Facile synthesis of 2-arylpyrroles from 4-oxo-butanoic acids and their use in the preparation of bis(pyrrolyl)methanes

Article abstract of DOI:10.3987/COM-06-10690

A range of 3-aroyl-propionic acids have been cyclised to unsaturated lactones which, upon reduction using DIBAL-H and reaction with an ammonia source, gave 2-arylpyrroles (Ar = Ph, 1-naphthyl, o-phenoxyphenyl and 4-methyl-2-methylsulfanylphenyl) in excellent yields. Reaction of 2,6-disubstituted aroylpropanals (Ar = 2,4,6-Me₃C₆H₂, anthracenyl and 2-Me-naphthalen-1-yl) with an ammonia source failed to generate pyrroles. The arylpyrroles react readily with ketones or aldehydes in ethanol or under eutectic mix melt conditions to give bis-(pyrrolyl)methanes in excellent isolated yields.

Full text of DOI:10.3987/COM-06-10690

HETEROCYCLES, Vol. 68, No. 6, 2006
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HETEROCYCLES, Vol. 68, No. 6, 2006, pp. 1121 - 1138. © The Japan Institute of Heterocyclic Chemistry
Received, 6th February, 2006, Accepted, 7th April, 2006, Published online, 11th April 2006. COM-06-10690
FACILE SYNTHESIS OF 2-ARYLPYRROLES FROM
4-OXO-BUTANOIC ACIDS AND THEIR USE IN THE
PREPARATION OF BIS(PYRROLYL)METHANES
David J. Jones† and Vernon C. Gibson§*
§Imperial College London, Exhibition Road, London, UK SW7 2AZ.
E-mail:v.gibson@imperial.ac.uk. Fax: 44 (0)207 5945810
Abstract – A range of 3-aroyl-propionic acids have been cyclised to unsaturated
lactones which, upon reduction using DIBAL-H and reaction with an ammonia source,
gave
2-arylpyrroles
(Ar
=
Ph,
1-naphthyl,
o-phenoxyphenyl
and
4-methyl-2-methylsulfanylphenyl) in excellent yields. Reaction of 2,6-disubstituted
aroylpropanals (Ar = 2,4,6-Me3C6H2, anthracenyl and 2-Me-naphthalen-1-yl) with an
ammonia source failed to generate pyrroles. The arylpyrroles react readily with
ketones or aldehydes in ethanol or under eutectic mix melt conditions to give
bis-(pyrrolyl)methanes in excellent isolated yields.
INTRODUCTION
General routes to substituted pyrroles have been much examined due to the ubiquitous role of pyrroles in
natural products and as key intermediates in drug manufacture.1 Recently, there has been a growing
interest in functionalized 2-arylpyrroles as precursors for the synthesis of: i.)
5,5-diaryl-4-bora-3a,4a-diaza-s-indacenes (BODIPY®) as dyes or chromophores, ii.) as end caps for
oligopyrroles in electrochemical studies of these conducting polymers or iii.) tris-(pyrrolyl)methanes or
amines as chelating ligands in anionic sensors. We were interested in developing routes to potentially
bidentate or tetradentate bis-(arylpyrrolyl)methanes or pyrrolylmethenes as C2-symmetric supporting
ligands in olefin oligomerisation/polymerisation catalysis, as indicated in Figure 1. Although there have
†
Current address: Bio21 Institute, University of Melbourne, 30 Flemington Road,
Melbourne, Victoria, Australia, 3052, e-mail: djjones@unimelb.edu.au.

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HETEROCYCLES, Vol. 68, No. 6, 2006
been a number of recent reports on the use of bis-(pyrrolyl)methane ligands in coordination chemistry or
in catalysis there has been no report where the steric environment around the metal centre has been
adjusted by altering the ortho-substituent of the pyrrole apart from bis-(iminopyrrolyl)methanes.
R2
R2
R1
R1
H
N
R R
H
N
R2
R1 R1
NH
R2
R3
D
R3
N
D
H
N
R R
H
N
R
R4
R4
Figure 1. Targeted 2,2'-(bis-5,5'-arylpyrrolyl)methanes or pyrrolylmethenes
Simple 2-arylpyrroles have been synthesized by the high temperature isomerization of 1-arylpyrrole,2
decarboxylation of arylpyrroles3 or more recently by coupling reactions,4 especially Suzuki5 or
Stille6methodologies, for example coupling 2-bromo N-Boc protected pyrroles with arylboronic acids to
generate a series of dyes with tunable characteristics (Ar = Ph, 1-naph, 2-MeOC6H4, 4-MeOC6H4 and
4-FC6H4), or coupling bromoarenes with 2-R3Sn functionalized N-Boc-pyrroles for oligopyrroles (Ar =
Ph, anthracenyl). As we were interested in generating a library of bispyrrolylmethanes or
arylpyrrolylimines, we decided to investigate alternative routes to the required 2-arylpyrroles, which may
offer general routes to large quantities of the required 2-arylpyrrole precursors avoiding the use of
expensive reagents or multi-step preparations of precursors. We turned to the synthesis of a 4-oxobutanal,
the Paal-Knorr precursor for pyrroles, and examined methods for its general synthesis.
R
R
O O
R
O
O
O
O
O
O
AlCl3
H+
A
B
C
+
+
+
OH
OH
[H]
O O
2
MgBr
O
O
R
R
- H2O
OH
O
Scheme 1. General synthetic routes to 4-aryl-4-oxobutanoic acids
After examining known routes to 4-oxobutanals, including C1 + C3,7 C2 + C27b,8 (especially the Trofimov
reaction or variations of this1a,1g,9) or C3 + C110 coupling chemistry, as well as alternative approaches, e.g.

