The reaction of N-magnesium derivatives of pyrroles with N- mesylchloromethylpyrroles: A synthesis of dipyrrylmethanes

Article abstract of DOI:10.1021/jo980573i

Attachment of an alkyl- or arylsulfonyl group at the nitrogen atom of a pyrrole reduces the aromaticity and electron availability of the system. This is confirmed by the structure of an N-tosylated chloromethylpyrrole determined by X-ray crystallography. In agreement, N-mesylated chloromethylpyrroles are handleable materials which react smoothly with N- magnesium derivatives of pyrroles to provide a novel route for synthesis of dipyrrylmethanes. Several examples of this synthesis are described, including the construction of molecules carrying deuterium at the interpyrrolic methylene group.

Full text of DOI:10.1021/jo980573i

J . Org. Chem. 1998, 63, 8163-8169
8163
Th e Rea ction of N-Ma gn esiu m Der iva tives of P yr r oles w ith
N-Mesylch lor om eth ylp yr r oles: A Syn th esis of Dip yr r ylm eth a n es
Andrew D. Abell,*,† Brent K. Nabbs,† and Alan R. Battersby‡
Department of Chemistry, University of Canterbury, Christchurch, New Zealand, and University
Chemical Laboratory, Lensfield Road, Cambridge CB2 1EW, U.K.
Received March 30, 1998
Attachment of an alkyl- or arylsulfonyl group at the nitrogen atom of a pyrrole reduces the
aromaticity and electron availability of the system. This is confirmed by the structure of an
N-tosylated chloromethylpyrrole determined by X-ray crystallography. In agreement, N-mesylated
chloromethylpyrroles are handleable materials which react smoothly with N-magnesium derivatives
of pyrroles to provide a novel route for synthesis of dipyrrylmethanes. Several examples of this
synthesis are described, including the construction of molecules carrying deuterium at the
interpyrrolic methylene group.
Sch em e 1
In tr od u ction
Dipyrrylmethanes, such as 5 and 6, are commonly
prepared by electrophilic attack by an azafulvene on an
R-unsubstituted pyrrole, such as 2, the former being
generated from an acetoxymethylpyrrole (e.g., 1), a
hydroxymethylpyrrole, or a chloromethylpyrrole under
acidic conditions.1-5 For a typical sequence see Scheme
1.2 This approach has also been successfully applied in
the synthesis of bilanes, for example, hydroxymethylbi-
lane 7,2,3 by coupling together two dipyrrylmethanes
(Scheme 1). Alternatively, electrophilic attack by an
azafulvene 9 at the substituted R position of a hydroxym-
ethylpyrrole 8, with subsequent elimination of formal-
dehyde, can give rise to a symmetrical dipyrrylmethane
of the type 10 (Scheme 2).1,6
In this paper, we report a synthesis of dipyrryl-
methanes based on the coupling of a ring-deactivated
chloromethylpyrrole and the N-magnesium derivative of
a pyrrole, prepared using methylmagnesium iodide. This
method avoids the acidic conditions employed in the
coupling procedures discussed above and directs the
coupling to give an unsymmetrical dipyrrylmethane (see
Schemes 7 and 8 for examples).
Simple N-magnesium derivatives of pyrroles have been
reported to react with alkylating agents to produce a
mixture of 2(R)- and 3(â)-alkylpyrroles, in which the 2
isomer usually predominates.7-9 To the best of our
knowledge, this work is the first report of a synthesis of
dipyrrylmethanes based on the use of pyrrolylmagnesium
salts. The reaction of an electrophile with a pyrrolyl
anion prepared by treatment of the corresponding pyrrole
with a base other than methylmagnesium iodide is
reported to give products of reaction at nitrogen.9,10 Such
N-alkylation is avoided by using the N-magnesium
derivatives.
† University of Canterbury.
‡ University Chemical Laboratory.
(1) (a) The Chemistry of Pyrroles; J ones, A. R., Bean, G. P., Eds.;
Academic Press: London, 1977; pp 356-357. (b) Comprehensive
Heterocyclic Chemistry; Katritzky, A. R., Rees, C. W., Eds.; Pergamon
Press: Oxford, 1984; Vol. 4.
(2) Battersby, A. R.; Fookes, C. J . R.; Gustafson-Potter, K. E.;
McDonald, E.; Matcham, G. W. J . J . Chem. Soc., Perkin Trans. 1 1982,
2413.
(3) Battersby, A. R.; Fookes, C. J . R.; Gustafson-Potter, K. E.;
McDonald, E.; Matcham, G. W. J . J . Chem. Soc., Perkin Trans. 1 1982,
2427.
(4) Wallace, D. M.; Leung, S. H.; Senge, M. D.; Smith, K. M. J . Org.
Chem. 1993, 58, 7245.
(5) Tietze, L. F.; Kettschau, G.; Heitmann, K. Synthesis 1996, 851.
(6) Tarlton, E. J .; MacDonald, S. F.; Baltazzi, E. J . Am. Chem. Soc.
1960, 82, 4389.
(7) Schloemer, G. C.; Greenhouse, R.; Muchowski, J . M. J . Org.
Chem. 1994, 59, 5230.
(8) Anderson, H. J .; Loader, C. E. In Pyrroles; J ones, R. A., Ed.; J ohn
Wiley & Sons: New York, 1990; Vol. 48, Part 1, pp 427-429.
(9) Reference 1a; Chapter 4.
(10) Abell, A. D.; Nabbs, B. K.; Battersby, A. R. J . Am. Chem. Soc.
1998, 120, 1741.
10.1021/jo980573i CCC: $15.00 © 1998 American Chemical Society
Published on Web 10/16/1998

8164 J . Org. Chem., Vol. 63, No. 23, 1998
Abell et al.
Sch em e 2
Sch em e 4a
Sch em e 3a
Sch em e 5a
Resu lts a n d Discu ssion
R-Formyldipyrrylmethanes of the type 5 (for specific
examples see 32 and 34) were selected for synthesis
because the 2-formyl group provides a suitable site for
elaboration into biologically important bilanes such as
the type 7, as shown in Scheme 1.2,3
Syn th esis of Sta r tin g Ma ter ia ls. The key starting
materials, 11 and 13, were conveniently prepared from
pyrrole-2-carboxaldehyde (12; Scheme 3). The N-meth-
anesulfonyl-2-chloromethylpyrrole 16a was also prepared
from 12 by N-mesylation, reduction, and introduction of
the chloro group (Scheme 3). Compound 16b was simi-
larly prepared from pyrrole-2-carboxaldehyde (Scheme
3).
