Efficient and versatile single pot approach to dipyrromethanes and bis(heterocyclyl)methanes

Article abstract of DOI:10.1016/j.tet.2005.04.029

An efficient single pot route is presented involving the use of O, N-perhydro 1,3-heterocycles as carbonyl equivalents for the synthesis of 5-substituted dipyrromethanes, 5,10-disubstituted tripyrranes and bis(heterocyclyl)methanes.

Full text of DOI:10.1016/j.tet.2005.04.029

Tetrahedron 61 (2005) 6614–6622
Efficient and versatile single pot approach to dipyrromethanes
and bis(heterocyclyl)methanes
†
*
Kamaljit Singh, Sonia Behal and Maninder Singh Hundal
Department of Applied Chemical Sciences and Technology, Guru Nanak Dev University, Amritsar 143 005, India
Received 16 December 2004; revised 30 March 2005; accepted 15 April 2005
Available online 23 May 2005
Abstract—An efficient single pot route is presented involving the use of O, N-perhydro 1,3-heterocycles as carbonyl equivalents for the
synthesis of 5-substituted dipyrromethanes, 5,10-disubstituted tripyrranes and bis(heterocyclyl)methanes.
q 2005 Elsevier Ltd. All rights reserved.
1. Introduction
azafulvenes and N-confused dipyrromethanes.1b–d,13a The
inaccessibility of functionalised carbonyls and the
occurrence of the side reactions associated with the direct
use of the labile carbonyl reagents pose additional
problems.14 An attractive small scale synthesis15 of
dipyrromethanes, in which pyrrole is used as reagent as
well as the solvent with a catalytic amount of an acid affords
good yields of dipyrromethanes bearing many types of
substituents at the meso carbon. Thus, considerable effort
for the development of methodologies for the synthesis of
these diverse building blocks has been invested, however
there still remains a scope for shorter and more efficacious
approaches to contribute towards achieving the synthesis of
these systems in a synthetically useful manner.
meso-Porphyrins and related systems such as calix[n]-
pyrroles and calix[n]phyrins are a venerable class of pyrrole
containing macrocycles and have gained considerable
importance.1 meso-Porphyrins display unique properties
and find application in phototherapeutics,2 biological
processes,3 optoelectronics,4 catalysis,5 biomimetic and
material chemistry6 etc. The level of architectural sophisti-
cation that has been achieved in such systems is closely tied
to the availability of suitable building blocks through
synthetic methodologies having flexibility for structural
modifications. One of the key features of the porphyrin
synthesis is the availability of 5-substituted dipyrro-
methanes and other related intermediates. These are the
key precursors not only for meso-porphyrins, but also
calix[4]pyrroles and calix[4]phyrin macrocycles, which are
well established as redox-active or optical sensors for
anions.7–11
The carbonyl character of the C-2 unit of perhydro-1,3-
heterocycles 1 and 2 has been amply demonstrated16–18 and
we have extensively used it to perform sensitive acid
catalysed condensations with a variety of nucleophiles and
have convincingly established19,20 the synthetic utility of
this approach. The merit of using oxazinanes and oxazoli-
dines, which are hemiaminals of carbonyls, stems from their
easy availability from a number of reagents including non-
Dipyrromethanes have been synthesized using a variety of
procedures.12 For example, the 5-unsubstituted dipyrro-
methane, has been prepared in three steps from pyrrole.12a
5-Aryldipyrromethanes have also been synthesized
indirectly, requiring either the elimination of a protecting
ester group from the pyrrole,12b or through the formation
of a Grignard reagent.12c A number of other syntheses of
dipyrromethanes are based on the direct condensation of
carbonyl reagents with pyrrole, but quite often the process is
plagued by the formation of undesired side products such as
carbonyls, as well as the flexibility in appending19f,g
variety of substituents at the C-2 of these reagents.
a
Herein we report the application of various oxazinanes and
an oxazolidine in the synthesis of a number of 5-substituted
dipyrromethanes in a synthetically useful manner.19i
Oxazinanes have been reacted with pyrrole and/or its
combination with other carbon nucleophiles under acid
(TFA) catalysed reaction conditions.19h All these reactions
can be visualized as an extension of carbon transfer
reactions (Folate model approach)19–21 as these perhydro
1,3-heterocycles have been regarded as models of the
N5,N10-methylenetetrahydrofolate coenzyme.
Keywords: Perhydro 1,3-heterocycles; Oxazinanes; Dipyrromethanes;
meso-Porphyrins; Bis(heterocyclyl)methanes.
*
Corresponding author. Tel.: C91 1832257227; fax: C91 1832258819;
e-mail: kamaljit19in@yahoo.co.in
† Department of Chemistry, for queries regarding the X-ray analysis.
0040–4020/$ - see front matter q 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2005.04.029

K. Singh et al. / Tetrahedron 61 (2005) 6614–6622
6615
2. Results and discussion
Keeping in view the importance of meso-Porphyrins,23–25
having aliphatic substituents at the meso-position and the
dearth of a general synthetic method for synthesis of the
corresponding precursor dipyrromethanes, we conducted
reactions of various C-2 alkyl oxazinanes with pyrrole.
Reaction of 2-methyl oxazinane 1i with pyrrole (1:4
stoichimetric ratio) using TFA (3.0 equiv) as catalyst at
reflux, furnished 5-methyldipyrromethane 4i in 40% yield.
Likewise, the reaction of 2-ethoxycarbonylmethyl oxa-
zinane 1j, and pyrrole furnished the corresponding dipyrro-
methane 4j and 5,10-di(2-ethoxycarbonylmethyl)tripyrrane
5b. Similar reaction of 2-cyanomethyl-3,4,4-trimethyl-
oxazolidine 2 with pyrrole, furnished the corresponding
5-cyanomethyldipyrromethane 4k in 50% yield. A very
small amount of the tripyrrane 5c was also isolated in this
reaction. Evidence for the existence of possible dia-
stereomers of the tripyrranes 5 could not be ascertanied
from the spectral data.
Treatment of 2-(4-methoxyphenyl)oxazinane 1a with
pyrrole (Scheme 1) in 1:4 stoichiometric ratio in anhydrous
acetonitrile–TFA (3.0 equiv) solution, under a blanket of
dry nitrogen gas furnished 5-(4-methoxyphenyl)dipyrro-
methane 4a1b and 5,10-di[(4-methoxy)phenyl]tripyrrane
5a.22 Similar reactions of appropriate 2-substituted oxa-
zinanes 1b–1g with pyrrole under a similar set of conditions,
furnished the corresponding 5-substituted dipyrromethanes
4b–4g, generally in good yield (Table 1). All these products
are reasonably stable at ambient temperature, but some of
these dipyrromethanes show tendency to turn pale green
upon prolonged storage at ambient temperature. Using this
method, no evidence of the formation of N-confused
dipyrromethanes was found, as observed by others.1b–e
Further, using this method, we have scaled up the reactions
to isolate the dipyrromethanes 4a and 4d upto five g scale.
