Reduction of 1-Acylpyrazolinium Salts

Article abstract of DOI:10.1007/BF00742841

Activation of the C=N bond in the 1-acylpyrazoline molecule may take place during the formation of a complex with boron trifluoride (coordination at the oxygen atom of the acetyl group) or in the case of protonation at the N(2) atom of pyrazoline ring.Activated 1-acetylpyrazolines are readily reduced with lithium aluminium hydride to 1-ethylpyrazolidines.The hydrochlorides of 1-acetylpyrazolidines undergo reaction without prior deprotonation.Aluminium hydride reduces 1-acetylpyrazoline bases to 1-ethylpyrazolidined also through prior complexing at the N(2) atom of the pyrazoline ring.