Amantini et al.
never been used as 2π components, although they are a
promising starting material for the synthesis of func-
tionalized R-amino acids. Some examples involving 3-
and (b) the results of our recent work6e where [4 + 2]
cycloadducts coming from the reaction of 3-nitrocou-
marins with vinyl ethers were converted in water into
chromanols and tetrahydrofuro- and tetrahydropyrano-
chromenes, we hypothesized that 3-nitrocoumarins could
be converted, in an aqueous medium, into benzofurans.
If this transformation is preceded by their Diels-Alder
reaction with 1,3-dienes, dihydrodibenzo[b,d]furans could
be prepared starting from 3-nitrocoumarins by carrying
out the following reaction sequence in water: Diels-
Alder/hydrolysis/decarboxylation/Nef/cyclodehydration.
7
a-d
substituted coumarins such as 3-alkoxycarbonyl,
3-
carbonyl,7d 3-vinyl, and 3-cyano derivatives have been
7e
7b,f
reported.
R-Nitroalkenes are attractive building blocks because
they can be used as 4π or 2π components in [4 + 2] cyclo-
additions6
e,8,9
and as Michael acceptors and the nitro
10
functionality can be easily converted to an amino or a
carbonyl group.11 While the use of R-nitroalkenes as 4π
8
components has been widely investigated, their behavior
Considering that the synthesis in water of 3-nitrocou-
9
5a,6e
as 2π components has only been sporadically studied.
marins was developed in this laboratory
via one-pot
Recent papers from this laboratory6 have described
the use of R-nitroalkenes as 4π components in [4 + 2]
cycloadditions in water. The reactions occurred in a
fast and highly endo-selective way in heterogeneous
phase under mild conditions without the use of catalysts.
c,e
consecutive Knoevenagel-Pinner reactions between o-
hydroxybenzaldehydes and nitroacetonitrile, dihydrod-
ibenzo[b,d]furans can be prepared by a sequence of
reactions carried out in water starting from suitably
functionalized salycilaldehydes.
(
E)-2-Aryl-1-cyano-1-nitroethenes gave highly asym-
Here we report the use of 3-nitrocoumarins as 2π
components in [4 + 2] cycloadditions with 1,3-dienes
carried out in water, under solventless conditions, and
in organic solvent for comparison to give nitrotetrahy-
drobenzo[c]chromenones and their conversion to dihy-
drodibenzo[b,d]furans in water. These latter compounds
are practically unknown in the literature. To our knowl-
edge, only two examples in the course of a cathodic
6
c
metric cycloadditions, and 3-nitrocoumarins allowed
chromene derivatives to be prepared by a one-pot pro-
cedure.6
On the basis of (a) the possibility that a δ-nitro alcohol
could be converted into a dihydrofuran derivative via one-
pot Nef-cyclodehydration reactions carried out in water
e
1
2
(6) (a) Fringuelli, F.; Germani, R.; Pizzo, F.; Santinelli, F.; Savelli,
electroreduction of dibenzofurans have been reported.
G. J . Org. Chem. 1992, 57, 1198-1202. (b) Ye, D.; Fringuelli, F.;
Piermatti, O.; Pizzo, F. J . Org. Chem. 1997, 62, 3748-3750. (c)
Fringuelli, F.; Matteucci, M.; Piermatti, O.; Pizzo, F.; Burla, M. C. J .
Org. Chem. 2001, 66, 4661-4666. (d) Attanasi, O. A.; De Crescentini,
L.; Filippone, P.; Fringuelli, F.; Mantellini, F.; Matteucci, M.; Piermatti,
O.; Pizzo, F. Helv. Chim. Acta 2001, 84, 513-525. (e) Amantini, D.;
Fringuelli, F.; Pizzo, F. J . Org. Chem. 2002, 67, 7238-7243.
Resu lts a n d Discu ssion
3-Nitrocoumarin (1a ) was used to study its conversion
into benzofuran. NaBH reduction of 1a in water at room
4
(7) (a) Ohkata, K.; Miyamoto, K.; Matsumura, S.; Akiba, K. Tetra-
temperature gave 3-nitrochroman-2-one (2) very quickly
with a 75% yield, which, under strong basic conditions
hedron Lett. 1993, 34, 6575-6578. (b) Taylor, E. C.; Strojny, E. J . J .
Am. Chem. Soc. 1960, 82, 5198-5202. (c) Bennabi, S.; Narkunan, K.;
Rousset, L.; Bouchu, D.; Ciufolini, M. A. Tetrahedron Lett. 2000, 41,
(NaOH 3 M), hydrolyzed and decarboxylated affording
8
873-8876. (d) Yamashita, M.; Okuyama, K.; Kawasaki, I.; Ohta, S.
nitrophenol 3 (Scheme 1). This product was then isolated
in 98% yield by acidifying the alkaline reaction mixture.
Quickly pouring the sodium salt of 3 into an ice-cooled
Tetrahedron Lett. 1995, 36, 5603-5606. (e) Minami, T.; Matsumoto,
Y.; Nakamura, S.; Koyanagi, S.; Yamaguchi, M. J . Org. Chem. 1992,
5
7, 167-173. (f) ApSimon, J . W.; Holmes, A. M.; J ohnson, I. Can J .