Some of the products, for instance, 4h obtained by reacting
1h and pyrrole are formed in much superior yields than the
reported methods.1b Thus, the oxazinane route has been
quite useful where conventional routes employing direct use
of aldehydes face limitations.
We further envisaged, that if N-methyl pyrrole was reacted
with oxazinanes, the orientation of the electrophile (C-2 unit
of oxazinanes in this case), could be directed at the 2- or
3-position owing to enhanced nucleophilic character of
Scheme 1. Formation of dipyrromethanes 4 and tripyrranes 5.

6616
K. Singh et al. / Tetrahedron 61 (2005) 6614–6622
Table 1. Synthesis of aryldipyrromethanes 4a–t and tripyrranes 5a–e from oxazinanes 1a–l and oxazolidine 2
Sr. no.
Reagents
Product
Yield (%)a
Time (h)
1/2
3
4
5
4
5
1
2
3
4
5
6
7
8
1a
1b
1c
1d
1e
1f
1g
1h
1i
1j
2
1g
1f
3a
3a
3a
3a
3a
3a
3a
3a
3a
3a
3a
3b
3b
3b
3b
3b
3b
3b
3b
3b
4a
4b
4c
4d
4e
4f
4g
4h
4i
4j
4k
4l
4m
4n
4o
4p
4q
4r
4s
5a
—
—
—
—
—
—
—
—
5b
5c
—
—
—
5d
—
—
—
—
5e
40
65
60
25
65
50
80
64
40
35
50
56
42
62
55
52
35
35
28
60
15
—
—
—
—
—
—
—
—
15
15
—
—
—
14
—
—
—
—
13
5
4.5
4.5
6
3.5
3.5
3
4.5
7
16
12
3
3
3
4
5
4.5
4.5
6
9
10
11
12
13
14
15
16
17
18
19
20
1e
1a
1b
1c
1l
1d
1h
4t
5
a Pyrrole (4.0 mmol), 1/2 (1.0 mmol), TFA (3.0 mmol).
pyrrole as has been observed by us in reactions of similar
carbon nucleophiles.21c,26 Thus, the reaction of oxazinanes
1 with N-methyl pyrrole were conducted and the products
5-substituted di(N,N0-dimethyl)dipyrromethanes 4l–4s
(Scheme 1, Table 1), were obtained, exclusively indicating
the formation of 2,20-methylene bridged dipyrromethanes
only. It was attested by X-ray crystallographic analysis of 4l
and the formation of any 3,30-methylene bridged dipyrro-
methane was ruled out.
The stereo-view and the crystallographic numbering of 4l is
shown in Figure 1. The structure consists of two crystal-
lographically independent molecules without any short
contacts in the asymmetric unit. In the packing pattern
one molecule in the asymmetric unit H-bonds to the
neighbouring symmetry related molecule through nitro
oxygen O3i to form C16–H162/O3i, with C16/O3
i
˚
˚
distance 3.465(1) A, H162/O3 2.58(1) A and :C16–
H162/O3i 1538 (where iZKx, yK1, z). While in the
Figure 1. X-ray structure of 4l showing the stereo view of the molecule and the labeling scheme used in the structure analysis.

K. Singh et al. / Tetrahedron 61 (2005) 6614–6622
6617
Scheme 2. Formation of mixed dipyrromethanes 6.
second molecule of the asymmetric unit, the nitro oxygen
O2 forms a H-bond with hydrogen of the methyl group C27
attached symmetry related pyrrole, such that the C27–
agents.30,31 The unsymmetrical bis(heterocyclyl)methanes
are far less explored; in fact, some structurally simple
bis(heterocyclyl)methanes, especially with two different
heterocyclic ring systems are, not known.32 The few
synthetic procedures available have only led to a limited
number of compounds of this class. Carbon nucleophiles
have displayed unique reactivity at our hands.19c,d Alkyl-b-
aminocrotonates reacted with oxazinanes to furnish sym-
metrical 4-substituted 1,4-dihydropyridines, while two
different enamines react in 1:1 stoichiometric ratio with
perhydro 1,3-heterocycles to furnish unsymmetrical 4-sub-
stituted 1,4-dihydropyridines, almost exclusively. We
envisaged, reacting combinations of different C-nucleo-
philes: pyrrole, N-methyl pyrrole and indole with oxa-
zinanes, unsymmetrical bis(heterocycyl)methanes could be
obtained.
ii
ii
ii
˚
˚
H27/O2 with C27/O2 3.448(34) A, H27/O2 2.57 A
and :C27–H27/O2ii 1578, (where iiZKxC1, yC0.5,
KzC2). Also it is noteworthy that the 4-nitrophenyl
substituted methylene bridge is attached to the 2-position
of pyrrole and not the 3-position. Both the N-methyl pyrrole
units are twisted out of plane owing to the steric hindrance
of the methyl substituents and the 4-nitrophenyl group is
also syn periplanar with respect to the pyrrole units. The
moieties surrounding the meso-carbon atoms form a
tetrahedral geometry.27 The bond angles and bond lengths
of the N-methyl pyrrole units are normal.28
The reactions of N-methyl pyrrole with oxazinanes were
than those of unsubstituted pyrrole and thus the isolation of
products was relatively easier. The tripyrranes 5d and 5e
were also isolated from the reaction of N-methyl pyrrole
with 1a and 1h.
Thus, the reactions of oxazinanes with a combination of
pyrrole, N-methyl pyrrole and indole, under acid catalysed
reaction conditions have been conducted and the unsym-
metrical bis(heterocyclyl)methanes are obtained as depicted
in Schemes 2 and 3. Oxazinane 1a was reacted with pyrrole
3a and N-methyl pyrrole 3b in 1:2:2 stoichiometric ratio in
anhydrous acetonitrile and using TFA (3.0 equiv) as catalyst
Such bis(heterocyclyl)methanes are also of interest to the
food industry as they are present as natural compounds in
food and beverage items29 and are also used as flavour
Scheme 3. Reactions of oxazinanes 1 with N-methyl pyrrole 3b and indole. Formation of unsymmetrical bis(heterocyclyl)methanes 7.

