Regiochemistry of the photostimulated reaction of the phthalimide anion with 1-iodoadamantane and tert-butylmercury chloride by the SRN1 mechanism

Article abstract of DOI:10.1021/jo010756w

The photostimulated reaction of the phthalimide anion (1) with 1-iodoadamantane (2) gave 3-(1-adamantyl) phthalimide (3) (12%) and 4-(1-adamantyl) phthalimide (4) (45%), together with the reduction product adamantane (AdH) (21%). The lack of reaction in the dark and inhibition of the photoinduced reaction by p-dinitrobenzene, 1,4-cyclohexadiene, and di-tert-butylnitroxide indicated that 1 reacts with 2 by an S_RN1 mechanism. Formation of products 3 and 4 occurs with distonic radical anions as intermediates. The photoinduced reaction of anion 1 with tert-butylmercury chloride (10) affords 4-tert-butylphthalimide (11) as a unique product. By competition experiments toward 1, 1-iodoadamantane was found to be ca. 10 times more reactive than tert-butylmercury chloride.

Full text of DOI:10.1021/jo010756w

1012
J . Org. Chem. 2002, 67, 1012-1015
Sch em e 1
Regioch em istr y of th e P h otostim u la ted
Rea ction of th e P h th a lim id e An ion w ith
1-Iod oa d a m a n ta n e a n d ter t-Bu tylm er cu r y
Ch lor id e by th e SRN1 Mech a n ism
Manuel Bajo Maquieira, Alicia B. Pen˜e´n˜ory,* and
Roberto A. Rossi*
the ET does not occur spontaneously, it can be induced
by light or by FeBr2 in DMSO.
The alkyl halides that react by the SRN1 mechanism
are those that have a relatively low reactivity toward
polar nucleophilic substitution.1c,f For instance, 1-halo-
INFIQC, Departamento de Quı´mica Orga´nica, Facultad de
Ciencias Quı´micas, Universidad Nacional de Co´rdoba,
Ciudad Universitaria, 5000 Co´rdoba, Argentina
penenory@dqo.fcq.unc.edu.ar
Received J uly 26, 2001
adamantanes as well as other bridgehead halides react
3a
with Ph2P-,3 Ph2As-,
and Me3Sn- 4 ions. Also, the
reaction of 1-iodoadamantane (1-IAd) with carbanions,5
PhS-,6,7 PhSe-,6 and PhTe- 6 ions has been reported.
It is known that N-centered nucleophiles react with
different substrates to give N-substitution or C-substitu-
tion and both N- and C-substitution. Thus, the photoin-
duced reaction of the anion of 2-aminonaphthalene with
iodobenzene affords mainly 1-phenyl-2-aminonaphtha-
lene (47%) and N-phenyl-2-aminonaphthalene (1%). How-
ever, with 1-iodonaphthalene only C-substitution is
observed.8 Several anions derived from nitrogen hetero-
cycles react with aryl radicals on carbon. With the anion
of pyrrole, only substitution at the carbon center is
observed, the 2-position being more reactive than the
3-position.9 For example, in the reaction of 4-chloropyr-
idine with pyrrole anion induced by electrodes, 2-(4-
pyridyl) pyrrole (60%) and 3-(4-pyridyl) pyrrole (3%) were
obtained and no N-substitution is observed.9 In contrast,
it was found that alkyl substrates with EWG yield
N-substitution products after reaction with N-centered
nucleophiles derived from azoles,10 nitroimidazoles,11
pyrimidine,12 purine,13 etc. There is only one example in
the literature of the reaction of an alkyl substrate without
EWG with nitrogen nucleophiles in which tert-butyl-
Abstr a ct: The photostimulated reaction of the phthalimide
anion (1) with 1-iodoadamantane (2) gave 3-(1-adamantyl)
phthalimide (3) (12%) and 4-(1-adamantyl) phthalimide (4)
(45%), together with the reduction product adamantane
(AdH) (21%). The lack of reaction in the dark and inhibition
of the photoinduced reaction by p-dinitrobenzene, 1,4-
cyclohexadiene, and di-tert-butylnitroxide indicated that 1
reacts with 2 by an SRN1 mechanism. Formation of products
3 and 4 occurs with distonic radical anions as intermediates.
The photoinduced reaction of anion 1 with tert-butylmercury
chloride (10) affords 4-tert-butylphthalimide (11) as a unique
product. By competition experiments toward 1, 1-iodoada-
mantane was found to be ca. 10 times more reactive than
tert-butylmercury chloride.
