Hydroxylamines, trifluoromethylation

It is stable in the absence of light or air for 3—5 years but sunlight or irradiation with UV light converts it to o-nitroso-N,N bis(trifluoromethyl)-hydroxylamine, (F3C)2NONO (Ref 8). It reacts... 

Nucleophilic Perfluoroalkylation of Nitrones The reaction of a,N-diaryl nitrones with (trifluoromethyl)trimethylsilane (TMSCF3) gives O-trimethylsilyl ethers of a-(trifluoromethyl)-hydroxylamines. This reaction is initiated by potassium ten -butoxide. Removal of the trimethylsilyl group on acid treatment leads to a-(trifluoromethyl)hydroxylamines, whereas catalytic hydrogenation gives a-(trifluoromethyl)amines (Scheme 2.194). 

Nitrosating agents, 22 144, 145 Nitrosation, electrophilic, 22 144-152 Nitrosoarene complexes, osmium, 37 254 iV-Nitrosobis(trifluoromethyl) amine, 16 29, 30 )-Nitrosobis(trifluoromethyl) hydroxylamine, 16 46... 

V,/V-Bis(trifluoromethyl)hydroxylamine (5) is oxidized with potassium permanganate in acetic acid to an interesting free-radical compound, bis(trifluoromethyl)nitroxid-A7-yl(6), a pink-violet gas which condenses to a deep brown-violet liquid.246 Various oxidizing agents are effective in the oxidation of 5 to the corresponding nitroxyl 6.247 The best appears to be cerium(IV) salts either in the solid state or in aqueous acid solution.247 Efficient oxidation processes have been developed using aqueous potassium persulfate solutions, or electrochemical oxidation with cerium(III) nitrate and sodium nitrate in dilute nitric acid.247... 

Dehydrofluorination of lV,0-bis(trifluoromethyl)hydroxylamine (14) with potassium fluoride gives, in excellent yield, the perfluorinated oxime ether 15 with aC = N bond.109... 

Hydroxylamine N-Trifluoromethyl-N-( 1,1,2-trifl uoro-propyl)-EI6a/l. 149 (En + H2)... 

Hydroxylamine N-Difluoroincthy-Icn-O-heptafluorisopropyl-E 16a/1. 292 (-HF -> C = N) Propane llexafluoro-2-nitroso-2-trifluoromethyl- ElOb,. 346 (En + NOF/KF or N204/KF)... 

N-(2-Fluoro-phenyl) Trifluoro-EI0b, 36 (Ar H -f Ar F) N-(4-Fluoro-phenyl) Trifluoro-EI0b,. 36 (Ar-H -f Ar-E) Carbamidoyl Fluoride N-Phenyl-N-trifluoromethyl- F4, 1208 (Ar-NCS + HgF2 COF2/CsF) Hydroxylamine N-(4-Eihenyl-tetrafluoro-phenyl)- EI6a/l, 5f. (F -b NH-OH)... 

Hydroxylamine 0-Allyl-N-(4.5-dihydro-2-imidazolyl)-N-(6-fluoro-2-trifluoromethyl-phenyl)-E16a/1. 296 (OH OR)... 

A solution 0.1 mole of 2-ethoxymethyleneacetoacetic acid 4-trifluoromethylanilide (30.1 g) in 60 ml of ethanol is added dropwise at 5-10°C to the mixture of 0.11 mole of hydroxylamine hydrochloride (7.65 g) in 50 ml of water and 0.11 mole of sodium hydroxide (4.4 g) in 10 ml of water. The mixture is heated under reflux for 15 min. The crystals which are precipitated after cooling are filtered off, washed with water and dried. 19.6 g (72.6% of theory) of crystalline 5-methylisoxazole-4-carboxylic acid 4-trifluoromethyl-anilide are thus obtained, melting point (after recrystallization from toluene) 166.5°C. 

Nitroso compounds, such as nitro.sobenzene, react in a facile manner to aflbrd the O-silylatcd trifluoromethylated hydroxylamines. e,g. 43, quantitatively the adduct 43 slowly decomposes to unidentified materials. This again shows that in order for trimcthyl(trifluoro-methyl)silanc to react successfully the generation of an oxy anionic intermediate species is highly desirable. 

Examples of reactions which have used 1,2-diketones and ammonia with or without added aldehyde include the isolation of good yields of lophine (2,4,5-triphenylimidazole) from benzil and ammonia, a rather elegant synthesis of 4,5-di-t-butylimidazole (135), and the preparation of a series of 2-aryl-5-trifluoromethyl-4-phenylimidazoles (136) from 3,3,3-trifluoro-l-phenylpropane-l,2-dione monohydrate (Scheme 74). Additionally, the formation of 1-hydroxyimidazole 3-oxides (137) from a-diketones, hydroxylamine and aldehydes (74CI(L)38), and the preparations of 2,2 -bis- (138) and 2,2, 2"-tris-imidazolyls (139) from benzil, ammonia and polyformyl aromatics provide further examples of this versatile reaction (Scheme 74). There is yet some doubt about the pathway or pathways involved in these... 

Perfluoroalkylbenzothiazoles are obtained by the reaction of 2-aminothio-phenol with fluorinated /1-diketones or /l-chloro-a -(trifluoromethyl)-acrolein (91TL643). With hydroxylamine, the products are 5-hydroxy-A2-isoxazolines (87GEP3603291). 

Using jS-alkyl- -methoxyvinyl trifluoromethyl ketones allows the preparation of various heterocyclic compounds with a CF3-group (95JHC739, 99JFC(99)177). Often carried out by cyclocondensation with hydroxylamine, semicarbazide, thiosemicarbazide, phenylhydrazine, and urea (Scheme 99). 

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