6618
K. Singh et al. / Tetrahedron 61 (2005) 6614–6622
Table 2. Reaction of pyrrole 3a and N-methyl pyrrole 3b with oxazinanes 1
4. Experimental
Sr. no.
Oxazinane 1
Products [Yield (%)]a
4.1. General
4
4
6
All melting points are determined in capillaries. 1H
(200 MHz) and 13C NMR (50 MHz) spectra were run on
Bruker AC 200 instrument of the Department of Chemistry,
using TMS as the internal standard. Mass (70 eV) spectra
were performed on Shimadzu GCMS QP 2000
spectrometer. Elemental analyses of the samples were
performed on and Perkin–Elmer 2400 CHN elemental
analyser at microanalytical laboratory RSIC, Punjab
University, Chandigarh and at RSIC, Central Drug Research
Institute, Lucknow, India.
1
2
3
4
5
1a
1e
1f
1g
1h
4a (12)
4e (12)
4f (14)
4g (20)
4h (20)
4o (15)
4n (15)
4m (20)
4l (15)
4t (10)
6a (15)
6b (16)
6c (14)
6d (15)
6e (15)
Formation of dipyrromethanes 4/6.
a Pyrrole (2.0 mmol), N-methyl pyrrole (2.0 mmol), 1 (1.0 mmol), TFA
(3.0 mmol).
and 4a, 4o and 6a were obtained (Scheme 2). Similar
reactions of oxazinanes 1e–h with a mixture of pyrrole and
N-methyl pyrrole in anhydrous acetonitrile, under the
similar set of conditions furnished the corresponding
products 4/6 (Table 2). None of these reactions showed
any preference for the exclusive formation of the mixed
pyrrole product 6a.
Separation of various products was carried out by flash
chromatography on silica gel (60–120 mesh). All solvents
MeCN (P2O5), THF (Na-benzophenone ketyl), hexane
(sodium) and ethyl acetate (anhydrous K2CO3) were dried
and distilled before use.
Likewise, the reaction of oxazinane 1a with N-methyl
pyrrole 3b and indole, in 1:2:2 stoichiometric ratio, in
anhydrous acetonitrile and catalysed by TFA (3 equiv)
furnished after flash chromatography 4o and the desired
3-[(1-methyl-1H-pyrrole-2-yl)-(4-methoxyphenyl)-methyl]-
1H-indole 7a. Similar reaction of oxazinane 1f with indole
and N-methyl pyrrole furnished corresponding dipyrro-
methane 4m and 3-[(1-methyl-1H-pyrrole-2-yl)-(4-nitro-
phenyl)-methyl]-1H-indole 7b, albiet in poor yield (12%).
Indoles having 2,7-positions activated towards electrophiles
such as carbonyl compounds constitute precursors for
performing direct synthesis of calix[n]indoles.33 In none
of these reactions however, the formation of such 2,7-
disubstituted indolyl products was detected.
The reagents such as 2-amino-2-methyl-1-propanol,
2-methyl-2,4-pentanediol, aldehydes, nitriles, pyrrole,
N-methyl pyrrole etc. were purchased from Sigma-Aldrich
Co., USA. Oxazinanes and oxazolidines were synthesised
following the reported procedures.19f,20
4.2. Reactions of perhydro 1,3-heterocycles with pyrrole/
N-methyl pyrrole. Synthesis of dipyrromethanes 4 and
tripyrranes 5. General procedure. A solution of freshly
distilled pyrrole (4.0 mmol)/N-methyl pyrrole (2.0 mmol)
and oxazinane 1 (1.0 mmol)/oxazolidine 2 (1.0 mmol) in
anhydrous acetonitrile (dried over P2O5) (30 mL) was
stirred under N2 for 15 min, followed by addition of TFA
(3.0 mmol) and heated under reflux until the reaction was
completed (TLC). The reaction was cooled to room
temperature and basified with cold aqueous sodium
bicarbonate solution (5% w/v) and extracted with ethyl
acetate (3!30 mL). The combined organic extracts were
dried over anhydrous sodium sulphate and the solvent was
removed under reduced pressure on a rotary evaporator. The
residue was chromatographed over silica gel G (60–120
mesh) using hexane, or a mixture with ethyl acetate, as
eluent. In many cases repeated crystallisations were
performed to obtain analytically pure samples suitable for
microanalytical analysis. Using the above procedure the
following products were synthesized.
Thus, it has been found that the unsymmetrical bis(hetero-
cyclyl)methanes are formed, although not exclusively,
through the acid catalysed reactions of oxazinanes with a
mixture of N-methyl pyrrole and indole.
3. Conclusions
Perhydro 1,3-heterocyles, versatile reagents have been
employed for the synthesis of dipyrromethanes as well as
bis(heterocyclyl)methanes. It has been found that: (i)
perhydro 1,3-heterocycles offer a dependable alternative
to carbonyl compounds in the synthesis of these important
intermediates for the synthesis of meso-tetraarylporphyrins
and related pyrrolic macrocycles; (ii) the reactions are
relatively clean, as polymeric side products are not formed
in any significant quantity; (iii) relatively much lower
stoichiometric amounts of reactants, compared to the
reported methods, are used for the reactions and the
products are formed in moderate to good yields without
any detectable N-confused dipyrromethanes; (iv) the
approach is flexible to incorporate a number of substituent
variations, at the transferred C-2 unit of the perhydro 1,3-
heterocycles, owing to easy functionalisation of the latter.
This aspect is conspicuously lacking in the aldehyde
approach owing to the non-availability of many function-
alized aldehydes.
4.2.1. 5-(4-Methoxyphenyl)dipyrromethane (4a).1b
Colourless powder. Yield: 0.10 g, 40%. Mp: 99 8C. IR
(KBr): 2935, 2835, 1710, 1607, 1508, 1245 cmK1. 1H NMR
(CDCl3): d 3.89 (s, 3H, OMe), 5.47 (s, 1H, meso H), 6.01
(m, 2H, 2!ArH), 6.01 (m, 2H, 2!CH), 6.26 (dd, JZ2.9,
!1.0 Hz, 2H, 2!CH), 6.74 (m, 2H, 2!CH), 6.94
(AA0BB0, 2H, JZ8.3 Hz, 2!ArH), 7.97 (br, 2H, D2O
exchangeable, 2!NH). 13C NMR (CDCl3): d 42.8, 55.0,
106.1, 106.8, 108.0, 113.1, 113.6, 116.9, 117.4, 129.1,
134.1, 158.1. MS: m/z 252. Anal. Cacld for C16H16N2O: C
76.19, H 6.34, N 11.11. Found: C 76.34, H 6.56, N 11.32.