The R-benzyloxycarbonyl-R-formylpyrroles 19a 10 and
19b10 provided access to the acetal 23, the chlorometh-
ylpyrrole 26a , and its deuterated analogue 26b (see
Schemes 4 and 5). The deuterated analogue 19b was
itself prepared by Vilsmeier formylation of pyrrole 1810
using dimethylformamide-d6 (Scheme 4). The acetal 23
was prepared from 19a as illustrated in Scheme 4. In a
key step, the benzyloxycarbonyl group of 19a served to
deactivate the pyrrole and hence facilitate the introduc-
tion of the acetal (conditions a in Scheme 4) to yield 20.
The benzyloxycarbonyl group was then removed by
standard sequence 20 to 23.
A similar debenzylation and decarboxylation sequence
on separate samples of 19a and 19b was used10 to
prepare the R-formylpyrroles 17a and 17b (Scheme 4).10
These aldehydes were then used in the preparation of
26a and 26b (Scheme 5). The synthetic sequence em-
ployed here was analogous to that used in the synthesis
of 16, i.e., N-mesylation and reduction to give the
hydroxymethylpyrroles 25a and 25b, which were con-
verted into the chloromethyl analogues by reaction with
methanesulfonyl (mesyl) chloride (Scheme 5). An O-
mesyl derivative of 25a is the probable intermediate for
26a but was not isolated due to its rapid reaction with
ionic chloride. However, the O-mesylate was detected by
1H NMR spectroscopy in a reaction of 25a with meth-
anesulfonic anhydride in an NMR tube at -30 °C.
Syn th esis of Dip yr r ylm eth a n es. In an initial ex-
periment, 12 was deprotonated with methylmagnesium
iodide to give the corresponding N-magnesium salt which
precipitated from the reaction mixture (Scheme 6).
Excess methyl iodide was added, and after the mixture
was stirred for 3 h, a homogeneous solution was obtained;
however, workup gave recovered starting material 12.
We reasoned that methylation had taken place on the

Synthesis of Dipyrrylmethanes
Sch em e 6a
J . Org. Chem., Vol. 63, No. 23, 1998 8165
Sch em e 7a
F igu r e 1. ORTEP diagram of 16b showing the crystal-
lographic numbering scheme.
dipyrrylmethane 29 in admixture with 12. The coupling
appeared to proceed exclusively at the R position, with
none of the alternative â-coupled product being isolated.
Treatment of 29 with pyridinium tosylate gave the
dipyrrylmethane 31 (60% over both steps), which was
fully characterized. A reaction of the N-magnesium salt
of 11 with 16a , followed by the addition of aqueous
hydrochloric acid, gave 31 directly in 63% yield (Scheme
7) from which 32 was obtained in 85% yield by heating
with aqueous sodium hydroxide. The dipyrrylmethane
32 has previously been prepared, in modest yield, by
formylation of 2,2′-dipyrrylmethane, itself prepared by
sodium borohydride reduction of 2,2′-dipyrryl ketone.11
The thioacetal 13 was similarly treated with methyl-
magnesium iodide, and the product was coupled with 16a
to give the protected dipyrrylmethane 30 (Scheme 7).
Again, no â-coupled product was evident by 1H NMR
spectroscopy. Reaction of 30 with mercuric chloride then
gave 31 in 40% overall yield (two steps).
This approach to dipyrrylmethanes was further ex-
tended with the preparation of 34a and its deuterated
analogue 34b (Scheme 8). Compounds 34 are useful
synthetic precursors to biologically important bilanes,3,12
and the deuterium label in 34b provides a potentially
useful marker for biosynthetic studies. To this end, the
pyrrole 23 was reacted first with methylmagnesium
iodide and then with the N-mesylchloromethylpyrrole
26a , followed by acidic hydrolysis to give 34a in 75% yield
(Scheme 8). An analogous sequence using the deuterated
analogue 26b, but worked up with acetic acid, gave the
doubly protected dipyrrylmethane 33, which was hydro-
lyzed with aqueous hydrochloric acid to the dipyrryl-
methane 34b in good yield.
formyl oxygen, rather than on a carbon of the pyrrole, to
give 27. This had then hydrolyzed to 12 on workup
(Scheme 6). In contrast, the treatment of 12 with sodium
hydride and then with mesyl chloride gave 14a , the
product of reaction at the pyrrolic nitrogen (Scheme 3).
The foregoing complication is not possible with the acetal
11. Indeed, reaction of 11 with methylmagnesium iodide,
followed by the addition of an excess of methyl iodide,
gave an inseparable mixture of the R- and â-methylated
pyrroles 28 and starting material 12 in a ratio of 2:5
(Scheme 6).
Next, we turned our attention to the coupling of 11
with the chloromethylpyrrole 16a (Scheme 7) bearing an
N-mesyl group to stabilize the system. Hydroxymethyl-
and chloromethylpyrroles, lacking an N-mesyl or related
group, are reactive and labile,10 whereas 16a and its
synthetic precursor 15a were stable compounds. The
effect of an electron-withdrawing group (EWG) on the
nitrogen of a chloromethylpyrrole was shown by deter-
mining the structure of the N-p-toluenesulfonyl (tosyl)
derivative 16b by X-ray analysis (see Figure 1 and later
for a discussion).
X-r a y Str u ctu r e Deter m in a tion . The structure of
16b was determined to show the preferred conformation
in the solid state and to measure the effect of an electron-
withdrawing substituent (e.g., tosyl) on the nitrogen of
the pyrrole ring. A search of the Cambridge Crystal-
lographic Data Base revealed few reported structures of
N-tosyl- and N-mesylpyrroles.13
The N-magnesium salt derived from 11 was reacted
with the N-mesylchloromethylpyrrole 16a (Scheme 7).
Workup with acetic acid gave the doubly protected
(11) Clezy P. S.; Liepa, A. J .; Webb, N. W. Aust. J . Chem. 1972, 25,
1991.
(12) Abell, A. D., unpublished data.

8166 J . Org. Chem., Vol. 63, No. 23, 1998
Abell et al.
Sch em e 8a
F igu r e 2. X-ray crystallographic conformation of 16b.
