Rhodium-Mediated Dipolar Cycloaddition of Diazoquinolinediones

Article abstract of DOI:10.1021/jo982503h

As an entry to furoquinoline structures of natural origin, the rhodium-mediated dipolar cycloaddition of diazoquinolinediones with alkenes and alkynes has been examined. Because of the unsymmetrical nature of the diazo compounds, both linear and angular furoquinoline products are possible. For the most part, a mixture of regioisomers is generated in moderate to good yields, though in a few cases dominant products are obtained in high yields. The products can be further converted to naturally occurring alkaloids such as isodictamnine. A novel observation in this work is that catalytic quantities of acid enhance the yield and regiochemical control in the cycloaddition.

Full text of DOI:10.1021/jo982503h

3642
J . Org. Chem. 1999, 64, 3642-3649
Rh od iu m -Med ia ted Dip ola r Cycloa d d ition of Dia zoqu in olin ed ion es
Michael C. Pirrung* and Florian Blume
Department of Chemistry, Levine Science Research Center, Box 90317, Duke University,
Durham, North Carolina 27708-0317
Received December 23, 1998
As an entry to furoquinoline structures of natural origin, the rhodium-mediated dipolar cycloaddition
of diazoquinolinediones with alkenes and alkynes has been examined. Because of the unsymmetrical
nature of the diazo compounds, both linear and angular furoquinoline products are possible. For
the most part, a mixture of regioisomers is generated in moderate to good yields, though in a few
cases dominant products are obtained in high yields. The products can be further converted to
naturally occurring alkaloids such as isodictamnine. A novel observation in this work is that catalytic
quantities of acid enhance the yield and regiochemical control in the cycloaddition.
In tr od u ction
The furoquinoline alkaloids are an extremely diverse
set of natural products that are the most widely distrib-
uted of quinoline alkaloids.1 They are primarily isolated
from Rutaceae and often incorporate a terpenoid frag-
ment. Members of the group have vasoconstrictive,
antidiuretic, antiarrhythmic, spasmolytic, sedative, and
hypothermic effects.2 Biological properties also include
photosensitization for DNA damage and mutation3 and
antineoplastic4/antimicrobial5/antimalarial6 activity. Most
of the known alkaloids in the group are linearly fused
and O-alkylated and fall into the dictamnine class. A few
alkaloids in the isodictamnine class are instead alkylated
at the N-1 position. In rare cases, related angularly fused
furo[3,4-d]quinoline structures have been found in Na-
ture.
While they are of relatively modest complexity by
today’s standards of organic synthesis, a number of
synthetic approaches to the furoquinoline alkaloids have
been reported, primarily by Grundon.7 Other workers
have achieved total syntheses of dictamnine8 and isopla-
tydesmine,9 inter alia.
The method we have developed for the synthesis of
complex polyheterocyclic systems using the dipolar cy-
(1) Grundon, M. F. Nat. Prod. Rep. 1990, 7, 131-8. Scheuer, P. J .
In Chemistry of Alkaloids; Pelletier, S. W., Ed.; Van Nostrand
Reinhold: New York, 1970; pp 355-65. Openshaw, H. T. Alkaloids
1967, 9, 223-67. Mester, J ., Waterman, P. G., Grundon, M. F., Eds.;
Chemistry and Chemical Taxonomy of the Rutales, Annual Proceedings
of the Phytochemical Society of Europe; Academic Press: London, 1983;
No. 22, pp 31-95.
cloaddition of rhodium carbenoids to polar olefins10
seemed ideal for the preparation of furoquinoline alka-
loids (eq 1) and, with the available asymmetric rhodium
catalysts,11 might be able to provide access to single
enantiomers of the natural products. The mechanism
that we have proposed for the production of dipolar
(2) Petit-Pali, G.; Rideau, M.; Chenieux, J . C. Planta Med. Phytother.
1982, 16, 55-72.
(3) Schimmer, O.; Kuhne, I. Mutat. Res. 1991, 249, 105-10. Paulini,
H.; Waibel, R.; Schimmer, O. Mutat. Res. 1989, 227, 179-86. Schim-
mer, O.; Leimeister, U. Arch. Pharm. 1988, 321, 637. Haefele, F.;
Schimmer, O. Mutagenesis 1988, 3, 349-353. Paulini, H.; Schimmer,
O. Mutagenesis 1987, 2, 271-273. Ashwood-Smith, M. J .; Towers, G.
H. N.; Abramowski, Z.; Poulton, G. A.; Liu, M. Mutat. Res. 1982, 102,
401-412.
(4) Svoboda, G. H.; Poore, G. H.; Simpson, P. J .; Boder, G. B. J .
Pharm. Sci. 1966, 55, 758-768.
(5) Wolters, B.; Eilert, U. Planta Med. 1981, 43, 166-74.
(6) Basco, L. K.; Mitaku, S.; Skaltsounis, A. L.; Ravelomanantsoa,
N.; Tillequin, F.; Koch, M.; Le Bras, J . Antimicrob. Agents Chemother.
1994, 38, 1169-71.
(8) Yazima, T.; Munakata, K. Agr. Biol. Chem. 1980, 44, 235-243.
Sato, M.; Kawakami, K.; Kaneko, C. Chem. Pharm. Bull. 1987, 35,
1319-21.
(9) Coppola, G. M. J . Heterocycl. Chem. 1983, 20, 1589.
(10) Pirrung, M. C.; Zhang, J .; McPhail, A. T. J . Org. Chem. 1991,
56, 6269. Pirrung, M. C.; Lee, Y. R. Tetrahedron Lett. 1994, 35, 6231.
Pirrung, M. C.; Zhang, J .; Morehead, A. T., J r. Tetrahedron Lett. 1994,
35, 6229. Pirrung, M. C.; Lackey, K.; Zhang, J .; Sternbach, D. D.;
Brown, F. J . Org. Chem. 1995, 60, 2112. Pirrung, M. C.; Lee, Y. R. J .
Am. Chem. Soc. 1995, 117, 4814. Pirrung, M. C.; Lee, Y. R. J . Chem.
Soc., Chem. Commun. 1995, 673. Pirrung, M. C.; Lee, Y. R. Tetrahedron
Lett. 1996, 37, 2391.
(7) Tuppy, H.; Boehm, F. Angew. Chem. 1956, 68, 388. Grundon,
M. F.; McCorkindale, N. J . J . Chem. Soc. 1957, 2177. Clark, E. A.;
Grundon, M. F. J . Chem. Soc. 1964, 4169. Chaimberlain, T. R.;
Grundon, M. F. J . Chem. Soc. C 1971, 910.
