Alkenes oxidative trifluoromethylation

Oxidative trifluoromethylation of terminal alkenes with sp C-CF3 bond formation occurs under mild conditions using (thiophene-2-carbonyloxy)copper (CuTc) as a catalyst, DIAB as the oxidant, and nucleophilic CFgSiMeg as the source of... 

In 1959 Carboni and Lindsay first reported the cycloaddition reaction between 1,2,4,5-tetrazines and alkynes or alkenes (59JA4342) and this reaction type has become a useful synthetic approach to pyridazines. In general, the reaction proceeds between 1,2,4,5-tetrazines with strongly electrophilic substituents at positions 3 and 6 (alkoxycarbonyl, carboxamido, trifluoromethyl, aryl, heteroaryl, etc.) and a variety of alkenes and alkynes, enol ethers, ketene acetals, enol esters, enamines (78HC(33)1073) or even with aldehydes and ketones (79JOC629). With alkenes 1,4-dihydropyridazines (172) are first formed, which in most cases are not isolated but are oxidized further to pyridazines (173). These are obtained directly from alkynes which are, however, less reactive in these cycloaddition reactions. In general, the overall reaction which is presented in Scheme 96 is strongly... 

Another convenient entry to fused cyclobutene-1,2-diesters was via site selective modification of the norbomene rt-bond in Smith s fe-alkene 49, e.g. treatment with 3,6-di(2 -pyridyl)-s-tetrazine 51 followed by DDQ oxidation afforded the cyclobutene-derivative 53 <97AA119>, while direct coupling with 3,5-f> (trifluoromethyl)-l,3,4-oxadiazo]e 54 furnished the tas(cyclobutene-l,2-diester) 55 (Scheme 6) <97SL196>. 

Studies on acetylenic molecules have been less extensive than those on alkenes diphenylacety-lene is converted at — 78 °C in Freon in the presence of calcium oxide with 2.5 equivalents of trifluoromethyl hypofluorite into l,l,2-trifluoro-l,2-diphenyl-2-(trifluoromethoxy)ethane (31) in 75% yield.37... 

Iodine-catalysed hydroperoxidation of cyclic and acyclic ketones with aqueous hydrogen peroxide in acetonitrile is an efficient and eco-friendly method for the synthesis of gem -dihydroperoxides and the reaction is conducted in a neutral medium with a readily available low-cost oxidant and catalyst.218 Aryl benzyl selenoxides, particularly benzyl 3,5-bis(trifluoromethyl)phenyl selenoxide, are excellent catalysts for the epoxidation of alkenes and Baeyer-Villiger oxidation of aldehydes and ketones with hydrogen peroxide.219 Efficient, eco-friendly, and selective oxidation of secondary alcohols is achieved with hydrogen peroxide using aqueous hydrogen bromide as a catalyst. Other peroxides such as i-butyl hydroperoxide (TBHP), sodium... 

Cycloaddition with activated alkenes Reaction between 3-substi-tuted imidazole 1-oxides 228 and 2,2-bis(trifluoromethyl)ethene-l,l-di-carbonitrile leads to 2-(l,3-dihydro-2H-imidazol-2-ylidene)malononitriles 304 (2006HCA1304). 

E)-3-Arylidenethiochroman-4-oncs possess thioether and oi,[)-unsaturatcd ketone functionalities both of which are susceptible to oxidation by DMD. In fact, chemoselective oxidation at sulfur is observed with a separable mixture of the sulfoxide and sulfone being produced in >5 1 ratio. A similar situation holds for the related thioflavanones. Epoxidation of the alkenic double bond in the thiochromanone 1,1-dioxides alone can be achieved using methyl(trifluoromethyl)-dioxirane (Scheme 65) <1994T13113>. However, reaction of NaOCl with 3-arylidenethioflavanones gives the epoxide and subsequent oxidation with DMD then gives a mixture of the sulfoxide and sulfone <2003MRC193>. 

The conversion of alkenes to oxiranes using ketone catalysts in the presence of a terminal oxidant such as Oxone has proved to be an important advance in the past decade, especially for the formation of chiral oxiranes (see Section 1.03.4.3.3(ii)). The conversion of alkenes to oxiranes has been comprehensively reviewed <20020R219>. The formation of the dioxirane species usually proceeds in situ, whether it be the formation of methyl(trifluoromethyl)-dioxirane in an academic setting <1995JOC3887>, or under conditions amenable to large-scale conversion of aromatic alkenes to oxiranes (oxone, acetone, ethyl acetate, no phase-transfer catalysis) <20020PD405>. 

Methyl(trifluoromethyl)dioxiiane (TFDO), prepared from 1,1,1-trifluoroacetone and KHSOg, is more reactive than DMDO by a factor of 600. In addition to facile epoxidation of alkenes, TFDO can be used to regioselectively oxidize tertiary over secondary C-H bonds via an oxenoid (butterfly) mechanism. ... 

A method for the transformation of alkenes into the corresponding ot-CFs-substituted ketones is obtained from the combination of photo-redox-catalysed trifluoromethylation, and oxidation mediated by an alkojysulfonium ion. In this context, the photocatalyst/ac-[Ir(ppy)3] plays a key role in achieving the keto-trifluoromethylation of C=C bonds in a regioselective manner. ... 

Tomita R, Yasu Y, Koike T, Akita M (2014) Cranbining photoredox-catalyzed trilluoro-methylation and oxidation with DMSO facile synthesis of a-trifluoromethylated ketones from aromatic alkenes. Angew Chem Int Ed 53 7144—7148. doi 10.1002/anie.20I403590... 

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