Trifluoromethylated compounds

Herbicides can be grouped according to common stmctural features. Sometimes the assignment is arbitrary when there are a multitude of functional groups, eg, acifluorfen which is a diphenyl ether (phenoxy compound) as well as a trifluoromethyl compound. 

Miscellaneous Trifluoromethyl Compounds. The herbicides in this group are used for a wide variety of weed-control purposes. Acifluorfen, lactofen [77501-63-4] and oxyfluorfen are used for selective, pre-, and post-emergence weed control in croplands. Fluorochloridone is used for selective, pre-emergence weed control in cropland, and fluridone, fomesafen, and mefluidide [53780-34-0] are used for post-emergence control (296). Fluridone is also used as an aquatic herbicide (2). 

Aromatic thio orthoesters are successfully converted into trifluoromethyl arenes by treatment with a pyridinium polyhydrogen fluoride-A -halo imide reagent. The reactions are conducted at -30 to -20 °C, and the nature of A-halo imide is critical both 1,3-dibromo-5,5-dimethylhydantoin and A-bromosuccin-imide give similar yields of trifluoromethyl compounds [5] (equation 7)... 

Under Barbier conditions, trifluoromethyl bromide reacts with electrophiles, such as aldehydes, Orkelo esters, activated esters, and anhydrides in the presence of pyridine to give trifluoromethylated compounds [35, 45 46] (equations 34 37)... 

Table 15 [S 19 56, 59 93 107 108 109, 110, 111, 112 113, 114] contams NMR data for a vanety of tnfluoromethyl compounds that do not fit into the more common categones already covered Most carbon-attached tnfluoromethyl (CF3-C) F-NMR signals fall in the 25 ppm range from -60 to -85 ppm, a notable exception being trifluoromethylacetylenes, with signals at approximately -50 ppm Trifluoromethylated compounds in which the CFj is directly bonded to an atom orlier carton are considered in Table 16 [57 59,95 109,115,116 117 118,119,120 121 122, 123 124, 125] These heteroatom contaming compounds are of interest to both organic and morganic chemists and have been studied by NMR for numerous reasons...

Table IS. NIVfR Data for Miscellaneous Trifluoromethyl Compounds...

A number of unusual aliphatic trifluoromethyl compounds have been obtained from 4-hexafluoroisopropylidene-2-phenyl-5-oxazolone (4) 10 The latter was prepared as shown in Eq. (2). The ease of formation... 

This formulation is supported by the proton resonance spectrum of the trifluoromethyl compound 101 which shows that it exists in the CH form shownd However, strong electron-withdrawing groups in the 4-position apparently lead to enolization, and compound 102, for example, gives an intense color with ferric chloride, - Other 4-acylated oxazol-5-ones are often formulated as 103 (see, e.g, reference 113). Tautomerism of the type illustrated by the equilibrium 104 103 has been discussed (see reference 115 for further references). 

The kinetics of protodeboronation of a range of substituted benzeneboronic acids in aqueous sulphuric acid mixtures were also examined. Good first-order kinetics were obtained in all cases except for the 3-fluoro compound (due to the sulphonation side reaction) and the 3-trifluoromethyl compound, which hydrolysed, hydrogen fluoride being produced the rates with this latter compound were only followed to 30 % reaction. The kinetic details are summarised in Table 190, from... 

Facile synthesis of optically active trifluoromethylated compounds asymmetric Diels-Alder reaction of trifluoromethylated ot, -unsaturated sulfonamide under high-pressure conditions [79]... 

The state of the synthetic art in this area, in 1979, is much more satisfactory. During the past decade, several new synthetic developments have occurred such that we are closer to the point where the limitations upon synthesis of trifluoromethyl compounds are related more to stability problems in isolated cases, and are not nearly so much due to lack of widely applicable synthetic techniques. We find ourselves, for example, in a position in 1979 where the germanium compound, Ge(CF3)4, which in the past decade, was considered by many workers to be of insufficient stability to permit isolation, has been prepared by four independent methods and is known to be stable to over 100°C. Many of these new synthetic techniques have emerged from studies conducted in our laboratory at the University of Texas and previously... 

The primary products are the trifluoromethyl compounds. The per-fluoroethyl species are considered to arise through an unusual mechanistic process (20), instead of being generated directly, as penta-... 

Other alkylgold(III) compounds are [Au2(/r-X)2(CF3)4] (X = Br, I) synthesized by co-condensation of gold with CF3Br and CF3I, respectively, and may be sublimed at room temperature.1654 Trifluoromethylated compounds are potentially useful precursors for CVD studies as they are expected to show enhanced volatility.1655 m-[Au(CF3)2I(PMc3)] is formed in quantitative yield by oxidative addition of trifluoromethyl iodide to [Au(CF3)(PMe3)], the reaction is proposed to proceed via radical intermediates.1524,1656... 

Some typical carbon NMR data for trifluoromethyl compounds are provided in Scheme 5.26. 

Attempted syntheses of trifluoromethyl derivatives of germanium, tin, and lead by thermal decarboxylation either resulted in decomposition of the trifluoroacetate without forming carbon dioxide (22,39,40) or gave carbon dioxide but no trifluoromethyl organometallic (22). In the latter case, the metal fluoride was detected. This suggests that the trifluoromethyl compound is thermally unstable and decomposes by fluoride abstraction. 

Therefore, achievement of this desired substitution, particularly the formation of a carbon-carbon bond at the a position is one of most important goals of modern organofluorine chemistry. Although anodic substitution is a characteristic of certain electrolytic reactions, no results pertaining to the electrolytic substitution of trifluoromethylated compounds have been reported. Recently, the use of the electrochemical technique has opened new avenues for the realization of such nucleophilic substitution [40-42] and construction of a carbon-carbon bond [43-45]. 

In the course of studies on azide-tetrazole equilibria, some azido derivatives 73 of this ring system have been subjected to X-ray structure elucidation <2005JST(751)65>. These derivatives proved to be mainly planar and the least planar part of these molecules were the azide moieties. In both cases (72 R= H and Me), formation of hydrates were also observed. Crystallographic analysis of the trifluoromethyl compound was described by Lange et al. <1997APH299>, and structure elucidation of the nucleoside analogue 74 was reported by Stanovnik et al. <1998JHC513>. 

In Scheme 20, another ring closure starting from 5-aminotetrazole is shown, which should be discussed in more detail. Nenajdenko and co-workers carried out studies on ring closure reactions taking place between 1,1,1-trifluoro-4-sulfonyl-but-3-ene-2,2-diols 107 and a series of aminoazoles <2002S901>. They found that the reaction can take place in two different ways and, thus, the isomers 108 and 109 can be formed. Reaction of 107 with 5-aminotetrazole 106 was found to proceed regioselectively, and yielded the 5-trifluoromethyl compound 108 as the main product in good yield (72%). The other isomer 109 was found only in traces. 

The anodic oxidation of trifluoroacetic acid affords the trifluoromethyl radical CFj. Addition of this radical to unsaturated heterocycles can produce bis(trifluoromethylated) compounds (Scheme 119) [225]. 

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