(11) Pirrung, M. C.; Zhang, J . Tetrahedron Lett. 1992, 33, 5987.
10.1021/jo982503h CCC: $18.00 © 1999 American Chemical Society
Published on Web 04/28/1999

Rhodium Dipolar Cycloaddition
J . Org. Chem., Vol. 64, No. 10, 1999 3643
Ta ble 1. AM1-Ca lcu la ted Atom ic Ch a r ges of
Qu in olin ed ion e An ion s
a synthesis of isodictamnine. It includes a provocative,
novel observation that acid can influence the course of
these reactions.
R1 ) H, R1 ) Me, R1 ) MOM, R1 ) Bz, R1 ) Me,
R2 ) H
R2 ) H
R2 ) H
R2 ) H R2 ) OMe
(a) Mulliken Charges
Resu lts
N1
C2
-0.326
0.358
-0.344
0.358
-0.308
0.367
-0.276
0.341
-0.271
0.365
We first aimed to predict the regiochemical outcome
of the dipolar cycloaddition with alkenes (based on the
mechanistic rationale in eq 1) using theoretical methods.
Reasoning that ring closure of a zwitterion such as 3
would likely occur at the site of highest electron density,
we performed Spartan AM1 calculations on a range of
substituted quinolinedione anions. In the synthetic study,
the R group could presumably be introduced for the
purpose of controlling regiochemistry. Collected in Table
1 is the charge distribution in the quinolone portion of
these zwitterions, expressed either as the Mulliken
charges or the atomic charges from an electrostatic
potential map. In all cases but 14, the O2 position is more
negative, suggesting that the linear isomer should be
favored.
O2
C3
H3
C4
O4
O4-O2
sum
-0.495
-0.526
0.136
0.317
-0.479
0.016
-0.454
-0.558
0.146
0.295
-0.449
0.005
-0.499
-0.525
0.138
0.319
-0.472
0.027
-0.471
-0.566
0.145
0.291
-0.449
0.022
-0.484
-0.524
0.138
0.316
-0.478
0.006
-1.015
-1.006
-0.980
-0.985
-0.938
(b) Atomic Charges from Electrostatic Potential
-0.614
0.785
-0.668
-0.914
0.205
0.699
-0.647
0.021
N1
C2
O2
C3
H3
C4
O4
-0.558
0.783
-0.619
-0.971
0.236
0.656
-0.606
0.013
-0.496
0.773
-0.658
-0.937
0.211
0.723
-0.643
0.015
-0.506
0.763
-0.635
-0.694
0.228
0.669
-0.619
0.016
-0.371
0.727
-0.641
-0.897
0.206
0.687
-0.646
-0.005
-0.935
O4- O2
sum
-1.154
-1.079
-1.027
-0.794
cycloadducts in the reactions of cyclic rhodium carbenoids
with olefins involves initial cyclopropanation, ring open-
ing to a zwitterion, and ring closure. It is also possible
that the zwitterion is formed directly. In the case of a
diazoquinolinedione (1), it is readily seen that regio-
chemical issues arise. Since most of our earlier studies
have not addressed regiochemistry, the behavior of such
unsymmetrical diones might yield further mechanistic
insight. Likewise, with acetylenic dipolarophiles, we have
provided a mechanistic explanation that could be further
amplified by consideration of regiochemistry (eq 2).
Several novel 4-hydroxy-2-quinolones () quinolinedi-
ones) were needed to investigate the influence of sub-
stituents on reactivity and regiochemistry. The parent
compound 15 is commercially available. The N-methyl-
4-hydroxy-2-quinolones 16 and 17 were prepared by
cyclization of the corresponding anthranilic acids with
acetic anhydride in acetic acid (70% and 39%, respec-
tively).12 The N-prenyl-4-hydroxy-2-quinolone 19 was
prepared by the method of Coppola,13 wherein an N-
alkylated isatoic anhydride participates in a Dieckmann-
like condensation (eq 3). The N-benzyl-4-hydroxy-2-
(12) Buckle, D. R.; Cantello, B. C. C.; Smith, H.; Spicer, B. A. J .
Med. Chem. 1975, 18, 726-732.
(13) Coppola, G. M.; Hardtmann, G. E.; Pfister, O. R. J . Org. Chem.
1976, 41, 825-831. Hardtman, G. E.; Koletar, G.; Pfister, O. R. J . Org.
Chem. 1975, 12, 565-572.
This report describes the rhodium-mediated dipolar
cycloaddition of diazoquinolinediones and its application
to the preparation of furoquinoline alkaloids, including

3644 J . Org. Chem., Vol. 64, No. 10, 1999
Pirrung and Blume
d. Other olefins examined included phenyl vinyl sulfide
and phenyl vinyl sulfoxide, which complex with the
catalyst (as evidenced by a color change) and thereby
prevent reaction. Isoprene and vinyltrimethoxysilane also
do not give cycloadducts. The catalysts examined in this
study include rhodium anisoate, pivalate, adaman-
tanoate, tricyanoacetate, and acetate. Only the first three
electron-rich catalysts show any catalytic activity.
Diazo compound 22 showed no reaction under any of
a wide variety of reaction/catalyst conditions examined.
It could also be converted to an N-acetyl derivative that
readily evolved nitrogen (even at 0 °C) with rhodium
pivalate, but no dipolar cycloadducts could be isolated.
The N-methyl diazoquinolinedione 23 undergoes cy-
cloaddition with vinyl acetate under rhodium pivalate
catalysis to give a mixture of regioisomers (eq 5). The
quinolone 18 was prepared by condensation of N-benzyl-
aniline with malonic acid (eq 4).14 The poor solubility
properties of these compounds make them resistant to
conventional purification schemes (recrystallization, chro-
matography). In our hands, the best choice has been
precipitation by centrifugation.