The second point to note regarding the crystal struc-
ture of 16b is that the tosyl group adopts the expected
tetrahedral geometry about S(1) [O(2)-S(1)-O(1) 120.7°,
N(1)-S(1)-C(7) 105.4°, N(1)-S(1)-O(1) 104.2°, N(1)-
S(1)-O(2) 106.9°, C(7)-S(1)-O(1) 109.3°, and C(7)-
S(1)-O(2) 109.2°]. The X-ray structures of related
N-mesyl- and N-tosylpyrroles reveal that the sulfonyl
group adopts a pseudostaggered orientation with respect
to the pyrrole ring,13c,14 where the S-methyl or aryl vector
is almost perpendicular to the pyrrole ring plane. The
structure of 16b reported here displays a significant
deviation from this staggered geometry as depicted in
Figure 2, left-hand structure [C(7)-S(1)-N(1)-C(2) 78.9°
and C(7)-S(1)-N(1)-C(5) -102.5°]. The equivalent
conformation adopted by the S-pyrrole vector shows an
even greater deviation from a staggered geometry as
depicted in Figure 2, right-hand structure [C(12)-C(7)-
S(1)-N(1) 71.8° and C(12)-C(7)-S(1)-N(1) -108.2°].
Finally, the sum of the angles at nitrogen [C(2)-N(1)-
S(1) 129.1°, C(2)-N(1)-C(5) 107.7°, and C(5)-N(1)-S(1)
123.3°] is 360.1°, which is consistent with a planar
nitrogen.
Sch em e 9
In summary, we have developed a short, convenient,
and versatile synthetic route to dipyrrylmethanes which
involves the coupling of a pyrrolyl-N-magnesium salt
(derived from either an oxygen acetal or a thioacetal of
pyrrole-2-carboxaldehyde) with a ring-deactivated chlo-
romethylpyrrole. The coupling occurs at the R position
of the pyrrolyl nucleus, with none of the alternative
â-coupled products being isolated. The reaction sequence
has also been used to incorporate a deuterium label into
the dipyrrylmethane to build useful biological probes for
the study of the biosynthesis of natural porphyrins and
related pigments.12 Finally, the influence of an N-tosyl
group on the aromaticity of the pyrrole ring was exam-
ined by determination of the crystal structure of N-
tosylchloromethylpyrrole 16b.
A perspective drawing of 16b, with atomic labeling, is
presented in Figure 1. The first point to note regarding
this structure is that the N(1)-C(2) and N(1)-C(5) bond
lengths are relatively long [1.412(3) and 1.392(3) Å,
respectively] as compared to pyrroles without an electron-
withdrawing substituent on nitrogen.14 In addition, the
C(2)-C(3) and C(4)-C(5) bond lengths are relatively
short [1.353(4) and 1.342(4) Å, respectively]. These
observations show that the aromaticity of the pyrrole ring
is significantly reduced by introduction of an EWG (e.g.,
tosyl) on nitrogen. The result is that derivatives of the
general type 38 (see Scheme 9 and 16b for a specific
example) are stable entities which are suitable for
controlled reaction with a nucleophile (a pyrrolyl-N-
magnesium salt in this study) to give 37b (compounds
31 and 34 in this study). This is in agreement with our
recent report10 that an electron-withdrawing substituent
on nitrogen of an hydroxymethyl- or chloromethylpyrrole
of the general type 38 suppresses formation of a highly
reactive azafulvenium species (e.g., 39 in Scheme 9).
Related azafulvenes of the type 36 have been postulated
to account for the increased reactivity of pyrroles of the
type 35 with a nucleophile to give 37a (Scheme 9).
Exp er im en ta l Section
Gen er a l Meth od s. Melting points are uncorrected. NMR
spectra were recorded at 250, 300, or 400 MHz (1H) and at 63
or 75 MHz (13C) in the specified solvent and at a probe
temperature of 23 °C, unless otherwise specified. Light
petroleum refers to a hydrocarbon fraction of bp 60-70 °C.
Tetrahydrofuran (THF) was freshly distilled from sodium and
benzophenone, and all reactions were carried out under an
atmosphere of nitrogen. Solutions were dried with MgSO4
prior to evaporation under reduced pressure, unless otherwise
specified.
[1-(Meth a n esu lfon yl)p yr r ol-2-yl]m eth a n ol (15a ). A so-
lution of 12 (200 mg, 2.10 mmol) in dry THF (2 mL) was added
to a stirred suspension of sodium hydride (76 mg of an 80%
suspension in oil washed twice with dry light petroleum, 2.52
mmol, 1.2 equiv) in THF (6 mL). The resulting mixture was
stirred at room temperature for 15 min. A solution of mesyl
chloride (236 µL, 2.94 mmol, 1.4 equiv) in dry THF (2 mL)
was slowly added, and the mixture was stirred for 60 min at
room temperature. Water (10 mL) was added, the THF was
removed, and the resulting mixture was extracted with dichlo-
(13) (a) Bennet, A. J .; Somayaji, V.; Brown, R. S.; Santarsiero, B.
D. J . Am. Chem. Soc. 1991, 113, 7563. (b) Allen, F. H.; Battersby, A.
R.; De Voss, J . J .; Doyle, M. J .; Raithby, P. R. Acta Crystallogr., Sect.
C 1989, C45, 692. (c) Beddoes, R. L.; Dalton, L.; J oule, J . A.; Mills, O.
S.; Street, J . D.; Watt, C. I. F. J . Chem. Soc., Perkin Trans 2 1986,
787.
(14) Chadwick, D. J . In Pyrroles; J ones, R. A., Ed.; J ohn Wiley &
Sons: New York, 1990; Vol. 48, Part 1, pp 22-30.

Synthesis of Dipyrrylmethanes
J . Org. Chem., Vol. 63, No. 23, 1998 8167
romethane (10 mL). The aqueous phase was re-extracted with
dichloromethane (3 × 15 mL), and the combined organic
phases were washed with saturated aqueous sodium hydrogen
carbonate (10 mL), water (10 mL), and brine (10 mL), dried,
and evaporated to give 14a as a pale yellow oil which solidified
on standing: mp 41-42 °C (lit.15 43-44 °C).
Ben zyl 5-(5,5-Dim eth yl-1,3-d ioxa n -2-yl)-3-m eth oxyca r -
bon yleth yl-4-m eth oxyca r bon ylm eth ylp yr r ol-2-ylca r box-
ylate (20). The formylpyrrole 19a17 (6 g), 2,2-dimethylpropane-
1,3-diol (22.6 g), and p-toluenesulfonic acid (500 mg) were
heated under reflux in 1,2-dichloroethane (20 mL) in
a
modified Dean-Stark apparatus in which the solvent passed
through 4 Å sieves before returning to the flask. After 45 min,
the solution was shaken with saturated aqueous sodium
hydrogen carbonate (30 mL), and the organic layer was
separated, washed with water (20 mL), dried, and evaporated.
