Synthesis of 1,1-difluoro-2-azaperhalo-1-butenes and their conversion to oxaziridines

Abstract

At elevated temperatures, IV-chlorodifluoromethanimine (CF2=NC1) adds to perhaloalkenes of the type CF2=CFX, forming CF2=NCF2CFXC1 (X = F, Cl, Br) in good yields. Reaction of these butenes with trifluoromethyl hydroperoxide (CF3OOH) gives CF3OOCF2NHCF2CFXCl, and subsequent treatment with KHF2 forms the corresponding oxaziridine, 0CF2NCF2CFXC1, in excellent yield. Eight new compounds, along with the previously reported CF2=NCF2CF2C1, were characterized by their IR, NMR, and mass spectra and physical properties.The synthesis of l,l-difluoro-2-azaperhalo-l-alkenes or IV-(perhaloalkyl)difluoromethanimines of the type CF2= NRX is very difficult, and only a few such compounds are known. Examples have, in general, been prepared by pyrolysis of perfluoro tertiary amines and by the pyrolysis of perfluoro-2-alkyl-l,2-oxazetidines or the corresponding copolymer formed from RfNO and CF2=CF23 (eq 1-3). In 750 °C (C2F5)3N-* C2F5N=CF2 + fluorocarbons (1) C2F5N -0 550 °C cf2-cf2 c2f5n = cf2 + cof2 (2) c2f5 -(-N-0-CF2CF2 450 C2F5N=CF2 t C0F2 (3) the case of perfluoro-2-azapropene, more practical methods of synthesis have been developed by utilizing (CF3)2NC-(O)F, available from electrochemical fluorination of (C-H3)2NC(0)F,4 or C13CN=CC12 from high-temperature chlorination of (CH3)2NC(0)C15 (eq 4-7). (CF3)2NC(0)F 575 °C> CF3N=CF2 + COF2 (4) (CH3)2NC(0)C1 CI2, hv CI2, carbon C1,CN=CC12 120°C 200

Polyfluorinated Oxaziridines: Synthesis and Reactivity

“…2-(Pentafluorothio)-3,3-difluorooxaziridine ( 2b ) and a series of (polyfluoroethyl)-3,3-difluorooxaziridines 2c − e were prepared in a similar manner (eq 1).

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“…While syntheses of fluorinated oxaziridines through oxidation of corresponding imines are similar to those of corresponding non-fluorinated analogues, the syntheses of starting perfluorinted imines are quite specific. Terminal imines of type 1 are made either by pyrolysis of the corresponding oxazetidines 18 or by radical addition of CF 2 NX (X = Cl, Br) to fluorinated ethylenes . In both routes the yields of products are quite high (80−95%), but the starting materials are rather exotic.…”

“…Terminal imines of type 1 are made either by pyrolysis of the corresponding oxazetidines 18 or by radical addition of CF 2 dNsX (X ) Cl, Br) to fluorinated ethylenes. 13 In both routes the yields of products are quite high (80-95%), but the starting materials are rather exotic. Two approaches to internal imines of type 4 are based on reactions of commercially available perfluorinated tertiary amines which themselves are produced by electrochemical fluorination and readily available from distributors such as Aldrich Co. Pyrolysis of (R f ) 3 N (R f ) C 2 F 5 , C 3 F 7 , C 4 F 9 ) at 650 °C in a flow system results in formation of CF 3 NdCFR f ′ (R f ′ ) CF 3 , C 2 F 5 , C 3 F 7 ).…”

“…This absorption can be attributed to vibration of oxaziridine ring. 4,12,13 In perfluoro-2,3-dialkyloxaziridines 5 the absorption is slightly shifted and appears between 1420 and 1410 but at 1439 cm -1 for compounds 5a having bulky i-C 3 F 7 group at nitrogen. 14,24 In the case of polyfluorooxaziridines containing three perfluoroalkyl groups connected to the heterocycle, 14 the band has low intensity and appears in the region 1420-1400 cm -1 .…”

“…In the mass spectra (EI) of polyfluorinated oxaziridines the parent ions are usually absent; however, CI mass spectra of these compounds exhibit a high-intensity M + 1 ion. 4,13,15,[24][25][26] Interesting information is obtained from 19 F NMR spectra of polyfluorinated oxaziridines. The nitrogen and carbon atoms in perfluoro-2,3-dialkyloxaziridines are stereogenic, and it results in the magnetic nonequivalence of fluorine atoms in CF 2 groups connected to these atoms.…”