Facile method for synthesis and polymerization of 1-allenyl-3-methyl- and 1- allenyl-5-methylpyrazoles

It is well known that imputing of allenyl group into heterocyclic systems, particularly in pyrazole structure allows to obtain modified and applied compounds with practically interesting properties. In this research we have synthesized methyl group substituted allenyl pyrazoles, aiming to obtain conjugated and novel polymers with azole fragment in the side chain, the radical polymerization of those were carried out. 1-Allenyl-3-methyl and 1-allenyl-5-methylpyrazoles were synthesized by isomerization of 1-propargyl-3-methyl and 1-propargyl-5-methylpyrazoles, respectively, using KOH dissolved in the isopropanol, as a result yielding 50-55% of allenyl pyrazoles. Obtained allenyl pyrazoles have been easily polymerized using azobisisobutyronitrile (AIBN) as radical initiator, thermal polymerization was also performed, resulting of linear oligomers with η= 0,015–0,025 dl/g viscosity. Polymerization of some isomers of 1-allenyl pyrazoles has been studied by gas-liquid chromatography, the structures of obtained polymers were identified by IR and NMR spectroscopy methods. It was found out that in the case of radical polymerization, when methyl group was located at the 3-position of the pyrazole ring, it polymerized faster under the same conditions compared to the isomer with the methyl group at the position 5. We have showed dependence of polydispersity of obtained poly(1-allenyl-3-methylpyrazole) samples from the synthesis route using the light scattering method.