Iodine(III)-mediated aromatic amidation vs olefin amidohydroxylation. The amide N-substituent makes the difference

Article abstract of DOI:10.1016/j.tet.2004.06.007

A series of N-methoxy- and N-para-methoxyphenylacetamides simultaneously substituted at the α position by a benzyl and an allyl group have been treated with phenyliodine(III)bis(trifluoroacetate) to generate stabilized N-acylnitrenium intermediates. It ha

Full text of DOI:10.1016/j.tet.2004.06.007

Tetrahedron 60 (2004) 6533–6539
Iodine(III)-mediated aromatic amidation vs
olefin amidohydroxylation.
The amide N-substituent makes the differenceq
*
Sonia Serna, Imanol Tellitu, Esther Domınguez, Isabel Moreno and Raul SanMartin
*
´
´
´ ´ ´ ´
Departamento de Quımica Organica II, Facultad de Ciencia y Tecnologıa, Universidad del Paıs Vasco—Euskal Herriko Unibertsitatea
(UPV/EHU) Apdo. 644-48080 Bilbao, Spain
Received 9 March 2004; revised 10 May 2004; accepted 3 June 2004
Available online 19 June 2004
Abstract—A series of N-methoxy- and N-para-methoxyphenylacetamides simultaneously substituted at the a position by a benzyl and an
allyl group have been treated with phenyliodine(III)bis(trifluoroacetate) to generate stabilized N-acylnitrenium intermediates. It has been
observed that, when starting from N-methoxy substituted amides, such intermediates are intramolecularly trapped by nucleophilic arene rings
to render the quinolinone skeleton. Alternatively, under the same reaction conditions, N-para-methoxyphenylamides afford pyrrolidinone
derivatives through an olefin amidohydroxylation process.
q 2004 Elsevier Ltd. All rights reserved.
1. Introduction
During the optimization of both protocols it was found that
substitution on the amidic nitrogen played a determinant
role in the success of the experiment. Thus, while the
aromatic amidation protocol was best carried out on
N-methoxy substituted amides, as 1 (see Scheme 1), the
N-para-methoxyphenyl (PMP) substituted amides of type 3
were selected as the derivatives of choice to perform the
amidohydroxylation process. Alerted by this intriguing
observation, we were aware that a remarkable effect on the
chemoselective outcome of the reaction would arise if the
nitrenium intermediate were generated on a doubly-benzyl
and allyl-substituted N-methoxy (or N-para-methoxy-
phenyl) acetamides of type 7 and 8. According to our
expectations, this intermediate would be eventually trapped
univocally with only one of the internal nucleophiles. The
results presented here will confirm this hypothesis.
With the aim of developing the enormous potentiality that
some hypervalent iodine reagents can provide in organic
synthesis,1 our group started a program directed to expand
the applicability of phenyliodine(III)bis(trifluoroacetate)
(PIFA) in heterocyclic chemistry.2 Attracted by the clean
transformations usually achieved, the mild conditions
employed, and the low toxicity associated to it, we decided
to expand the use of this iodine(III) reagent in new synthetic
challenges. Thus, we have recently reported the synthesis of
different heterocycle-fused quinolinones3 of type 2 and 1,4-
diazepin-2-ones4 by an electrophilic aromatic amidation
process, and the synthesis of the isoquinolinone and
isoindolinone skeletons5 of type 4 by a novel olefin
amidohydroxylation reaction promoted by PIFA (see
Scheme 1).6 To explain the observed behavior, it is
accepted7 that when the mildly oxidant I(III) reagent reacts
with properly substituted amides N-acylnitrenium inter-
mediates are generated. Finally, in the presence of
nucleophilic species, the so-obtained electrophilic inter-
mediates are trapped intramolecularly to form new C–N
linkages.
q Supplementary data associated with this article can be found in the online
version, at doi: 10.1016/j.tet.2004.06.007
Keywords: Hypervalent iodine; Quinolinones; Pyrrolidinones; N-
acylnitrenium; PIFA.
*
Corresponding authors. Tel.: þ34-94-601-5438; fax: þ34-94-601-2748;
Scheme 1. PIFA-mediated aromatic amidation and olefin amidohydroxyl-
ation reactions.
e-mail address: qoptecoi@lg.ehu.es
0040–4020/$ - see front matter q 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2004.06.007

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S. Serna et al. / Tetrahedron 60 (2004) 6533–6539
2. Results and discussion
nitrenium ion generated was trapped by the olefin fragment
with total chemoselectivity to afford pyrrolidinone 10a in
good yield without affecting the integrity of the benzyl
group. Due to the instability of this pyrrolidinone com-
pound, a full characterization was carried out on the
corresponding reduced derivative 11a, which was obtained
by treatment of the crude 10a with BH3·SMe2.
Amide precursors 7 and 8 were prepared (see Scheme 2) in a
two-step sequence starting from commercially available
hydrocinnamic acids 5a-d, which were alkylated with allyl
bromide under basic (LDA) conditions in good (69–98%)
yields. With these substrates in hand, two series of amides
were synthesized. Thus, by treatment of carboxylic acids
6a-d with methoxylamine hydrochloride, amides 7a-d were
easily obtained when the reaction was assisted by the
uronium-coupling reagent TBTU.8 Alternatively, a combi-
nation of carbodiimide EDC and hydroxybenzotriazole
HOBt was required to optimize the reaction of acids 6a-d
with para-anisidine to render amides 8a-d.9
A number of 3-allyl-quinolin-2-ones of type 9 can be found
in Nature.10 For that reason, and in order to test the potential
effect that substitution can exert on the chemoselectivity of
the process, we decided to prepare a series of methoxy-
substituted quinolinones 9a-d from 7a-d. In addition, and
trying to get more information about the behavior of these
amide precursors under the action of the oxidative I(III)
reagent, a further reaction condition was tested on
methoxyamides 7a-d. It has been previously shown that
TFA, employed as an additive in CH2Cl2 as solvent, can
activate the cyclization of such kind of substrates.7c In
Scheme 4 a comparison of both methods is presented.
Scheme 2. Reagents and conditions: (i) LDA, AllylBr, THF, 0 8C to rt;
(ii) for 7 series: NH2OMe·HCl, Et3N, TBTU, MeCN; (ii) for 8 series:
p-anisidine, EDC·HCl, Et3N, HOBt, CH2Cl2, rt. Overall yields: 59% for 7a,
70% for 7b, 54% for 7c, 63% for 7d, 63% for 8a, 78% for 8b, 60% for 8c,
54% for 8d.