The residue was chromatographed on silica (diethyl ether/
hexane, 0:1-1:1) to give a solid which was recrystallized from
diethyl ether/hexane to give 20 as a colorless solid (6.38 g,
82%): mp 96-97 °C; IR (CHCl3) 3440, 2955, 2850, 1725, 1695
This sample was dissolved in dry diethyl ether (10 mL) at
0 °C, zinc borohydride (15.0 mL of a 0.14 M solution in dry
diethyl ether, 2.10 mmol) was added, and the mixture was
stirred at 0 °C for 30 min. Water (2 mL) and glacial acetic
acid (2 mL, 10% solution in water) were carefully added. The
separated aqueous phase was re-extracted with dichlo-
romethane (2 × 10 mL), and the combined organic phases were
washed with water (2 × 10 mL) and brine (10 mL), dried, and
evaporated. The resultant oil was purified by flash chroma-
tography on silica (ethyl acetate/light petroleum, 1:1.6) to give
15a as a pink solid (317 mg, 86% overall) which was further
purified by sublimation under reduced pressure: mp 67-68
°C (lit.10 67-68 °C); IR (CHCl3) 3587, 1178, 1142 cm-1; 1H NMR
(CDCl3, 300 MHz) δ 3.30 (s, 3H), 4.77 (s, 2H), 6.25 (m, 1H),
6.31 (m, 1H), 7.16 (m, 1H); 13C NMR (CDCl3, 75 MHz) δ 42.8,
56.3, 111.1, 115.2, 123.1, 133.4. Anal. Calcd for C6H9NO3S:
C, 41.13; H, 5.18; N, 7.99. Found: C, 41.11; H, 5.24; N, 8.30.
[1-(4-Meth ylph en ylsu lfon yl)pyr r ol-2-yl]m eth an ol (15b).
12 (105 mg, 1.11 mmol) was treated with tosyl chloride (306
mg, 1.60 mmol, 1.4 equiv) as described for the preparation of
14a . The resulting oil was purified by flash chromatography
on silica (ethyl acetate/light petroleum, 1:2) to give 14b (272
mg, 99%) as a pink solid: mp 92-94 °C (lit.16 94 °C).
A sample of 14b (82 mg, 0.33 mmol) was reduced with zinc
borohydride (2.35 mL of a 0.14 M solution in dry diethyl ether,
0.33 mmol) using the method described for 15a . Purification
of the product by flash chromatography on silica (ethyl acetate/
light petroleum, 1:2) gave 15b as a pale pink solid (75 mg,
91%): mp 94-96 °C (lit.16 97 °C); IR (CHCl3) 3582, 1367, 1175,
1150 cm-1; 1H NMR (CDCl3, 300 MHz) δ 2.38 (s, 3H), 2.95 (br
s, 1H), 4.59 (s, 2H), 6.21-6.25 (m, 2H), 7.25-7.29 (m, 3H),
7.70 (m, 2H); 13C NMR (CDCl3, 75 MHz) δ 21.4, 56.6, 111.7,
114.9, 123.3, 126.5, 130.0, 134.4, 135.8, 145.1; HRMS calcd
for C12H13NO3S 251.0616, found 251.0615.
1
cm-1; H NMR (CDCl3, 400 MHz) δ 0.76 (s, 3H), 1.20 (s, 3H),
2.50 (m, 2H), 2.98 (m, 2H), 3.55 (s, 2H), 3.60 (s, 3H), 3.65 (s,
3H), 3.59 and 3.69 (ABq, J ) 11.3 Hz, 4H), 5.29 (s, 2H), 5.50
(s, 1H), 7.37 (m, 5H), 9.17 (br s, 1H). Anal. Calcd for C25H31
-
NO8: C, 63.41; H, 6.60; N, 2.98. Found: C, 63.49; H, 6.53; N,
2.98.
5-(5,5-Dim et h yl-1,3-d ioxa n -2-yl)-3-m et h oxyca r b on yl-
et h yl-4-m et h oxyca r b on ylm et h ylp yr r ol-2-ylm et h a n oic
a cid (21). A solution of 20 (1.5 g, 3.2 mmol) in THF (40 mL),
containing triethylamine (3 drops), was stirred with 10% Pd
on C (175 mg), under an atmosphere of hydrogen, for 1.25 h.
The catalyst was removed by filtration through Celite, and the
filtrate was evaporated to dryness. The residue was recrystal-
lized from dichloromethane/hexane to give 21 (1.16 g, 96%):
mp 130-133 °C; IR (CHCl3) 3430, 3250, 2940, 1725, 1660 cm-1
.
1H NMR (CDCl3, 400 MHz) δ 0.77 (s, 3H), 1.21 (s, 3H), 2.59 (t,
J ) 8 Hz, 2H), 3.02 (t, J ) 8 Hz, 2H), 3.57 (s, 2H), 3.64 (s,
3H), 3.66 (s, 3H), 3.60 and 3.70 (ABq, J ) 11 Hz, 4H), 5.52 (s,
1H), 9.30 (br s, 1H). Anal. Calcd for C18H25NO8: C, 56.39; H,
6.57; N, 3.65. Found: C, 56.09; H, 6.73; N, 3.58.
2-(5,5-Dim et h yl-1,3-d ioxa n -2-yl)-4-m et h oxyca r b on yl-
eth yl-3-m eth oxyca r bon ylm eth ylp yr r ole (23). To a stirred
solution of 21 (1.0 g, 2.6 mmol) in methanol (30 mL) was added
a solution of sodium hydrogen carbonate (570 mg) in water (7
mL). An aqueous solution of iodine and potassium iodide (5.5
mL, 0.5 M I2 and 1.0 M KI) was then added over 30 min, and
the resultant solution was stirred at room temperature for a
further 1 h. Aqueous 10% sodium thiosulfate was added to
remove the excess iodine, and the resultant mixture was
partitioned between water (80 mL) and dichloromethane (50
mL). The organic layer was separated, and the aqueous phase
was re-extracted with dichloromethane (2 × 20 mL). The
combined organic extracts were washed with water (30 mL),
dried, and evaporated to give the iodopyrrole 22 as a pale
yellow oil, which crystallized on standing (909 mg, 75%): 1H
NMR (CDCl3, 400 MHz) δ 0.76 (s, 3H), 1.22 (s, 3H), 2.45 (m,
2H), 2.67 (m, 2H), 3.53 (s, 2H), 3.65 (s, 3H), 3.66 (s, 3H), 3.59
and 3.67 (ABq, J ) 10.9 Hz, 4H), 5.48 (s, 1H), 8.38 (br s, 1H);
HRMS calcd for C17H24NO6I 465.0648, found 465.0674.