HETEROCYCLES, Vol. 68, No. 6, 2006
1123
ozonolysis of 5-oxopent-1-ene11 or methathesis,12 we decided that the available routes were either too
complicated, formed highly functionalized products or were not sufficiently general. The commercially
available, or readily synthesized, 4-oxobutanoic acids (see Scheme 1) appeared to offer a key source of
the required 4 carbon synthon for the Paal-Knorr synthesis of the pyrrole framework. We report here the
facile generation of the 4-aryl-4-oxobutanal by DIBAL-H (i-Bu2AlH) reduction of
5-aryl-3H-furan-2-ones formed from 4-aryl-4-oxobutanoic acid and their conversion into 2-arylpyrroles.
The pyrroles have been used to generate new asymmetric bidentate and tetradentate
bis-(pyrrolyl)methanes.
RESULTS AND DISCUSSION
The initial target for this research was the previously reported unsaturated lactam
5-phenyl-1,3-dihydro-pyrrolidin-2-one (3a) formed by cyclisation of the commercially available
benzoylpropionic acid to the unsaturated γ-lactone (5-phenyl-3H-furanone) followed by reaction with
NH3 in ethanol (Scheme 2).
H
N
O O
O
O
O
a
b
OH
1a
2a
3a
c
d
H
N
O O
e
H
4a
5a
Scheme 2. Synthesis of 5-phenylpyrrole; (a) Ac2O, cat H+ (b) NH3, EtOH, reflux
(c) LiAlH4 (d) DIBAL-H, -78°C, H+ (e) NH4OAc, EtOH
It was expected that a simple reduction would then allow formation of the required pyrrole. During this
work it was realized that formation of the γ-lactone effectively protected the arylketone as an enolester.
This should allow reduction using DIBAL-H to the required Paal-Knorr precursor, the ketoaldehyde,
allowing access not only to the required pyrroles but also the analogous furans and thiophenes. Reaction
of 2a with 1.1 eq. of DIBAL-H followed by an acid workup resulted in formation of the required
ketoaldehyde (4a) (in > 95 % NMR yield). Reaction of the crude intermediate (4a) with NH4OAc
resulted in quantitative formation (NMR) of phenylpyrrole (5a) proving the synthetic route from
4-oxo-butanoic acids in three simple reaction steps in a high overall isolated yield (>90%).

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HETEROCYCLES, Vol. 68, No. 6, 2006
An extensive literature search indicated only two previously reported DIBAL-H reductions of unsaturated
γ-lactones to form keto-aldehydes or furans. Reduction of 5-alkyl-3H-furanones to form ketoaldehydes
as perfume precursors13 and a recent report, published after the commencement of this study, of the
isomeric 5-alkyl-5H-furanones as intermediates in the synthesis of Litseaverticillols A, C, D, F and G.14
An alternate, direct palladium catalyzed reduction of 1a to 4a has recently been reported in the presence
of excess pivalic anhydride,15 while reactions using triethyl orthoformate or orthoacetate result in
moderate yields of ketoaldehydes and 2 or 2,5-furans via intermediate 3 carboxy species.16
The simplicity of the new methodology encouraged development of the chemistry and a range of
keto-acids were formed using the routes outlined in Scheme 1, 1d and 1e Path A, 1b and 1g17,18 Path B
and 1b, 1c and 1f via intermediate 4-oxobutenoic acids (Ar = 1-naphthyl (I), o-(Ph)C6H4 (II) and
9-anthracenyl (III)) Path C, Scheme 3. The majority of the keto-acids have been previously reported,
1b, d, e, f and g,17,19 or are commercially available, i.e. benzoylpropionic acid (1a). The keto-acids were
cyclised using Ac2O in an acid catalyzed reaction (yields > 80%, non-optimized) and reduced with
DIBAL-H at low temperature. Reaction of the crude products (4a-d) with NH4OAc generated the
required pyrroles in excellent overall recrystallized yield, generally > 75%. However keto-acids (1e-g),
with di-ortho-substituted aryl groups, were cyclised and reduced to form the required ketoaldehydes
(4h-j) but did not generate the required pyrrole on reaction with an ammonia source. This is presumably
due to the sterically demanding aryl substituents impeding nucleophilic attack on the arylketone by
ammonia or the enamine formed from 4e-g upon reaction with the ammonia source.
H
N
O O
O O
O
Ar
O
Ar
b
a
c
Ar
OH
Ar
H
1
2
4
5
5a Ar = Ph
1a Ar = Ph
1b Ar = 1-Napthyl
1c Ar = o-(PhO)C6H4
1d Ar = 4-Me-2(MeS)C6H4
1e Ar = Mesityl
5b Ar = 1-Napthyl
5c Ar = o-(PhO)C6H4
5d Ar = 4-Me-2(MeS)C6H4
1f Ar = Anthracenyl
1g Ar = 2-Me-napth-1-yl
Scheme 3. Substituted pyrrole synthesis from 4-keto-butanoic acids, a. Ac2O,
b. DIBAL-H, –78°C, c. NH4OAc
Reaction of 2-phenylpyrrole with a range of ketones R2CO (R = Ph, Py or R,R = fluorenyl) allowed a new
set of bis(pyrrolyl)methanes, (6a-c), to be generated (Figure 2). Blocking the pyrrole 2-position enables
reactions to be carried out under eutectic mix melt conditions, resulting in yields of > 95% (NMR, crude

HETEROCYCLES, Vol. 68, No. 6, 2006
1125
product). Similarly, reaction of naphthalenyl- or 2-phenoxyphenyl-pyrroles allowed generation of
potentially C2-symmetric bis(pyrrolyl)methanes (7a) and tetradentate bis(pyrrolyl)methanes (8a-b).
R'
R'
H
N
H
R
R
R
H
R
[H+]
Ar
N
N
2
+
O
Ar = Ph
Ar = 1-naphthyl
Ar = o-(PhO)C6H4
Ar = Ph 6a
5a
5b
5c
R,R = fluorenyl
R = Ph
R = Py
6b
6c
Ar = Naphthyl 7a
Ar = o-(PhO)C6H4 8a
8b
R,R = fluorenyl
R,R = fluorenyl
R = Ph
Figure 2. Synthesis of new bis(pyrrolyl)methanes
In summary, we have developed a facile synthesis of 2-arylpyrroles from 4-oxobutanoic acids via
cyclization and subsequent DIBAL-H reduction of resultant unsaturated furanones. The 4-oxobutanoic
acids are readily generated by simple Friedel-Crafts or Grignard chemistry using succinic anhydride as a
C4 synthon or via condensation of arylketones with glyoxylic acid and reduction of the substituted acrylic
acids. We are currently exploiting this chemistry to develop routes to substituted pyrroles as precursors
to bis(pyrrolyl)methanes. The metal complexation chemistry of the bis(pyrrolyl)methanes is currently
under investigation.
EXPERIMENTAL
1
2’-Phenoxyacetophenone20 was prepared by literature methods. 1H-1H, H-13C correlation and DEPT
spectra were recorded on all compounds and NOESY spectra were collected, where required, to identify
proton proximity.
4-Naphthalen-1-yl-4-oxobut-2-enoic acid (I)
A solution of 1-acetylnaphthalene (50 g, 0.294 mol) and glyoxylic acid monohydrate (27 g, 0.35 mol) in
acetic acid 25 mL containing a catalytic amount of p-toluenesulphonic acid (0.25 g) was refluxed
1
overnight. A sample was taken for H NMR and indicated 90% completion of reaction. The reaction
mix was cooled and ether (200 mL) added. The reaction mix was washed with 4 x 100 mL of water,
dried over Na2SO4, filtered and the solvent removed. The residue was triturated in hexane and the crude
product collected by filtration. Analytically pure material was obtained by recrystallization from ethanol.
Yield 51.2 g (77%).21, 22 1H NMR (400 MHz, CDCl3) δ 8.57(d, J = 82 Hz, Ar-H), 7.91(pseudo-t, 2H J =
8.5 Hz, Ar-H) overlapping 7.87(, 1H J = 15.8 Hz, CH), 7.53-7.67(m, 3H, Ar-H), 6.83(d, 1H J = 15.8 Hz,
CH), COOH not identified. 13C{1H} NMR (100 MHz, CDCl3) δ 192.8, 170.7, 142.0, 133.9, 133.9, 131.6,