The radical nucleophilic substitution, or SRN1, is an
excellent means of effecting the nucleophilic substitution
of different types of aromatic and aliphatic substrates
with electron-withdrawing groups (EWG) possessing
suitable leaving groups. Also, it has been reported that
aliphatic substrates without EWG groups such as the
cycloalkyl, bicycloalkyl, and neopentyl halides react by
this mechanism.1 This SRN1 reaction involves radicals and
radical anions as intermediates and proceeds by a chain
mechanism, whose propagation steps are outlined in
Scheme 1.
In aliphatic systems without a π* MO that stabilizes
the radical anion (RX)-•, this is not an intermediate, and
eqs 1 and 3 occur simultaneously (dissociative electron
transfer) (eq 1,3).2 However, this chain process requires
an initiation step, that is, the generation of the radical
(R•) or the radical anion (RX)-• intermediates.1 In a few
systems, spontaneous electron transfer (ET) from the
nucleophile to the substrate has been observed. When
(3) (a) Rossi, R. A.; Palacios, S. M.; Santiago, A. N. J . Org. Chem.
1982, 47, 4654-4657. (b) Bornancini, E. R. N.; Alonso, R. A.; Rossi, R.
A. J . Org. Chem. 1987, 52, 2166-2170. (c) Santiago, A. N.; Morris, D.
G.; Rossi, R. A. J . Chem. Soc., Chem. Commun. 1988, 220-221. (d)
Santiago, A. N.; Takeuchi, K.; Ohga, Y.; Nishida, M.; Rossi, R. A. J .
Org. Chem. 1991, 56, 1581-1584. (e) Santiago, A. N.; Iyer, V. S.;
Adcock, W.; Rossi, R. A. J . Org. Chem. 1988, 53, 3016-3020. (f).
Lukach, A. E.; Morris, D. G.; Santiago, A. N.; Rossi, R. A. J . Org. Chem.
1995, 60, 1000-1004.
(4) (a) Adcock, W.; Gangodawila, H. J . Org. Chem. 1989, 54, 6040-
6047. (b) Ashby, E. C.; Sun, X.; Duff, J . L. J . Org. Chem. 1994, 59,
1270-1278. (c) Adcock, W.; Clark, C. I. J . Org. Chem. 1995, 60, 723-
724.
(5) (a) Borosky, G. L.; Pierini, A. B.; Rossi, R. A. J . Org. Chem. 1990,
55, 3705-3707. (b) Rossi, R. A.; Pierini, A. B.; Borosky, G. L. J . Chem.
Soc., Perkin Trans. 2 1994, 2577-2581.
(6) Palacios, S. M.; Alonso, R. A.; Rossi, R. A. Tetrahedron 1985,
41, 4147-4156.
* Fax: 54-351-4333030. Phone: 54-351-4334170/73.
(1) For reviews on SRN1, see: (a) Rossi, R. A.; de Rossi, R. H.
Aromatic Substitution by the SRN1 Mechanism; ACS Monograph 178;
American Chemical Society: Washington, DC, 1983. (b) Bowman, W.
R. Chem. Soc. Rev. 1988, 17, 283-316. (c) Rossi, R. A.; Pierini, A. B.;
Palacios, S. M. Adv. Free Rad. Chem. 1990, 193-252. (d) Save´ant, J .
M. Adv. Phys. Org. Chem. 1990, 26, 1-130. (e) Norris, R. K. In
Comprehensive Organic Synthesis; Trost, B. M., Ed.; Pergamon: 1991;
Vol. 4, p 451. (f) Rossi, R. A.; Pierini, A. B.; Pen˜e´n˜ory, A. B. In The
Chemistry of Functional Groups; Patai, S., Rappoport, Z., Eds.; Wiley:
Chichester, 1995; Supl. D2, Chapter 24, pp 1395-1485. (g) Rossi, R.
A.; Pierini, A. B.; Santiago, A. N. In Organic Reactions; Paquette, L.
A., Bittman, R., Eds.; J ohn Wiley & Sons, Inc.: New York, 1999; Vol.
54, pp 1-271.
(7) Ahbala, M.; Hapiot, P. K.; Houmam, A.; J ouini, M.; Pinson, J .;
Save´ant, J . M. J . Am. Chem. Soc. 1995, 117, 11488-11498.
