First Diels-Alder reaction of pyrazolyl imines under microwave irradiation

Synlett

Volumn , Issue 10, 1998, Pages 1069-1070

  Díaz Ortiz, Angel ^a   Carrillo, José R ^a   Gómez Escalonilla, María J ^a   De La Hoz, Antonio ^a   Moreno, Andrés ^a   Prieto, Pilar ^a  

^a UNIVERSITY OF CASTILLA LA MANCHA   (Spain)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 0000109633     PISSN: 09365214     EISSN: None     Source Type: Journal    
DOI: 10.1055/s-1998-1881     Document Type: Article

References (14)

1. Carruthers, W. Cycloaddition Reactions in Organic Synthesis, Pergamon Press, Oxford, 1990.
2. Elguero, J. Comprehensive Heterocyclic Chemistry, 1984, 5, 247; Potts, K.T., Ed., Pergamon Press, Oxford, 1984.
3. Sepulveda-Arques, J.; Abarca-Gonzalez, B.; Medio-Simón, M. Adv. Heterocycl. Chem., 1995, 63, 339.
4. For example, see: (a) Hardy, C.R. Adv. Heterocycl. Chem., 1984, 36, 343;
5. (b) Molina, P.; Arques, A.; Fresneda, P.M.; Vinader, M.V.; Foces-Foces, M.C.; Hernández Cano, F. Chem. Ber., 1989, 122, 307;
6. (c) Benoit, R.; Dupas, G.; Bourguignon, J.; Quéguiner, G. Synthesis, 1987, 1124;
7. (d) Bare, T.M.; McLaren, Ch.D.; Campbell, J.B.; Firor, J.W.; Resch, J.F.; Walters, C.P.; Salama, A.I.; Meiners, B.A.; Patel, J.B. J. Med. Chem., 1989, 32, 2561;
8. (e) Sanghvi, Y.S.; Larson, S.B.; Robins, R.K.; Revankar, G.R. J. Chem. Soc. Perkin Trans 1, 1990, 2943.
9. Only two examples have been reported for the preparation of pyrazolo[3,4-b]pyridines by cycloaddition reactions: (a) Hasnaoui, A.; El Messaoudi, M.; Lavergne, J.P. J. Heterocycl. Chem., 1985, 22, 25 from 1,2,4-trizepine;
10. (b) Möhrle, H.; Dwuletzki, H. Chem. Ber., 1986, 119, 3591 from cyclic ketene N,O-acetals.
11. Compound 1 was prepared from 1-ethyl-5-aminopyrazole and p-methoxybenzaldehyde: Organic Syntheses, Vol. I, pag. 80, Wiley;
12. compound 2 from 1-ethyl-5-aminopyrazole and the Vielsmeier reagent: Synthesis, 1982, 1084.
13. Experimental procedure: A mixture of the 2-azadiene (1 mmol) and the nitroalkene (2 mmol) was irradiated at atmospheric pressure in a focused microwave reactor Prolabo MX350 with measurement and control of power and temperature by infrared detection for the time and at the power indicated in Table 1. The crude reaction was purified by flash chromatography on silica gel (Merck type 60 230-400 mesh).
14. Loss of stable and/or volatile molecules in the course of cycloaddition reactions is a well known process. See ref. 1.