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130.4, 129.5, 128.7, 128.4, 126.9, 125.5, 124.4. IR (KBr: CO cm-1) υ 1700, 1667. CI-MS (m/z)
244(M+NH4+ 85%), 246(MH2+NH4+ 100%). Anal. Calcd. for C14H10O3: C, 74.33; H, 4.46. Found: C
74.42; H, 4.46.
4-Oxo-4-(2-phenoxyphenyl)but-2-enoic acid (II)
As above for I. Yield 71%. 1H NMR (400 MHz, CDCl3) δ 11.50(br s, 1H, COOH), 7.91(d, 1H J = 15.6
Hz, CH), 7.81(dd, 1H J = 7.8 & 1.8 Hz, He), 7.46(ddd, 1H J = 8.7 & 7.0 & 1.4 Hz, Hc), 7.37(brdd, 2H J =
6.5 & 5.4 Hz, m-Ph-H), 7.21(dt, 1H J = 7.5 & 1.0 Hz, Hd), 7.16(tt, 1H J = 7.4 & 1.1 Hz, p-Ph-H),
7.01(brd, 2H J = 8.7 Hz, o-Ph-H), 6.93(dd, 1H J = 8.3 & 0.9 Hz, Hb), 6.70(d, 1H J = 15.6 Hz, CH).
13C{1H} NMR (100 MHz, CDCl3) δ 190.5, 171.0, 156.7, 155.9, 142.2, 134.5, 131.0, 130.1, 129.4, 129.3,
124.3, 123.6, 119.1, 118.9. IR (KBr: CO cm-1) υ 1700, 1663. CI-MS (m/z) 286(M+NH4+ 100%),
269(M+H+ 60%). Anal. Calcd for C16H12O4: C 71.64; H 4.51. Found: C 71.63; H 4.37.
4-Anthracen-9-yl-4-oxobut-2-enoic acid (III)
As above for I. Crude material was obtained by slurrying in CHCl3 and collecting the red crystalline
material, which was identified as the CHCl3 adduct. Dried in a vacuum oven overnight at 60 °C. Yield
72%. Analytically pure material obtained by recrystallization from toluene / ethanol.23,24 1H NMR (400
MHz, methanol-d4) δ 8.59(s, 1H, H5), 8.03-8.07(m, 2H, H4), 7.73-7.77(m, 2H, H1), 7.44-7.52(m, 4H, H3 &
H2), 7.44 (d, 1H J = 15.9 Hz, CH), 6.20(d, 1H J = 15.9 Hz, CH), COOH not identified. C{1H} NMR
13
(100 MHz, methanol-d4) δ 201.2, 168.1, 142.6, 136.8, 134.0, 132.4, 130.5, 130.0, 129.5, 128.3, 126.7,
125.5. IR (KBr: CO cm-1) υ 1700, 1661. CI-MS (m/z) 294(M+NH4+ 10%), 144(NapthOH 100%). Anal.
Calcd for C18H12O3: C 78.25; H 4.38. Found C 78.17, H 4.29.
4-Naphthalen-1-yl-4-oxo-butyric acid (1b)
Method A. To a solution of I (50 g, 0.221 mol) in 100 mL of 90/10 HOAc/H20 was added zinc dust
(excess) in portions until no further reaction was noted. The reaction mix was diluted with 200 mL of 2
M HCl and 200 mL of ether added. The mix was filtered to remove excess zinc dust and the organic
phase separated and washed with 100 mL 2 M HCl then 3 x 100 mL of distilled water. The ether layer
was dried over Na2SO4, filtered and the solvent removed in vacuo to leave a crude product which was
slurried in cold 96% ethanol and the product recovered by filtration. Yield 44.6 g (88%).
Method B: A Grignard formed from 1-bromonapthalene (100g, 0.483 mole) was added to a slurry of
succininc anhydride (50 g, 0.50 mol) in 500 mL of thf at 0°C. The solution was allowed to warm to rt
and then refluxed for 4 h. To the cooled solution was added 500 ml of 2M HCl and 500 mL of ether.

