Synthesis of 2,2′-bipyridyl derivatives using aza Diels-Alder methodology

Article abstract of DOI:10.1016/S0040-4039(02)02670-9

Amidrazone 1 and the tricarbonyl derivatives 2a-c gave the triazines 3a-c, respectively, which reacted with 2,5-norbornadiene 4 in boiling ethanol yielding the corresponding novel 2,2′-bipyridines 5a-c in good yield. Triazine 6 gave the 2,2′-bipyridyl der

Full text of DOI:10.1016/S0040-4039(02)02670-9

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 44 (2003) 693–694
Synthesis of 2,2%-bipyridyl derivatives using aza Diels–Alder
methodology
a,
b
a
Stephen P. Stanforth, * Brian Tarbit and Michael D. Watson
a
School of Applied Sciences, University of Northumbria, Newcastle upon Tyne NE1 8ST, UK
Seal Sands Chemicals Ltd., Seal Sands Road, Seal Sands, Middlesbrough TS2 1UB, UK
b
Received 5 November 2002; accepted 22 November 2002
Abstract—Amidrazone 1 and the tricarbonyl derivatives 2a–c gave the triazines 3a–c, respectively, which reacted with 2,5-norbor-
nadiene 4 in boiling ethanol yielding the corresponding novel 2,2%-bipyridines 5a–c in good yield. Triazine 6 gave the 2,2%-bipyridyl
derivative 7 (65%) with compound 4 in 1,2-dichlorobenzene at 140°C. © 2003 Elsevier Science Ltd. All rights reserved.
2
,2%-Bipyridyl and its derivatives are important hetero-
with unsymmetrical tricarbonyl compounds have not
been studied in detail and this reaction provides a
useful method for the synthesis of substituted triazines.
cyclic molecules and they have found extensive use in
many areas of chemistry. Particularly interesting are
their application as metal chelating ligands and in this
1
4
2
The aza Diels–Alder reactions between triazines and the
context 2,2%-bipyridyl derivatives bearing pendant chiral
acetylene equivalent, 2,5-norbornadiene 4 has fre-
7
substituents have recently been employed in the asym-
quently been used to prepare pyridines and triazines
3
metric synthesis field. In view of the extensive interest
3a–c were therefore reacted with 2,5-norbornadiene 4.
These reactions were initially performed in 1,2-
dichlorobenzene solution at 140°C but since it was
often difficult to remove the last traces of 1,2-
dichlorobenzene in the work-up procedure we subse-
quently found that boiling ethanol was a suitable
solvent and a ‘one-pot’ reaction allowed the prepara-
tion of the required pyridines 5a–c without the need to
isolate the triazine intermediates 3a–c. Thus, amidra-
zone 1, tricarbonyls 2a–c and an excess of 2,5-norbor-
nadiene 4 were heated in ethanol at reflux for 20 hours
giving the required 2,2%-bipyridyls 5a–c respectively in
80–87% overall yields.
in 2,2%-bipyridyls, we embarked upon the preparation of
a series of functionalised 2,2%-bipyridyls 5a–c from tri-
azine precursors 3a–c using the aza Diels–Alder
methodology that we have successfully applied to the
4
synthesis of other pyridine derivatives.
5
Amidrazone 1 was prepared from 2-cyanopyridine and
hydrazine hydrate and was reacted with the unsymmet-
6
rical tricarbonyl derivatives 2a–c in boiling ethanol
solution to yield the novel 1,2,4-triazines 3a–c respec-
tively (90–97% yield) (Scheme 1). With the exception of
a few isolated examples, the reactions of amidrazones
Scheme 1.
Keywords: 2,2%-bipyridyls; aza Diels–Alder reaction; 1,2,4-triazines.
*
Corresponding author. Tel.: 0191 2274784; fax: 0191 2273519; e-mail: steven.stanforth@unn.ac.uk
0
040-4039/03/$ - see front matter © 2003 Elsevier Science Ltd. All rights reserved.
PII: S0040-4039(02)02670-9

6
94
S. P. Stanforth et al. / Tetrahedron Letters 44 (2003) 693–694
Scheme 2.
Both C1 and C -symmetrical 2,2%-bipyridyls bearing
References
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an aza Diels–Alder reaction with 2,5-norbornadiene 4.
Triazine derivatives 3a–c are sufficiently reactive to
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