We first examined the behavior of amides 7a and 8a under
the action of the I(III) reagent. Typically, a solution of
1.5 equiv. of PIFA in CF3CH2OH is added to a cold
(220 8C) solution of the amide in the same solvent (,5 mg/
mL). When the starting material is consumed (,1 h), the
reaction mixture is washed with Na2CO3 (10% aq.) and
extracted with CH2Cl2. Finally, the residue is column
chromatographed to afford the final products.
Scheme 4. Reagents and conditions: (i) PIFA, CF3CH2OH, 220 8C (Condt.
A); (i) PIFA, TFA, CH2Cl2, 0 8C (Condt. B).
Analogously, we next tried to expand the ability of PIFA to
generate a series of pyrrolidinones 10 from the correspond-
ing N-para-methoxyphenyl substituted amides 8 under the
usual conditions depicted above (Scheme 5).
As originally planned, the optimized conditions employed
for this transformation led to the construction of the
quinolinone skeleton 9a starting from amide 7a (see
Scheme 3). By altering the temperature and the solvent of
the reaction (CH2Cl2), lowered yields were obtained but, in
all cases, the allylic residue remained intact. Alternatively,
amide 8a was treated with PIFA under the same reaction
conditions described above. In this case, the N-acyl-
Scheme 5. Reagents and conditions: (i) PIFA, CF3CH2OH, 0 8C to rt;
(ii) BH3·SMe2, THF, rt. Overall yields: 72% for 11a, 68% for 11b, 67% for
11c, 59% for 11d.
As expected, in all cases under study, the action of PIFA on
amides 8a-d rendered chemoselectively pyrrolidinones
10a–d as a series of unstable derivatives that were
immediately reduced to the corresponding pyrrolidines
11a-d in good overall yields.
The main observation that can be concluded from our
experiments is that the cyclization process can take two
Scheme 3. Reagents and conditions: (i) PIFA, CF3CH2OH, 220 8C (75%
for 9a); (ii) BH3·SMe2, THF, 0 8C to rt (72% for 11a two steps).

S. Serna et al. / Tetrahedron 60 (2004) 6533–6539
6535
different pathways depending on the nature of the amide
3. Conclusions
N-substituent to afford either quinoline or pyrrolidine
skeletons. To sum up, when starting from N-methoxyamides
7a-d quinolinones 9a-d are obtained in all cases in moderate
to good yields, along with the corresponding aza-spiro
derivatives 12c and 12d, via intermedium B, when starting
from 7c and 7d, respectively. In the latter cases, a methoxy
group located in para position to the alkyl chain is
responsible for the corresponding ipso attack of the internal
electrophile.11 When applying TFA as an activating agent,
such process becomes dominant. Alternatively, inter-
medium A can be also trapped by the olefin fragment,
when starting from amides 8a-d, to form the heterocyclic
core C stabilized as an aziridinium ion by the donating
properties of the para-methoxyphenyl (PMP) group. This
new intermediate is opened by a free trifluoroacetate group
(delivered from PIFA), and the resulting non-isolated
trifluoroacetylester is hydrolyzed during the work up
(Na2CO3, H2O) to render derivatives 10a-d. A plausible
mechanism for these transformations is shown in Figure 1.
In summary, the present work shows that the substituent
required to stabilize the N-acylnitrenium intermediates
generated by the action of PIFA on properly substituted
amides can exert a selective control in the course of the
cyclization reaction of 2-allyl-2-benzylacetamides to afford
either 3-allyl-quinolin-2-ones or 3-benzyl-pyrrolidin-2-ones
in good yields and complete selectivity.
4. Experimental
Melting points were measured in a Bu¨chi apparatus and are
uncorrected. Infrared spectra were recorded on a Perkin–
Elmer R-1420 infrared spectrophotometer as KBr plates or
as neat liquids and peaks are reported in cm21. NMR spectra
were recorded on a Bruker ACE-250 instrument (250 MHz
for 1H and 62.83 MHz for 13C) at 20 8C. Chemical shifts (d)
were measured in ppm relative to chloroform (d¼7.26 for
1H or 77.00 for 13C) as internal standard. Coupling
constants, J, are reported in hertz. DEPT experiments
were used to assist with the assignation of the signals.
HRMS spectra were recorded at the University of Vigo on a
VG Autospec M instrument.
4.1. General procedure for the a-alkylation of
hydrocinnamic acids 5a-d
4.1.1. Synthesis of 2-allyl-3-phenylpropionic acid (6a).
n-BuLi (26.2 mL, 1.6 M in n-hexane, 42 mmol) was added
onto a cold (0 8C) solution of iPr2NH (5.9 mL, 42 mmol) in
30 mL of THF, and the mixture was stirred for 30 min.
Then, a solution of hydrocinnamic acid 5a (3.0 g,
19.9 mmol) in 20 mL of THF was added dropwise over
20 min and stirring was continued for 30 min at the same
temperature. The addition of allyl bromide (1.8 mL,
20.9 mmol) was followed by stirring until total consumption
of the starting material (tlc, hexanes/EtOAc, 7/3, 6 h). For
the work up, pH was adjusted to 2 by addition of HCl (3 M)
and the organic layer was washed with a saturated aqueous
solution of NaHCO3. Then, pH of the aqueous layer was
adjusted to 2 and extracted with EtOAc. The combined
organic extracts were dried with Na2SO4, filtered, and the
solvent was evaporated under vacuum. The residue was
purified by column chromatography (hexanes/EtOAc, 75/
25) to afford carboxylic acid 6a as a colorless oil (69%).12
4.1.2. 2-Allyl-3-(3-methoxyphenyl)propionic acid (6b).
According to the general procedure carboxylic acid 6b was
obtained as a colorless oil from 5b in 98% yield after
purification by column chromatography (hexanes/EtOAc,
Figure 1. Proposed mechanisms for the transformation of amides 7 into
quinolinones 9, aza-spiro derivatives 12, and pyrrolidines 10a-d.
1
No simple explanation can be argued to justify these results.
If we consider an electronic control in the reaction, no
substantial differences can be estimated between the
methoxy and the para-mehoxyphenyl groups. For that
reason, we propose that steric effects may govern the course
of the reaction since both groups have a significant
difference in size volume. In fact, the notorious decrease
in the yield for the transformation of amide 7d into the
1,6,7,8-tetramethoxy substituted quinolinone 9d as a result
of a steric hindrance between methoxy groups in 1 and 8
positions, supports this suggestion.