Diazotransfer15 with mesyl azide in ethanol results in
the conversion of these 4-hydroxy-2-quinolones in 63-
90% yields to the diazoquinolinediones 22-26, which
precipitate from solution. Small quantities of azo com-
pounds are also formed, which can be removed by
filtration through silica gel (THF).
assignment of the structures of these products is readily
made on the basis of spectral properties, primarily NMR,
and particularly the downfield shift (δ >8.0 ppm) of the
peri hydrogen at the 5-position of the linear isomer. With
rhodium adamantanoate, only the angular isomer 27 is
formed, but in lower yield. The aromatization of the
linear 28 yields a surprising result: formation of the
angular isomer, a known but unnatural product called
pseudoisodictamnine (eq 6). Presumably, its formation
involves prior acid-catalyzed equilibration of 27 and 28,
though no direct evidence for this process could be
garnered. Thermal equilibration of isodictamnine and
pseudoisodictamnine has also been reported.16 With
trimethylsilylacetylene as the dipolarophile, regiochemi-
Because of low solubility of the diazoquinolinediones
in most solvents usually employed for rhodium-based
carbenoid chemistry, decomposition reactions were con-
ducted at 55 °C by slow addition of 22-26 in powder form
to the neat alkene (vinyl acetate) or alkyne (trimethyl-
silylacetylene (20-fold excess) in fluorobenzene) over 2-3
(14) Kappe, T.; Aigner, R.; Hohengassner, P.; Stadlbauer, W. J .
Prakt. Chem. 1994, 336, 596-601.
(15) Regitz, M.; Schwall, H.; Heck, G.; Eistert, B.; Bock, G. Liebigs
Ann. Chem. 1965, 690, 125. Regitz, M. Diazoalkane: Eigenschaften und
Synthesen; Georg Thieme Verlag: Stuttgart, 1977 (Regitz, M.; Maas,
G. Diazo compounds: properties and synthesis; Academic Press:
Orlando, 1986).

Rhodium Dipolar Cycloaddition
J . Org. Chem., Vol. 64, No. 10, 1999 3645
Ch a r t 1. Rea ction of Dia zoqu in olin ed ion es w ith Vin yl Aceta te
cal control and yield are diminished, but the separable
products 29 and 30 are readily desilylated with tetra-n-
butylammonium fluoride to provide the isodictamnine
isomers, which gave data identical to literature reports.
The influence of substitution on the diazoquinolinedi-
one (i.e., 23-26) on dipolar cycloadditions with vinyl
acetate and trimethylsilylacetylene catalyzed by rhodium
pivalate is summarized in Charts 1 and 2. Late in this
investigation, it was discovered that the addition of a few
drops of HCl ethanolate to the reaction mixture affects
both the efficiency and selectivity of the reaction, gener-
ally in favor of the linear isomer, in reactions with vinyl
acetate. Notable is the cycloaddition of 24, favoring the
linear isomer by a margin of ∼7:1 (95% combined yield).
Furthermore, this additive enables cycloadditions with
vinyl acetate to be conducted at room temperature with
enhanced selectivity (eqs 8 and 9), though requiring
longer reaction times. This acid effect is less dramatic
with trimethylsilylacetylene, primarily increasing the
yield but not affecting the favored regioisomer. Control
experiments show that acid alone does not affect any of
the starting materials or products.
amounts of the regioisomers in cycloadditions to vinyl
acetate. As no change in the product distributions was
observed over time, we believe this reaction is under
kinetic control. Sterics seem to have little, if any, influ-
ence on the product ratios. On the other hand, in
cycloadditions with trimethylsilylacetylene, the angular
furoquinoline, which is known to be more thermodynami-
cally stable, is invariably favored. We suggest this
regiochemistry is under thermodynamic control, with
equilibration occurring among intermediates such as 7.
Discu ssion
Any explanation for the regiochemical outcome in the
dipolar cycloaddition of diazoquinolinediones must be
tempered by the modest levels of selectivity and seem-
ingly spurious divergence of reactivity with small changes
in structure and conditions. Nevertheless, it seems likely
that balanced electron density at oxygen in the putative
zwitterions 3 is reflected in the production of similar
The rationale for the addition of acid to the dipolar
cycloaddition reaction was that protonation of zwitterion
3 would likely favor tautomer 32, as is the case with the
4-hydroxy-2-quinolones. Such a cation would be expected
to close on O2 to generate the linear isomer. The
(16) Tuppy, H.; Boehm, F. Mh. Chem. 1956, 87, 735-740.

3646 J . Org. Chem., Vol. 64, No. 10, 1999
Pirrung and Blume
Ch a r t 2. Rea ction of Dia zoqu in olin ed ion es w ith Tr im eth ylsilyla cetylen e
Ta ble 2. Rea ction s of Dia zoqu in olin ed ion es w ith
Vin yl Aceta te
enhancement of the production of linear isomers in the
presence of acid supports this theory.
In summary, the methodology developed here may be
useful in the preparation of polyheterocyclic ring systems
based on quinolones. The results also support previously
proposed mechanisms for the dipolar cycloaddition.
diazo compd
angular
yield (%)
linear
yield (%)
23
24
25
26
23/HCl
24/HCl
25/HCl
26/HCl
27
34
36
38
27
34
36
38
44
25
20
41
21
11
12
47
28
35
37
31
28
35
37
31
27
70
19
11
57
83
25
50
Exp er im en ta l Section
Gen er a l Meth od s. All purchased chemicals were used
without further purification unless noted otherwise. Chemical
suppliers used were Aldrich and VWR. All flash chromatog-
raphy was done using silica gel 60 (230-400 mesh ASTM).
Chromatographic analyses were performed on precoated alu-
minum TLC silica gel plates. Indicators used: UV short wave
light, phosphomolybdic acid dip (in EtOH). All reported Rf
values are from TLC in 1:1 pentane/ethyl acetate. All rhodium-
(II) carboxylate catalysts were synthesized from commercially
available carboxylic acids by exchange with rhodium acetate.
All reactions were performed under argon atmosphere.
Gen er a l P r oced u r e for Dia zo Tr a n sfer of 4-Hyd r oxy-
2-qu in olon es. The 4-hydroxy-2-quinolone was suspended in
a minimum amount of cold ethanol (usually about 3 M). The
suspension was cooled in an ice bath, and 2 equiv of Et3N was
added. After 0.5 h, mesyl azide (1.1 equiv) was added, and the
reaction mixture was allowed to slowly warm to room tem-
perature. After 12 h, the solid product was filtered and washed
with ether. The crude product was, if necessary, purified by
recrystallization from ethanol or acetone or by passing it
through a plug of silica (THF).
Gen er a l P r oced u r es for 1,3-Dip ola r Ad d ition of Dia -
zoqu in olin ed ion es. A. To a solution of olefin (20 mmol) in 1
mL of fluorobenzene kept at 55 °C was added 6.1 mg (0.01
mol %) rhodium(II)pivalate and, in small portions, 1 mmol of
the diazo compound. The reaction was followed to completion
by TLC. The solvent was removed in vacuo, and the residue
was purified by flash chromatography on silica gel using a
ether/pentane gradient with concentrations of ether increasing
from 0% to 100%.
