Synthesis of 2-Nitro 1,3-Dienes. Useful Intermediates in the Preparation of Unsaturated 1,4-Dicarbonyl Compounds

Article abstract of DOI:10.1016/0040-4039(91)80097-P

2-Nitro 1,3-dienes have been obtained from conjugated dienes via a nitroselenation-elimination sequence.The elimination of the selenium moiety is catalyzed by base.Several of the 2-nitro 1,3-dienes were isolated, whereas others were generated in situ and used for further reaction.They were found to react readily with enol ethers to give nitronic esters, which sequently were transformed to unsaturated 1,4-dicarbonyl compounds.

Full text of DOI:10.1016/0040-4039(91)80097-P

Tetrahedron Letters, Vo132, No,40, pp 5607-5610, 1991
Printed m Great Britain
0040-4039/91 $3 00 + .~
Pergamon Press pie
Synthesis of 2-Nitro 1,3-Dienes. Useful Intermediates in the Preparation of Unsaturated
1,4-Dicarbonyl Compounds
Jan-E. Biickvall,* Ulrika Karlsson, and Rafael Chinchilla
Department ofOrganic Chemistry, University
Box 531, S-751 21 Uppsala, Sweden
Abstract. 2-Nitro 1,3-dienes have been obtained from conjugated dienes via
a
nitroselenation-elimination sequence. The elimination of the selenium moiety is
catalyzed by base. Several of the 2-nitro 1,3-dienes were isolated, whereas others were
generated in situ and used for further reacuon. They were found to react readily with
enol ethers to give nitronic esters, which subsequently were transformed to unsaturated
1,4-dicarbonyl compounds.
The utility of electron-deficient conjugated dienes as building blocks in organic synthesis has recently
been demonstrated.1-4 The synthetic importance of these dienes is increased if the electron-withdrawing group
allows further functionalization and/or can be removed, as is the case for arylsulfonyl1 and nitro5 groups. Whxle
there are many examples of the use of sulfonyldienes,1'2 only a limited amount of work has been done on
nitrodienes.3
We now report the synthesis of 2-nitro 1,3-dienes by means of a sequence that involves the nitroselenation
of the corresponding conjugated dienes3e followed by a base-catalyzed elimination of the phenylseleno group.
When the resulting nitrodiene was not highly reactive towards dimerization, its isolation and purification was
accomphshed. The more reactive nitrodienes were generated in situ and used directly in the appropriate reaction.
In this communication we describe the cycloaddition of these 2-mtro 1,3-dienes with enol ethers and the
subsequent transformation of the nitronate cycloadducts to 1,4-dicarbonyl compounds. The latter compounds
constitute potential precursors for the synthesis of naturally occurring products.6
When the the nitroselenation adducts from conjugated dienes were treated with a catalytic amount of a
base such as N,N-dimethylaminopyridine (DMAP), a mild elimination of the phenylseleno group took place.
This ehmination, which is facilitated by the electron-withdrawing nitro group, produces PhSeH but the latter is
oxidized in situ by air to give PhSeSePh.7 Table I shows some nitrodienes which were isolated and
characterized. However, in several other cases it was not possible to xsolate the corresponding 2-nitro 1,3-dlene
due to rapid dimerization.
Nitroalkenes have been shown to react with electron-rich olefins such as enamines, aUylsilanes, enolates,
and silyl enol ethers to give nitronates.8,9 Usually, these reactions were performed in the presence of a Lewis
5607