70/30). H NMR: d 2.26–2.47 (m, 2H, CH2–CHvCH2),
2.74–2.85 (m, 2H, CHCO, CHaAr), 2.99 (dd, J¼15.8,
9.9 Hz, 1H, CHbAr), 3.80 (s, 3H, OCH3), 5.08–5.16 (m,
2H, CHvCH2), 5.72–5.88 (m, 1H, CHvCH2), 6.77–6.81
(m, 3H, Harom), 7.22 (t, J¼7.9 Hz, 1H, Harom), 11.1 (sa, 1H,
COOH). 13C NMR: d 35.5, 37.2 (CH2), 46.9 (CH), 55.0
(OCH3), 117.5 (CHvCH2), 111.8, 114.6, 121.2, 129.4,
134.6 (t-Carom, CHvCH2), 140.3, 159.5 (q-Carom), 181.3
(CO). IR (film): 2900–3200 (OH), 1707 (CO). MS (EI) m/z
(%): 220 (Mþ, 24), 122 (100), 121 (58). HRMS calculated
for C13H16O3 220.1099, found 220.1085.

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S. Serna et al. / Tetrahedron 60 (2004) 6533–6539
4.1.3. 2-Allyl-3-(3,4-dimethoxyphenyl)propionic acid
(6c). According to the general procedure carboxylic acid
6c was obtained as a white solid from 5c in 74% yield after
purification by column chromatography (hexanes/EtOAc,
55/45) followed by crystallization from n-pentane. Mp:
64–65 8C (n-pentane). Lit.13 65–67 8C (benzene–hexane).
5.83 (m, 1H, CHvCH2), 6.71–6.77 (m, 3H, Harom), 7.17 (t,
J¼7.9 Hz, 1H, Harom), 8.29 (s, 1H, NH). 13C NMR: d 36.3,
38.3 (CH2), 46.2 (CH), 55.1, 64.2 (OCH3), 117.4
(CH2vCH), 111.7, 114.6. 121.3, 129.4, 134.9 (t-Carom
,
CHvCH2), 140.7, 159.6 (q-Carom), 171.9 (CO). IR (film):
3177 (NH), 1648 (CO). MS (El) m/z (%): 249 (Mþ, 3), 203
(12), 121 (100). HRMS calculated for C14H19NO3
249.1365, found 249.1375.
4.1.4. 2-Allyl-3-(3,4,5-trimethoxyphenyl)propionic acid
(6d). According to the general procedure carboxylic acid 6d
was obtained as a white solid from 5d in 68% yield after
purification by column chromatography (hexanes/EtOAc,
40/60) followed by crystallization from hexanes. Mp: 85–
4.2.3. 2-Allyl-3-(3,4-dimethoxyphenyl)-N-methoxy-pro-
pionamide (7c). According to the general procedure
amide 7c was obtained as a colorless oil from 6c in 73%
yield after purification by column chromatography
(hexanes/EtOAc, 45/55) followed by crystallization from
1
87 8C (hexanes). Lit.14 87–89 8C. H NMR: d 2.24–2.44
(m, 2H, CH2–CHvCH2), 2.66–2.81 (m, 2H, CHCO,
CHaAr), 2.91 (dd, J¼10.3, 5.6 Hz, 1H, CHbAr), 3.80 (s,
9H, 3£OCH3), 5.06–5.13 (m, 2H, CHvCH2), 5.69–5.86
(m, 1H, CHvCH2), 6.39 (s, 2H, Harom). 13C NMR: d 35.6,
37.6 (CH2), 46.9 (CH), 55.9, 60.7 (OCH3), 117.5
(CHvCH2), 105.7, 134.6 (t-Carom, CHvCH2), 134.4,
136.4, 153.0 (q-Carom), 180.8 (CO). IR (KBr): 3000–3300
(OH), 1707 (CO). MS (El) m/z (%): 280 (Mþ, 30), 182 (71),
181 (100). HRMS calculated for C15H20O5 280.1311, found
280.1302.
1
n-pentane. Mp: 60–62 8C (n-pentane). H NMR: d 2.14–
2.31 (m, 2H, CHa–CHvCH2, CHCO), 2.35–2.52 (m, 1H,
CHb–CHvCH2), 2.70 (dd, J¼13.5, 5.1 Hz, 1H, CHaAr),
2.87 (dd, J¼13.5, 9.9 Hz, 1H, CHbAr), 3.57 (s, 3H,
NHOCH3), 3.83 (s, 3H, OCH3), 3.84 (s, 3H, OCH3),
5.04–5.14 (m, 2H, CHvCH2,), 5.67–5.83 (m, 1H,
CHvCH2), 6.68–6.78 (m, 3H, Harom), 7.92 (s, 1H, NH).
13C NMR: d 36.3, 37.8 (CH2), 46.2 (CH), 55.7, 64.2
(OCH3), 117.2 (CH2vCH), 111.0, 112.1. 120.8, 134.9
(t-Carom, CHvCH2), 131.7, 147.4, 148.6 (q-Carom), 172.0
(CO). IR (KBr): 3178 (NH), 1654 (CO). MS (El) m/z (%):
279 (Mþ, 12), 151 (100). HRMS calculated for C14H19NO3
279.1471, found 279.1476.
4.2. General procedure for the synthesis of N-methoxy-
amides 7a-d
4.2.1. Synthesis of 2-allyl-N-methoxy-3-phenylpropion-
amide (7a). Et3N (0.3 mL, 2.1 mmol) was added dropwise
onto a solution of carboxylic acid 6a (200 mg, 1.05 mmol)
and NH2OMe·HCl (91 mg, 1.1 mmol) in MeCN (14 mL) as
solvent. After stirring the mixture at room temperature for
30 min, TBTU (351 mg, 1.1 mmol) was added and the
stirring was continued during 60 min. For the work-up, a
saturated solution of NaCl (10 mL) was added and the
solution was extracted with EtOAc (3£15 mL). The
combined organic extracts were washed with HC1 5% aq.
(15 mL), water (15 mL), 5% aq. NaHCO3 (15 mL) and
water again (15 mL). The organic layer was dried with
Na2SO4, filtered, and the solvent was evaporated under
vacuum. The residue was purified by column chromato-
graphy (hexanes/EtOAc, 45/55) to afford amide 7a as a
4.2.4. 2-Allyl-N-methoxy-3-(3,4,5-trimethoxyphenyl)-
propionamide (7d). According to the general procedure
amide 7d was obtained as a colorless oil from 6d in 92%
yield after purification by column chromatography
1
(hexanes/EtOAc, 40/60). H NMR: d 2.16–2.26 (m, 2H,
CHa–CHvCH2, CHCO), 2.35–2.47 (m, 1H, CHb–
CHvCH2,), 2.64 (dd, J¼13.6, 4.7 Hz, 1H, CHaAr), 2.84
(dd, J¼13.6, 9.3 Hz, 1H, CHbAr), 3.53 (s, 3H, NHOCH3),
3.74 (s, 3H, OCH3), 3.76 (s, 6H, 2£OCH3), 4.99–5.09 (m,
2H, CHvCH2), 5.63–5.79 (m, 1H, CHvCH2), 6.34 (s, 2H,
Harom), 8.77 (s, 1H, NH). 13C NMR: d 36.5, 38.5 (CH2), 46.0
(CH), 55.9, 60.6, 64.0 (OCH3), 117.3 (CH2vCH), 105.7,
134.9 (t-Carom, CHvCH2), 135.0, 136.2, 152.9 (q-Carom),
171.9 (CO). IR (film): 3176 (NH), 1654 (CO). MS (El) m/z
(%): 309 (Mþ, 15), 181 (100). HRMS calculated for
C16H23NO5 309.1576, found 309.1575.