HETEROCYCLES, Vol. 68, No. 6, 2006
1127
The phases were separated and the organic phase washed with 500 mL, 2 M HCl and 3 x 500 mL of
distilled water. The organic phase dried over Na2SO4 and the solvent removed under vacuum. The
crude product was slurried in cyclohexane and filtered. Yield 48 g (44%).19g,i 1H NMR (400 MHz,
CDCl3) δ 8.63(dd, 1H J = 7.7 & 0.9 Hz, Hg), 8.01(d, 1H J = 8.2 Hz, Hc), 7.95(dd, 1H J = 7.2 & 1.2 Hz,
Ha), 7.88(dd, 1H J = 8.0 & 1.5, Hd), 7.49-7.61(m, 3H, Hf, He & Hb), 3.93(t, 2H J = 6.4 Hz, CH2), 2.90(t,
2H J = 6.4 Hz, CH2), COOH not identified. C{1H} NMR (100 MHz, CDCl3) δ 178.8, 135.2, 133.9,
13
132.9, 130.1, 128.4, 128.0, 127.8, 126.5, 125.7, 124.3, 84.8, 360.3, 28.4. IR (KBr: CO cm-1) υ 1718, 1691.
CI-MS (m/z) 246(M+NH4+ 100%), 229(M+H+ 80%). Anal. Calcd for C14H12O3: C, 73.67; H, 5.30. Found
C, 73.80; H, 5.19.
4-Oxo-4-(2-phenoxyphenyl)butyric acid (1c)
As above for I. Yield 94.5 %. 1H NMR (400 MHz, CDCl3) δ 11.60(s, 1H, COOH), 7.88(dd, 1H J = 7.8
& 1.8 Hz, He), 7.43(ddd, 1H J = 8.6 & 7.0 & 1.5 Hz, Hd) overlapping 7.38(dd, 2H J = 8.6 & 7.5 Hz,
m-Ph-H), 7.05(m, 2H, Hd & p-Ph-H), 7.05(br d, 2H, o-Ph-H), 6.89(dd, 1H J = 8.3 & 0.9 Hz, Hb), 3.37(t,
2H J = 6.4 Hz, CH2), 2.74(t, 2H J = 6.4 Hz, CH2). C{1H} NMR (100 MHz, CDCl3) δ 199.0, 179.1,
13
156.6, 156.1, 133.8, 130.7, 130.1, 129.3, 124.1, 123.4, 119.2, 118.9, 38.2, 28.5. IR (KBr: CO cm-1) υ
1709, 1671. CI-MS (m/z) 288(M+NH4+ 95%), 271(M+H+ 100%). Anal. Calcd for C16H14O4 : C, 71.10; H
5.22. Found: C, 70.90; H, 5.16.
4-(5-Methyl-2-methylsulfanyl-phenyl)-4-oxo-butyric acid (1d)
To a mechanically stirred, degassed slurry of 4-methylsulfanyltoluene (138.23 g, 1.0 mol) and succinic
anhydride ( 100.0 g, 1.0 mol) in 1.5 L of DCM at –20°C was slowly added AlCl3 (266.6 g, 2 mol) and the
red solution allowed to warm to rt over 4 h. The reaction mix was deactivated by pouring onto 3 L of
ice and 1 L of 2M HCl. The organic phase was separated, the aqueous phase extracted with 500 mL of
DCM and the combined organic extracts washed with 500 mL of 2 M HCl then 3 x 500 mL of distilled
water. The organic fraction was dried over Na2SO4, filtered and the DCM removed under vacuum to
leave a crude product which was slurried in a minimum of 96 % ethanol, filtered and washed with 2 x 100
mL of 96% ethanol. The crude material was dried in vacuum oven at 60°C overnight. Analytically
pure material was obtained by recrystallization from toluene / ethanol. Yield 211.0 g (88.5%).19a,25,26 1
H
NMR (400 MHz, CDCl3) δ 7.69(d, 1H J = 1.8 Hz, He), 7.30(ddd, 1H J = 8.2 & 1.8 & 0.5 Hz, Hc), 7.21(d,
1H J = 8.2 Hz, Hb), 3.29(t, 2H J = 6.7 Hz, CH2), 2.81(t, 2H J = 6.7 Hz, CH2), 2.40(s, 3H, SMe), 2.37(s,
3H, Me). C{1H} NMR (100 MHz, CDCl3) δ 198.7, 179.1, 172.1, 139.0, 133.7, 133.4, 133.3, 130.9,
13

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125.3, 34.5, 28.2, 20.7, 16.1. IR (KBr: CO cm-1) υ 1700, 1667. CI-MS (m/z) 256(M+NH4+ 100%),
239(M+H+ 30%). Anal. Calcd for C12H14O3S: C, 60.48; H, 5.92. Found: C, 60.45; H, 5.78.
4-Oxo-4-(2,4,6-trimethylphenyl)butyric acid (1h)
Made as for 1d above by Friedel-Crafts chemistry. Analytically pure material obtained by
recrystallization from hot heptane. Yield 19.2g (FW 220.26 95.1%).27 1H NMR (400 MHz, CDCl3) δ
7.261(s, 2H, m-Ph-H), 3.03(t, 2H J = 6.5 Hz, CH2), 2.77(t, 2H J = 6.5 Hz, CH2), 2.28(s, 3H, Me), 2.201(s,
6H, Me), COOH not located. 13C{1H} NMR (100 MHz, CDCl3) δ 208.2, 177.9, 138.7, 138.6, 132.7, 128.5,
39.2, 27.4, 21.0, 19.0. IR (KBr: CO cm-1) υ 1715, 1697. CI-MS (m/z) 238(M+NH4+ 100%), 221(M+H+
100%). Anal. Calcd for C13H16O3: C, 70.89; H, 7.32. Found: C, 70.84; H, 7.41.
4-Anthracen-9-yl-4-oxo-butyric acid (1i)
A deep yellow solution of anthracenoyl acrylic acid (III) (20g, 72.4 mmol) in ethanol containing 0.5 g of
Pd/C was placed in a Parr reactor and pressurized with 4 Bar of H2. The reaction was monitored by
opening the reactor every hour and stopped when the yellow color was discharged and an off white
precipitate had formed. The solids were dissolved in toluene, filtered and the solvent removed under
vacuum to leave a product which could be used without further purification. Analytically pure material
was obtained by recrystallization from toluene / ethanol. Yield 19.5 g (96.8 %).28,29 1H NMR (250 MHz,
acetone-d6) δ 10.90(s, 1H, OH), 8.64(s, 1H, H5), 8.11-8.14(m, 2H, H4), 8.03-8.06(m, 2H, H1), 7.52-7.58(m,
4H, H3 & H2), 3.39(t, 2H J = 5.95 Hz, CH2), 2.94(t, 2H J = 5.95 Hz, CH2). C{1H} NMR (100 MHz,
13
acetone-d6) δ 208.4, 174.3, 137.4, 132.0, 129.5, 128.9, 127.8, 127.5, 126.5, 125.4, 41.5, 27.8. IR (KBr:
CO cm-1) υ 1700br. CI-MS (m/z) 296(M+NH4+ 100%), 279(M+H+ 30%). Anal. Calcd for C18H14O3: C,
77.68; H, 5.07. Found: C, 77.67; H, 5.15.
4-(2-Methylnaphthalen-1-yl)-4-oxo-butyric acid (1j)
A Grignard reagent made from 1-bromo-2-methylnaphthalene (90% dried by passage through a basic
alumina column, 90 g, 0.40 mol) in thf was slowly added to a slurry of succinic anhydride (40 g, 0.40
mol) in 100 mL of thf at 0oC. The reaction mix was allowed to warm to rt and then refluxed for 4 h.
The cooled solution was deactivated by addition of 100 mL of 2 M HCl, extracted with 2 x 100 mL of
ether. The combined organic fractions were washed with distilled water (3 x 100 mL), dried over
Na2SO4, filtered and the solvent removed under reduced pressure. The residue was slurried in hexane
and the crude product collected by filtration.
Analytically pure material was obtained by
recrystallization from toluene / ethanol. Yield 33.0 g (39.2%, theoretical 50%) cf ref.17 1H NMR (400