(8) Pierini, A. B.; Baumgartner, M. T.; Rossi, R. A. Tetrahedron Lett.
1987, 28, 4653-4656.
(9) Chahma, M.; Combellas, C.; Thiebault, A. Synthesis-Stuttgart
1994, 366-368.
(10) Beugelmans, R.; Lechevalier, A.; Kiffer, D.; Maillos, P. Tetra-
hedron Lett. 1986, 27, 6209-6212.
(11) Benhida, R.; Charbaoui, T.; Lechevallier, A.; Beugelmans, R.
Bull. Soc. Chim. Fr. 1994, 131, 200-209.
(12) Benhida, R.; Gharbaoui, T.; Lechevallier, A.; Beugelmans, R.
Nucleosides & Nucleotides 1994, 13, 1169-1177.
(2) Save´ant, J . M. Adv. Electron-Transfer Chem. 1994, 4, 53-116
and references therein.
(13) Gharbaoui, T.; Benhida, R.; Lechevallier, A.; Maillos, P.;
Beugelmans, R. Nucleosides & Nucleotides 1994, 13, 1161-1168.
10.1021/jo010756w CCC: $22.00 © 2002 American Chemical Society
Published on Web 01/09/2002

Notes
J . Org. Chem., Vol. 67, No. 3, 2002 1013
Ta ble 1. Rea ction s of 1 w ith 2 in DMSOa
products, yield %
experiment
conditions
I-
AdH
3
4
1
2
3
dark, 180 min
hν, 60 min
6
<1
6
53
67
68
72
10
50
48
58
<2
<7
7
35c
40
hν, 300 min
hν, 180 min
hν, 180 min
hν, 180 min
hν, 180 min
hν, 180 min
hν, 180 min
dark, 180 min
hν, 180 min
10
19
21
<1
3
11
4b
5d
6e
2c
35c
45
12
7f
<1
2.5
20
18
8g
9h
10h
11h,e
7
13i
<1
<1
7 should lose a proton to afford radical dianions 8 and 9
(eq 6), which continue the chain propagation cycle. The
driving force of this reaction is the aromatization to the
benzene ring. Radical dianions have also been reported
as intermediates in the propagation cycle of the SRN1
reaction of the nucleophiles derived from 2-naphthol and
analogues with o-dihalobenzenes.17
a
Reactions were performed with 1 (16.4 × 10-2 M) and 2
(8.3 × 10-2 M) in DMSO and quantified by GC with the internal
b
standard method. Part of AdH is lost during workup. In the
presence of 18-crown-6. c Isolated yield. In the presence of 18-
d
crown-6 and pinacolone enolate ion (16.4 × 10-2 M). e In the
presence of p-dinitrobenzene (20 mol %). f In the presence of 1,4-
cyclohexadiene (80 mol %). g In the presence of di-tert-butylnitrox-
h
ide (20 mol %). Reaction carried out with the anion of 1,3-
indandione 12 (16.4 × 10-2 M) and 2 (8.3 × 10-2 M) in DMSO.
i
Together with 17% of the substitution product 13 and 1-ada-
mantanol (3%).
mercury chloride was reported to react by the SRN
1
mechanism with the anion of the phthalimide to give
substitution on the nitrogen.14
The lack of studies about the reactions of N-centered
anions with radicals from aliphatic substrates without
EWG has encouraged us to investigate the reactivity of
the phthalimide anion with different substrates and the
regiochemistry of the coupling reaction with radicals.
In the photoinduced reaction of the phthalimide anion
1 with 1-iodonaphthalene, we found no substitution
products and only the reduction product naphthalene was
formed (39%). This reaction does not proceed in the dark.
These results can be ascribed to a poor reactivity of the
1-naphthyl radicals toward nucleophile 1, in comparison
with a competitive reduction process. Thus, a photoin-
duced ET from 1 to 1-iodonaphthalene followed by
fragmentation of the C-I bond in the radical anion
intermediate yields the 1-naphthyl radicals, which are
reduced to the corresponding naphthalene by hydrogen
atom abstraction from the solvent.15
The photostimulated reaction of 1 with 1-iodoadaman-
tane 2 gave 3-(1-adamantyl) phthalimide (3) and 4-(1-
adamantyl) phthalimide 4, together with the reduction
product adamantane (AdH) (eq 4). This reaction does not
take place in the dark, and the photostimulated reaction
was strongly inhibited by p-dinitrobenzene (radical anion
trap) and partially by 1,4-cyclohexadiene and di-tert-
butylnitroxide (as radical traps) (Table 1). These results
indicate that 1 reacts with 2 by an SRN1 mechanism.