1
colorless oil (86%). H NMR: d 2.20–2.30 (m, 1H, CHa–
CHvCH2), 2.37–2.47 (m, 2H, CHb–CHvCH2, CHCO),
2.75 (dd, J¼13.5, 5.1 Hz, 1H, CHaPh), 2.92 (dd, J¼13.5,
8.3 Hz, 1H, CHbPh), 3.48 (s, 3H, OCH3), 5.00–5.12 (m,
2H, CHvCH2), 5.68–5.84 (m, 1H, CHvCH2), 7.15–7.27
(m, 5H, Harom), 9.80 (s, 1H, NH). 13C NMR: d 36.2, 38.0
(CH2), 45.1 (CH), 63.6 (OCH3), 116.9 (CHvCH2), 126.1,
128.1, 128.9, 135.0 (t-Carom, CHvCH2), 139.1 (q-Carom),
171.7 (CO). IR (film): 3166 (NH), 1655 (CO). MS (El) m/z
(%): 219 (Mþ, 2), 178 (21), 91 (100). HRMS calculated for
C13H17NO2 219.1259, found 219.1254.
4.3. General procedure for the synthesis of N-para-
methoxyphenylamides 8a-d
4.3.1. Synthesis of 2-allyl-N-(para-methoxyphenyl)-3-
phenylpropionamide (8a). A solution of carboxylic acid
6a (300 mg, 1.6 mmol) in CH2Cl2 (2 mL) and a solution of
p-anisidine (291 mg, 2.4 mmol) in CH2Cl2 (2 mL) were
added sequentially to a cold (0 8C) solution of EDC·HCl
(454 mg, 2.4 mmol) and HOBt (299 mg, 2.2 mmol) in the
same solvent (4 mL). Then, Et3N, (0.3 mL, 2.4 mmol) was
added dropwise and the mixture was stirred at the same
temperature for 2 h and at rt until total consumption of the
starting material (tlc, 14 h). For the work-up the mixture was
diluted with water (15 mL) and extracted with CH2Cl2
(3£20 mL). The combined organic extracts were washed
with HC1 5% aq. (2£15 mL) and with a saturated solution
of NaHCO3 (2£15 mL), dried over Na2S04, filtered, and the
solvent was evaporated under vacuum. The residue was
4.2.2. 2-Allyl-N-methoxy-3-(3-methoxyphenyl)-pro-
pionamide (7b). According to the general procedure
amide 7b was obtained as a colorless oil from 6b in 71%
yield after purification by column chromatography
1
(hexanes/EtOAc, 50/50). H NMR: d 2.21–2.30 (m, 2H,
CHa–CHvCH2, CHCO), 2.39–2.51 (m, 1H, CHb–
CHvCH2), 2.73 (dd, J¼13.3, 4.9 Hz, 1H, CHaAr), 2.89
(dd, J¼13.3, 9.1 Hz, 1H, CHbAr), 3.54 (s, 3H, NHOCH3),
3.76 (s, 3H, OCH3), 5.02–5.13 (m, 2H, CHvCH2,), 5.66–

S. Serna et al. / Tetrahedron 60 (2004) 6533–6539
6537
purified by crystallization from Et2O to afford amide 8a as a
1
white solid (92%). Mp: 109–110 8C (Et2O). H NMR: d
2H, Harom). 13C NMR: d 36.8, 39.1 (CH2), 50.6 (CH), 55.3,
55.8, 60.7 (OCH3), 117.2 (CHvCH2), 105.7, 113.8, 121.8,
135.4 (t-Carom, CHvCH2), 130.6, 136.2, 153.03, 156.3
(q-Carom), 172.5 (CO). IR (KBr): 3307 (NH), 1660 (CO).
MS (El) m/z (%): 385 (Mþ 33), 344 (12), 221 (76), 204 (47),
181 (99), 123 (100), 108 (19). HRMS calculated for
C22H27NO5 385.1889, found 385.1893.
2.24–2.34 (m, 1H, CHa–CHvCH2), 2.46–2.66 (m, 2H,
CHb–CHvCH2, CHCO), 2.81 (dd, J¼13.5, 5.1 Hz, 1H,
CHaPh), 2.99 (dd, J¼13.5, 8.7 Hz, 1H, CHbPh), 3.72 (s, 3H,
OCH3), 5.05–5.16 (m, 2H, CHvCH2), 5.75–5.91 (m, 1H,
CHvCH2), 6.73 (d, J¼8.7 Hz, 2H, Harom), 7.17–7.28 (m,
7H, Harom), 7.64 (s, 1H, NH). 13C NMR: d 36.6, 38.5 (CH2),
49.8 (CH), 55.2 (OCH3), 117.0 (CH2vCH), 113.7, 122.3,
126.2, 128.3, 128.8, 135.3 (t-Carom, CHvCH2), 130.5,
139.4, 156.2, (q-Carom), 172.7 (CO). IR (KBr): 3295 (NH),
1654 (CO). MS (El) m/z (%): 295 (Mþ, 32), 254 (27), 123
(100), 108 (21). HRMS calculated for C19H21NO2
295.1572, found 295.1582.