T a b l e I. Synthesis of 2-mtro-l,3-dienes.a
D~ene
Reaebon
Nitrodlenec
Y~eld~ (%)
45
time b (h)
20
~
NO2
©
a
In
a
typical reacuon, 1 mmol of the &ene was nlttoselenated as previously
described?e The crude extract was dissolved m 2 mL of methylene chloride and 5
mg of DMAP were added. The m~xture was stirred and when the reacnon was
complete (followed by t.1 c.) the solvent was evaporated and the nitrodiene purified
by Kugelrohr distillation b Starting from the nitroselenatlon adduct, c Characterized
by IH NMR and 13C NMR d Isolated yxeld based on the starting diene.
acid catalyst m order to enhance the electrophthc~ty of the mtroalkene Reaction of mtrodiene 3 with ethyl vinyl
ether in methylene chloride afforded the nitronate 4 In almost quantitative y~eld Hydrolysis of 4 under the usual
Nef con&tlons 1° gave the aldehyde 5 (Scheme I).
Scheme I
NO2
- O , , ~ 1 0 - ,..OEt
O
3
4
5
Because of problems with the lsolauon of some of these 2-nitro 1,3-&enes we decided to study their
m s m t
generatzon m the presence of the enol ether. In most cases, th~s actually gave a better yield of the nitronate (from
the &ene) Table I1 shows the results obtained m the synthesis of unsaturated dlcarbonyl compounds with a
series of representative dienes as starting materials and Scheme II summarizes the experimental method as
exemphfied by entraes 4 and 6
The synthesis of 1-mtro 1,3-dienes has been reported,3a but procedures for the preparation of the
corresponding 2-mtro 1,3-dienes have revolved unsatisfactory reaction conditions. 3b Recently, Barco et aI 3c.3d
described the preparation of some nitroalcohols that act as precursors for 2-nitro 1,3-dienes The present
procedure wa mtroselenation seems to be the more general one for these synthetically useful compounds.

5609
Table H. Preparation of unsaturated 1,4-dicarbonyl compounds.
Entry
Diane
Reaction
timea(h)
Nitronate b,c
Ytaldd(%)
Dicarbonyl
compounde
Ytelde(%)
95
b
OMe
O
~
K
45
O
OMe
O
~
o +
0 . , i
57
53
90
96
O
O
-
OMe
OMa
O
~
a
~
4a
b
O
38
50
~
95
50
o..o.O.Mpe
O
~
b . ~ o. OEt
O
42
CHO
93
~
"ON~I O _OEI
O
62 ~ C H O
30
aFrom the nitroselenyl adduct, bennies 1-5: Obtained by reaction with CH2=CH(OMe)CH3;
entries 6 and 7: Obtained by reaction with CH2=CHOEt. cCharacterized by IR, 1H NMR
and 13C NMR. dlsolated yield after flash chromatography based on the corresponding
diane, abased on the nitronate.
Scheme II
O
N O 2
-O. +.o.?R1R2
~ , , , , ,SePh
6
R1=Me,El; R2=Me,H
agents, i. PhSeBr, HgCI2, AgNO2; li. DMAP, CH2 =CH(OMe)CH3 (or CH2 =CHOEt); iii. 10% HC1