2-Ch lor om eth yl-1-m eth a n esu lfon ylp yr r ole (16a ). Me-
syl chloride (46 µL, 0.58 mmol, 1.5 equiv) was added to an ice-
cooled and stirred solution of 15a (67 mg, 0.38 mmol) and N,N-
diisopropylethylamine (100 µL, 0.58 mmol, 1.5 equiv) in
dichloromethane (2 mL). After it was stirred for 20 min, the
solution was warmed to room temperature over 30 min, then
diluted with dichloromethane (10 mL), and washed with iced
water (10 mL), cold aqueous hydrochloric acid (10%, 10 mL),
and saturated aqueous sodium hydrogen carbonate (10 mL).
The organic phase was dried and evaporated to give 16a as
an orange oil (65 mg, 87%), which was subsequently used
without purification: IR (CHCl3) 1369, 1180 cm-1 1H NMR
;
(CDCl3, 300 MHz) δ 3.40 (s, 3H), 4.94 (s, 2H), 6.27 (m, 1H),
6.43 (m, 1H), 7.21 (m, 1H); 13C NMR (CDCl3, 75 MHz) δ 37.8,
43.2, 111.5, 117.1, 124.2, 130.0; HRMS calcd for C6H8NO2S
(M - Cl) 158.0276, found 158.0276.
Adams catalyst (50 mg) was stirred in methanol (15 mL)
under hydrogen for 2 h. A solution of the preceding iodopyrrole
22 (820 mg, 1.76 mmol) in methanol (15 mL) containing
triethylamine (400 µL) was added and the mixture was stirred
under hydrogen for 15 h at room temperature. The catalyst
was removed by filtration through Celite, and the filtrate was
evaporated to dryness. Water (20 mL) and dichloromethane
(25 mL) were added, and the organic phase was separated,
washed with water, dried, and evaporated to give 23 as an
unstable pale yellow oil, which was used quickly without
further purification (539 mg, 90%): IR (CHCl3) 3430, 2940,
2-Ch lor om et h yl-1-(4-m et h ylp h en ylsu lfon yl)p yr r ole
(16b). The N-tosylhydroxymethylpyrrole 15b (70 mg, 0.28
mmol) was treated with mesyl chloride (33 µL, 0.42 mmol, 1.5
equiv) under the conditions used for the preparation of 16a .
The resulting oil was purified by flash chromatography on
silica (ethyl acetate/light petroleum, 1:2) to give 16b as a pale
pink solid (62 mg, 83%). This was recrystallized from ethyl
acetate/light petroleum to give pale yellow crystals: mp 84 °C;
IR (CHCl3) 1371, 1190, 1175, 1150, 1123 cm-1
;
1H NMR
1
1720, 1660 cm-1; H NMR (CDCl3, 400 MHz) δ 0.75 (s, 3H),
(CDCl3, 300 MHz) δ 2.39 (s, 3H), 4.83 (s, 2H), 6.24 (m, 1H),
6.36 (m, 1H), 7.27-7.33 (m, 3H), 7.78 (m, 2H); 13C NMR
(CDCl3, 75 MHz) δ 21.5, 37.2, 111.6, 116.9, 124.3, 127.1, 129.8,
130.3, 135.7, 145.2. Anal. Calcd for C12H12ClNO2S: C, 53.43;
H, 4.48; N, 5.19. Found: C, 53.88; H, 4.65; N, 5.00.
1.21 (s, 3H), 2.53 (t, J ) 8 Hz, 2H), 2.72 (t, J ) 8 Hz, 2H), 3.50
(s, 2H), 3.64 (s, 6H), 3.61 and 3.67 (ABq, J ) 11 Hz, 4H), 5.50
(s, 1H), 6.46 (d, J ) 2.4 Hz, 1H), 8.24 (br s, 1H); HRMS calcd
for C17H25NO6 339.1682, found 339.1676.
[for m yl-2H ]-2-F or m yl-1-m et h a n esu lfon yl-4-m et h oxy-
ca r bon yleth yl-3-m eth oxyca r bon ylm eth ylp yr r ole (24b)
(15) Merrill, B. A.; LeGoff, E. J . Org. Chem. 1990, 55, 2904.
(16) Prinzbach, H.; Bingmann, H.; Fritz, H.; Markert, J .; Knothe,
L.; Eberbach, W.; Brokatzky-Geiger, J .; Sekutowski, J . C.; Kru¨ger, C.
Chem. Ber. 1986, 119, 616.
(17) Battersby, A. R.; Hunt, E.; McDonald, E.; Paine, J . B., III;
Saunders, J . J . Chem. Soc., Perkin Trans. 1 1976, 1008.

8168 J . Org. Chem., Vol. 63, No. 23, 1998
Abell et al.
an d Its Un labeled An alogu e 24a. The deuterated formylpyr-
role 17b10 (500 mg, 1.96 mmol) was added portionwise to a
stirred suspension of sodium hydride (170 mg, 60% dispersion
in oil washed three times with hexane) in THF (30 mL). After
45 min of stirring at room temperature, mesyl chloride (500
µL, 6.46 mmol) was added, and the THF was evaporated.
Water (150 mL) was added and shaken with dichloromethane
(4 × 50 mL), the organic layer was washed with sodium
hydrogen carbonate (50 mL, 10% aqueous) and water (50 mL),
dried, and evaporated. Chromatography on silica using diethyl
ether and recrystallization of the product from dichloromethane/
diethyl ether/hexane gave the pyrrole 24b (608 mg, 93%) as
calcium carbonate (11 mg, 0.11 mmol) in 80% aqueous aceto-
nitrile (1.5 mL). The mixture was stirred at room temperature
for 1 h, then dichloromethane (20 mL) was added, and the
mixture was filtered. The organic phase was separated, and
the aqueous phase was re-extracted with dichloromethane (2
× 5 mL). The combined organic phases were washed with
saturated aqueous sodium hydrogen carbonate (10 mL) and
brine (10 mL), dried, and evaporated. Flash chromatography
of the residue on silica (ethyl acetate/light petroleum, 1:2) gave
31 (8 mg, 83%), which was recrystallized from methanol to
give pale orange needles: mp 141-142 °C; IR (CHCl3) 3431,
1651, 1367, 1191 cm-1; 1H NMR (acetone-d6, 300 MHz) δ 3.00
(s, 3H), 4.15 (s, 2H), 5.93 (m, 1H), 6.00 (dd, J ) 3.9 and 2.4
Hz, 1H), 6.11 (m, 1H), 6.80 (dd, J ) 3.9 and 2.4 Hz, 1H), 7.00
(m, 1H), 9.31 (s, 1H), 10.86 (br s, 1H); 13C NMR (acetone-d6,
75 MHz) δ 25.9, 42.1, 110.4, 111.3, 113.9, 121.1, 122.5, 131.9,
133.1, 138.4, 178.3. Anal. Calcd for C11H12N2O3S: C, 52.37;
H, 4.79; N, 11.10. Found: C, 52.52; H, 4.86; N, 11.09.