4.4. General procedure for the cyclization of amides
7a–d with PIFA
4.4.1. Synthesis of 3-allyl-1-methoxyquinolin-2-one (9a).
A solution of PIFA (147 mg, 0.34 mmol) in CF3CH2OH
(10 mL) was added onto a cold (220 8C) solution of amide
7a (50 mg, 0.23 mmol) in 10 mL of the same solvent. The
mixture was stirred at the same temperature until total
consumption of the starting material (tlc, 60 min). The
reaction was quenched with 10 mL of Na2CO3 (aq. 10%)
and extracted with CH2Cl2 (3£15 mL). The combined
organic extracts were washed with a saturated solution of
NaCl (15 mL), dried over Na2SO4, filtered, and the solvent
was removed under vacuum. The residue was purified by
column chromatography (hexanes/EtOAc, 75/25) to afford
quinolinone 9a as a colorless oil which was crystallized
from n-pentane (75%). Mp: 63–65 8C (n-pentane). 1H
NMR: d 2.15–2.27 (m, 1H, CHa–CHvCH2), 2.62–2.77
(m, 3H, CHb–CHvCH2, H-3, H-4a), 2.94 (dd, J¼19.8,
9.91 Hz, 1H, H-4b), 3.9 (s, 3H, OCH3), 5.04–5.12 (m, 2H,
CHvCH2), 5.72–5.88 (m, 1H, CHvCH2), 7.03 (t,
J¼7.1 Hz, 1H, Harom), 7.14–7.31 (m, 3H, Harom). 13C
NMR: d 29.4, 33.9 (CH3), 40.3 (CH), 62.4 (OCH3), 117.7
4.3.2. 2-Allyl-3-(3-methoxyphenyl)-N-(para-methoxy-
phenyl)propionamide (8b). According to the general
procedure amide 8b was obtained as a white solid from
6b in 80% yield after crystallization from Et2O. Mp:
1
78–79 8C (Et2O). H NMR: d 2.27–2.36 (m, 1H, CHa–
CHvCH2), 2.39–2.61 (m, 2H, CHb–CHvCH2, CHCO),
2.81 (dd, J¼13.5, 5.1 Hz, 1H, CHaAr), 2.97 (dd, J¼13.5.
8.7 Hz, 1H, CHbAr), 3.72 (s, 3H, OCH3), 3.76 (s, 3H,
OCH3), 5.06–5.18 (m, 2H, CHvCH2), 5.76–5.92 (m, 1H,
CHvCH2), 6.73–6.81 (m, 5H, Harom), 7.15–7.22 (m, 4H,
Harom, NH). 13C NMR: d 36.7, 38.6 (CH2), 50.2 (CH), 54.9,
55.3 (OCH3), 117.2 (CH2vCH), 111.8, 113.8. 114.3, 121.2,
122.1, 129.4, 135.4 (t-Carom, CHvCH2), 130.5, 141.1,
156.3, 159.6 (q-Carom), 172.5 (CO). IR (KBr): 3283 (NH),
1649 (CO). MS (El) m/z. (%): 325 (Mþ, 21), 284 (24), 123
(100), 121 (52), 108 (21). HRMS calculated for C20H23NO3
325.1678, found 325.1694.
(CHvCH2), 112.0, 123.5, 127.6, 128.0, 134.9 (t-Carom
,
CHvCH2), 123.3, 137.4 (q-Carom), 167.3 (CO). IR (KBr):
1684 (CO). MS (El) m/z (%): 217 (Mþ, 100), 186 (52), 146
(67), 117 (76). HRMS calculated for C13H15NO2 217.1103,
found 217.1092.
4.3.3. 2-Allyl-3-(3,4-dimethoxyphenyl)-N-(para-
methoxyphenyl)propionamide (8c). According to the
general procedure amide 8c was obtained as a white solid
from 6c in 81% yield after crystallization from Et2O. Mp:
123–124 8C (Et2O). 1H NMR: d 2.25–2.33 (m, 1H, CHa–
CHvCH2), 2.39–2.58 (m, 2H, CHb–CHvCH2, CHCO),
2.74 (dd, J¼13.5, 4.3 Hz, 1H, CHaAr), 2.93 (dd, J¼13.5,
8.7 Hz, 1H, CHbAr), 3.71 (s, 3H, OCH3), 3.73 (s, 3H,
OCH3), 3.80 (s, 3H, OCH3), 5.03–5.15 (m, 2H, CHvCH2),
5.73–5.89 (m, 1H, CHvCH2), 6.68–6.77 (m, 5H, Harom),
7.11 (sa, 1H, NH), 7.22 (d, J¼8.7 Hz, 2H, Harom). 13C NMR:
d 36.7, 38.1 (CH2), 50.2 (CH), 55.1, 55.4, 55.6 (OCH3),
116.9 (CH2vCH), 111.0, 112.0, 113.7, 120.7, 121.9, 135.4
(t-Carom, CH2vCH), 130.6, 132.0, 147.2, 148.1, 156.1
(q-Carom), 172.7 (CO). IR (KBr): 3319 (NH), 1654 (CO).
MS (El) m/z (%): 355 (Mþ, 44), 314 (63) 191 (68), 151
(100), 123 (89), 108 (26). HRMS calculated for C21H25NO4
355.1784, found 355.1770.
4.4.2. 3-Allyl-l,6-dimethoxyquinolin-2-one (9b). Accord-
ing to the general procedure quinolinone 9b was obtained as
a colorless oil from 7b in 65% yield after purification by
column chromatography (hexanes/EtOAc, 80/20) which
was triturated with n-pentane. Mp: 40–41 8C (n-pentane).
1H NMR: d 2.13–2.26 (m, 1H, CHa–CHvCH2), 2.58–
2.73 (m, 3H, CHb–CHvCH2, H-3, H-4a), 2.91 (dd,
J¼19.8, 9.91 Hz, 1H, H-4b), 3.79 (s, 3H, OCH3), 3.89 (s,
3H, OCH3), 5.03–5.11 (m, 2H, CHvCH2), 5.71–5.89 (m,
1H, CHvCH2), 6.72 (d, J¼2.8 Hz, 1H, Harom), 6.80 (dd,
J¼8.9, 2.8 Hz, 1H, Harom), 7.11 (d, J¼8.9 Hz, 1H, Harom).
13C NMR: d 29.7, 33.8 (CH2), 40.3 (CH), 55.4, 62.3
(OCH3), 117.7 (CHvCH2), 112.1, 113.2, 114.2, 134.9
(t-Carom, CHvCH2), 124.8, 130.9, 155.9 (q-Carom), 166.6
(CO). IR (KBr): 1678 (CO). MS (El) m/z (%): 247 (Mþ, 96),
217 (55), 188 (25), 175 (88), 162 (100). HRMS calculated
for C14H17NO3 247.1208, found 247.1204.
4.3.4. 2-Allyl-N-(para-methoxyphenyl)-3-(3,4,5-tri-
methoxyphenyl)propionamide (8d). According to the
general procedure amide 8d was obtained as a white solid
from 6d in 80% yield after crystallization from Et2O. Mp:
120–121 8C (Et2O). 1H NMR: d 2.24–2.33 (m, 1H, CHa–
CHvCH2), 2.38–2.59 (m, 2H, CHb–CHvCH2, CHCO),
2.72 (dd, J¼13.3, 4.4 Hz, 1H, CHaAr), 2.92 (dd, J¼13.3,
9.3 Hz, 1H, CHbAr), 3.69 (s, 6H, 2£OCH3), 3.73 (s, 3H,
OCH3), 3.77 (s, 3H, OCH3), 5.03–5.16 (m, 2H, CHvCH2),
5.73–5.89 (m, 1H, CHvCH2), 6.37 (s, 2H, Harom), 6.76 (d,
J¼8.9 Hz, 2H, Harom) 7.07 (sa, 1H, NH), 7.22 (d, J¼8.9 Hz,
4.4.3.