4.2.2. 5-(3,4-Dimethoxyphenyl)dipyrromethane (4b).
Colourless powder. Yield: 0.18 g, 65%. Mp: 128 8C. IR
(KBr): 3429, 3366, 3092, 2963, 2931, 2833, 1593 cmK1. 1H

K. Singh et al. / Tetrahedron 61 (2005) 6614–6622
6619
NMR (CDCl3): d 3.83 (s, 3H, OMe), 3.93 (s, 3H, OMe),
5.42 (s, 1H, meso CH), 5.93 (s, 2H, 2!CH), 6.16 (m, 2H,
CH), 6.68 (m, 2H, CH), 6.76 (m, 3H, ArH), 7.95 (br, 2H,
D2O exchangeable, 2!NH). 13C NMR (CDCl3): d 43.5,
55.8, 107.1, 108.3, 111.1, 111.7, 117.2, 120.3, 132.7, 134.6,
147.9, 148.9. MS: m/z 282 (MC). Anal. Cacld for
C17H18N2O2: C 72.34, H 6.38, N 9.92. Found: C 72.45, H
6.45, N 9.78.
1469 cmK1. 1H NMR (CDCl3): d 3.94 (s, 2H, meso H), 6.07
(m, 2H, 2!CH), 6.15 (q, 2H, JZ2.4 Hz, 2!CH), 6.62 (m,
2H, 2!CH), 7.67 (br, 2H, D2O exchangeable, 2!NH). 13
C
NMR (CDCl3): d 26.3, 106.1, 108.4, 117.1, 128.8, 129.3.
MS: m/z 146 (MC). Anal. Calcd for C9H10N2: C 73.97, H
6.84, N 19.17. Found: C 74.17, H 6.62, N 19.34.
4.2.9. 5-Methyldipyrromethane (4i). Greenish sticky
solid. Yield: 0.07 g, 40%. IR (KBr): 3388, 3345, 3099,
1560, 1512 cmK1. 1H NMR (CDCl3): d 1.62 (d, JZ4.8 Hz,
3H, Me), 4.14 (q, JZ4.8 Hz, 1H, meso H), 6.04 (m, 2H, 2!
CH), 6.15 (m, 2H, 2!CH), 6.54 (m, 2H, 2!CH), 7.68 (br,
2H, D2O exchangeable, 2!NH). 13C NMR (CDCl3): d 20.5,
31.6, 104.9, 107.6, 108.0, 117.1, 134.8. MS: m/z 160 (MC).
Anal. Calcd for C10H12N2: C 75.0, H 7.50, N 17.50. Found:
C 74.78, H 7.63, N 17.38.
4.2.3. 5-(3,4,5-Trimethoxyphenyl)dipyrromethane (4c).
Off-white powder. Yield: 0.19 g, 60%. Mp: 164 8C. IR
(KBr): 2925, 2841, 1712, 1609, 1513, 1242 cmK1. 1H NMR
(CDCl3): d 3.81(s, 6H, 2!OMe), 3.87 (s, 3H, OMe), 5.46
(s, 1H, meso H), 6.01 (s, 2H, 2!CH), 6.25 (m, 2H, 2!CH),
6.48 (s, 2H, 2!CH), 6.76 (m, 2H, ArH), 8.08 (br, 2H, D2O
exchangeable, 2!NH). 13C NMR (CDCl3): d 44.1, 56.0,
60.8, 105.4, 107.1, 108.3, 117.0, 132.1, 136.6, 137.7, 153.2.
MS: m/z 312 (MC). Anal. Calcd for C18H20N2O3: C 69.23,
H 6.41, N 8.97. Found: C 69.47, H 6.21, N 9.03.
4.2.10. 5-(2-Ethoxycarbonylmethyl)dipyrromethane
(4j). Greenish sticky solid. Yield: 0.08 g, 35%. IR (KBr):
1
3389, 2931, 1740, 1680, 1354 cmK1. H NMR (CDCl3): d
4.2.4. 5-Phenyldipyrromethane (4d).1b Pale yellow
crystals. Yield: 0.06 g, 25%. Mp: 101 8C. IR (KBr): 2935,
1.22 (t, 3H, JZ7.0 Hz, Me), 2.98 (d, JZ7.0 Hz, 2H,
CH2COO–), 4.11 (q, JZ7.0 Hz, 2H, COOCH2Me), 4.55 (t,
JZ7.0 Hz, 1H, meso H), 5.99 (s, 2H, 2!CH), 6.12 (m, 2H,
2!CH), 6.68 (m, 2H, 2!CH), 8.29 (br, 2H, D2O
exchangeable, 2!NH). 13C NMR (CDCl3): d 14.0, 33.7,
40.1, 60.7, 105.1, 105.2, 107.9, 117.0, 131.7, 131.7, 172.6.
MS: m/z 232 (MC). Anal. Calcd for C13H16N2O2: C 67.24,
H 6.89, N 12.06. Found: C 67.44, H 6.59, N 12.26.
1
2835, 1508, 1245 cmK1. H NMR (CDCl3): d 5.58 (s, 1H,
meso H), 5.86 (s, 2H, 2!CH), 6.17 (m, 2H, 2!CH), 6.75
(m, 2H, 2!CH), 7.5 (m, 5H, ArH), 8.09 (br, 2H, D2O
exchangeable, 2!NH). 13C NMR (CDCl3): d 43.6, 107.7,
108.6, 117.8, 122.1, 123.2, 129.4, 130.8, 134.5, 144.4. MS:
m/z 222 (MC). Anal. Cacld for C15H14N2: C 81.08, H 6.30,
N 12.61. Found C 81.38, H 6.56, N 12.90.
4.2.11. 5-Cyanomethyldipyrromethane (4k). Yellowish
thick liquid. Yield: 0.07 g, 35%. IR (KBr): 3390, 3346,
2270, 1560, 1512 cmK1. 1H NMR (CDCl3): d 2.94 (dd, JZ
1.5, 6.0 Hz, 2H, CH2CN), 4.41 (dt, JZ1.5, 6.0 Hz, 1H, meso
H), 6.13 (m, 4H, 4!CH), 6.62 (m, 2H, 2!CH), 8.09 (br,
2H, D2O exchangeable, 2!NH). 13C NMR (CDCl3): d 24.1,
34.6, 96.2, 105.5, 108.4, 118.2, 130.0. MS: m/z 185 (MC).
Anal. Calcd for C11H11N3: C 71.35, H 5.94, N 22.70. Found:
C 71.55, H 6.08, N 22.93.
