94444-84-5Relevant academic research and scientific papers
The Regioselectivity in the Formation of Pyrazolines and Pyrazoles from Nitrile Imines
Hassaneen, Hamdi M.,Hilal, Rifaat H.,Elwan, Nehal M.,Harhash, Abdelhamid,Shawali, Ahmad S.
, p. 1013 - 1016 (2007/10/02)
The 1,3-cycloaddition of the nitrile imines 2a-e to the carbon-carbon double bond in benzalacetophenone leads to the formation of 4-phenyl-5-benzoylpyrazolines 3a-e which were converted into 4-phenyl-5-benzoylpyrazoles 5a-e upon treatment with chloranil in xylene.However, the cycloaddition of 2a-e to the carbon-carbon double bond in the enol tautomer of dibenzoylmethane gives the regioisomers 5-phenyl-5-hydroxy-4-benzoylpyrazolines which loose elements of water to yield 4-benzoyl-5-phenylpyrazoles 6a-e.The orientation in these reactions are interpretted in terms of the Frontier Molecular Orbital theory.The structures of the products 3,5 and 6 were substantiated by their chemical reactions and alternate synthesis whereever possible.