Ta ble 3. Rea ction s of Dia zoqu in olin ed ion es w ith
Tr im eth ylsilyla cetylen e
diazo compd
angular
yield (%)
linear
yield (%)
23
24
25
29
39
41
29
39
41
40
47
30
57
52
48
30
40
42
30
40
42
12
8
6
18
13
9
23/HCl
24/HCl
25/HCl
B. To a solution of 6.1 mg (0.01 mol %) of rhodium(II)-
pivalate in 2 mL of vinyl acetate kept at 55 °C was added, in
small portions, 1 mmol of diazo compound over a period of 48
h. Addition of 0.01 mol % of 1 M HCl-etherate (0.02 mL)
increased the total yield and favored the linear furoquinoline
adducts.
Results are summarized in Tables 2 and 3.
1-Meth yl-4-h yd r oxy-2-qu in olon e (16). According to a
literature procedure,17 a solution of N-methylanthranilic acid
(9.1 g, 60 mmol) in 30 mL acetic anhydride and 30 mL acetic
acid was refluxed for 5 h. The reaction mixture was poured
with stirring onto 300 mL of ice/water. The solid was filtered
and dissolved in a minimum amount of warm aqueous NaOH.
Solids were removed by filtration, and the filtrate was acidified
(17) Lutz, R. F.; Codington, J . F.; Rowlett, R. J . J . Am. Chem. Soc.
1946, 68, 1810.

Rhodium Dipolar Cycloaddition
J . Org. Chem., Vol. 64, No. 10, 1999 3647
to pH 4 with concentrated HCl. The product was filtered,
washed with copious amounts of water, and dried in vacuo:
Rf ) 0.06, white powder, 7.35 g, 70%; mp 263-264 °C (ethanol).
Spectral/physical data were consistent with literature data.18
1-Meth yl-4-h yd r oxy-6-m eth oxy-2-qu in olon e (17). To a
mixture of 2.40 g (17.5 mmol) of N-methyl-p-anisidine and 3.65
g (35 mmol) of malonic acid was added 15 mL of POCl3. The
solution was heated at 90 °C for 1 h and then poured onto
ice/water. The solution was brought to pH 14, filtered, and
acidified to pH 4-5. Filtration afforded 17: Rf ) 0.10, yellow
powder, 39%; mp 293 °C (ethanol); 1H NMR (DMSO-d6) δ 3.49
(s, 3H), 3.79 (s, 3H), 5.86 (s, 1H), 7.25 (dd, J ) 6.1, 9.1 Hz,
1H), 7.31 (d, J ) 2.9 Hz, 1H), 7.41 (d, J ) 9.1 Hz, 1H), 11.33
(s, 1H); 13C NMR δ 28.5, 40.1, 40.3, 55.4, 98.4, 104.8, 116.1,
116.7, 119.7, 134.5, 153.8, 160.4, 162.1. Spectral/physical data
were consistent with literature data.19
1-Meth yl-3-d ia zoqu in olin e-2,4-d ion e (23). By the gen-
eral procedure: 3.50 g (20 mmol) 16; 4.04 g (40 mmol) Et3N;
2.66 g (22 mmol) MsN3. Rf ) 0.56, pale yellow needles, 3.62 g,
90%; mp 164 °C (ethanol); 1H NMR (CDCl3) δ 3.53 (s, 3H),
7.22-7.27 (m, 2H), 7.65 (dt, J ) 1.6, 7.3 Hz, 1H), 8.17 (dd, J
) 1.5, 7.9 Hz, 1H); 13C NMR (CDCl3) δ 29.3, 115.0, 120.7, 123.0,
126.7, 135.2, 141.5, 159.2, 174.5, 174.8; IR 2169, 1634, 1602
cm-1; LR MS 202 (MH+). Anal. Calcd for C10H7N3O2: C, 59.70;
H, 3.51; N, 20.89. Found: C, 59.81; H, 3.53; N, 20.85. Spectral/
physical data were consistent with literature data.22
1-Meth yl-6-m eth oxy-3-d ia zoqu in olin e-2,4-d ion e (24).
By the general procedure: 1.37 g (6.68 mmol) 17; 5 mL EtOH;
1
Rf ) 0.6, yellow needles, 73%; mp 162 °C (ethanol); H NMR
(CDCl3) δ 3.56 (s, 3H), 3.88 (s, 3H), 7.18-7.27 (m, 2H), 7.62
(d, J ) 2.8 Hz, 1H); 13C NMR δ 29.4, 55.9, 107.9, 108.2, 111.9,
112.1, 116.6, 121.3, 123.7, 135.7, 155.5; IR 2152 cm-1. Anal.
Calcd for C11H9N3O2: C, 57.14; H, 3.92; N, 18.17. Found: C,
57.23; H, 4.01; N, 18.07.
1-Ben zyl-4-h yd r oxy-2-qu in olon e (18). A solution of N-
benzylaniline (3.66 g, 20 mmol) and malonic acid (2.60 g, 25
mmol) in 20 mL of POCl3 was heated for 1 h at 90 °C. The
black syrup was poured onto ice-water and basified to pH 14
with NaOH pellets. After filtration, the liquid was acidified
to pH 4-5 with concentrated HCl. Filtration through a plug
of silica (THF) gives 18: Rf ) 0.01, pale ochre solid, 46%; mp
1-Ben zyl-3-d ia zoqu in olin e-2,4-d ion e (25). By the general
procedure: 251 mg (1.0 mmol) of 18; 3 mL of EtOH; Rf ) 0.65,
orange needles, 63%; mp 151 °C (ethanol); 1H NMR (CDCl3) δ
5.40 (s, 2H), 7.14-7.36 (m, 7H), 7.50 (dt, J ) 1.5, 7.9 Hz, 1H),
8.18 (dd, J ) 1.3, 7.9 Hz, 1H); 13C NMR δ 45.8, 115.9, 120.8,
123.1, 126.7, 127.6, 128.9, 135.1, 135.6, 140.8; IR 2144, 1659,
1638, 1601, 1373 cm-1. Anal. Calcd for C16H11N3O2: C, 69.31;
H, 4.00; N, 15.15. Found: C, 69.37; H, 4.10; N, 15.06.
1-(3′-Meth yl-2′-bu ten yl)-3-diazoqu in olin e-2,4-dion e (26).