4.2.5. 5-(2-Nitrophenyl)dipyrromethane (4e).12f Yellow
sticky solid. Yield: 0.18 g, 65%. IR (KBr): 3381, 3340,
1
3103, 1560, 1513, 1356 cmK1. H NMR (CDCl3): d 5.86
(m, 2H, meso H and CH), 6.14 (m, 3H, 3!CH), 6.71 (m,
2H, 2!CH), 7.41 (m, 4H, ArH), 8.18 (br, 2H, D2O
exchangeable, NH). 13C NMR (CDCl3): d 38.8, 107.4,
108.5, 117.6, 127.7, 129.3, 130.8, 130.9, 133.0, 137.2,
148.4. MS: m/z 267 (MC). Anal. Calcd for C15H13N3O2: C
67.41, H 4.86, N 15.73. Found: C 67.62, H 4.90, N 15.81.
4.2.12.
5-(4-Nitrophenyl)di(N,N0-dimethyl)pyrro-
4.2.6. 5-(3-Nitrophenyl)dipyrromethane (4f). Pale yellow
solid. Yield: 0.14 g, 50%. Mp: 153 8C. IR (KBr): 3389,
methane (4l). Yellow crystals. Yield: 0.17 g, 56%. Mp:
116 8C. IR (KBr): 3388, 3367, 1512, 1346 cmK1. 1H NMR
(CDCl3): d 3.40 (s, 6H, 2!NMe), 5.38 (s, 1H, meso H), 5.48
(m, 2H, 2!CH), 06.04 (m, 2H, 2!CH), 6.62 (m, 2H, 2!
CH), 7.30 (AA BB0, 2H, JZ8.0 Hz, 2!ArH), 8.16
(AA0BB0, 2H, JZ8.0 Hz, 2!ArH). 13C NMR (CDCl3): d
30.9, 33.8, 106.8, 109.4, 122.6, 123.7, 129.6, 131.8, 148.3.
MS: m/z 295 (MC). Anal. Calcd for C17H17N3O2: C 69.15,
H 5.76, N 14.23. Found: C 69.39, H 5.89, N 14.52.
1
3346, 3098, 1560, 1512, 1354 cmK1. H NMR (CDCl3): d
5.60 (s, 1H, meso H), 5.87 (s, 2H, 2!CH), 6.17 (m, 2H, 2!
CH), 6.77 (s, 2H, 2!CH), 7.52 (m, 4H, ArH), 8.10 (br, 2H,
D2O exchangeable, 2!NH). 13C NMR (CDCl3): d 43.6,
107.8, 108.7, 118.0, 122.1, 123.2, 129.4, 130.9, 134.5,
144.4, 148.4. Anal. Calcd for C15H13N3O2: C 67.41, H 4.86,
N 15.73. Found: C 67.65, H 4.64, N 15.51.
4.2.7. 5-(4-Nitrophenyl)dipyrromethane (4g).1b Green
crystals. Yield: 0.22 g, 80%. Mp: 159 8C. IR (KBr): 3395,
4.2.13.
5-(3-Nitrophenyl)di(N,N0-dimethyl)pyrro-
methane (4m). Yellow crystals. Yield: 0.18 g, 62%. Mp:
142 8C. IR (KBr): 3392, 3346, 1560, 1512, 1354 cmK1. 1H
NMR (CDCl3): d 3.39 (s, 6H, 2!NMe), 5.38 (s, 1H, meso
H), 5.46 (m, 2H, 2!CH), 6.02 (m, 2H, 2!CH), 6.60 (m,
2H, 2!CH), 7.46 (m, 2H, 2!ArH), 8.14 (m, 2H, 2!ArH).
13C NMR (CDCl3): d 33.8, 41.5, 106.7, 109.4, 121.9, 122.6,
123.6, 129.3, 131.9, 134.9, 143.6, 148.4. MS: m/z 295 (MC).
Anal. Calcd for C17H17N3O2: C 69.15, H 5.76, N 14.23.
Found: C 69.45, H 5.97, N 14.55.
1
3358, 1512, 1346 cmK1. H NMR (CDCl3): d 5.57 (s, 1H,
meso H), 5.75 (m, 2H, 2!CH), 6.0 (m, 2H, 2!CH), 6.66
(m, 2H, 2!CH), 7.39 (AA0BB0, 2H, JZ9.0 Hz, 2!ArH),
8.09 (AA0BB0, 2H, JZ9.0 Hz, 2!ArH), 10.18 (br, 2H, D2O
exchangeable, 2!NH). 13C NMR (CDCl3): d 43.3, 106.7,
107.2, 117.3, 122.9, 129.1, 131.4, 145.9, 151.0. MS: m/z 267
(MC). Anal. Calcd for C15H13N3O2: C 67.41, H 4.86, N
15.73. Found: C 67.53, H 4.75, N 15.58.
4.2.8. Dipyrromethane (4h).1b Colourless crystals. Yield:
0.09 g, 64%. Mp: 75 8C. IR (KBr): 2897, 1715, 1656, 1562,
4.2.14.
methane (4n). Greenish yellow solid. Yield: 0.12 g, 42%.
5-(2-Nitrophenyl)di(N,N0-dimethyl)pyrro-

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K. Singh et al. / Tetrahedron 61 (2005) 6614–6622
Mp: 158 8C. IR (KBr): 3390, 3348, 1560, 1513, 1356 cmK1
.
121.4, 128.1, 128.3, 128.6. MS: m/z 250 (MC). Anal. Calcd
for C17H18N2: C 81.60, H 7.20, N 11.20. Found: C 81.28, H
7.46, N 11.35.
1H NMR (CDCl3): d 3.42 (s, 6H, 2!NMe), 5.29 (s, 1H,
meso H), 5.44 (m, 2H, CH), 6.00 (m, 2H, 2!CH), 6.59 (m,
2H, 2!CH), 7.11 (d, 1H, ArH), 7.44 (t, 1H, ArH), 7.49 (t,
1H, ArH), 7.98 (d, 1H, ArH). 13C NMR (CDCl3): d 33.6,
36.4, 106.5, 109.2, 122.3, 124.7, 127.7, 131.0, 131.5, 133.1,
136.5, 148.6. MS: m/z 295 (MC). Anal. Calcd for
C17H17N3O2: C 69.15, H 5.76, N 14.23. Found: C 69.42,
H 5.99, N 14.51.
4.2.20. Di(N,N0-dimethyl)pyrromethane (4t). White solid.
Yield: 0.11 g, 60%. Mp: 111 8C. IR (KBr): 3115, 2918,
2849, 1690, 1490, 1321 cmK1. 1H NMR (CDCl3): d 3.48 (s,
6H, 2!NMe), 3.86 (s, 2H, meso CH2), 5.82 (m, 2H, 2!