HETEROCYCLES, Vol. 68, No. 6, 2006
1129
MHz, CDCl3) δ 11.60(br s, 1H, OH), 7.83(d, 1H J = 7.8 Hz, Naphth-H), 7.79(d, 1H J = 8.4 Hz, Hc),
7.65(d, 1H J = 8.0 Hz, naphth-H), 7.43-5.51(m, 2H, He & Hf), 7.31(d, 1H J = 8.4 Hz, Hb), 3.21(t, 2H J =
6.3 Hz, CH2CH2CO2H), 2.91(t, 2H J = 6.3 Hz, CH2CH2CO2H), 2.43(s, 3H, Me). 13C{1H} NMR (100 MHz,
CDCl3) δ 207.8, 178.5, 137.6, 131.7, 130.5, 129.3, 129.0, 128.5, 128.2, 127.0, 125.5, 123.9, 39.7, 27.5,
19.2. IR (KBr: CO cm-1) υ 1711, 1701. CI-MS (m/z) 260(M+NH4+ 100%). Anal. Calcd for C15H14O3 : C,
74.36; H, 5.82. Found: C, 74.19; H, 5.86.
5-Phenyl-3H-furan-2-one (2a)
Benzoylpropionic acid (83 g, 466 mmol), was slurried in 100 mL of Ac2O with 50 mL of HOAc
containing a catalytic amount of p-toluene sulphonic acid (0.5 g). The slurry was allowed to stir for 4 h
during which time the initial solid dissolved giving a clear warm solution before the product precipitated.
The slurry was diluted with 150 mL of distilled water, stirred for 30 min and the product collected by
filtration to give an off white crystalline solid which was washed with 50/50 H2O/HOAc then H20 and
dried in a vacuum oven at 60°C overnight. The crude product could be used without further purification.
Analytically pure material was obtained by sublimation. Yield 62 g (84%).30-33 1H NMR (250 MHz,
CDCl3) δ 7.60(m, 2H J = 3.9 & 0.8 Hz, o-Ph-H), 7.36-7.42(m, 3H, p & m-Ph-H), 5.79(t, 1H J = 1.4 Hz,
CH), 3.42(d, 2H J = 1.4 Hz, CH2). 13C{1H} NMR (100 MHz, CDCl3) δ 176.0, 153.9, 129.6, 128.7, 128.4,
124.7, 97.7, 34.7. IR (KBr: CO cm-1) υ 1804, 1786. CI-MS (m/z) 178(M+NH4+ 100%), 161(M+H+ 50%).
Anal. Calcd for C10H8O2: C, 74.99; H, 5.03. Found: C, 74.80, H, 4.74.
5-Naphthalen-1-yl-3H-furan-2-one (2b)
1
As above for 2a. Yield 38.5 g (93.4%). H NMR (400 MHz, CDCl3) δ 8.28(brd, 1H J = 7.8 Hz, Hg),
7.88-7.92(m, 2H, Ar-H), 7.71(brd, 1H J = 7.1 Hz, Ha), 7.47-7.58(m, 3H, Ar-H), 5.81(t, 1H J = 2.4 Hz,
CH), 3.40(d, 2H J = 2.4 Hz, CH2). 13C{1H} NMR (100 MHz, CDCl3) δ 176.0, 154.1, 133.7, 130.5, 130.3,
128.7, 127.0, 126.9, 126.5, 126.2, 125.0, 124.9, 103.0, 34.7. IR (KBr: CO cm-1) υ 1795. CI-MS (m/z)
228(M+NH4+ 100%), 211(M+H+ 25%). Anal. Calcd for C14H10O2: C, 79.98; H, 4.79. Found: C, 79.83; H,
4.90.
5-(2-Phenoxylphenyl)-3H-furan-2-one (2c)
As above for 2a. Yield 71%. 1H NMR (400 MHz, CDCl3) δ 7.77(dd, 1H J = 7.8 & 1.6 Hz, Ha), 7.378(dd,
2H J = 8.5 & 7.5 Hz, m-PhH), 7.29(dt, 1H J = 7.8 & 1.7 Hz, Hc), 7.13-7.19(m, 2H, Hb & p-Ph-H), 7.02(br
dd, 2H J = 8.6 & 1.0 Hz, o-Ph-H), 6.90(dd, 1H J = 7.7 & 1.5 Hz, Hd), 6.15(t, 1H J = 2.7 Hz, CH), 3.40(d,
2H J = 2.7 Hz, CH2). 13C{1H} NMR (100 MHz, CDCl3) δ 175.6, 156.0, 154.9, 149.7, 130.2, 130.0, 127.7,

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HETEROCYCLES, Vol. 68, No. 6, 2006
123.9, 123.5, 119.7, 118.9, 118.7, 104.0, 35.0. IR (KBr: CO cm-1) υ 1710. CI-MS (m/z) 270(M+NH4+
100%), 253(M+H+ 20%). Anal. Calcd for C16H12O3: C, 76.18; H, 4.79. Found: C, 76.29; H, 4.92.
5-(4-methyl-2-methylsulfanylphenyl)-3H-furan-2-one (2d)
1
As above for 2a. Yield 85%. H NMR (400 MHz, CDCl3). δ 7.47(s, 1H, He), 7.14-7.21(m, 2H, Hb &
Hc), 6.08(t, 1H J = 2.5 Hz, CH), 3.46(d, 2H J = 2.5 Hz, CH2), 2.49(s, 3H, SMe), 2.33(s, 3H, Me). 13C{1H}
NMR (100 MHz, CDCl3) δ 175.6, 151.8, 134.8, 133.8, 130.5, 129.0, 126.8, 126.4, 104.2, 35.1, 20.8, 16.4.
IR (KBr: CO cm-1) υ 1784. CI-MS (m/z) 238(M+NH4+ 100%), 221(M+H+ 75%). Anal. Calcd for
C12H12O2S: C, 65.43; H, 5.49. Found: C, 65.63; H, 5.42.
5-(2,4,6-Trimethylphenyl)-3H-furan-2-one (2e)
As above for 2a. The off white solid was recrystallized from ether at low temperature. Yield 7.5g
(82%).19b 1H NMR (250 MHz, CDCl3) δ 6.91(s, 2H, m-Ph-H), 5.39(t, 1H J = 2.4 Hz, CH), 3.43(d, 2H J =
2.4 Hz, CH2), 2.30(s, 9H, Me). C{1H} NMR (100 MHz, CDCl3) δ 176.7, 153.3, 139.5, 137.8, 128.4,
13
126.1, 103.6, 34.4, 21.2, 20.2. IR (KBr: CO cm-1) υ 1814. CI-MS (m/z) 220(M+NH4+ 100%). Anal. Calcd
for C13H14O2: C, 77.20; H 6.98. Found: C, 77.09; H, 6.90.
5-Anthracen-9-yl-3H-furan-2-one (2f)
As above for 2a. Yield 96.7%. 1H NMR (400 MHz, CDCl3) δ 8.538(s, 1H, H5), 8.18(br d, 2H J = 8.7 Hz,
H4), 8.02(br d, 2H J = 8.6 Hz, H1), 7.47-7.56(m, 4H, H3 & H2), 5.81(t, 1H J = 2.4 Hz, CH), 3.701(d, 2H J
13
= 2.4 Hz, CH2). C{1H} NMR (100 MHz, CDCl3) δ 176.5, 151.5, 131.1, 130.6, 129.8, 128.7, 126.8,
125.5, 125.4, 122.9, 107.0, 34.8. IR (KBr: CO cm-1) υ 1785sh, 1772. CI-MS (m/z) 278(M+NH4+ 100%).
Anal. Calcd for C14H10O2: C, 83.06; H, 4.65. Found: C, 83.39; H, 4.76.
5-(2-Methylnaphthalen-1-yl)-3H-furan-2-one (2g)
As above for 2a but the reaction required heating for 4 h at 60°C to complete reaction. The product was
a tacky oil which solidified on standing. Yield 83% cf ref.17 1H NMR (250 MHz, CDCl3) δ 7.96(br d,
1H J = 7.3 Hz, Ar-H), 7.83(brd, J = 8.3 Hz, Hd & Ar-H), 7.42-7.55(m, 3H, Ar-H), 7.37(d, 1H J = 8.4 Hz,
Hc),5.60(t, 1H J = 2.4 Hz, CH), 3.56(d, 2H J = 2.4 Hz, CH2), 2.53(s, 3H, Me). 13C{1H} NMR (100 MHz,
CDCl3) δ 176.4, 152.2, 136.4, 132.2, 131.8, 129.9, 128.4, 128.1, 126.9, 125.4, 125.2, 124.7, 105.2, 34.5,
20.6. IR (KBr: CO cm-1) υ 1792. CI-MS (m/z) (M+H+ 100%). Anal. Calcd for C15H12O2: C, 80.34; H, 5.39.
Found: C, 80.51; H, 5.49.