The formation of the substitution products 3 and 4 can
be rationalized as follows. The 1-adamantyl radicals 5,
formed by a dissociative ET to 2, react with the nucleo-
phile 1 at positions 3- and 4- affording distonic radical
anions 6 and 7, respectively (eq 5). No addition to the
nitrogen is observed. As far as we know there are few
examples of the formation of distonic radical anion in the
coupling of a radical and a nucleophile.16 To yield the
observed products, the intermediate radical anions 6 and
The unexpected regiochemistry of this reaction could
be ascribed to differences in the activation energy for the
coupling reactions leading to the C-N or C-C bond
formation, although the C-N product is thermodynami-
cally more favorable.18
There is a slight increase in products 3 and 4 when
the reaction is carried out in the presence of 18-crown-6
and pinacolone enolate ions as an entrainment reagent.
(Table 1, experiments 4 and 5). The formation of products
3 and 4 is opposite to those reported on the reaction of 1
(16) In the reaction of 1 with isobutirophenone anion, the main
product is the coupling of adamantyl radicals in the para position of
the nucleophile to give also a distonic radical anion. See: Lukach, A.
E.; Santiago, A. N.; Rossi, R. A. J . Org. Chem. 1997, 62, 4262-4265.
(17) Baumgartner, M. T.; Pierini, A. B.; Rossi, R. A. J . Org. Chem.
1993, 58, 2593-2598.
(14) Russell, G. A.; Khanna, R. K. Tetrahedron 1985, 41, 4133-4145.
(15) The hydrogen abstraction rate constant for 1-naphthyl radicals
from DMSO was estimated to be 1 × 108 s-1: M’Halla, F.; Pinson, J .;
Saveant, J . M. J . Am. Chem. Soc. 1980, 102, 4120-4127.
(18) Baumgartner, M. T.; Pen˜e´n˜ory, A. B.; Pierini, A. B. Unpublished
results.

1014 J . Org. Chem., Vol. 67, No. 3, 2002
Notes
with tert-butylmercury chloride (10) in which tert-butyl
radicals couple on the nitrogen.14 We repeated the reac-
tion under the same experimental conditions, and we
found that the only substitution product formed is 4-tert-
butylphthalimide (11) (20% isolated yield) (eq 8).19 The
crude reaction product was analyzed by GC-MS, and not
even traces of other possible coupling products were
observed.
From these results, it is concluded that alkyl radicals
without EWG react sluggishly with nitrogen-centered
nucleophiles. The phthalimide anion (1) couples with
1-adamantyl and tert-butyl radicals mainly at the 4-posi-
tion to give a new C-C bond, and no coupling at the
nitrogen took place.
Exp er im en ta l Section
Gen er a l Meth od s. Irradiation was conducted in a reactor
equipped with two 250 W UV lamps emitting maximally at 350
nm (Philips Model HPT, water-refrigerated). 1H and 13C NMR
spectra were recorded on a Bruker 200 spectrometer, and all
spectra are reported in δ (parts per million) relative to Me4Si,
with CDCl3, CD2Cl2, CD3SOCD3, or CD3COCD3 as solvents.
HRDEIMS were recorded at Mc Master Regional Centre for
Mass Spectrometry, Mc Master University, Canada. Gas chro-
matographic analyses were performed on a Hewlett-Packard
5890 Series II apparatus with a flame-ionization detector and
the data system Hewlett-Packard 3396 Series II integrator, on
a 5 m capillary column packed with methyl silicone gum of a
0.53 mm × 2.65 µm film thickness. GS/MS analyses were carried
out on a Shimadzu GC-MS QP 5050 spectrometer, employing a
30 m × 0.12 mm DB-5 MS column. IR spectra were recorded on
a Nicolet Avatar 360 FT-IR spectrometer. The column chroma-
tography was performed on silica gel (70-230 mesh ASTM).
Potentiometric titration on halide ions was performed in a pH
meter (Orion, model 420 A), using an Ag/Ag+ electrode and a
AgNO3 solution as a standard. Melting points were obtained on
an Electrothermal 9100 apparatus and were not corrected.
