ORGANOFLUORINE COMPOUNDS AND FLUORINATING AGENTS .16. MONOALKYLATIONSAND CYCLOADDITIONS WITH TRANS-3,3,3-TRIFLUORO-1-NITROPROPENE

Monoalkylations of different nucleophilic azoles were investigated wit h the electron-deficient trans-3,3,3-trifluora-1-nitropropene (1) as a lkylating reagent without addition of any catalyst. In each case, the bonding of the alkene at the azole occurs regioselectively at the trif luoromethyl-substituted C atom of the alkene, whereas the azoles react at different positions depending on the electron density of the heter ocycles. Thus, 1-methyl-pyrrole (2) reacted with 1 under C-C bond form ation giving the two regioisomers 2-(1-trifluoromethyl-2 nitroethyl)-1 -methyl-pyrrole (3) (major product) and -(1-trifluoromethyl-2-nitroeth yl)-1-methyl-pyrrole (4). The less nucleophilic pyrazole (5), 1,2,4-tr iazole (7), 3-bromo-1,2,4-triazole (9), and 3,5-dibromo-1,2,4-triazole (12) gave exclusively the corresponding N-alkyl azoles 1-(1-trifluoro methyl-2-nitroethyl)-pyrazole (6), 1-(1-trifluoromethyl-2-nitroethyl)- 1,2,4-triazole -1-(1-trifluoromethyl-2-nitroethyl)-1,2,4-triazole -1-( 1-trifluoromethyl-2-nitroethyl)-1,2,4-triazole (II), and 3,5-dibromo-1 -(1-trifluoromethyl-2 nitroethyl)-1,2,4-triazole (13), respectively. T he enantiomeric pairs of the chiral monoalkyl-azoles could not be sepa rated. Moreover, we used trans-3,3,3-trifluoro-1-nitropropene (1) as a dienophile in Diels-Alder cycloadditions with cyclopentadiene (14), c yclohexa-1,3-diene (16), and furan (18). Two diastereomeric products ( 15A/15B, 17A/17B, and 19A/19B), which could not be separated by column chromatography, are formed from each diene. All compounds were charac terized by H-1, C-13, and F-19 NMR data.