HETEROCYCLES, Vol. 68, No. 6, 2006
1131
Hb
Hc
Ha
H
N
Hd
He
H1
Hg
H2
H3
Hf
Proton labelling for aryl-pyrroles
2-Phenylpyrrole (5a)
A slurry of 2a (25 g, 156.0 mmol) in anhydrous toluene (1L) at –78°C was slowly added DIBAL-H (114
mL of 1.5 M, 171.1 mmol) over 1 h. The solution was reacted at -78°C for 4 h then deactivated by slow
addition of HOAc (50 mL) at –78°C. After allowing the reaction mix to warm to rt, distilled water (200
mL) was added and the organic phase separated. The organic phase was then washed with brine (3 x
200 mL). A sample of the organic phase was taken and dried under vacuum. Diagnostic peaks for the
1
keto-aldehyde (4a): H NMR (250 MHz, CDCl3): δ 9.89(s, 1H, CHO), 3.32(t, 2H J = 6.3 Hz,
CH2CH2CHO)34, 2.92(t, 2H J = 6.3 Hz, CH2CH2CHO).7b To the toluene fraction was added NH4OAc (24
g, excess) and the toluene removed under reduced pressure. The residue was extracted with toluene,
washed with distilled water (3 x 100 mL), dried over Na2SO4 and the solvent removed under reduced
pressure to generate a product which could be used without further purification. Analytically pure
material was obtained by sublimation. Yield 14.7 g (65%). 1H NMR (400 MHz, CDCl3): δ 8.43(br s, 1H,
NH), 7.49(br dd, 2H J = 8.3 & 1.2 Hz, o-Ph-H), 7.39(t, 2H J =7.8 Hz, m-Ph-H), 7.24(tt, 1H J = 7.4 &
1.1 Hz, p-Ph-H), 6.86-6.88(m, 1H, H1), 6.55-6.57(m, 1H, H3), 6.33(pseudo-q, 1H J = 2.9 Hz, H2) 13C{1H}
NMR (100 MHz, CDCl3): δ 132.8, 132.1, 128.9, 126.2, 123.9, 118.9, 110.1, 105.9. CI-MS (m/z):
144(M+H+ 100%). Anal. Calcd for C10H9N: C, 83.88; H 6.34; N 9.78. Found: C, 83.98; H, 6.46; N, 9.81.
Lit.40
2-(1-Naphthalenyl)pyrrole (5b)
As above for 5a. Diagnostic peaks of the keto-aldehyde (4b) 1H NMR (250 MHz, CDCl3) δ 9.93(s, 1H,
CHO), 3.36(t, 2H J = 6.2 Hz, CH2CH2CHO), 2.99(t, 2H J = 6.2 Hz, CH2CH2CHO). Product
recrystallized from hexane at low temperature. Yield 55.3%.5d,e,9e,35,36 1H NMR (400 MHz, CDCl3) δ
8.42(br s, 1H, N-H), 8.31-8.34(m, 1H, Hg), 7.90-7.93(m, 1H, Ar-H), 7.83(pent, 1H J = 4.8 Hz, Ar-H),
7.485-7.551(m, 8H, Ar-H), 6.982(ddd, 1H J = 3.4 & 1.9 & 0.7 Hz, H1), 6.552(ddd, 3.7 & 2.3 & 1.2 Hz,
H3), 6.44(pseudo-q, 1H J = 2.91 Hz, H2). 13C{1H} NMR (100 MHz, CDCl3) δ 134.0, 131.5, 131.4, 130.5,