Meth od B. Methylmagnesium iodide (0.52 mL of a 2.0 M
solution in dry diethyl ether, 1.04 mmol) was added to a stirred
solution of 1118 (201 mg, 1.11 mmol) in THF (3 mL) under the
conditions used above for 13 to generate the N-magnesium
derivative. This was reacted with the chloromethylpyrrole 16a
(61 mg, 0.32 mmol), again exactly as for the preparation of
30. After 2 h of stirring, water (1 mL) was added followed by
aqueous glacial acetic acid (10%, 5 mL), and the mixture was
stirred for 10 min. Dichloromethane (10 mL) was added, and
the separated organic phase, together with subsequent dichlo-
romethane washings (2 × 10 mL) of the aqueous phase, was
washed with saturated aqueous sodium hydrogen carbonate
(10 mL) and brine (10 mL), dried, and evaporated. Flash
chromatography of the residue on silica (ethyl acetate/light
petroleum, 1:6) gave 11 (104 mg) and an inseparable mixture
of 12 and 29 (1:3 by 1H NMR), which was used in the next
step without further purification. 29 (as assigned from the
mixture): 1H NMR (CDCl3, 300 MHz) δ 0.77 (s, 3H), 1.23 (s,
3H), 2.58 (s, 3H), 3.63 (m, 4H), 4.13 (s, 2H), 5.39 (s, 1H), 5.91
(m, 1H), 6.10 (m, 1H), 6.16 (m, 1H), 6.20 (m, 1H), 7.08 (m,
1H), 8.51 (br s, 1H).
colorless needles: mp 62-64 °C; HRMS calcd for C13H16
NO7S 332.0792, found 332.0792.
D
The unlabeled formylpyrrole 24a was similarly prepared
from 17a . Recrystallization from dichloromethane/diethyl
ether/hexane gave 24a as colorless needles: mp 64-65 °C; IR
(CHCl3) 3000, 2950, 1725, 1640 cm-1; λmax 290, 258 nm; 1H
NMR (CDCl3, 400 MHz) δ 2.59 (t, J ) 7.5 Hz, 2H), 2.75 (t, J
) 7.5 Hz, 2H), 3.52 (s, 3H), 3.68 (s, 3H), 3.72 (s, 3H), 3.84 (s,
2H), 7.31 (s, 1H), 9.95 (s, 1H); 13C NMR (CDCl3, 63 MHz) δ
19.6, 30.2, 33.6, 43.5, 51.8, 52.4, 126.0, 126.4, 129.9, 133.1,
170.1, 172.6, 178.7. Anal. Calcd for C13H17NO7S: C, 47.12;
H, 5.17; N, 4.23. Found: C, 47.20; H, 5.45; N, 4.20.
[m eth ylen e-2H1]-2-Hyd r oxym eth yl-1-m eth a n esu lfon yl-
4-m eth oxyca r bon yleth yl-3-m eth oxyca r bon ylm eth ylp yr -
r ole (25b) an d Its Un labeled An alogu e 25a. The formylpyr-
role 24a (400 mg, 1.21 mmol) in dichloromethane (20 mL) and
methanol (10 mL) was stirred at 0 °C. Sodium borohydride
(70 mg) was added, and after a further 10 min at 0 °C,
dichloromethane (75 mL) was added. The solution was washed
with aqueous oxalic acid (15 mL, 5%) and water (15 mL), dried,
and evaporated. Recrystallization of the residue from dichlo-
romethane/diethyl ether/hexane gave 25a (392 mg, 97%), as
needles: mp 95-96.5 °C; IR (CHCl3) 3350, 2910, 1720, 1350
cm-1; 1H NMR (CDCl3, 400 MHz) δ 2.56 (m, 2H), 2.70 (m, 2H),
3.10 (t, J ) 6.6 Hz, 1H), 3.35 (s, 3H), 3.49 (s, 2H), 3.67 (s, 3H),
3.73 (s, 3H), 4.76 (d, J ) 6.6 Hz, 2H), 6.94 (s, 1H); 13C NMR δ
(CDCl3, 63 MHz) 20.3, 29.7, 33.9, 43.1, 51.6, 52.6, 53.8, 119.2,
120.2, 124.5, 132.1, 172.5, 173.0. Anal. Calcd for C13H19
-
A solution of the crude 29 (81 mg, 0.24 mmol) and PPTS
(6.0 mg, 0.02 mmol, 0.1 equiv) in 50% aqueous acetone (4 mL)
was stirred at reflux for 45 min. Dichloromethane (10 mL)
was added, and the separated organic phase, together with
subsequent dichloromethane washings (2 × 5 mL) of the
aqueous phase, was washed with saturated aqueous sodium
hydrogen carbonate (10 mL) and brine (10 mL), dried, and
evaporated. Purification of the residue by flash chromatog-
raphy on silica (ethyl acetate/light petroleum, 2:3) gave 31 (48
mg, 60% overall for both steps) showing spectroscopic data
identical to those above.
NO7S: C, 46.84; H, 5.74; N, 4.20. Found: C, 46.90; H, 5.85;
N, 4.20.
Sodium borodeuteride reduction of 24b as described above
1
gave the deuterated hydroxymethylpyrroles 25b. Its H NMR
spectrum was identical to that of 25a except for δ 3.10 (d, J )
6.6 Hz, 1H), 4.74 (d, J ) 6.6 Hz, 1H); HRMS calcd for C13H18
DNO7S 334.0945, found 334.0948.
