Unsaturated nitrogen compounds containing fluorine. Part 19. Cycloaddition reactions of 2,5-dichloro-1,1,1,6,6,6-hexafluoro-3,4-diazahexa-2,4-diene with cycloalkenes and cyclodienes

Article abstract of DOI:10.1016/0022-1139(95)03227-5

Thermal reaction (20-70 deg C) of the dichloroazine CF3CCl=NN=CClCF3, 2, with cyclopentene (in CH2Cl2 solvent), cycloheptene, indene, acenaphthylene, 2,3-dihydrofuran, 3,4-dihydro-2H-pyran, norbornadiene and dicyclopentadiene afforded, as the major product in each case, the corresponding rearranged <3 + 2> cycloadduct 3 containing a grouping.The direction of cycloaddition to the unsymmetrical carbocycles indene and cyclopentadiene was consistent with the reactions being LUMO (azine)-HOMO (dipolarophile) controlled.On attempted chromatographic purification on silica gel, the rearranged adducts 3 were hydrolysed to the corresponding amides 4 (-->).The cyclopentene reaction, unexpectedly, also gave the cyclopentadiene <3 + 2> cycloadduct 3b, while from the norbornadiene reaction a hydrolysed 2:1 adduct 9 (4percent) was isolated by chromatography.Other products obtained by chromatographic separation from the 3,4-dihydro-2H-pyran reaction were the substituted azine (5) (29percent), equimolar amounts of the ketone (6) (18percent) and the chlorohydrazone (7) (18percent), possibly arising via the <3 + 2> cycloadduct 15 of 5 and the pyran, and the hydrazone (8) (4percent), formed via 15 or by hydrolysis of the amide 4g.Treatment of amide 4d, derived from indene with ethanolic methylamine, gave the expected amino compound 21a (94percent) and CF3CONHMe (22) (91percent).In contrast, treatment of the exo-amide 4h, derived from norbornadiene with ethanolic methylamine, afforded the N-formyl compound 23 (87percent), while corresponding treatment of a mixture of the exo- and endo-amides (4h and 4i) gave the exo- and endo-amino compounds (21b and 21c) (88percent), together with compound 22 (ca. 10percent) and the azapropenylindazole 24 (ca. 5percent); compound 24 hydrolysed to 23 on storage.It is proposed that the amines 21b and 21c arose mainly via the sequence: --> (24)--> (23)-->. - Keywords: Unsaturated nitrogen compounds; Cycloaddition reactions; Dichlorohexafluorodiazahexadiene; NMR spectroscopy; IR spectroscopy; Mass spectrometry