Haloacetylated enol ethers:16[5] regiospecific synthesis of 5-trichloromethyl-pyrazoles

摘要

The regiospecific synthesis and isolation of three series of 5-trichloromethyl-pyrazoles 2f-j,3a-j and 4a-j fromthe cyclocondensationof 1,1,1-trichloro-4-alkoxy-3-alken-2-ones (1a-f) or trichloroacetyl containing #beta#-diketones (1g-j) with dry hydrazine and phenyl-hydrazine is reported.It was established by ~1H- and ~(13)C-NMR spectroscopy that the 5-hydroxy-5-trichloromethyl-4,5-dihydro-1H-pyrazole intermediates 2a-j were formed quantitatively.