-
5-(1,3-Dith iola n -2-yl)-1′-m eth a n esu lfon yl-2,2′-d ip yr r yl-
m eth a n e (30). Methylmagnesium iodide (0.55 mL of a 2.0
M solution in dry diethyl ether, 1.10 mmol) was added to a
stirred solution of 134 (200 mg, 1.17 mmol) in THF (3 mL)
cooled in an ice-sodium chloride bath (-10 °C). This orange
suspension was stirred at -10 °C for 30 min and then at room
temperature for a further 30 min before being lowered to -10
°C in preparation for rapid addition of the chloromethylpyrrole
16a (65 mg, 0.33 mmol) in dry THF (2 mL). The cooling bath
was removed, and after the reaction mixture had been stirred
at room temperature for 2 h, diethyl ether and excess saturated
aqueous ammonium chloride were added. The organic phase
was separated, washed with saturated aqueous ammonium
chloride, dried, and evaporated. Flash chromatography on
silica (ethyl acetate/light petroleum, 1:8) of the resulting oil
gave recovered 13 (134 mg) and 30 which crystallized at 0 °C
(55 mg, 50%) and was recrystallized from methanol: mp 108
Meth od C. The N-magnesium salt of 11 was reacted with
16a as described in method B. The preparation was worked
up by the addition of water (1 mL) followed by dilute aqueous
hydrochloric acid (5 mL). The mixture was then stirred for
10 min and extracted with dichloromethane as described in
method B. Purification of the resulting oil by flash chroma-
tography on silica (ethyl acetate/light petroleum, 1:2) gave 31
1
(24 mg, 63%) showing H NMR data as above.
5-F or m yl-2,2′-d ip yr r ylm eth a n e (32). Aqueous sodium
hydroxide (5 M, 1 mL) was added to a stirred solution of 31
(23 mg, 0.09 mmol) in methanol (4 mL), and the mixture was
heated at reflux for 3 h. Saturated aqueous ammonium
chloride was added, the mixture was extracted with dichlo-
romethane (3 × 10 mL), and the combined organic phases were
washed with water (2 × 10 mL), dried, and evaporated. The
resulting oil was purified by flash chromatography on silica
(ethyl acetate/light petroleum, 1:2) to give 32 (13 mg, 85%)
which was recrystallized from ethyl acetate/light petroleum:
mp 118 °C (lit.11 120-121 °C); IR (CHCl3) 3470, 3433, 3292,
1
°C; IR (CHCl3) 3441, 3009, 2932, 1364, 1180 cm-1; H NMR
(CDCl3, 300 MHz) δ 2.57 (s, 3H), 3.36 (m, 4H), 4.11 (s, 2H),
5.73 (s, 1H), 5.81 (m, 1H), 6.04 (m, 1H), 6.17 (m, 1H), 6.21 (m,
1H), 7.08 (m, 1H), 8.52 (br s, 1H); 13C NMR (CDCl3, 75 MHz)
δ 26.0, 39.8, 42.0, 49.2, 107.3, 108.5, 111.1, 113.6, 122.2, 127.7,
129.1, 132.5. Anal. Calcd for C13H16N2O2S3: C, 47.54; H, 4.91;
N, 8.53; S, 29.28. Found: C, 47.28; H, 4.88, N, 8.74; S, 29.37.
5-For m yl-1′-m eth an esu lfon yl-2,2′-dipyr r ylm eth an e (31).
Meth od A. A solution of 30 (12 mg, 0.04 mmol) in 80%
aqueous acetonitrile (1.5 mL) was added to a stirred mixture
of mercury(II) chloride (20 mg, 0.07 mmol) and powdered
1
3032, 3013, 1645 cm-1; H NMR (CDCl3, 300 MHz) δ 4.02 (s,
2H), 6.03 (m, 1H), 6.11 (m, 1H), 6.16 (dd, J ) 3.9 and 2.4 Hz,
1H), 6.67 (m, 1H), 6.95 (dd, J ) 3.9 and 2.4 Hz, 1H), 9.18 (br
(18) Loader, C. E.; Anderson, H. J . Synthesis 1978, 295.

Synthesis of Dipyrrylmethanes
J . Org. Chem., Vol. 63, No. 23, 1998 8169
s, 1H), 9.30 (s, 1H), 11.10 (br s, 1H); 13C NMR (CDCl3, 75 MHz)
δ 26.5, 106.6, 108.3, 110.6, 117.6, 124.6, 127.4, 132.0, 142.2,
178.7; HRMS calcd for C10H10N2O 174.0793, found 174.0796.
3,4′-Dim eth oxyca r bon yleth yl-3′,4-d im eth oxyca r bon yl-
m e t h y l-5-fo r m y l-1′-m e t h a n e s u lfo n y l-2,2′-d ip y r r y l-
m eth a n e (34a ) a n d Its [2H1]-An a logu e 34b. Mesyl chloride
(40 µL, 1.5 equiv) was added to an ice-cooled solution of 25a
(110 mg) in dichloromethane (2 mL) containing N,N-diisopro-
pylethylamine (92 µL, 1.5 equiv). Stirring was continued at 0
°C for 20 min and for a further 30 min at room temperature.
The solution was diluted with dichloromethane (10 mL) and
washed successively with ice water, cold dilute aqueous
hydrochloric acid, and saturated aqueous sodium hydrogen
carbonate. The organic phase was dried and evaporated, to
give the chloromethylpyrrole 26a (91 mg, 86%): 1H NMR
(CDCl3, 250 MHz) δ 2.56 (m, 2H), 2.70 (m, 2H), 3.32 (s, 3H),
3.49 (s, 2H), 3.67 (s, 3H), 3.69 (s, 3H), 4.97 (s, 2H), 6.98 (s,
1H); 13C NMR (CDCl3, 63 MHz) δ 20.3, 29.9, 33.6, 35.4, 43.2,
51.7, 52.3, 120.4, 122.5, 125.6, 127.7, 172.9, 170.5; m/z (FD)
organic phase was separated, dried, and evaporated to give
the labeled dipyrrylmethane 34b as an oil: 1H NMR (CD2Cl2,
400 MHz) δ 4.13 (s, 1H), otherwise identical to the spectrum
of 34a ; 13C NMR (CDCl3, 63 MHz) δ 18.7, 20.4, 21.4 (t, CHD),
29.5, 30.8, 33.4, 34.7, 41.9, 51.6, 51.8, 52.2, 53.1, 119.1, 119.9,
122.7, 124.8, 128.0, 129.1, 133.6, 171.3, 172.9, 173.0, 173.2,
177.3.