By the general procedure: Rf ) 0.72, pink needles, 69%; mp
105 °C (ethanol); 1H NMR (CDCl3) δ 1.59 (s, 3H), 1.75 (s, 3H),
4.75 (d, J ) 5.9 Hz, 2H), 5.12 (t, J ) 5.9 Hz, 1H), 7.18-7.24
(m, 2H), 7.59 (t, J ) 11.6, 1H), 8.16 (dd, J ) 1.5, 7.9 Hz, 1H);
13C NMR (CDCl3) δ 17.6, 25.0, 40.0, 114.8, 117.9, 120.2, 122.1,
126.0, 134.4, 136.2, 140.1, 158.3, 174.9; IR (KBr) 2965, 2142,
1658, 1637, 1601, 1376 cm-1. Anal. Calcd for C14H13N3O2: C,
65.87; H, 5.13; N, 16.46. Found: C, 65.94; H, 5.18; N, 16.35.
1-Acetoxy-5-m eth yl-2,3-d ih yd r ofu r o[3,4-d ]qu in olin -4-
on e (27). General procedure B: 201 mg of 23; Rf ) 0.51, yellow
solid; mp 135 °C (ether/pentane), 44% (w/o HCl) or 21% (w/
HCl). At room temperature with HCl-etherate 2% of this
product was formed: 1H NMR (CDCl3) δ 2.13 (s, 3H), 3.21 (dd,
J ) 2.2, 7.1 Hz, 1H), 3.50 (dd, J ) 7.2, 17.1 Hz, 1H), 3.72 (s,
3H), 7.00 (dd, J ) 2.2, 17.1 Hz, 1H), 7.28 (obscured by CDCl3),
7.40 (d, J ) 8.6, 1H), 7.61 (dt, J ) 1.3, 8.6 Hz, 1H), 7.80 (dd,
J ) 1.3, 7.9 Hz, 1H); 13C NMR (CDCl3) δ 20.3, 28.5, 33.5, 98.5,
106.2, 111.3, 113.9, 121.2, 122.5, 130.6, 139.9, 160.0, 160.2,
168.9; IR 2989, 1745, 1665, 1634, 1595, 1247 cm-1; LR MS
260 (MH+); HR MS calcd for C14H13NO4 259.0844, found
259.0853 (M+). Anal. Calcd for C14H13NO4: C, 64.86; H, 5.05;
N, 5.40. Found: C, 64.82; H, 5.10; N, 5.38.
2-Acetoxy-9-m eth yl-2,3-d ih yd r ofu r o[2,3-b]qu in olin -4-
on e (28). General procedure B (same as for 27): Rf ) 0.02,
colorless needles; mp 183 °C (THF/pentane), 27% (w/o HCl)
or 57% (w/HCl), 58% (at rt w/HCl); 1H NMR (CDCl3) δ 2.16 (s,
3H), 3.29 (dd, J ) 2.2, 16.0 Hz, 1H), 3.55 (dd, J ) 7.2, 16.0
Hz, 1H), 3.74 (s, 3H), 6.93 (dd, J ) 2.2, 7.2 Hz, 1H), 7.40-
7.45 (m, 2H), 7.65 (t, J ) 1.2 Hz, 1H), 8.48 (dd, J ) 1.3, 8.0
Hz, 1H); 13C NMR (CDCl3) δ 20.3, 28.5, 33.5, 98.4, 106.1, 111.2,
113.9, 121.2, 122.4, 130.6, 139.9, 160.0, 160.1, 168.8; IR (KBr)
1763, 1630, 1588, 1517, 942 cm-1; FAB MS 260.09 (MH+); HR
MS calculated for C14H13NO4 259.0844, found 259.0844 (M+).
Anal. Calcd for C14H13NO4: C, 64.86; H, 5.05; N, 5.40. Found:
C, 62.94; H, 5.29; N, 5.27.
1
288 °C (ethanol); H NMR (DMSO-d6) δ 5.44 (s, 2H), 5.98 (s,
1H), 7.15-7.28 (m, 7H), 7.48 (t, J ) 7.7 Hz, 1H), 7.90 (d, J )
7.7 Hz, 1H), 11.60 (s, 1H); 13C NMR (DMSO-d6) δ 44.3, 79.4,
116.1, 120.0, 122.6, 125.4, 126.2, 127.0, 128.4, 135.0, 140.1,
158.8, 174.5; IR 2558 (broad), 1540, 1245 cm-1. Anal. Calcd
for C16H13NO2: C, 76.48; H, 5.21; N, 5.57. Found: C, 76.23;
H, 5.38; N, 5.58. Spectral/physical data were consistent with
literature data.14
1-(3′-Meth yl-2′-bu ten yl)isa toic An h yd r id e (20). To a
suspension of isatoic anhydride (1.63 g, 10 mmol) in DMF was
added K2CO3 (0.83 g, 0.06 mol). After 1 h, 1-bromo-3-methyl-
2-butene (1.25 g, 0.012 mol) was added, and the reaction was
stirred for 20 h. Most of the DMF was removed in vacuo. The
oily mixture was then poured onto 20 mL of ice/water. The
solid product was filtered, washed with copious amounts of
water, and dried in vacuo to give pale brown crystals: Rf )
0.55, 93%; mp 119 °C (ethanol); 1H NMR (CDCl3) δ 1.74 (s,
3H), 1.85 (s, 3H), 4.67 (d, J ) 6.2, 2H), 5.17 (dt, J ) 1.2, 6.2
Hz, 1H), 7.12 (d, J ) 8.5, 1H), 7.28 (d, J ) 7.5, 1H), 7.72 (dt,
J ) 8.6, 1.4, 1H), 8.14 (dd, J ) 7.9, 1.2). Anal. Calcd For C13H13
-
NO3: C, 67.52; H, 5.67; N, 6.06. Found: C, 67.29; H, 5.69; N,
6.10.
1-(3′-Meth yl-2′-bu ten yl)-4-h yd r oxy-2-qu in olon e (19). To
NaH (0.17 g, 0.007 mol, 60% in mineral oil, pentane washed)
in 4 mL of DMF was added in portions diethyl malonate (1.12
g, 0.007 mol). When the evolution of H2 ceased, the solution
was stirred for 15 min and was placed in an oil bath at 80 °C.
