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Diazo Strategy for the Synthesis of Pyridazines: Pivotal Impact of the Configuration of the Diazo Precursor on the Process
Author(s) -
Nikolaev Valerij A.,
Cantillo David,
Kappe C. Oliver,
Medvedev Jury J.,
Prakash G. K. Surya.,
Supurgibekov Murat B.
Publication year - 2016
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201503448
Subject(s) - diazo , tandem , isomerization , intramolecular force , chemistry , wittig reaction , cis–trans isomerism , cycloaddition , stereochemistry , combinatorial chemistry , medicinal chemistry , organic chemistry , catalysis , materials science , composite material
Phosphazenes of vinyldiazocarbonyl compounds having cis stereochemistry of the functional groups on the vinyl bond readily produce pyridazines by a diaza‐Wittig process, whereas their counterparts with trans configuration remain intact under similar reaction conditions. Upon UV irradiation trans ‐phosphazenes furnish pyridazines through a tandem trans ‐to‐ cis isomerization followed by intramolecular cyclization. At elevated temperatures trans ‐(triphenyl)phosphazenes dissociate to give the initial vinyldiazo compounds, which produce pyrazoles in high yields. The first theoretical study on the mechanism of the diaza‐Wittig process by DFT calculations at the M06‐2X/6‐31G(d) level of theory suggest that for the cis ‐phosphazenes a rapid tandem [2+2] cycloaddition/cycloelimination process with low energy barriers is preferred over trans isomers.