3-Allyl-l,6,7-trimethoxyquinolin-2-one
(9c).
According to the general procedure quinolinone 9c was
obtained as a colorless oil from 7c in 66% yield after
purification by column chromatography (hexanes/EtOAc,
1
60/40). H NMR: d 2.11–2.24 (m, 1H, CHa–CHvCH2),
2.56–2.67 (m, 3H, CHb–CHvCH2, H-3, H-4a), 2.86 (dd,
J¼20.1, 10.3 Hz, 1H, H-4b), 3.84 (s, 3H, OCH3), 3.89 (s,
6H, 2£OCH3), 5.02–5.09 (m, 2H, CHvCH2), 5.70–5.89

6538
S. Serna et al. / Tetrahedron 60 (2004) 6533–6539
(m, 1H, CHvCH2), 6.67 (s, 1H, Harom), 6.78 (s, 1H, Harom).
13C NMR: d 29.1, 33.8 (CH2), 40.6 (CH), 56.2, 56.3, 62.4
(OCH3), 117.6 (CHvCH2), 97.6, 111.8, 135.0 (t-Carom,
CHvCH2), 114.6, 130.9, 145.0, 148.4 (q-Carom), 166.8
(CO). IR (film): 1678 (CO). MS (El) m/z (%): 277 (Mþ, 39),
247 (100), 232 (40), 205 (81), 192 (39), 162 (20). HRMS
calculated for C15H19NO4 277.1314, found 277.1310.
129.1 (t-Carom), 139.9, 140.0 (q-Carom), 141.5, 142.0 (q-
Carom), 152.7–153.2 (q-Carom). IR (film): 3000–3400 (OH),
1508 (CvC). MS (El) m/z (%): 315 (Mþþ18, 20), 136
(100). HRMS calculated for C19H23NO2 297.1729, found
297.1727.
4.5.2. 2-Hydroxymethyl-l-(para-methoxyphenyl)-4-(3-
methoxyphenyl)pyrrolidine (11b). According to the
general procedure pyrrolidine 11b was obtained as a
colorless oil from 8b in 68% yield after purification by
column chromatography (hexanes/EtOAc, 20/80). Mixture
4.4.4. 3-Allyl-l,6,7,8-tetramethoxyquinolin-2-one (9d).
According to the general procedure quinolinone 9d was
obtained as a white solid from 7d in 41% yield after
purification by column chromatography (hexanes/EtOAc,
50/50) and then by crystallization from n-pentane. Mp:
59–61 8C (n-pentane). 1H NMR: d 2.11–2.23 (m, 1H,
CHa–CHvCH2), 2.59–2.72 (m, 3H, CHb–CHvCH2,
H-3, H-4a), 2.82 (dd, J¼20.2, 10.5 Hz, 1H, H-4b), 3.83 (s,
3H, OCH3), 3.87 (s, 3H, OCH3), 3.90 (s, 3H, OCH3), 3.98 (s,
3H, OCH3), 5.04–5.10 (m, 2H, CHvCH2), 5.74–5.90 (m,
1H, CHvCH2), 6.45 (s, 1H, Harom). 13C NMR: d 31.3, 33.3
(CH2), 41.6 (CH), 56.1, 60.9, 61.4, 62.9 (OCH3), 117.4
(CHvCH2), 106.6, 135.3 (t-Carom, CHvCH2), 122.9,
126.0, 142.6, 144.4 150.3 (q-Carom), 168.7 (CO). IR
(KBr): 1684 (CO). MS (El) m/z (%): 307 (Mþ, 75), 276
(100), 222 (93), 206 (56). HRMS calculated for C16H21NO5
307.1420, found 307.1412.
1
of diastereoisomers 1.8/1. H NMR: d 1.40–1.66 (m, 4H,
2£H-3a, 2£H-3b), 2.04–2.14 (m, 1H, H-4 min.), 2.16–2.29
(m, 1H, H-4 maj.), 2.55–2.74 (m, 4H, 2£CH2Ph), 2.89–
3.15 (m, 4H. 2£H-5a, 2£H-5b), 3.21 (sa, 2H, 2£OH,
exchange with D2O), 3.35–3.42 (m, 2H, 2£CHaOH), 3.52–
3.58 (m, 2H, 2£CHbOH), 3.73 (s, 6H, 2£OCH3), 3.76–3.92
(m, 8H, 2£H-2, 2£OCH3), 6.56 (d, J¼9.1 Hz, 2H, Harom
maj.), 6.61 (d, J¼9.1 Hz, 2H, Harom min.), 6.72–6.77 (m,
10H, Harom), 7.20 (m, 2H, Harom). 13C NMR: d 35.9, 37.8
(CH2), 36.3, 38.6 (C-4), 39.8, 40.4 (CH2), 48.8, 50.4 (CH2),
55.1, 55.7 (OCH3), 67.0, 67.1 (CH2OH), 69.3, 70.9 (C-2),
111.3, 111.4 (t-Carom), 114.8, 114.9 (t-Carom), 115.0, 115.1
(t-Carom), 115.8 (t-Carom), 121.5 (t-Carom), 129.4 (t-Carom),
141.6, 142.0 (q-Carom), 152.6 (q-Carom), 159.6 (q-Carom). IR
(film): 2900–3450 (OH), 1508 (CvC). MS (El) m/z (%):
345 (Mþþ18, 21), 136 (100). HRMS calculated for
C20H25NO3 327.1834, found 327.1837.
4.5. General procedure for the amidohydroxylation of
amides 7a-d with PIFA
4.5.1. Synthesis of 4-benzyl-2-hydroxymethyl-1-(para-
methoxyphenyl)pyrrolidine (11a). A solution of PIFA
(219 mg, 0.51 mmol) in 7 mL of CF3CH2OH was added
onto a cold (220 8C) solution of amide 8a (100 mg,
0.34 mmol) in 7 mL of the same solvent, and the mixture
was stirred until total consumption of the starting material
(tlc, 80 min). Then, 10 mL of Na2CO3 (aq. 10%) were added
and the aqueous phase was extracted with CH2Cl2
(3£15 mL). The combined organic extracts were washed
with a saturated solution of NaCl (15 mL), dried over
Na2SO4, filtered, and the solvent was removed under
vacuum. Without any further purification, the resulting
residue was dissolved in THF (4 mL), cooled to a 0 8C, and
BH3·SMe2 (1.7 mL, 2 M in THF, 3.4 mmol) was added
dropwise. The reaction mixture was stirred at room
temperature until total consumption of the starting material
(tlc, 10 h). Then, MeOH was added slowly and the stirring
was continued for 15 min. The solvent was removed under
vacuum, and treatment with MeOH was repeated twice
more. The final residue was purified by column chroma-
tography (hexanes/EtOAc, 30/70) to afford pyrrolidine 11a
as a colorless oil (72%). Mixture of diastereoisomers 1.8/1.