To this solution 1.15 g (0.005 mol) of 20 in 3 mL of DMF was
added dropwise over a period of 15 min. The mixture was
heated for 18 h at 120 °C and cooled and the solid removed by
filtration to give a white powder: Rf ) 0.06, 63%; mp 257 °C
(ethanol); 1H NMR (DMSO-d6) δ 1.64 (s, 3H), 1.80 (s, 3H), 4.78
(s, 2H), 5.02 (s, 1H), 5.93 (s, 1H), 7.18-7.89 (m, 4H), 11.50 (s,
1H); 13C NMR δ 17.8, 25.0, 97.7, 114.3, 116.0, 120.0, 120.8,
123.0, 130.9, 134.6, 138.9, 160.9, 162.0; IR (KBr) 2550, 1641,
1596 cm-1. Anal. Calcd for C14H15NO2: C, 73.34; H, 6.59; N,
6.11. Found: C, 73.18; H, 6.64; N, 6.05.
3-Dia zo-1H-qu in olin -2,4-d ion e (22). By the general pro-
cedure: 3.22 g (20 mmol) 15; 4.04 g (40 mmol) Et3N; 2.66 g
(22 mmol) MsN3; Rf ) 0.36, pale pink needles, 2.88 g, 72%;
5-Meth yl-2-tr im eth ylsilylfu r o[3,4-d]qu in olin -4-on e (29).
General procedure A: 201 mg of 23, 1.96 g of trimethylsily-
acetylene; Rf ) 0.58, colorless needles; mp 80 °C (ether/
pentane), 40% (w/o HCl), 57% (w/HCl); 1H NMR (CDCl3) δ 0.38
(s, 9H), 3.79 (s, 3H), 7.26 (s, 1H), 7.32 (t, J ) 7.3 Hz, 1H), 7.45
(d, J ) 8.5 Hz, 1H), 7.56 (dt, J ) 7.3, 1.3 Hz, 1H), 8.08 (dd, J
) 6.8, 1.3 Hz, 1H); 13C NMR (CDCl3) δ -2.4, 28.7, 112.7, 114.3,
114.9, 117.0, 120.8, 121.4, 128.7, 137.4, 157.8, 159.0, 162.6;
LR MS 272 (MH+); HR MS calcd for C15H17NO2Si 271.1028,
1
mp 236 °C (ethanol); H NMR (DMSO-d6) δ 7.17 (t, J ) 7.8
Hz, 2H), 7.63 (t, J ) 7.8 Hz, 1H), 7.84 (d, J ) 7.8 Hz, 1H),
11.37 (s, 1H); 13C NMR (CDCl3) δ 78.4, 115.5, 118.3, 122.2,
124.8, 134.8, 140.0, 158.8, 175.6; IR (KBr) 3192, 2161, 1669,
1636, 1610 cm-1. Spectral/physical data were consistent with
literature data.20,21
(18) Saalfrank, R. W.; Ho¨rner, B. Chem. Ber. 1993, 126, 841-4.
(19) Bessonova, I. A.; Yumisov, S. Khim. Prir. Soedin 1976, 3, 320-
328.
(20) Misra, B. K.; Rao, Y. R.; Mahapatra, S. N. Indian J . Chem.
1983, 22B, 562-4.
(21) Kappe, T.; Lang, G.; Pongratz, E. J . Chem. Soc., Chem.
Commun. 1984, 6, 338-9.
(22) Eistert, B.; Donath, P. Chem. Ber. 1973, 106, 1537-48.

3648 J . Org. Chem., Vol. 64, No. 10, 1999
Pirrung and Blume
found 271.1033 (M+). Anal. Calcd for C15H17NO2Si: C, 66.39;
H, 6.31; N, 5.16. Found: C, 66.44; H, 6.34; N, 5.22.
J ) 2.8 Hz, 1H); 13C NMR (CDCl3) δ 21.0, 31.8, 32.8, 55.8,
96.4, 98.3, 106.5, 115.9, 121.2, 127.7, 133.0, 156.2, 159.2, 169.4,
173.2; IR 2923, 1763, 1588, 1556, 1519 cm-1; HR MS calcd for
9-Meth yl-2-tr im eth ylsilylfu r o[2,3-b]qu in olin -4-on e (30).
General procedure A (same as for 29): Rf ) 0.33, white solid,
mp 160 °C (THF/pentane), 12% (w/o HCl) 18% (w/HCl); 1H
NMR (CDCl3) δ 0.35 (s, 9H), 3.95 (s, 3H), 7.28 (s, 1H), 7.37 (t,
J ) 7.4 Hz, 1H), 7.48 (d, J ) 8.4 Hz, 1H), 7.69 (dt, J ) 1.0, 8.3
Hz, 1H), 8.55 (dd, J ) 1.0, 7.9 Hz); 13C NMR (CDCl3) δ -2.5,
30.7, 106.7, 113.3, 116.9, 121.7, 124.6, 126.8, 131.3, 137.5,
C
15H15NO5 289.0950, found 289.0938 (M+). Anal. Calcd for
C15H15NO5: C, 62.28; H, 5.23; N, 4.84. Found: C, 62.22; H,
5.30; N, 4.80.
2-Acet oxy-5-b en zyl-2,3-d ih yd r ofu r o[3,4-d ]q u in olin -4-
on e (36). General procedure B: 277 mg of 25; Rf ) 0.39, white
powder; mp 133 °C (ether/pentane), 20% (w/o HCl) or 12% (w/
1
HCl); H NMR (CDCl3) δ 2.15 (s, 3H), 3.29 (dd, J ) 1.4, 17.1
155.8, 158.3, 172.6; LR MS 272 (MH+). Anal. Calcd for C15H17
-
Hz, 1H), 3.57 (dd, J ) 7.1, 17.1 Hz, 1H), 4.12 (s (br), 2H), 7.05
(dd, J ) 1.4, 7.1 Hz, 1H), 7.18-7.31 (m, 7H), 7.46 (t, J ) 7.6
Hz, 1H), 7.81 (d, J ) 7.6 Hz, 1H); 13C NMR (CDCl3) δ 20.4,
33.6, 44.9, 98.5, 106.0, 111.6, 114.8, 121.3, 122.6, 125.8, 126.5,
128.1, 130.6, 136.0, 139.5, 160.2, 160.6, 168.8; IR 2922, 1767,
1666 cm-1; FAB MS 336.12; HR MS calcd for C20H17NO4
335.1157, found 335.1158 (MH+). Anal. Calcd for C20H17NO4:
C, 71.63; H, 5.11; N, 4.18. Found: C, 71.51; H, 5.18; N, 4.15.
