Abstract
1,3-Disubstituted 1H -pyrazole-4-carbaldehyde-N ,N -dimethylhydrazones 1 reacted with the Vilsmeier-Haack
reagent, corresponding to the aza-enamine concept, in an electrophilic
substitution reaction at the azomethine C-atom yielding the 1,4,5-triaza-pentadienium
salts 2 . These were hydrolysed to give
2-hydrazono-2-(1H -pyrazole-4-yl)ethanals 3 . The electrophilic attack did not take
place at the vinylogous position 5′ of the pyrazoles.
Key words
aza-enamines - hydrazones - heterocycles - formylation - α-oxoethanals
References
1a Brehme R.
Nikolajewski HE.
Z.
Chem.
1968,
8:
226
1b Brehme R.
Nikolajewski HE.
Tetrahedron
Lett.
1982,
23:
1131
1c Brehme R.
Nikolajewski HE.
Tetrahedron
1969,
25:
1159
1d Brehme R.
Nikolajewski HE.
Tetrahedron
1976,
32:
731
1e Brehme R.
Chem.
Ber.
1990,
123:
2039
1f Brehme R.
Stroede B.
J. Prakt. Chem.
1987,
329:
246
1g Brehme R.
Klemann A.
Tetrahedron
1987,
43:
4113
2a Kamitori Y.
Hojo M.
Masuda R.
Fujitani T.
Ohara S.
Yokoyama T.
J.
Org. Chem.
1988,
53:
129
2b Kamitori Y.
Hojo M.
Masuda R.
Yoshida T.
Ohara S.
Yamada K.
Yoshikawa N.
J. Org. Chem.
1988,
53:
519
2c Kamitori Y.
Hojo M.
Masuda R.
Ikemura T.
Mori Y.
Tetrahedron
Lett.
1993,
34:
5135
3 Fernandez R.
Lasaletta JM.
Synlett
2000,
1228
4 Enders D.
Syrig R.
Raabe G.
Fernandez R.
Gasch C.
Lasaletta JM.
Llera JM.
Synthesis
1996,
48
5 Enders D.
Bolkenius M.
Vasquez J.
Lassaletta JM.
Fernandez R.
J.
Prakt. Chem.
1998,
340:
281
6 Enders D.
Vazquez J.
Raabe G.
Eur.
J. Org. Chem.
2000,
893
7a Stork G.
Brizzolara A.
Landesman H.
Szmuszkovicz J.
Terrell R.
J. Am. Chem. Soc.
1963,
85:
207
7b Otto P.
Feiler LA.
Huisgen R.
Angew.
Chem.
1968,
80:
759
7c Hünig S.
Hübner K.
Benzing E.
Chem. Ber.
1962,
95:
926
7d Kühne ME.
Garbacik Th.
J.
Org. Chem.
1970,
35:
1555
7e Effenberger E.
Menzel P.
Seufert W.
Chem. Ber.
1979,
112:
1660
8 Brehme R.
Gründemann E.
Schneider M.
J.
Prakt. Chem.
2000,
342:
700
9 Kirschke K. In
Houben-Weyl, Hetarene III/2
4th
ed., Vol. E8b:
Thieme;
Stuttgart:
1994.
p.399
10 Becker HOG.
Einführung
in die Elektronentheorie organisch-chemischer Reaktionen
3rd
ed.:
VEB Deutscher Verlag der Wissenschaften;
Berlin:
1974.
p.438
11 Sheldrick GM.
Acta
Crystallogr., Sect. A
1990,
46:
467
12 Complete crystallographic data have
been deposited at the Cambridge Crystallographic Data Centre under
the numbers CCDC 206302 for 3a , CCDC 206303
for 3c and CCDC 206304 for 4e .
Copies can be obtained from CCDC, 12 Union Road, Cambridge CB2 1EZ,
UK (e-mail: deposite@ccdc.cam.ac.uk).