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HETEROCYCLES, Vol. 68, No. 6, 2006
128.4, 127.5, 126.4, 126.1, 126.0, 125.8, 125.5, 118.4, 109.49, 109.47. CI-MS (m/z) 194(M+H+ 100%).
Anal. Calcd for C14H11N: C, 87.01; H, 5.74; N, 7.25. Found: C, 87.21; H, 5.62; N, 7.33.
2-(2-Phenoxyphenyl)pyrrole (5c)
As above for 5a, yield 90.5%. Diagnostic peaks for the keto-aldehyde (4c). 1H NMR (250 MHz, CDCl3)
δ 9.84(s, 1H, CHO), 3.38(t, 2H J = 6.2 Hz, CH2), 2.84(t, 2H J =6.2 Hz, CH2). Analytically pure material
obtained by recrystallization from ethanol. 1H NMR (400 MHz, CDCl3) δ 9.67(brs, 1H, NH), 7.77(dd, 1H
J = 7.5 & 1.9 Hz, He), 7.39(dd, 2H J = 8.2 & 7.7 Hz, m-Ph-H), 7.09-7.2(m, 5H, Hc & Hd and o & p-Ph-H),
6.85-6.90(m, 2H, Hb & pyrrol-H1), 6.723(brs, 1H, pyrrol-H3), 6.33(pseudo-q, 1H J = 3.0 Hz, pyrrol-H2).
13C{1H} NMR (100 MHz, CDCl3) δ 156.5, 152.5, 130.0, 129.0, 127.0, 126.7, 124.0, 123.9, 123.6, 119.4,
119.3, 118.7, 109.1, 106.9. CI-MS (m/z) 236(M+H+ 100%). Anal. Calcd for C16H13NO: C, 81.68; H, 5.57;
N, 5.95. Found: C, 81.78; H, 5.54; N, 5.78.
2-(4-methyl-2-methylsulfanyphenyl)pyrrole (5d)
1
As above for 5a, yield 83.4%. {Diagnostic peaks for the keto-aldehyde (4d), H NMR (250 MHz,
CDCl3) δ 9.84 (s, 1H, CHO), 3.24(t, 2H J = 6.4 Hz, CH2), 2.861(t, 2H J =6.4 Hz, CH2), 2.31(s, 3H, Me),
2.29(s, 3H, Me)}. Analytically pure material obtained by recrystallization from ethanol at low
temperature. 1H NMR (400 MHz, CDCl3) δ 9.69(br s, 1H, NH), 7.35(br d, 1H J = 1.1 Hz, p-Ph-H), 7.30(d,
1H J = 7.9 Hz, m-Ph-H), 6.85-6.90(dd, 1H J = 7.9 & 1.1 Hz, o-Ph-H),6.90(br, 1H, pyrrol-H1), 6.53(br, 1H,
pyrrol-H3), 6.30(pseudo-q, 1H J = 2.2 Hz, pyrrol-H2), 2.35(s, 3H, Me), 2.33(s, 3H, SMe). C{1H} NMR
13
(100 MHz, CDCl3) δ 136.7, 132.9, 131.0, 130.8, 129.8, 129.5, 127.7, 127.4, 118.4, 109.0, 108.7, 21.0,
17.8. CI-MS (m/z) 204(M+H+ 100%). Anal. Calcd for C16H13NO: C, 70.98; H, 6.45; N, 6.89. Found: C,
70.85; H, 6.57; N, 6.69.
2-(2,4,6-Trimethylphenyl)pyrrole (5e)
Attempted Prep. Diagnostic peaks for the keto-aldehyde (4e), 1H NMR (250 MHz, CDCl3) δ 9.91(s, 1H,
CHO). 6.85(s, 2H, m-Ph), 3.04(t, 2H J = 6.1 Hz, CH2), 2.88(t, 2H J = 6.1 Hz, CH2), 2.28(s, 3H, Me),
2.21(s, 6H, Me).
2-(9-Anthracenyl)pyrrole (5f)
Attempted Prep. Diagnostic peaks for the keto-aldehyde (4f), 1H NMR (250 MHz, CDCl3) δ 10.04(s, 1H,
CHO), 3.39(t, 2H J = 5.9 Hz, CH2), 3.09(t, 2H J =5.9 Hz, CH2).
2-(2-Methylnaphthalen-1-yl)pyrrole (5g)

HETEROCYCLES, Vol. 68, No. 6, 2006
1133
Attempted Prep. Diagnostic peaks for the keto-aldehyde (4g), 1H NMR (250 MHz, CDCl3) δ 9.97(s, 1H,
CHO), 3.12(t, 2H J = 5.9 Hz, CH2), 2.99(t, 2H J =5.9 Hz, CH2), 2.43(s, 3H, Me).
9,9-Bis-(5-phenylpyrrol-2-yl)fluorene (6a)
Method A: Phenylpyrrole (5a) (1.43 g, 10.0 mmol) and fluorenone (2.0 g, excess) were dissolved in
EtOH (5 mL) and heated for 16 h with a catalytic amount of formic acid. The reaction was monitored
by 1HNMR spectroscopy and allowed to react until no pyrrole remained. The product was recovered by
filtration and washed with EtOH. Yield 1.35g (55%).
Method B: Phenylpyrrole (5a) (1.43 g, 10.0 mmol) and fluorenone (1.0 g, excess) were heated for 16 h at
100°C under dinitrogen with a catalytic amount of formic acid. The product was slurried in EtOH and
recovered by filtration and then washed with EtOH. Yield 2.15g (88%). Crystals suitable for structural
analysis can be grown by slow vapor diffusion of hexane into a toluene solution of 6a.
HII
HIII
Hb
HI
Hc
Ha
HIV
H
N
2
H3
H2
1H NMR (400 MHz, CDCl3): δ 8.21(brs, 2H, NH), 7.83(d, 2H J = 7.6 Hz, fluor-H), 7.60(d, 2H J = 7.5 Hz,
fluor-H), 7.45(dt, 2H J = 7.2 & 0.8 Hz, fluor-H), 7.29-7.39(m, 10H, Ar-H, 7.17(tt, 2H J = 7.1 & 1.6 Hz,
m-Ph), 6.45(dd, 2H J = 3.5 & 2.7 Hz, pyr-H), 6.18(dd, 2H J = 3.5 & 2.7 Hz, pyr-H). 13C{1H} NMR (100
MHz, CDCl3): δ 148.8, 139.7, 133.9, 132.5, 131.8, 128.8, 128.4, 128.1, 126.2, 125.3, 123.7, 120.6, 109.4,
106.3. CI-MS (m/z): 449(M+H+ 100%), 306(M-(Phenyl-pyrrole)+H+ 70%). Anal. Calcd for C33H24N2: C,
88.36; H, 5.39; N, 6.25. Found: C, 88.14; H, 5.54; N, 6.37.
1,1-Bis-(5-phenylpyrrol-2-yl)diphenylmethane (6b)
1
As above 6a (Method B) Yield 89% H NMR (400 MHz, CDCl3) δ 8.21(s, 2H, NH), 7.23-7.38(m, 18H,
Ar-H), 7.18(t, 2H J = 7.2 Hz, Ar-H), 6.51(t, 2H J = 3.0 Hz, H3), 6.09(t, 2H J = 3.0 Hz, H2). 13C{1H} NMR
(100 MHz, CDCl3) δ 145.5, 136.1, 132.6, 131.8, 129.3, 128.9, 128.1, 127.1, 126.1, 123.6, 111.6, 105.9,
56.2. CI-MS (m/z) 451(M+H+ 2.5%), 144(Phenyl-pyrrole+H+ 100%). Anal. Calcd for C33H26N2: C, 87.97;
H, 5.82; N, 6.22. Found: C, 87.85; H, 5.86; N, 6.32.