2-Acet oxy-9-b en zyl-2,3-d ih yd r ofu r o[2,3-b]q u in olin -4-
on e (37). General procedure B (same as for 36): Rf ) 0.01,
white solid; mp 195 °C (THF/pentane), 19% (w/o HCl) or 25%
NO2Si: C, 66.39; H, 6.31; N, 5.16. Found: C, 66.45; H, 6.26;
N, 5.13.
2-Acetoxy-9-(3′-m eth yl-2′-bu ten yl)-2,3-d ih yd r ofu r o[2,3-
b]qu in olin -4-on e (31). General procedure B: 255 mg of 26;
Rf ) 0.01, pale yellow powder; mp 190 °C (THF/pentane), 11%
(w/o HCl), 50% (w/HCl) or 71% (at room temperature w/HCl);
1H NMR (CDCl3) δ 1.74 (s, 3H), 1.84 (s, 3H), 2.14 (s, 3H), 3.28
(dd, J ) 2.1, 15.9 Hz, 1H), 3.54 (dd, 7.0, 15.9 Hz, 1H), 4.78 (d,
J ) 6.4 Hz), 5.22 (t, J ) 6.4 Hz, 1H), 6.93 (dd, 2.1, 7.0 Hz,
1H), 7.35-7.43 (m, 2H), 7.59 (t, J ) 8.4 Hz, 1H), 8.47 (dd, J )
1.3, 8 Hz); 13C NMR (CDCl3) δ 17.5, 20.2, 25.0, 32.0, 42.5, 96.1,
97.6, 114.3, 117.0, 122.7, 126.0, 130.6, 136.9, 137.2, 158.8,
168.6; HR MS calcd for C18H19NO4 313.1314, found 313.1301
(M+). Anal. Calcd for C18H19NO4: C, 69.00; H, 6.11; N, 4.47.
Found: C, 66.96; H, 6.31; N, 4.33.
1
(w/HCl); H NMR (CDCl3) δ 2.10 (s, 3H), 3.33 (d, J ) 5.5 Hz,
1H), 3.59 (dd, J ) 6.7, 15.6 Hz), 5.41 (s, 2H), 6.95 (d, J ) 6.0
Hz, 1H), 7.14-7.37 (m, 7H), 7.51 (t, J ) 7.3 Hz, 1H), 8.48 (d,
J ) 7.3 Hz, 1H); 13C NMR (CDCl3) δ 20.2, 32.1, 47.4, 96.1,
97.6, 114.6, 122.9, 125.5, 126.2, 127.3, 130.7, 134.3, 137.4,
159.2, 168.6, 173.3. LR MS 335.12. HR MS calcd for C20H17
-
-
NO4 335.1157, found 335.1154 (MH+). Anal. Calcd for C20H17
NO4: C, 71.63; H, 5.11; N, 4.18. Found: C, 71.65; H, 5.23; N,
4.14.
2-Acetoxy-5-(3′-m eth yl-2′-bu ten yl)-2,3-d ih yd r ofu r o[3,4-
d ]qu in olin -4-on e (38). General procedure B: 255 mg of 26;
Rf ) 0.36, pale brown solid; mp 116 °C (ether/pentane), 41%
(w/o HCl), 47% (w/HCl) or 4% (at room temperature w/HCl);
1H NMR (CDCl3) δ 1.72 (s, 3H), 1.91 (s, 3H), 2.13 (s, 3H), 3.22
(dd, J ) 1.9, 17.1 Hz, 1H), 3.50 (dd, 7.2, 17.1 Hz, 1H), 4.95 (d,
J ) 5.3 Hz, 2H), 5.14 (t, J ) 5.3 Hz, 1H), 7.00 (dd, 1.9, 7.2 Hz,
1H), 7.21-7.37 (m, 2H), 7.57 (t, J ) 8.0 Hz, 1H), 7.79 (d, J )
7.9 Hz, 1H); 13C NMR δ 17.6, 20.3, 25.0, 33.5, 39.8, 98.5, 106.2,
111.5, 114.4, 118.8, 121.0, 122.6, 130.5, 135.3, 139.4, 159.7,
160.2, 168.8. Anal. Calcd for C18H19NO4: C, 69.00; H, 6.11; N,
4.47. Found: C, 68.88; H, 6.18; N, 4.45.
8-Meth oxy-5-m eth yl-2-tr im eth ylsilylfu r o[3,4-d ]qu in o-
lin -4-on e (39). General procedure A: 231 mg of 24, 1.96 g of
trimethylsilylacetylene; Rf ) 0.50, colorless needles, mp 138
1
°C (ether/pentane), 47% (w/o HCl) or 52% (w/HCl); H NMR
(CDCl3) δ 0.38 (s, 9H), 3.78 (s, 3H), 3.96 (s, 3H), 7.16 (dd, J )
2.9, 9.2 Hz, 1H), 7.27 (s, 1H), 7.38 (d, J ) 9.2 Hz), 7.49 (d, J
) 2.9 Hz); 13C NMR (CDCl3) δ -2.4, 28.8, 55.1, 102.6, 113.2,
115.4, 115.8, 117.2, 117.3, 132.0, 154.1, 157.4, 158.5, 162.6;
HR MS calcd for C16H19NO3Si 301.1134, found 301.1121 (M+).
6-Meth oxy-9-m eth yl-2-tr im eth ylsilylfu r o[2,3-b]qu in o-
lin -4-on e (40). General procedure A (same as for 39): Rf )
0.25, colorless needles; mp 166 °C (THF/pentane), 8% (w/o HCl)
1
or 13% (w/HCl); H NMR (CDCl3) δ 0.34 (s, 9H), 3.95 (s, 6H),
7.27-7.33 (m, 2H), 7.99 (d, J ) 2.8 Hz, 1H); 13C NMR δ -2.6,
30.8, 54.9, 106.1, 115.0, 116.4, 121.3, 125.1, 131.8, 137.3, 154.5,
155.9, 157.7, 171.4; HR MS calcd for C16H19NO3Si 301.1134,
found 301.1138 (M+).
5-Ben zyl-2-tr im eth ylsilylfu r o[3,4-d]qu in olin -4-on e (41).
