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Organic Synteses vol 70 - Meyers A.I.

Meyers A.I. , Boecman R.K. Organic Synteses vol 70 - John Wiley & Sons, 1992. - 163 p.
ISBN 0-471-57743
Download (direct link): organicsynthesesvol701992.pdf
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85
dicarboxylate with electron-rich carbon dienophiles6d and heterodienophiles,4a>b'c respectively. Complete surveys of the reported Diels-Alder reactions of dimethyl
1,2,4,5-tetrazine-3,6-dicarboxylate have been compiled.4 Reductive ring contraction of the substituted dimethyl 1,2-diazine-3,6-dicarboxylate [4 + 2] cycloadducts effected by zinc in acetic acid provides the corresponding substituted dimethyl pyrrole-2,5-dicarboxylates.60'7 Table III details representative examples of this general reductive ring contraction reaction.7.8
This approach to 1,2-diazine and pyrrole introduction based on the inverse electron demand Diels-Alder reaction of dimethyl 1,2,4,5-tetrazine-3,6-dicarboxylate complements the [4 + 2] cycloaddition reactions of a range of electron-deficient heterocyclic azadienes which permits the divergent preparation of a range of heterocyclic agents employing a common dienophile precursor, Scheme I.
1. Department of Chemistry, Purdue University, West Lafayette, IN 47907.
2. The procedure described for the preparation of dimethyl 1,2,4,5-tetrazine-3,6-dicarboxylate is an adaptation of two detailed preparations: (a) Spencer, G. H., Jr.; Cross, P. C.; Wiberg, K. B. J. Chem. Phys. 1961, 35, 1939; (b) Sauer, J.; Mielert, A.; Lang, D.; Peter, D. Chem. Ber. 1965, 98, 1435. (c) The oxidation of dimethyl dihydro-1,2,4,5-tetrazine-3,6-dicarboxylate to dimethyl 1,2,4,5-tetrazine-3,6-dicarboxylate using nitrous gases is a modification of a previously described procedure,20 see: Boger, D. L.; Coleman, R. S.; Panek, J. S.; Huber,
F. X.; Sauer, J. J. Org. Chem. 1985, 50, 5377. For the original description of the base-promoted dimerization of ethyl diazoacetate, see: Curtius, Th.; Darapsky, A.; Müller, E. Chem. Ber. 1906, 39, 3410; 1907,40, 84; 1908, 41, 3161; Curtius, Th.; Lang, J. J. Prakt. Chem. 1888, 38, 531; Hantzsch, A.; Lehmann, M. Chem. Ber. 1900, 33, 3668; Hantzsch, A.; Silberrad, O. Chem. Ber. 1900, 33, 58.
8f>
3. Fieser, L. F.; Fieser, M. "Reagents for Organic Synthesis"; Wiley: New York, 1967; Vol. 1, p. 1276.
4. (a) Neunhoeffer, H.; Wiley, P. F. "The Chemistry of Heterocyclic Compounds" In "Chemistry of 1,2,3-Triazines and 1,2,4-Triazines, Tetrazines, and Pentazines"; Wiley: New York; 1978, Vol. 33; (b) Boger, D. L. Tetrahedron 1983, 39, 2869; (c) Boger, D. L. Chem. Rev. 1986, 86, 781; (d) Boger, D. L.; Weinreb, S. M. "Hetero Diels-Alder Methodology in Organic Synthesis"; Academic Press, FL; 1987; (e) Weinreb, S. M.; Staib, R. R. Tetrahedron 1982, 38, 3087.
5. Houk, K. N. J. Am. Chem. Soc. 1973, 95, 4092.
6. (a) Boger, D. L.; Panek, J. S. J. Org. Chem. 1983, 48, 621; (b) Boger, D. L.; Panek, J. S. Tetrahedron Lett. 1983, 24, 4511; (c) Boger, D. L.; Panek, J. S. J. Am. Chem. Soc. 1985, 107, 5745; (d) Boger, D. L.; Coleman, R. S.; Panek, J.
S.; Yohannes, D. J. Org. Chem. 1984, 49, 4405.
7. Bach, N. J; Kornfeld, E. C.; Jones, N. D.; Chaney, M. O.; Dorman, D. E.; Paschal, J. W.; Clemens, J. A.; Smalstig, E. B. J. Med. Chem. 1980, 23, 481.
8. For additional examples, see: Boger, D. L.; Patel, M. J. Org. Chem. 1988, 53, 1405.
87
Scheme 1
Г
R = H
= CO2CH3
R^VR
N^N
R
R = H = СОгВ = SCH3
R
N "N R = CO2CH3 N^N =SCH3
R
R = CO2CH3 -SCH3
R = C02CH3 = SCH3
і- и = «
I-»- =H
R = C02CH3
RH
TABLE I
Diels-Alder Reactions of Dimethyl 1,2,4,5-Tetrazine-3,6-dicarboxyiate: 1,2-Diazine Introduction“
Entry
Dienophile
Conditions
Equiv. Temp °C (time hr) 1,2-Diazine
% Yield
y
OSiEt,
Me-
X- morphofine apyrroicfind
X-OSi(CH3)3 * morphoSne »p/rrottcfne
Or
Me
X
a
a
1.5,25(12)
2-6,25(12)
2,25(48)
2,25(48)
1.5.25(12)
1.25(5)
1.2,25(1.5)
1.5,25(12)
C02CH3
N N
C02CH3
COJZH3
N
N
C02CH3
C02CH3
C02CH3 CO,CH,
V
CO,CH,
1 87
1 trace
2 70 trace
3 85
4 92
87
trace
CH3O^OCH3
T
1.5,25(0.5)
CH30
CO,CH3
N
I
N
co2ch3
5 65
10
11
RO^OCHgPh
T
R - Si(Me)2-t*Bu 1 5,5-25(0.5)
PhCH20-=—H 2-3.25(6)
PhCH20.
C02CH3
N
i
N
C02CH3
6 33
82
CH3O^OCH3
12
2.5,101(3)
CY
C02CH3
N i
spN
0 C02CH3
7 71
CH302C
13
C02CH3
1,25(5) CH302C 3 69
C02CH3
(a) All Diels-Aldor reaction« worn currmd out In dloxans
TABLE II
Diels-Alder Reaction of Dimethyl 1,2,4,5-Tetrazine-3,6-dicarboxylate with C=N Heterodienophiles63-0
Product
% Yield
•'N ^ "'v£.n v^C02C H3
CH302C N
68
37
ch3o2c^'n
65
27
Dienophile
Concftions
Temp °C (time hr)a
NH
X = SCH3 = OB = NH2 = NEt2
80(20)
80(8-12)
25(5)
25-50(25)
NH
X = SCH3
= oa = nh2
80(24)
60(10)
25(5)
N C02CH3 r II
ch3o2c"^n
r1 = r2 = h X = SCH3
= oa r1 » och3 r2 = h
X=SCH3 R1 » OCH3 R2= N02 X = SCH3
80(4)
80(20)
80(4)
80(20-24)
70
33
78
82
(a) All Diels-Alder reactions were carried out in dioxane.
<) 0
TABLE III
Reductive Ring Contraction of Substituted Dimethyl 1,2-Diazine-3,6-dlcart)oxylates: Pyrrole Introduction6“1
Entry
1,2-Diazine
Conditions
Tamp “C (time hr)
Pyrrole
%Yield
C02CH3
N
C02CH3
COgCHa
N
N
C02CH3
C02CH3
CO2CH3
C02CH3
4 №y^N
C02CH3
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