Chem. 1982, 60, 308-316.
8) For recent references on the use of R-nitroalkenes as 4π
components, see: (a) Denmark, S. E.; Thorarensen, A. Chem. Rev.
996, 96, 137-166. (b) Uittenbogaard, R. M.; Seerden, J .-P. G.;
4
2 4
.6 M H SO aqueous solution (Nef conditions) allowed
(
the isolation of the 1-benzofuran (4) in 68% yield.
1
The behavior of 3-nitrocoumarins 1a -c, 5, and 6 as
2π components in the Diels-Alder reactions with 1,3-
butadienes 7-11 and cyclopentadiene (12) (Scheme 1)
was then investigated in water, under solventless condi-
tions, and in organic solvent.
Scheeren, H. W. Tetrahedron 1997, 53, 11929-11936. (c) Avalos, M.;
Babiano, R.; Cintas, P.; Higes, F. J .; J im e´ nez, J . L.; Palacios, J . C.;
Silva, M. A. J . Org. Chem. 1999, 64, 1494-1502. (d) Kuster, G. J .;
Kalmoua, F.; de Gelder, R.; Scheeren, H. W. Chem. Commun. 1999,
8
2
4
2
55-856. (e) Denmark, S. E.; Herbert, B. J . Org. Chem. 2000, 65,
887-2896. (f) Denmark, S. E.; Cottel, J . J . J . Org. Chem. 2001, 66,
276-4284. (g) Denmark, S. E.; Gomez, L. Org. Lett. 2001, 3, 2907-
910.
In water, the cycloadditions of 1a with 7-9 occurred
under heterogeneous conditions and were faster (90 °C,
(
9) For recent references on the use of R-nitroalkenes as 2π
components, see: (a) J ung, M. E.; Grove, D. D. Chem. Commun. 1987,
53-755. (b) Ono, N.; Miyake, H.; Kamimura, A.; Kaji, A. J . Chem.
3
h) than when carried out in a homogeneous toluene
7
solution (90 °C, 21-30 h) (Table 1, entries 1-6). With
cyclopentadiene (12), the Diels-Alder reaction occurred
at a lower temperature but the reactivity was the same
in both aqueous and organic media (Table 1, entries 14,
15). High yields were always observed. The presence of
the nitro group strongly increased the dienophilicity of
the double bond of the coumarin moiety. Coumarin failed
to react with 1,3-butadiene and isoprene (8) but reacted
with 2,3-dimethyl-1,3-butadiene (9) under severe condi-
tions with a low yield (260 °C, 40 h, 22%).13
Soc., Perkin Trans. 1 1987, 1929-1935. (c) Fuji, K.; Tanaka, K.; Abe,
H.; Itoh, A.; Node, M.; Taga, T.; Miwa, Y.; Shiro, M. Tetrahedron:
Asymmetry 1991, 2, 1319-1327. (d) Serrano, J . A.; Caceres, L. E.;
Rom a´ n, E. J . Chem. Soc., Perkin Trans. 1 1995, 1863-1871. (e) Node,
M.; Nishide, K.; Imazato, H.; Kurosaki, R.; Inoue, T.; Ikariya, T. Chem.
Commun. 1996, 2559-2560. (f) Barluenga, J .; Aznar, F.; Ribas, C.;
Vald e´ s, C. J . Org. Chem. 1997, 62, 6746-6753.
(
10) (a) Barrett, A. G. M.; Graboski, G. G. Chem. Rev. 1986, 86, 751-
62. (b) Ballini, R.; Bosica, G.; Tetrahedron Lett. 1996, 37, 8027-8030.
c) Seebach, D.; Lyapkalo, I. M.; Dahinden, R. Helv. Chim. Acta 1999,
2, 1829-1842. (d) Versleijen, J . P. G.; Van Lensen, A. M.; Feringa,
7
(
8
B. L. Tetrahedron Lett. 1999, 40, 5803-5806. (e) Berner, O. M.;
Tedeschi, L.; Enders, D. Eur. J . Org. Chem. 2002, 1877-1894 and
references therein. (f) Duursma, A.; Minnaard, A. J .; Feringa, B. L. J .
Am. Chem. Soc. 2003, 125, 3700-3701. (g) Boiteau, J .-G.; Imbos, R.;
Minnaard, A. J . Feringa, B. L. Org. Lett. 2003, 5, 681-684.
(12) (a) Belkasmioui, A.; Simonet, J . Bull. Soc. Chim. Fr. 1989, 699-
702. (b) N u¨ nnecke, D.; Voss, J . Acta Chem. Scand. 1999, 53, 824-
829.
(13) Adams, R.; McPhee, W. D.; Carlin, R. B.; Wicks, Z. W. J . Am.
Chem. Soc. 1943, 65, 356-360.
(
11) (a) Rosini, G.; Ballini, R. Synthesis 1988, 833-847. (b) The
Chemistry of Nitro and Nitroso Groups; Patai, S., Ed.; Wiley Inter-
science: New York, 1969/1970; Parts 1 and 2. (c) Ono, N. The Nitro
Group in Organic Synthesis; Wiley-VCH: New York, 2001.
9
264 J . Org. Chem., Vol. 68, No. 24, 2003