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HETEROCYCLES, Vol. 68, No. 6, 2006
1,1-Bis-(5-phenylpyrrol-2-yl)dipyrid-2-ylmethane (6c)
Phenylpyrrole (5a) (1.43 g, 10.0 mmol) and dipyridylketone (1.2 g, excess) were dissolved in 5 mL of
EtOH and heated to reflux. The reaction was monitored by NMR and allowed to react until no pyrrole
remained. The product was recovered by filtration and washed with EtOH. Yield 1.88g (83%). 1H NMR
(400 MHz, CDCl3) δ 10.21(s, 2H, NH), 8.63(d, 2H J = 4.0 Hz, HIV), 7.64(dt, 2H J = 7.8 & 1.5 Hz, HII),
7.50(d, 4H J = 7.8 Hz, Ha), 7.36(t, 4H J = 7.7 Hz, Hb), 7.17-7.21(m, 4H. Hc & HIII), 6.98(d, 2H J = 8.0
Hz, HI), 6.55(t, 2H J = 3.0 Hz, H3), 6.08(t, 2H J = 3.0 Hz, H2). 13C{1H} NMR (100 MHz, CDCl3) δ 165.6,
148.4, 137.0, 133.9, 132.8, 132.0, 128.8, 126.0, 123.7, 123.6, 121.7, 111.9, 105.5, 58.3. CI-MS (m/z)
453(M+H+ 8%), 144(Phenyl-pyrrole+H+ 100%). Anal. Calcd for C31H24N4: C, 82.27; H, 5.35; N, 12.38.
Found: C, 82.45; H, 5.45; N, 12.53.
9,9-Bis-(5-(1-naphthalenyl)pyrrol-2-yl)fluorene (7a)
2-Naphthalen-1-ylpyrrole (5b) (1 g, 5.17 mmol) and fluorenone (1 g, excess) were dissolved in 5 mL of
EtOH and heated to reflux. The reaction was monitored by NMR and allowed to react until no
naphthalenylpyrrole remained. The product was recovered by filtration and washed with EtOH.
Crystals suitable for structural analysis were grown by vapour diffusion of hexane into a toluene solution
of 7a. Yield 1.31g (92%). 1H NMR (400 MHz, CDCl3) δ 8.31(br s, 2H, NH), 8.27(br d, 2H J = 7.6 Hz,
Ar-), 7.87(dd, 2H J = 7.7 & 1.8 Hz, Ar-H), 7.83(ddd, 2H J = 7.4 & 1.3 & 0.6 Hz, Ar-H), 7.87(br d, 2H J
= 7.7 Hz, Ar-H), 7.71(ddd, 2H J = 7.5 & 1.2 & 0.6 Hz, Ar-H), 7.38-7.52(m, 12H, Ar-H), 6.43(dd, 2H J =
3.5 & 2.7 Hz, Py-H), 6.28(dd, 2H J = 3.5 & 2.7 Hz, Py-H). C{1H} NMR (100 MHz, CDCl3) δ 149.1,
13
139.7, 134.0, 133.7, 131.3, 131.2, 130.4, 128.4, 128.3, 128.0, 127.4, 126.3, 125.93, 125.90, 125.7, 125.4,
125.3, 120.6, 109.6, 108.6, 84.9. CI-MS (m/z) 549(M+H+ 0.5%), 358(M-(Naphthalenyl-pyrrole)+H+
30%), 194(Naphthalenyl-pyrrole+H+ 100%). Anal. Calcd for C41H28N2: C, 89.75; H, 5.14; N, 5.11. Found:
C, 89.96; H, 4.91; N, 5.26.
9,9-Bis-(5-(2-phenoxyphenyl)pyrrol-2-yl)fluorene (8a)
As above for 6a (Method B). Yield 84 %. 1H NMR (400 MHz, CDCl3) δ 9.38(s, 2H, NH), 7.64-7.68(m,
4H, He & Fl-H), 7.27(dt, 2H J = 7.5 & 1.1 Hz, Hc), 7.17-7.24(m, 6H, Ar-H), 6.99-7.14(m, 8H, Ar-H),
6.89(dd, 2H J = 8.0 & 1.5 Hz, Hb), 6.74(br dd, 4H J = 8.7 & 1.1 Hz, Ar-H), 6.53(dd, 2H J = 3.7 & 2.7 Hz,
H2), 6.05(dd, 2H J = 3.7 & 2.7 Hz, H3). C{1H} NMR (100 MHz, CDCl3) δ 156.6, 150.9, 148.8, 139.5,
13
133.6, 129.7, 127.9, 127.8, 126.7, 126.5, 125.0, 124.5, 124.3, 123.0, 120.7, 120.2, 117.7, 107.8, 107.3,
55.9. CI-MS (m/z) 633(M+H+ 50%), 398(M-PhOC6H4-pyrrole+ 100%). Anal. Calcd for C45H32N2O2: C,
85.42; H, 5.10; N, 4.43. Found: C, 85.49; H, 5.16; N, 4.44.

HETEROCYCLES, Vol. 68, No. 6, 2006
1135
Bis-(5-(2-phenoxyphenyl)pyrrol-2-yl)diphenylmethane (8b)
As above for 6a (Method A). Yield 87 %. 1H NMR (400 MHz, CDCl3) δ 9.38(s, 2H, NH), 7.65(dd, 2H
J = 7.8 & 1.6 Hz, He), 7.20(t, 4H J = 7.9 Hz, Ar-H), 7.00-7.16(m, 16H, Ar-H), 6.79(dd, 2H J = 8.0 & 1.0
Hz, Hb), 6.73(d, 4H J = 7.9 Hz, Ar-H), 6.53(dd, 2H J = 3.4 & 2.9 Hz, H2), 6.00(dd, 2H J = 3.4 & 2.9 Hz,
H3). C{1H} NMR (100 MHz, CDCl3) δ 156.3, 151.7, 150.3, 145.4, 136.1, 129.6, 129.1, 127.8, 127.7,
13
126.6, 126.4, 124.0, 123.9, 123.4, 119.7, 118.6, 110.2, 107.0, 56.2. CI-MS (m/z) 635(M+H+ 15%),
402(M-PhOC6H4-pyrrole+ 45%), 236(PhOC6H4-pyrrole+H+ 100%). Anal. Calcd for C45H34N2O2: C, 85.15;
H, 5.40; N, 4.41. Found: C, 85.22; H, 5.53; N, 4.39.
ACKNOWLEDGMENTS:
Innovene and the Engineering and Physical Sciences Research Council (UK) are thanked for financial
support.
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