alexakis, C. Benhaim, Eur. J. Org. Chem. 2002,
3221–3236; b) S. V. Ley, A. W. Thomas, Angew. Chem.
2003, 115, 5558–5607; Angew. Chem. Int. Ed. 2003, 42,
5400–5449; c) S. R. Chemler, P. H. Fuller, Chem. Soc.
Rev. 2007, 36, 1153–1160; d) M. Carril, R. SanMartin,
E. Domꢄnguez, Chem. Soc. Rev. 2008, 37, 639–647.
[8] a) K. T. J. Loones, B. U. W. Maes, C. Meyers, J. Deruyt-
ter, J. Org. Chem. 2006, 71, 260–264; b) J. Yuen, Y.-Q.
Fang, M. Lautens, Org. Lett. 2006, 8, 653–656; c) L.
Zhang, H. C. Malinakova, J. Org. Chem. 2007, 72,
1484–1487; d) R. Martin, C. H. Laursen, A. Cuenca,
S. L. Buchwald, Org. Lett. 2007, 9, 3379–3382; e) A.
FranÅais, D. Urban, J.-M. Beau, Angew. Chem. 2007,
Acknowledgements
We wish to express our sincere gratitude to the National Sci-
ence Council of the Republic of China and National Taiwan
Normal University (99T3030-2 and 99D) for providing finan-
cial support for this work. DKB is grateful to MOFA for a
Taiwan Scholarship.
References
[1] a) W. Oppolzer, A. J. Kingma, S. K. Pillai, Tetrahedron
Lett. 1991, 32, 4893–4896; b) L. Levy, Drugs Future
1992, 17, 451–454; c) J. Drews, Science 2000, 287, 190–
194; d) P. Dauban, R. H. Dodd, Tetrahedron Lett. 2001,
42, 1037–1040; e) S. Hanessian, H. Sailes, E. Therrien,
Tetrahedron 2003, 59, 7047–7056; f) M. Jimꢂnez-Hop-
kins, P. R. Hanson, Org. Lett. 2008, 10, 2223–2226;
g) A. Zhou, D. Rayabarapu, P. R. Hanson, Org. Lett.
2009, 11, 531–534; h) R. C. Bernotas, R. J. Dooley, Tet-
rahedron 2010, 66, 2273–2276.
[2] a) A. A. Rubin, F. E. Roth, M. W. Winburg, J. G. Top-
liss, M. H. Sherlock, N. Sperber, J. Black, Science 1961,
133, 2067–2067; b) F. Chimenti, S. Vomero, V. Nacci,
M. Scalzo, R. Giuliano, M. Artico, Farmaco, Ed. Sci.
1974, 29, 589–597; c) G. Stefancich, R. Silvestri, E. Pag-
nozzi, M. Artico, J. Heterocycl. Chem. 1994, 31, 867–
869; d) K. Hemming, N. Patel, Tetrahedron Lett. 2004,
45, 7553–7556; e) N. Lebegue, S. Gallet, N. Flouquet,
Adv. Synth. Catal. 2011, 353, 41 – 48
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
47

Deepak Kumar Barange et al.
COMMUNICATIONS
119, 8816–8819; Angew. Chem. Int. Ed. 2007, 46, 8662–
8665; f) G. Kumaraswamy, K. Ankamma, A. Pitchaiah,
J. Org. Chem. 2007, 72, 9822–9825; g) Y. Ohta, H.
Chiba, S. Oishi, N. Fujii, H. Ohno, Org. Lett. 2008, 10,
3535–3538,. and references cited therein.
[12] J. D. Croxtall, L. J. Scott, Drugs Aging 2009, 26, 437–
446.
[13] a) K. Kacprzak, Synlett 2005, 943–946; b) W. Zhu, D.
Ma, Chem. Commun. 2004, 888–889.
[14] Z. Chen, J. Zhu, H. Xie, S. Li, Y. Wu, Y. Gong, Adv.
Synth. Catal. 2010, 352, 1296–1300.
[15] DMF is a weak Lewis base, which may be responsible
for formation of the desired product.
[9] T. Jin, S. Kamijo, Y. Yamamoto, Eur. J. Org. Chem.
2004, 3789–3791.
[10] a) D. K. Barange, T. C. Nishad, N. K. Swamy, V. Banda-
meedi, D. Kumar, B R. Sreekanth, K. Vyas, M. Pal J.
Org. Chem. 2007, 72, 8547–8550; b) C. Lane, V.
Snieckus, Synlett 2000, 1294–1296; c) J. Blanchet, T.
Macklin, P. Ang, C. Metallinos, V. Snieckus, J. Org.
Chem. 2007, 72, 3199–3206.
[11] A. L. Borror, E. Chinoporos, M. P. Filosa, S. R. Her-
chen, C. P. Petersen, C. A. Stern, K. D. Onan, J. Org.
Chem. 1988, 53, 2047–2052.
[16] Crystallographic data for the structure reported in this
publication have been deposited with the Cambridge
Crystallographic Data Centre as supplementary publi-
cation no CCDC 777830 (7a).These data can be ob-
tained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_re-
quest/cif or on application to CCDC, 12 Union Road,
Cambridge CB2 1EZ, U.K. (Fax: +44-1223/336-033; E-
mail: deposit@ccdc.cam.ac.uk).
48
asc.wiley-vch.de
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2011, 353, 41 – 48