CH), 6.03 (m, 2H, 2!CH), 6.55 (m, 2H, 2!CH). 13C NMR
(CDCl3): d 24.3, 31.6, 106.5, 107.5, 121.7, 125.3, 128.3,
129.0, 129.8. MS: m/z 174 (MC). Anal. Calcd for C11H14N2:
C 75.9, H 8.04, N 16.09. Found: C 75.69, H 7.92, N 16.34.
4.2.15. 5-(4-Methoxyphenyl)di(N,N0-dimethyl)pyrro-
methane (4o). Off-white crystals. Yield: 0.16 g, 55%. Mp:
82 8C. IR (KBr): 3381, 3340, 3103, 2954, 2931, 2835,
1
1710 cmK1. H NMR (CDCl3): d 3.37 (s, 6H, 2!NMe),
4.2.21. 5,10-Di[(4-methoxy)phenyl]tripyrrane (5a).
Green solid. Yield: 0.07 g, 15%. Mp: 85 8C. IR (KBr):
3.72 (s, 3H, OMe), 5.20 (s, 1H, meso H), 5.47 (s, 2H, 2!
CH), 6.12 (m, 2H, 2!CH), 6.57 (m, 2H, 2!CH), 6.85
(AA0BB0, 2H, JZ8 Hz, 2!ArH), 7.02 (AA0BB0, 2H, JZ
8 Hz, 2!ArH). 13C NMR (CDCl3): d 29.7, 32.7, 41.0, 55.2,
106.3, 108.7, 113.7, 121.9, 129.6, 133.3, 156.2. MS: m/z 280
(MC). Anal. Calcd for C18H20N2O: C 77.14, H 7.14, N
10.00 Found: C 76.34, H 6.66, N 11.34.
3010, 2945, 2839, 1703, 1593, 1512 cmK1 1H NMR
.
(CDCl3): d 3.73 (s, 6H, 2!OMe), 5.23 (s, 2H, 2! meso
H), 5.70 (m, 2H, 2!CH), 5.81 (m, 2H, 2!CH), 6.08 (m,
2H, 2!CH), 6.59 (m, 2H, 2!CH), 6.76 (AA0BB, 2H, JZ
8.0 Hz, 2!ArH), 7.07 (AA0BB, 2H, JZ8.0 Hz, 2!ArH).
13C NMR (CDCl3): d 43.0, 55.2, 107.0, 108.2, 113.8, 117.1,
129.3, 132.8, 134.2, 158.3. MS: m/z 437 (MC Calcd for
C28H27N3O2).
4.2.16. 5-(3,4-Dimethoxyphenyl)di(N,N0-dimethyl)pyrro-
methane (4p). Sticky solid. Yield: 0.16 g, 52%. IR (KBr):
2999, 2935, 2833, 1703, 1593, 1512 cmK1 1H NMR
.
4.2.22. 5,10-Di(2-ethoxycarbonylmethyl)tripyrrane (5b).
Sticky greenish compound. Yield: 0.06 g, 15%. IR (KBr):
(CDCl3): d 3.37 (s, 6H, 2!NMe), 3.79 (s, 3H, OMe),
3.84 (s, 3H, OMe), 5.18 (s, 1H, meso H), 5.53 (m, 1H, CH),
5.93 (s, 1H, CH), 6.02 (m, 3H, 3!CH), 6.53 (m, 5H, 2!CH
and 3!ArH). 13C NMR (CDCl3): d 33.8, 33.8, 41.4, 55.7,
106.3, 108.6, 120.1, 120.3, 120.6, 147.1, 148.7. MS: m/z 310
(MC). Anal. Calcd for C19H22N2O2: C 73.54, H 7.09, N
9.03. Found: C 73.90, H 7.39, N 10.14.
1
3391, 2931, 1742, 1683, 1354 cmK1. H NMR (CDCl3): d
1.41 (t, JZ5.5 Hz, 6H, 2! COOCH2CH3), 3.14 (d, JZ
7.0 Hz, 4H, 2!CH2COO), 4.28 (q, JZ5.5 Hz, 4H, 2!
COOCH2Me), 4.67 (t, JZ7.0 Hz, 2H, meso H), 6.05 (m,
4H, 2!CH2), 6.28 (m, 2H, 2!CH), 6.81 (m, 2H, 2!CH),
8.54 (br, 3H, D2O exchangeable, 3!NH). 13C NMR
(CDCl3): d 14.1, 33.8, 40.0, 43.5, 60.8, 105.2, 108.0,
117.1, 133.5, 134.1, 172.7. MS: m/z 397 (MC Calcd for
C22H27N3O4).
4.2.17. 5-(3,4,5-Trimethoxyphenyl)di(N,N0-dimethyl)-
pyrromethane (4q). White amorphous solid. Yield:
0.12 g, 35%. Mp: 89 8C. IR (KBr): 2932, 2847, 1714,
1
1612, 1515, 1239 cmK1. H NMR (CDCl3): d 3.35 (s, 6H,
4.2.23. 5,10-Di(cyanomethyl)tripyrrane (5c). Sticky
greenish compound. Yield: 0.05 g, 15%. IR (KBr): 3392,
2!NMe), 3.72 (s, 3H, OMe), 3.80 (s, 6H, 2!OMe), 5.15
(s, 1H, meso H), 5.50 (m, 2H, 2!CH), 5.99 (m, 2H, 2!
CH), 6.33 (m, 2H, 2!CH), 6.56 (m, 2H, 2!CH). 13C NMR
(CDCl3): d 33.8, 42.1, 55.7, 60.7, 105.8, 106.4, 108.7, 122.0,
133.3, 136.9, 153.1. MS: m/z 340 (MC). Anal. Calcd for
C20H24N2O3: C 70.58, H 7.05, N 8.23. Found: C 72.15, H
7.39, N 8.16.
1
3343, 2272, 1560, 1512 cmK1. H NMR (CDCl3): d 2.95
(m, 4H, 2!CH2CN), 4.38 (m, 2H, 2! meso H), 6.11 (m,
6H, 6! CH), 6.70 (m, 2H, 2! CH), 8.14 (br, 3H, D2O
exchangeable, 3! NH). 13C NMR (CDCl3): d 29.7, 40.2,
105.2, 108.0, 117.1, 118.6, 130.9, 132.2, 172.7. MS: m/z 303
(MC Calcd for C18H17N5).
4.2.18. 5-(2,3,4-Trimethoxyphenyl)di(N,N0-dimethyl)-
pyrromethane (4r). White amorphous solid. Yield:
0.12 g, 35%. Mp: 85 8C. IR (KBr): 2933, 2846, 1720,
4.2.24.
