[3+2] CYCLOADDITION REACTIONS OF 1-SUBSTITUTED 3,3,3-TRIFLUOROPROPENES WITH DIAZO COMPOUNDS AND NITRILIMINES – SYNTHESIS OF PYRAZOLINES AND PYRAZOLES

Abstract

1,3-Dipolar cycloaddition reactions of 3,3,3-trifluoropropene derivatives containing a sulfonyl, sulfamide, or sulfoximine substituent in position 1 with diazomethane proceed with the formation of 3-substituted 4-(trifluoromethyl)-4,5-dihydro-1H-pyrazoles and 3(trifluoromethyl)-1H-pyrazole, whereas reactions with ethyl diazoacetate and 2,2,2-trifluorodiazoethane lead to the formation of isomeric 5(3)-substituted 4-trifluoromethyl-3,4(4,5)-dihydro-2(1)H-pyrazoles and 4-substituted 5-(trifluoromethyl)-4,5-dihydro-1H-pyrazoles, the stability of which depends on the nature of the heteroatomic substituent. The cycloaddition of 1-sulfonyl- and 1-sulfamoyl-substituted derivatives of 3,3,3-trifluoropropene to C-carbethoxy-N-phenylnitrilimine gives rise to 4-substituted ethyl 1-phenyl-5-(trifluoromethyl)-4,5-dihydro-1H-pyrazole-3-carboxylates and ethyl 1-phenyl-4-(trifluoromethyl)-1H-pyrazole-3-carboxylate.