5610
In atyptcal procedure, the crude extract obtained from the nltroselenation of I mmol of the appropriate
dlene3e was dissolved in methylene chloride (2 mL). To this solunon were added 5 mg of DMAP and 1 mL of
the appropriate enol ether. The solution was stirred under reflux and after the necessary reaction time (monitored
by t.1 c ) the solvent was evaporated and the residue purified by flash chromatography on silica gel to give the
nltronic ester. A solution of this nitronate in methylene chloride (1 mL) was hydrolyzed with 0 5 mL of 10%
hydrochloric acid under reflux dunng 2 hours. The organic layer was washed with brine and water, dried
(MgSO4), and the solvent evaporated tn vacuo yielding the dicarbonyl compound.
Acknowledgments We thank the Swedish Natural Science Research Council for financial support. We
also thank Dr. Adolf Gogoll for has assistance m recording and interpretation of some of the NMR spectra
References and Notes
1.
(a) Andell, O.S ; B~ickvall, J.E. Tetrahedron Lett. 1985, 26, 4555. (b) Bhckvall, J.E.; Juntunen, S.K. J Am
Chem Soc. 1987, 109, 6396. (c) Backvall, J.E.; Juntunen, S.K.; Andell, O.S. Organic Synthesis 1989, 67,
105. (d) Cuvigny, T.; Herv6e du Penhoat, C.; Julia, M. Tetrahedron Lett. 1986, 42, 5329. (e) Fuchs, P L ;
Hardinger, S. A. J. Org. Chem 1987, 52, 2739. (f) B~ickvall, J E ; Nfijera, C ; Yus, M Tetrahedron Lett
1988, 29, 1445. (g) Back, T.G; Lai, E.K.Y.; Muralidharan, K.R. IbM 1989, 47, 6481. (h) Back, T.G;
Colhns. S. J Org Chem. 1981, 40, 3249. (1) Padwa, A.; Harrison, B.; Murphee, S S ; Yeske, P E. 1bid
1989, 54, 4232. (j) B~ickvall, J.E.; Juntunen, S.K. IbM 1988, 53, 2398. (k) Backvall, J.E ; Plobeck, N A.;
Juntunen, S.K. Tetrahedron Lett 1989, 30, 2589. (1) Backvall, J.E., Rise, F lbzd 1989, 30, 5347 (m)
Padwa, A., Harrison, B.; Norman, B H. Ibid 1989, 30, 3259
2.
3.
(a) Chou, T.S.; Hung, S.C., Tso, H.H. J Org. Chem 1987, 52, 3394. (b) Chou, T.S, Hung, S C IbM. 1988,
53, 3020 (c) Inomata, K.; Kmoshlta, H ; Takemoto, H., Murata, Y ; Kotak, H Bull Chem Soc Jpn. 1978,
51, 3341
(a) Bloom, A.J.; Mellor, J.M. J Chem Soc Perkin Trans 1 1987, 2737. (b) Berestovitskaya, V.M.;
Speranskli, E.M.; Perekahn, V V. Zh Org. Khtm 1979, 15, 164. (c) Barco, A., Benettl, S ; Pollini, G.P.;
Spalluto, G ; Zanirato, V. J Chem Soc, Chem Commun 1991, 390 (d) Barco, A., Benettl, S.; Polhm,
G.P.; Spalluto, G.; Zannato, V Tetrahedron Lett 1991, 32, 2517 (e) N~ijera, C.; Yus, M., Karlsson, U.;
Gogoll, A ; B~ickvall, J.E. Tetrahedron Lett. 1990, 31, 4199.
4.
5
Tarnchompoo, B.; Thebtaranonth, C.; Thebtaranonth, Y. Tetrahedron Lett 1987, 28, 6671.
For reviews, see: (a) Rosml, G, Balhm, R Syntheszs 1988, 833. (b) Seebach, D ; Colvm, E W., Lehr, F,
Weller, F Chzmta 1979, 33, 1. (c) Tamura, R ; Kamimura, A, Ono, N Synthesls 1991, 423.
For reviews, see: (a) Elhson, R.A Synthesis 1973, 397 (b) Ho, T L Synth. Commun 1974, 4, 265.
McKillop, A.; Koyuncu, D., Knef, A, Dumont, W.; Remer, P ; Trabelsl, M. Tetrahedron Lett 1990, 3l,
5007
6
7.
8
9
Denmark, S.E.; Dappen, M S.; Cramer, C.J. J Am Chem Soc 1986, 108, 1306, and references cited
therein.
(a) Denmark, S.E.; Cramer, C J ; Sternberg, J.A Helv. Chlm Acta 1986, 69, 1971. (b) Seebach, D.; Brook,
M.A. Can J. Chem 1987, 65, 836 (c) Yoshikoshi, A, Mlyashlta, M Acc Chem Res 1985, 18, 284. (d)
Nielsen, A.T, Archibald, T.G Tetrahedron, 1979, 26, 3475
10. Nef, J U ; Justus Ltebigs Ann Chem 1894, 280, 264.
(Received in UK 28 June 1991)