Cr ysta llogr a p h ic Str u ctu r e Deter m in a tion for Com -
p ou n d 16b by X-r a y An a lysis. C12H12ClNO2S: MW 269.74,
mp 84 °C, crystal dimensions 1.02 × 0.32 × 0.25 mm,
monoclinic, a ) 7.645(2) Å, b ) 15.689(5) Å, c ) 10.543(3) Å,
â ) 105.20(2)°, V ) 1220.3(6) Å3, space group P21/n, Z ) 4,
F(000) ) 560, Dcalc ) 1.468 mg/m3, absorption coefficient 0.472
mm-1, θ range for data collection 2.39-22.50, index ranges
-8 e h e 0, 0 e k e 16, -10 e l e 11, maximum and minimum
transmissions 0.3008 and 0.3345, data/restraints/parameters
1593/0/155, goodness of fit on F2 ) 1.097, final R indices [I >
2σ(I)] R1 ) 0.0330 and wR2 ) 0.0849, R indices (all data) R1 )
0.0378 and wR2 ) 0.0883, and largest difference peak and hole
353 (M+
-
37Cl), 351 (M+
-
35Cl).
0.284 and -0.207 eÅ-3
.
Methylmagnesium iodide (250 µL, 1.2 M in diethyl ether,
1.2 equiv) was added to a stirred solution of the pyrrole 23
(100 mg, 0.30 mmol) in THF (4 mL), and the resultant
heterogeneous mixture was stirred at room temperature under
argon for 1 h. The above chloromethylpyrrole 26a (in 1.5 mL
of THF) was added dropwise, and the mixture was stirred at
room temperature for 20 h. Water (1 mL) was added followed
by dilute aqueous hydrochloric acid (5 mL), and the mixture
was stirred for 10 min. Dichloromethane (20 mL) was added,
and the organic phase, together with subsequent dichlo-
romethane washings (2 × 10 mL) of the aqueous phase, was
washed with saturated aqueous sodium hydrogen carbonate
(10 mL) and brine (10 mL), dried, and evaporated. Preparative
TLC (ethyl acetate/diethyl ether, 1:2) gave the formylpyrrole
17a (13 mg, 15%) and the N-mesyldipyrrylmethane 34a as a
pale yellow oil (141 mg, 75% based on 23): IR (film) 2950,
The unit cell parameters were obtained by least-squares
refinement of the setting angles of 19 reflections with 4.25° e
2θ e 16.5° from a Siemens four-circle diffractometer. A unique
data set was measured at 293(2) K within a 2θmax ) 45° limit
(ω scans). Of the 1611 reflections obtained, 1593 were unique
(Rint ) 0.0051) and were used in the full-matrix least-squares
refinement.19 The intensities of 3 standard reflections, mea-
sured every 97 reflections throughout the data collection,
showed only 3.97% decay. The structure was solved by direct
methods.20 Hydrogen atoms were fixed in idealized positions.
All non-hydrogen atoms were refined with anisotropic atomic
displacement parameters. Neutral scattering factors and
anomalous dispersion corrections for non-hydrogen atoms were
taken from Ibers and Hamilton.21 Full details of the X-ray
structural determination of 16b have been deposited with the
Cambridge Crystallographic Data Centre (CCDC).
1
1730, 1640 cm-1; λmax 306 nm; H NMR (CD2Cl2, 400 MHz) δ
Ack n ow led gm en t. The work at Christchurch was
supported, in part, by a research grant from the Mars-
den Fund (New Zealand) and at Cambridge by a grant
from EPSRC (U.K.). We thank Professor W. T. Robinson
(Department of Chemistry, University of Canterbury,
Christchurch, New Zealand) for help with the X-ray
crystallography. We also thank Bruce Clark for running
the mass spectra.
2.41 (s, 3H), 2.52 (m, 2H), 2.57 (m, 2H), 2.69 (m, 2H), 2.87 (m,
2H), 3.57 (s, 2H), 3.64 (s, 3H), 3.66 (s, 3H), 3.67 (s, 3H), 3.81
(s, 3H), 3.77 (s, 2H), 4.15 (s, 2H), 6.91 (s, 1H), 9.51 (s, 1H),
10.10 (br s, 1H); HRMS calcd for C25H32N2O11S 568.1727, found
568.1731.
The above sequence was repeated using the deuterated
hydroxymethylpyrrole 25b in place of 25a . The resulting
labeled chloromethylpyrrole 26b was then reacted with the
N-magnesium salt of 23, prepared as described above, for 48
h. The addition of excess water and acetic acid followed by
preparative TLC (ethyl acetate/diethyl ether, 1:2) gave recov-
ered starting material 23 (26%) and the labeled dipyrryl-
methane 33b as a labile pale yellow oil (70%): 1H NMR
(CD2Cl2, 400 MHz) δ 1.24 (s, 3H), 1.37 (s, 3H), 2.33 (s, 3H),
2.43 (m, 2H), 2.56 (m, 2H), 2.67 (m, 2H), 2.78 (m, 2H), 3.47 (s,
2H), 3.55 (s, 2H), 3.62 (s, 3H), 3.64 (s, 3H), 3.66 (s, 3H), 3.75
(s, 3H), 4.04 (s, 1H), 5.34 (s, 1H), 6.90 (s, 1H), 9.36 (br s, 1H);
13C NMR (CD2Cl2, 63 MHz) δ 19.5, 20.8, 21.5 (t, CHD), 22.0,
23.0, 29.9, 30.1, 33.8, 35.7, 41.7, 51.8, 51.9, 52.0, 52.5, 71.7,
77.8, 96.3, 113.1, 118.9, 119.5, 123.8, 124.7, 126.4, 130.2, 172.9,
173.0, 173.8, 173.9.
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal
data and structure refinement, atomic coordinates, bond
lengths and angles, anisotropic displacement parameters, and
hydrogen coordinates (6 pages). This material is contained
in libraries on microfiche, immediately follows this article in
the microfilm version of the journal, and can be ordered from
the ACS; see any current masthead page for ordering
information.
J O980573I
(19) Sheldrick, G. M. SHELXL-93. J . Appl. Crystallogr., in press.
(20) Sheldrick, G. M. Acta Crystallogr., Sect. A 1990, 46, 467.
(21) Ibers, J . A., Hamilton, W. C., Eds. International Tables for
Crystallography; Kynoch Press: Birmingham, 1992; Vol. C.
The preceding dipyrrylmethane 33 in dichloromethane was
shaken with dilute aqueous hydrochloric acid for 10 min. The