Ma ter ia ls. tert-Butylmercury chloride21 (10) and 7-iodonor-
carane22 were synthesized as previously reported. Phthalimide
(Aldrich), t-BuOK (Aldrich), 18-crown-6 ether (ICN), 1-iodoada-
mantane (Aldrich), 1,3-indandione (Aldrich), isatin (Aldrich), and
1,8-naphthalimid (Aldrich) were commercially available and
used as received. DMSO (Carlo Erba) was distilled under
vacuum and stored over molecular sieves (4Å). The anions were
generated in situ by acid-base deprotonation using t-BuOK.
P h ot oin d u ced R ea ct ion s of An ion 1 w it h 2 (Gen er a l
P r oced u r e). The photochemical reaction was carried out in a
three-necked, 50 mL round-botton flask equipped with a nitrogen
gas inlet, a condenser with a cooling jacket, and a magnetic
stirrer. The flask was dried under vacuum, filled with nitrogen,
and then loaded with 30 mL of dried DMSO. To the degassed
solvent under nitrogen was added 7.5 mmol of t-BuOK, 5.0 mmol
of the nucleophile precursor, 7.5 mmol of 18-crown-6 ether, and
2.5 mmol of 2. After 3 h of irradiation, the reaction was quenched
with addition of ammonium nitrate in excess and 10 mL of
water, and then the mixture was extracted with diethyl ether.
The iodide ions in the aqueous solution were determined
potentiometrically. The ether extract was washed twice with
water and dried, and the products were quantified by GC with
the internal standard method.
To assess the relative reactivity of 2 and 10 toward
anion 1, we performed the corresponding competition
experiment in DMSO, using 8.3 × 10-2 M in both
substrates, and 6.7 × 10-2 M in the anion 1.20 After 3 h
of irradiation, 47.5% of product 4 and 5% of product 11
was quantified by GC with the internal standard method.
We found that 2 was ca. 10 times more reactive than 10;
this can be rationalized as 2 being a better electron
acceptor than 10.
No coupling products were formed in the photostimu-
lated reaction of 1 with neopentyl iodide and with
7-iodonorcarane, primary and secondary alkyl halides,
respectively. Nevertheless, dehalogenations were ob-
served in acceptable yields (60 and 62% iodide ion,
respectively).
The anion of 1,3-indandione 12, analogue to the
phthalimide anion (1) in which the NH moiety is replaced
by a methylene group, shows a different regiochemistry.
Thus, in the photostimulated reaction with 2 only the
C-substitution product 13 was obtained (17%), together
with adamantane (13%), adamantanol (3%), and iodide
ions (58%) (eq 9). This reaction does not occur in the dark
and is strongly inhibited by the presence of p-dinitroben-
zene (<2 and 5% iodide ion, respectively) (Table 1).
Anion 12 was not reactive toward tert-butylmercury
chloride (10) after 3 h of irradiation under the same
experimental conditions employed for the reaction with
2. This result is in agreement with the lower reactivity
shown by 10 in regard to 2, as was observed by competi-
tion experiments toward anion 1 (see above).
Other nucleophiles related to 1 such as the anions 14
and 15 were studied, but in the photostimulated reaction
with 2 only reduction to adamantane was obtained.
3-(1-Ad a m a n tyl) P h th a lim id e (3). Compound 3 was iso-
lated in 7% yield by silica gel chromatography with petroleum
ether/diethyl ether (80:20) as the eluent from the crude product
reaction. Compound 3 is a white solid: 1H NMR (CD3SOCD3) δ
1.27 (s), 1.81 (s), 2.17 (s), 7.65-7.81 (m) 11.33 (s); 13C NMR (CD3-
COCD3) δ 19.38, 27.04, 27.77, 31.16, 111.72, 120.05, 122.50,
125.46, 125.95, 142.58, 159.85, 160.88; IR (KBr) cm-1 3182, 1766,
1730, 1714, 1359, 1302, 1077, 743; MS (EI+) 282 (19.96), 281
(100.00) M+, 238 (13.23), 224 (61.61), 160 (13.45), 135 (5.90),
121 (69.05), 93 (31.60), 79 (50.35); HRMS (EI+) calcd 281.1416,
found 281.1359.
(19) The spectroscopic data from 1H NMR are essentially the same
as those previously reported in ref 14, but probably due to an
incomplete analysis of the reaction product (no 13C NMR or MS data
were available), the structure assignment was not correct.