5,10-Di[(4-methoxy)phenyl]tri(N,N0,N00-tri-
methyl)pyrrane (5d). Off-white solid. Yield: 0.07 g, 14%.
Mp: 75 8C. IR (KBr): 2937, 2835, 1708, 1487 cmK1. H
1
1
1612, 1511, 1242 cmK1. H NMR (CDCl3): d 3.39 (s, 6H,
NMR (CDCl3): d 3.38 (s, 9H, 3!NMe), 3.80 (s, 6H, 2!
OMe), 5.19 (s, 1H, meso H), 5.21 (s, 1H, meso H), 5.49 (m,
2H, 2!CH), 6.02 (m, 3H, 3!CH), 6.57 (m, 3H, 3!CH),
6.82 (m, 4H, 4!ArH), 7.04 (m, 4H, 4!ArH). 13C NMR
(CDCl3): d 33.8, 36.0, 41.0, 41.5, 55.1, 106.3, 108.7, 113.5,
121.8, 129.6, 133.8, 158.2. MS: m/z 479 (MC Calcd for
C31H33N3O2).
2!NMe), 3.61 (s, 3H, OMe), 3.82 (s, 3H, OMe), 3.86 (s,
3H, OMe), 5.55 (m, 3H, meso H and 2!CH), 5.98 (m, 2H,
2!CH), 6.54 (m, 4H, 2!CH and 2!ArH). 13C NMR
(CDCl3): d 33.9, 42.1, 56.0, 60.9, 105.8, 106.4, 108.8, 122.0,
133.3, 136.9, 153.1. MS: m/z 340 (MC). Anal. Calcd for
C20H24N2O3: C 70.58, H 7.05, N 8.23. Found: C 71.47, H
7.45, N 8.56.
4.2.19. 5-(Phenyl)di(N,N0-dimethyl)pyrromethane (4s).
White solid. Yield: 0.13 g, 52%. Mp: 84 8C. IR (KBr): 3117,
2937, 1487, 1450, 1294 cmK1. 1H NMR (CDCl3): d 3.37 (s,
6H, 2!NMe), 5.47 (s, 1H, meso CH), 5.94 (m, 2H, 2!CH),
6.01 (m, 2H, 2!CH), 6.55 (m, 2H, 2!CH), 7.28 (m, 5H,
5!ArH). 13C NMR (CDCl3): d 33.7, 42.3, 105.9, 108.6,
4.2.25. Tri(N,N0,N00-trimethyl)pyrrane (5e). Sticky solid.
Yield: 0.03 g, 13%. IR (KBr): 2907, 1716, 1656, 1567,
1469 cmK1. 1H NMR (CDCl3): d 3.38 (s, 3H, NMe), 3.52 (s,
6H, 2!NMe), 3.84 (s, 4H, 2! meso CH2), 5.71 (m, 2H,
2!CH), 5.80 (m, 2H, 2!CH), 6.02 (m, 2H, 2!CH), 6.55
(m, 2H, 2!CH). 13C NMR (CDCl3): 24.9, 30.4, 33.7, 106.0,

K. Singh et al. / Tetrahedron 61 (2005) 6614–6622
6621
1
106.5, 107.4, 121.6, 129.5, 129.7. MS: m/z 267 (MC Calcd
for C17H21N3).
14%. IR (KBr): 3388, 3364, 1560, 1512, 1357 cmK1. H
NMR (CDCl3): d 3.43 (s, 3H, NMe), 5.37 (s, 1H, meso H),
5.72 (m, 1H, CH), 5.91 (m, 1H, CH), 6.07 (m, 1H, CH), 6.19
(m, 1H, CH), 6.69 (m, 1H, CH), 6.74 (m, 1H, CH), 7.32 (m,
2H, 2!ArH), 7.67 (br, 1H, D2O exchangeable, NH), 8.21
(m, 2H, 2!ArH). 13C NMR (CDCl3): d 33.8, 43.8, 108.7,
108.7, 111.6, 123.8, 129.2, 146.9, 149.6. MS: m/z 281 (MC).
Anal. Calcd for C16H15N3O2: C 68.32, H 5.33, N 14.94.
Found: C 68.72, H 5.60, N 14.77.
4.3. Reactions of oxazinanes 1 with N-methyl pyrrole
with pyrrole/indole. Synthesis of bis(heterocycly)-
methanes 6 and 7. General procedure
A solution of freshly distilled N-methyl pyrrole (2.0 mmol)
with pyrrole (2.0 mmol)/indole (2.0 mmol) and oxazinane 1
(1.0 mmol) in anhydrous acetonitrile (30 mL) was stirred
under N2 for 15 min, followed by addition of TFA
(3.0 mmol) and heated under reflux at 80 8C till the reaction
completed (TLC). The reaction was cooled to room
temperature and basified with cold aqueous sodium
bicarbonate solution (5.0% w/v) and extracted with ethyl
acetate (3!30 mL). The combined organic extracts were
dried over anhydrous sodium sulphate and the solvent was
removed under reduced pressure on a rotary evaporator. The
residue was chromatographed over silica gel G (60–120
mesh) using hexane or a mixture with ethyl acetate, as
eluent and the compounds were rapidly isolated. Using the
above procedure, the following products were synthesized.
4.3.5. 1-methyl-2-[phenyl-(1H-pyrrol-2-yl)-methyl]-1H-
pyrrole (6e). White crystalline solid. Yield: 0.024 g, 15%.
Mp: 103 8C. IR (KBr): 3390, 3358, 1610 cmK1. H NMR
1
(CDCl3): d 3.42 (s, 3H, NMe), 3.94 (s, 2H, meso CH2), 6.05
(m, 2H, 2!CH), 6.14 (m, 2H, 2!CH), 6.54 (m, 1H, CH),
6.64 (m, 1H, CH), 7.20 (br, 1H, D2O exchangeable, NH).
13C NMR (CDCl3): d 25.4, 29.7, 33.6, 105.7, 106.6, 107.6,
106.3, 116.7, 121.7. MS: m/z 160 (MC). Anal. Calcd for
C10H12N2: C 75.00, H 7.50, N 17.50. Found: C 74.67, H
7.23, N 17.69.
4.3.6.