General procedure A (277 mg of 25, 1.96 g of trimethylsily-
lacetylene; Rf ) 0.80, colorless needles; mp 142 °C (ether/
pentane), 30% (w/o HCl), 48% (w/HCl); 1H NMR (CDCl3) δ 0.45
(s, 9H), 5.70 (s, 2H), 7.27-7.45 (m, 10H), 8.14 (d, J ) 7.3 Hz,
1H); 13C NMR (CDCl3) δ -2.4, 45.0, 113.1, 114.8, 115.2, 117.1,
120.9, 121.5, 125.8, 126.5, 128.0, 128.8, 136.1, 136.9, 158.1,
159.2, 162.8; HR MS calcd for C21H21NO2Si 347.1325, found
347.1327 (M+). Anal. Calcd for C21H21NO2Si: C, 72.59; H, 6.09;
N, 4.03. Found: C, 72.37; H, 6.16; N, 4.00.
9-Ben zyl-2-tr im eth ylsilylfu r o[2,3-b]qu in olin -4-on e (42).
General procedure A (same as for 41): 6% (w/o HCl) or 9%
(w/HCl), orange solid; mp 171 °C (THF/pentane); 1H NMR
(CDCl3) δ 0.32 (s, 9H), 5.66 (s (2H), 7.16-7.62 (m, 9H), 8.58
(dd, J ) 1.5, 8.1 Hz, 1H); 13C NMR (CDCl3) δ -1.8, 48.3, 114.9,
117.6, 122.6, 126.5, 127.7, 128.1, 129.1, 132.0, 135.15; LR MS
2-Acetoxy-8-m eth oxy-5-m eth yl-2,3-d ih yd r ofu r o[3,4-d ]-
qu in olin -4-on e (34). General procedure B: 231 mg of 24; Rf
) 0.12, white powder, 25% (w/o HCl) 11% (w/HCl), mp 130 °C
(ether/pentane); 1H NMR (CDCl3) δ 2.14 (s, 3H), 3.22 (dd, J )
2.3, 17.4 Hz, 1H), 3.51 (dd, J ) 7.2, 17.4 Hz, 1H), 3.70 (s, 3H),
3.87 (s, 3H), 7.01 (dd, J ) 2.3, 7.2 Hz, 1H), 7.17-7.34 (m, 3H);
13C NMR δ 21.1, 29.4, 34.3, 55.9, 99.1, 104.0, 107.4, 108.2,
112.5, 116.2, 120.9, 135.4, 154.6, 160.4, 169.6; LR MS 290
(MH+); HR MS calcd for C15H15NO5 289.0950, found 289.0945
(M+). Anal. Calcd for C15H15NO5: C, 62.28; H, 5.23; N, 4.84.
Found: C, 62.01; H, 5.28; N, 4.84.
2-Acetoxy-6-m eth oxy-9-m eth yl-2,3-d ih yd r ofu r o[2,3-b]-
qu in olin -4-on e (35). General procedure B (same as for 34):
Rf ) 0.01, yellow solid; mp 205 °C (THF/pentane), 70% (w/o
HCl) or 83% (w/HCl); 1H NMR (CDCl3) δ 2.16 (s, 3H), 3.28
(dd, J ) 2.1, 15.9 Hz, 1H), 3.54 (dd, J ) 6.9, 15.9 Hz, 1H),
3.72 (s, 3H), 3.94 (s, 3H), 6.92 (dd, J ) 2.1, 6.9 Hz, 1H), 7.24
(1H, obscured by CHCl3), 7.37 (d, J ) 9.1 Hz, 1H), 7.89 (d,

Rhodium Dipolar Cycloaddition
J . Org. Chem., Vol. 64, No. 10, 1999 3649
270 (MH+); HR MS calcd for C21H21NO2Si 347.1325, found
347.1330 (M+).
THF. Reaction was complete after 10 min. Column chroma-
tography yielded 27 mg (61%) of isodictamnine: Rf ) 0.15, pale
orange powder; mp 185-187 °C (THF/pentane) (lit.23 mp 187
°C); 1H NMR (CDCl3) δ 3.96 (s, 3H), 7.14 (d, J ) 1.0 Hz, 1H),
7.32 (d, J ) 1.0 Hz, 1H), 7.41 (t, J ) 7.9 Hz, 1H), 7.53 (d, J )
8.4 Hz, 1H), 7.74 (t, J ) 7.3 Hz, 1H), 8.59 (dd, J ) 7.9, Hz,
1H); 13C NMR (CDCl3) δ 30.7, 105.7, 107.2, 113.3,121.9, 124.5,
126.7, 131.4, 132.1, 137.2, 137.5, 172.6; LR MS 200 (MH+);
HR MS calcd for C12H9NO2 199.0633, found 199.0638 (M+).
Spectral/physical data consistent with literature data.23
P seu d oisod icta m n in e. (A) Refluxing 96 mg (0.37 mmol)
of 28 in 2 mL benzene with a catalytic amount of p-toluene-
sulfonic acid and subsequent chromatography with a gradient
of ether/pentane gave 33% (24 mg) of pseudoisodictamnine.
(B) To 285 mg (1.1 mmol) of 29 in 2 mL of THF was added 1.1
mL (1.1 mmol) of a 1 M solution of TBAF in THF. Immediate
reaction with a change in color to red gave pseudoisodictam-
nine in 87% yield (182 mg) after column chromatography: Rf
1
) 0.34, pale orange crystals; mp 133 °C (ether/pentane); H
NMR (CDCl3) δ 3.81 (s, 3H), 7.09 (d, J ) 1.9 Hz, 1H), 7.33 (dt,
J ) 0.7, 17.6 Hz, 1H), 7.47 (d, J ) 8.4 Hz, 1H), 7.57 (dt, J )
1.4, 7.3 Hz, 1H), 7.64 (d, J ) 1.9, 1H), 8.03 (dd, J ) 1.3, 7.8
Hz, 1H); 13C NMR (CDCl3) δ 28.8, 107.7, 112.5, 114.4, 114.7,
120.5, 121.6, 128.8, 137.4, 143.3, 154.4, 158.8; IR 1659, 1650
cm-1; HR MS calcd for C12H8NO2 198.0841, found 198.0547
(MH+). Anal. Calcd for C12H9NO2: C, 72.35; H, 4.55; N, 7.03.
Found: C, 72.23; H, 4.63; N, 7.00.
Ack n ow led gm en t. Partial financial support pro-
vided by PRF 32687-AC. The assistance of L. LaBean
in administrative support of this work is greatly
appreciated.
J O982503H
Isod icta m n in e. To 61 mg (0.23 mmol) of 30 in 2 mL of THF
was added 0.23 mL (0.23 mmol) of a 1 M solution of TBAF in
(23) Mammarella, C. A.; Comin, J . Anales Assoc. Quim. Argentina
1971, 59, 239-243.