1H NMR: d 1.39–1.65 (m, 4H, 2£H-3a, 2£H-3b),
1.99–2.12 (m, 1H, H-4 min.), 2.17–2.27 (m, 1H, H-4
maj.), 2.58–2.76 (m, 4H, 2£CH2Ph), 2.86 (sa, 2H, 2£OH,
exchange with D2O), 2.89–3.14 (m, 4H, 2£H-5a, 2£H-5b),
3.33–3.41 (m, 2H, 2£CHaOH), 3.50–3.57 (m, 2H,
2£CHbOH), 3.73 (s, 6H, 2£OCH3), 3.82–3.91 (m, 2H,
2£H-2), 6.54 (d, J¼9.1 Hz, 2H, Harom maj.), 6.59 (d,
J¼9.1 Hz, 2H, Harom min.), 6.73–6.76 (m, 4H, Harom),
7.15–7.32 (m, 10H, Harom). 13C NMR: d 36.0, 37.9 (CH2),
36.5, 38.9 (C-4), 39.8, 40.6 (CH2), 48.9, 50.6 (CH2), 55.7
(OCH3), 67.0, 67.2 (CH2OH), 69.3, 70.9 (C-2), 114.7, 114.8
(t-Carom), 115.1, 115.9 (t-Carom), 126.21 (t-Carom), 128.4,
4.5.3. 4-(3,4-Dimethoxyphenyl)-2-hydroxymethyl-1-
(para-methoxyphenyl)pyrrolidine (11c). According to
the general procedure pyrrolidine 11c was obtained as a
colorless oil from 8c in 67% yield after purification by
column chromatography (EtOAc). Mixture of diastereo-
isomers 1.7/1. 1H NMR: d 1.36–1.61 (m, 4H, 2£H-3a, 2£H-
3b), 2.00–2.09 (m, 1H, H-4 min.), 2.12–2.25 (m, 1H, H-4
maj.), 2.47–2.69 (m, 4H, 2£CH2Ph), 2.84–3.09 (m, 4H,
2£H-5a, 2£H-5b), 3.14 (sa, 2H, 2£OH, exchange with
D2O), 3.32–3.39 (m, 2H, 2£CHaOH), 3.48–3.58 (m, 2H,
2£CHbOH), 3.65 (s, 6H, 2£OCH3), 3.71–3.83 (m, 14H,
2£H-2. 4£OCH3), 6.50–6.58 (m, 4H, Harom), 6.66–6.78
(m, 10H, Harom). 13C NMR: d 35.8, 37.5 (CH2), 36.3, 38.3
(C-4), 39.3, 39.7 (CH2), 48.5, 50.1 (CH2), 55.6, 55.7, 55.8
(OCH3), 67.0, 67.1 (CH2OH), 69.4, 70.8 (C-2), 111.0, 112.3
(t-Carom), 114.7, 114.9 (t-Carom), 155.5, (t-Carom), 120.9
(t-Carom), 132.4, 132.5 (q-Carom), 141.8, 142.1 (q-Carom),
147.2 (q-Carom), 148.7 (q-Carom), 152.4, 152.8 (q-Carom). IR
(film): 3000–3400 (OH), 1508 (CvC). MS (El) m/z (%):
375 (Mþþ18, 16), 136 (100). HRMS calculated for
C21H27NO4 357.1940, found 357.1939.
4.5.4. 2-Hydroxymethyl-1-(para-methoxyphenyl)-4-
(3,4,5-trimethoxyphenyl)pyrrolidine (11d). According to
the general procedure pyrrolidine 11d was obtained as a
colorless oil from 8d in 67% yield after purification by
column chromatography (EtOAc). Mixture of diastereo-
isomers 1.7/1. 1H NMR: d 1.39–1.68 (m, 4H, 2£H-3a,
2£H-3b), 2.02–2.14 (m, 1H, H-4 min.), 2.17–2.33 (m, 1H,
H-4 maj.), 2.49–2.71 (m, 4H, 2£CH2Ph), 2.89–3.14 (m,
4H, 2£H-5a, 2£H-5b), 2.71 (sa, 2H, 2£OH, exchange with
D2O), 3.33–3.44 (m, 2H, 2£CHaOH), 3.54–3.60 (m, 2H,
2£CHbOH), 3.72–3.82 (m, 30H, 2£H-2, 4£OCH3), 6.37 (s,
4H, Harom), 6.54 (d, J¼8.9 Hz, 2H, Harom maj.), 6.59 (d,

S. Serna et al. / Tetrahedron 60 (2004) 6533–6539
6539
J¼8.9 Hz, 2H, Harom min.), 6.72–6.76 (m, 4H, Harom). 13
C
Int. 1997, 29, 409–458. (g) Varvoglis, A. Tetrahedron 1997,
53, 1179–1255. (h) Wirth, T.; Hirt, U. H. Synthesis 1999,
1271–1287. (i) Ochiai, M. Chem. Hypervalent Compd. 1999,
359–387. (j) Koser, G. F. Aldrichim. Acta 2001, 34, 89–102.
(k) Zhdankin, V. V.; Stang, P. J. Chem. Rev. 2002, 102,
2523–2584.
NMR: d 36.1, 37.9 (CH2), 36.3, 38.6 (C-4), 40.3, 40.8
(CH2), 48.9, 50.6 (CH2), 55.7, 56.0, 60.8 (OCH3), 67.2, 67.2
(CH2OH), 69.3, 70.9 (C-2), 105.8, 105.9 (t-Carom), 114.8,
115.3 (t-Carom), 116.2, (t-Carom), 135.6, 135.7 (q-Carom),
141.1, 141.6 (q-Carom), 152.8 (q-Carom), 153.1 (q-Carom),
153.4 (q-Carom). IR (film): 3100–3400 (OH), 1508 (CvC).
MS (El) m/z (%): 405 (Mþþ18, 17), 136 (100). HRMS
calculated for C22H29NO5, 387.2046 found 387.2043.
´
2. (a) Moreno, I.; Tellitu, I.; SanMartin, R.; Badıa, D.; Carrillo,
´
L.; Domınguez, E. Tetrahedron Lett. 1999, 40, 5067–5070.