3-[(1-Methyl-1H-pyrrole-2-yl)-(4-methoxy-
phenyl)-methyl]-1H-indole (7a). Off-white solid. Yield:
0.05 g, 15%. Mp: 94 8C. IR (KBr): 3350, 2933, 2833, 1708,
1610, 1510 cmK1. 1H NMR (CDCl3): d 3.39 (s, 3H, NMe),
3.75 (s, 3H, OMe), 5.50 (s, 1H, meso H), 5.57 (m, 1H, CH),
6.00 (m, 1H, C(2)indolyl H), 6.57 (m, 2H, CH), 6.80 (m, 2H,
2!ArH), 6.96 (m, 1H, ArH), 7.11 (AA0BB0, 2H, JZ8.0 Hz,
2!ArH), 7.28 (AA0BB0, 2H, JZ8.0 Hz, 2!ArH), 8.09 (br,
1H, D2O exchangeable, NH). 13C NMR (CDCl3): d 33.7,
40.1, 55.2, 106.2, 108.4, 111.0, 113.6, 119.0, 119.3, 119.6,
121.7, 122.0, 123.4, 126.7, 129.6, 134.9, 135.3, 136.6,
158.0. MS: m/z 316 (MC). Anal. Calcd for: C21H20N2O: C
79.74, H 6.32, N 8.86. Found: C 79.77, H 6.21, N 8.65.
4.3.1. 2-[(4-Methoxyphenyl)-(1H-pyrrole-2-yl)-methyl]-
1-methyl-1H-pyrrole (6a). Off-white sticky semi solid
Yield: 0.04 g, 15%. IR (KBr): 3100, 2955, 2840, 1703,
1593, 1512 cmK1. 1H NMR (CDCl3): d 3.49 (s, 3H, NMe),
3.91 (s, 3H, OMe), 5.42 (s, 1H, meso H), 5.87 (m, 1H, CH),
5.99 (m, 1H, CH), 6.22 (m, 1H, CH), 6.29 (m, 1H, CH), 6.69
(m, 2H, 2!CH), 6.69 (m, 2H, 2!CH), 6.96 (AA0BB0, 2H,
JZ8.0 Hz, 2!ArH), 7.21 (AA0BB0, 2H, JZ8.0 Hz, 2!
ArH), 8.0 (br, 1H, D2O exchangeable, NH). 13C NMR
(CDCl3): d 33.8, 41.9, 42.4, 106.0, 108.7, 108.90, 121.5,
121.9, 126.0, 126.6, 128.2, 128.3, 128.7, 133.5, 141.2. MS:
m/z 266 (MC). Anal. Calcd for C17H18N2O: C 77.69, H
6.76, N 10.52. Found: C 76.96, H 7.05, N 10.22.
4.3.7. 3-[(1-Methyl-1H-pyrrole-2-yl)-(4-nitrophenyl)-
methyl]-1H-indole (7b). Sticky solid. Yield: 0.04 g, 12%.
Mp: IR (KBr): 3345, 2940, 2835, 1706, 1610, 1540,
4.3.2. 1-Methyl-2-[(2-nitrophenyl)-(1H-pyrrol-2-yl)-
methyl]-1H-pyrrole (6b). Sticky solid. Yield: 0.05 g,
1
1326 cmK1. H NMR (CDCl3): d 3.52 (s, 3H, NMe), 5.60
1
16%. IR (KBr): 3389, 3358, 1560, 1513, 1356 cmK1. H
(m, 1H, meso H), 5.77 (m, 1H, CH), 6.12 (m, 1H,
C(2)indolyl H), 7.10 (m, 2H, 2!CH), 7.14 (m, 1H, ArH),
7.27 (m, 2H, ArH), 7.44 (m, 2H, 2!ArH), 7.65 (m, 1H,
ArH), 8.15 (m, 2H, 2!ArH), 8.19 (br, 1H, D2O exchange-
able, NH). 13C NMR (CDCl3): d 33.7, 40.5, 106.4, 108.7,
111.2, 116.9, 118.9, 119.5, 121.6, 122.2, 122.2, 123.5,
123.5, 126.1, 129.0, 133.4, 134.7, 136.5, 144.9, 148.2. MS:
m/z 331 (MC).
NMR (CDCl3): d 3.47 (s, 3H, NMe), 5.56 (s, 1H, meso H),
5.89 (m, 1H, CH), 6.01 (m, 1H, CH), 6.30 (m, 1H, CH), 6.59
(m, 1H, CH), 6.61 (m, 1H, CH), 6.73 (m, 1H, CH), 7.28 (m,
3H, 3!ArH), 8.04 (br, 1H, D2O exchangeable, NH), 7.9 (m,
1H, ArH). 13C NMR (CDCl3): d 33.8, 41.5, 108.6, 108.7,
108.9, 109.3, 121.9, 122.6, 123.4, 123.6. MS: m/z 281 (MC).
Anal. Calcd for C17H17N3O2: C 68.32, H 5.33, N 14.94.
Found: C 68.45, H 5.57, N 14.48.
4.3.3. 1-Methyl-2-[(3-nitrophenyl)-(1H-pyrrol-2-yl)-
methyl]-1H-pyrrole (6c). Yellowish sticky liquid. Yield:
Acknowledgements
0.05 g, 16%. IR (KBr): 3391, 3360, 1562, 1513, 1356 cmK1
.
The authors thank CSIR and UGC, New Delhi for financial
assistance.
1H NMR (CDCl3): d 3.41 (s, 3H, NMe), 5.33 (s, 1H, meso
H), 5.61 (m, 1H, CH), 5.81 (m, 1H, CH), 6.04 (m, 1H, CH),
6.15 (m, 1H, CH), 6.62 (m, 1H, CH), 6.73 (m, 1H, CH), 7.46
(m, 3H, 3!ArH), 8.04 (br, 1H, D2O exchangeable, NH),
8.11 (m, 1H, ArH). 13C NMR (CDCl3): d 33.8, 41.5, 108.6,
108.7, 108.9, 109.3, 121.9, 122.6, 123.4, 123.6. MS: m/z 281
(MC). Anal. Calcd for C16H15N3O2: C 68.32, H 5.33, N
14.94. Found: C 68.56, H 5.60, N 14.67.
References and notes
1. (a) Review article Burrell, A. K.; Officer, D. L.; Plieger, P. G.;
Reid, D. C. W. Chem. Rev. 2001, 2751 and references cited
therein. (b) Littler, B. J.; Miller, M. A.; Hung, C.-H.; Wagner,
R. W.; O’Shea, D. F.; Boyle, P. D.; Lindsey, J. S. J. Org.
4.3.4. 1-Methyl-2-[(4-nitrophenyl)-(1H-pyrrol-2-yl)-
methyl]-1H-pyrrole (6d). Sticky solid. Yield: 0.04 g,

6622
K. Singh et al. / Tetrahedron 61 (2005) 6614–6622
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