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Synthetic Communications
An International Journal for Rapid Communication of Synthetic Organic Chemistry
Volume 15, 1985 - Issue 3
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Original Articles

A Novel and Practical One Step Synthesis of 5,6-Dihydro -3-Phenyl-4H-Pyrrolo (1,2-b) Pyrazole (Withasomnine)

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Pages 259-265 | Published online: 05 Dec 2006

References

  • Schroter , H. B. , Neumann , D. , Katritzky , A. R. and Swinbourne , F. J. 1966 . Tetrahedron , 22 : 2895
  • Ranganathan , D. and Bamezai , S. 1983 . Tetrahedron Lett. , : 1067
  • Houk , K. N. , Sims , J. , Duke , R. E. , Strozier , R. W. and George , J. K. 1973 . J. Am. Chem. Soc. , 95 : 7287 (Houk, K. N., Sims, J., Duke, R. E., Strozier, R. W. and George, J. K., J. Am. Chem. Soc., 1973, 95, 7287; Houk, K. N., Sims, J., Watts, C. R. and Luskus, L. J., Ibid, 1973, 95, 7301), the likely outcome of the cyclo-addition involving 1 and phenyl acetylene would be the formation of the regio-isomer of 2, namely, iso Withasomnine (3) in larger amounts. However, in view of the highly strained nature of 1 coupled with the fact that sydnones demonstrate markedly less pronounced regio-selectivity, particularly with acetylenic polarophiles (Fleming, I., “Frontier Orbitals and Chemical Reactions”, John-Wiley, New York, 1982) made the possible prediction of the outcome of such an experiment uncertain
  • In addition to these, mention has been made of a synthesis of 2 by Dr. Schroter (Private communication quoted under ∗4 of paper by Onaka, T. ref. 6). However, we have not been able to find any details pertaining to this in the chemical literature
  • Morimoto , A. , Noda , K. , Watanabe , T. and Takasugi , H. 1968 . Tetrahedron Lett. , : 5707
  • Onaka , T. 1968 . Tetrahedron Lett. , : 5711
  • Kelly , I. R. and Montary , M. 1978 . Tetrahedron Lett. , : 4311 The reaction of 1 with phenyl acetylene in presence of powerful Lewis acid catalysts such as SnCl4 gave complex mixtures. The cyclo-addition of 1 with Ph-C°C-COOH — carried out to reverse the phenyl regio-selectivity — gave none of the anticipated adduct carboxylic acids but yielded small amounts of 2 and 3 and a nitrile acid arising from deep seated re-arrangement

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