(b) Moreno, I.; Tellitu, I.; Etayo, J.; SanMartin, R.;
´
Domınguez, E. Tetrahedron 2001, 57, 5403–5411.
´
(c) Moreno, I.; Tellitu, I.; SanMartin, R.; Domınguez, E.
4.5.5. Synthesis of 3-allyl-1-aza-1,7,9-trimethoxy-
spiro[4.5]deca-6,9-dien-2,8-dione
(12d).
Typical
Synlett 2001, 1161–1163. (d) Moreno, I.; Tellitu, I.;
´
Domınguez, E.; SanMartin, R. Eur. J. Org. Chem. 2002,
procedure. TFA (0.03 mL, 0.45 mmol) was added onto a
cold (0 8C) solution of amide 7d (70 mg, 0.23 mmol) in
CH2C12 (2 mL) and then a solution of PIFA (146 mg,
0.34 mmol) in 3 mL of the same solvent was added slowly.
The reaction mixture was stirred at the same temperature
until total consumption of the starting material (tlc, 90 min).
The reaction was quenched with 10 mL of a 10% aqueous
solution of Na2CO3, and the aqueous layer was extracted
with CH2C12 (3£15 mL). The combined organic extracts
were dried over Na2SO4, filtered, and the solvent was
removed under vacuum. The residue was purified by column
chromatography (CH2C12/EtOAc, 20/80) to afford the spiro
derivative 12d as a yellowish oil which was crystallized
from n-pentane (93%). Mp: 72–74 8C. 1H NMR: d 2.00 (dd,
J¼12.7, 9.5 Hz, 1H, H-4a), 2.21–2.38 (m, 2H, H-4b,
CHaHbCHvCH2), 2.65–2.77 (m, 2H, CHaHbCHvCH2,
H-3), 3.67 (s, 3H, OCH3), 3.74 (s, 3H, OCH3), 3.79 (s, 3H,
OCH3), 5.11–5.18 (m, 2H, CHvCH2), 5.64 (s, 2H, H-6,
H-10), 5.68–5.84 (m, 1H, CHvCH2). 13C NMR: d 35.1,
35.8 (CH2), 36.7 (CH), 55.4, 55.5, 65.4 (OCH3), 118.1
(CHvCH2), 113.6, 115.9, 133.8 (CHvC, CHvCH2), 61.4,
151.3, 151.6 (q-C), 172.6, 175.8 (CO). IR (KBr): 1707
(CO), 1684 (CON), 1619 (CvC). MS (EI) m/z (%): 293
(Mþ, 99), 262 (48), 252 (100), 192 (74). HRMS calculated
for C15H19NO5, 293.1263 found 293.1263.
2126–2135. (e) A review about the applications of hyper-
valent iodine reagents in oxidative coupling reactions in:
Moreno, I.; Tellitu, I.; Herrero, M. T.; SanMartin, R.;
´
Domınguez, E. Curr. Org. Chem. 2002, 4, 1433–1452.
´ ´
3. (a) Herrero, M. T.; Tellitu, I.; Hernandez, S.; Domınguez, E.;
Moreno, I.; SanMartin, R. ARKIVOC 2002, v, 31–37.
´
´
(b) Herrero, M. T.; Tellitu, I.; Domınguez, E.; Hernandez,
S.; Moreno, I.; SanMartin, R. Tetrahedron 2002, 58,
8581–8589.
´
4. (a) Herrero, M. T.; Tellitu, I.; Domınguez, E.; Moreno, I.;
SanMartin, R. Tetrahedron Lett. 2002, 43, 8273–8275.
´
(b) Herrero, M. T.; Correa, A.; Tellitu, I.; Domınguez, E.;
Moreno, I.; SanMartin, R. Tetrahedron 2003, 43, 7103–7110.
´
5. Serna, S.; Tellitu, I.; Domınguez, E.; Moreno, I.; SanMartin,
R. Tetrahedron Lett. 2003, 44, 3483–3486.
6. A related hydroamination process mediated by the I(V)
reagent IBX has been also described. See: Nicolaou, K. C.;
Baran, P. S.; Zhong, Y.-L.; Barluenga, S.; Hunt, K. W.;
Kranich, R.; Vega, J. A. J. Am. Chem. Soc. 2002, 124,
2233–2244, and references cited therein.
7. (a) Kikugawa, Y.; Kawase, M. Chem. Lett. 1990, 581–582.
(b) Romero, A. G.; Darlington, W. H.; Jacobsen, E. J.;
Mickelson, J. W. Tetrahedron Lett. 1996, 37, 2361–2364.
(c) Romero, A. G.; Darlington, W. H.; McMillan, M. W.
J. Org. Chem. 1997, 62, 6582–6587. (d) Chang, C.-Y.; Yang,
T.-K. Tetrahedron: Asymmetry 2003, 14, 2081–2085.
Acknowledgements
¨
8. (a) Koning, W.; Geiger, R. Chem. Ber. 1970, 103, 788–798.
´
(b) Chinchilla, R.; Dodsworth, D. J.; Najera, C.; Soriano, J. M.
Financial support from the University of the Basque
Country (9/UPV 41.310-13656/2001) and the Spanish
Ministry of Science and Technology (MCYT BQU 2001-
0313) is gratefully acknowledged. S. S. thanks the Basque
Government for a predoctoral scholarship.
Tetrahedron Lett. 2000, 41, 2463–2466.
9. Sukekatsu, N. Chem Lett. 1997, 1–2.
10. Michael, J. P. Nat. Prod. Rep. 2002, 19, 742–760, and
preceding articles in this series.
11. (a) Wardrop, D. J.; Basak, A. Org. Lett. 2001, 3, 1053–1065.
(b) Wardrop, D. J.; Zhang, W. Org. Lett. 2001, 3, 2353–2356.
(c) Wardrop, D. J.; Burge, M. S.; Zhang, W.; Ortiz, J. A.
Tetrahedron Lett. 2003, 44, 2587–2591. (d) Wardrop, D. J.;
Landrie, C. L.; Ortiz, J. A. Synlett 2003, 1352–1354.
12. Kim, D.; Li, Z.-H.; Lee, S. S.; Park, J.; Chung, S. J. Bioorg.
Med. Chem. 1998, 6, 239–249.
References and notes
1. For general reviews on polyvalent iodine compounds, see:
(a) Varvoglis, A. Chem. Soc. Rev. 1981, 10, 377–407.
(b) Moriarty, R. M.; Vaid, R. K. Synthesis 1990, 431–447.
(c) Varvoglis, A. The Organic Chemistry of Polycoordinated
Iodine; VCH: New York, 1992. (d) Stang, P. J.; Zhdankin,
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