(20) The following is the equation used in the evaluation of the
relative reactivity of 1-iodoadamantane (2) and tert-butylmercury
chloride (10) toward phthalimide anion (1):
kAda/kt-Bu ) [ln(AdaI)o/
(AdaI)o - (AdaNu)t]/[ln(t-BuHgCl)o/(t-BuHgCl)o - (t-BuNu)t], where
(AdaI)o and (t-BuHgCl)o are the initial concentrations and (AdaNu)t
and (t-BuNu)t are the concentrations of the products at time t. See:
Bunnett, J . F. Investigation of Rates and Mechanism of Reactions, 3rd
ed.; Lewis, E. S., Ed.; Wiley-Interscience: New York, 1974; Part I.
(21) Kharasch, M. S.; Swartz, S. J . Org. Chem. 1938, 3, 405-408.
(22) Dehmlow, E. V.; Stu¨tten, J . Tetrahedron Lett. 1991, 43, 6105-
6108.

Notes
4-(1-Ad a m a n tyl) P h th a lim id e (4). Compound 4 was iso-
J . Org. Chem., Vol. 67, No. 3, 2002 1015
2-(1-Ad a m a n tyl)-1,3-in d a n d ion e (13). Compound 13 was
isolated in 17% yield by silica gel chromatography with petro-
leum ether/diethyl ether (80:20) as the eluent from the crude
product reaction. Compound 13 is a yellow solid: 1H NMR
(CDCl3) δ 1.82 (6H, s), 1.99 (6H, s), 2.14 (3H, s), 3.20 (1H, s)
7.74-8.07 (4H, m); 13C NMR (CD2Cl2) δ 29.02, 36.56, 42.95,
43.92, 45.59, 119.31, 132.97, 141.33, 197.90; IR (KBr) cm-1 2901,
2850, 1714, 1602, 1574, 1453, 1254; MS (EI+) 281 (17.85), 280
(100.00) M+, 237 (9.08), 223 (28.91), 181 (34.58), 135 (8.42), 94
(23.93), 79 (20.65); HRMS (EI+) calcd 280.1463, found 280.1491.
lated in 35% yield by silica gel chromatography with petroleum
ether/diethyl ether (80:20) as eluent from the crude product
reaction. Compound 4 is a white solid: mp 251-252 °C; 1H NMR
(CD3SOCD3) δ 1.79 (6H, s), 1.96 (6H, s), 2.12 (3H, s), 7.77-7.95
(3H, m) 11.24 (1H, s); 13C NMR (CDCl3) δ 28.67, 36.43, 37.32,
42.93, 120.50, 123.41, 129.90, 131.01, 132.84, 159.09, 168.26,
168.66; IR (KBr) cm-1 3250, 1765, 1710, 1622, 1437, 1301, 1099,
1041, 751; MS (EI+) 282 (20.27), 281 (100.00) M+, 238 (17.33),
224 (46.06), 181 (63.64), 152 (18.48), 135 (16.52), 94 (65.16), 79
(49.89); HRMS (EI+) calcd 281.1416, found 281.1386.
4-ter t-Bu tylp h th a lim id e (11). Compound 11 was isolated
in 20% yield by silica gel chromatography with petroleum ether/
diethyl ether (90:10) as the eluent from the crude product
reaction. Compound 11 is a white solid: mp 142-143 °C; 1H
NMR (CDCl3) δ 1.44 (9H, s), 7.76-7.99 (3H, m) 10.00 (1H, s);
13C NMR (CD3COCD3) δ 32.18, 37.04, 121.44, 124.40, 132.24,
132.89, 135.05, 160.05, 170.01, 170.34; IR (KBr) cm-1 3218, 1769,
1717, 1608, 1475, 1297, 1084, 1034, 725; MS (EI+) 204 (3.53),
203 (14.15) M+, 188 (100.00), 160 (50.82), 145 (20.99), 115
(15.81), 102 (4.57), 89 (9.35), 71 (5.61), 57 (14.92); HRMS (EI+)
calcd 203.0946, found 203.0935.
Ack n ow led gm en t. This work was supported in part
by the Agencia Nacional de Promocio´n Cient´ıfica y
Te´cnica, SECYT-UNCba., and the Consejo Nacional de
Investigaciones Cient´ıficas y Te´cnicas (CONICET), Ar-
gentina. M.B.M. gratefully acknowledges the receipt of
a fellowship from CONICET.
Su p p or tin g In for m a tion Ava ila ble: 1H NMR, 13C NMR,
and mass spectra of compounds 3, 4, 11, and 13. This material
is available free of charge via the Internet at http://pubs.acs.org.
J O010756W