Diazomethane, reaction with fluorinated

Reactions of fluorinated dipolarophiles. Electron-deficient unsaturated species generally make better dipolarophiles, therefore, fluonnated alkenes become better dipolarophiles when vinylic fluonnes are replaced by perfluoroalkyl groups For example, perfluoro-2-butene is unreactive with diazomethane, but more highly substituted perfluoroalkenes, such as perfluoro-2-methyl-2-pentene, undergo cycloadditions in high yields [5] (equation 2) Note the regiospecificity that IS observed in this reaction... 

A seven-membered heterocycle is formed from the bicyclic heterocycle initially produced by the reaction of fluorine-containing cyclobutene with diazomethane due to a rearrangement leading to a high yield of the product (83JCS(CC)5). 

Ring-Fluorinated Pyrazolines Fluorinated olefins undergo 1,3-dipolar cycloaddition reactions with diazomethane to produce fluorinated pyrazolines. In some cases, these are not isolated but are directly converted to fluorinated cyclopropanes by extrusion of nitrogen, either thermally or photochemically. For example, reaction of a series of 2-aryl-3-fluoroacrylates with diazomethane produced intermediate fluorinated pyrazolines that were ponverted to a series of 1-aryl-l-cyclopropane carboxylates by irradiation at 3500 A (Fig. 3.75). The esters in turn were... 

The reaction of 81 with diazomethane is another example of nucleophilic cycloaddition process. Elimination of nitrogen from initially formed triazole 142 leads to aziridine 141. Vinylic fluorine in 81 can be replaced by chlorine using the reaction with ClSi(CH3)3/KF. Alternatively, chloride 143 can be prepared by the reaction of 81 with AlCl3. ... 

Reactions offluorinated dipoles. In recent years, much effort has been devoted to the preparation of tnfluoromethyl-substituted 1,3-dipoles with the goal of using them to introduce trifluoromethyl groups into five-membered nng heterocycles Fluorinated diazoalkanes were the first such 1,3-dipoles to be prepared and used in synthesis A number of reports of cycloadditions of mono- and bis(tnfluo-romethyl)diazomethane appeared prior to 1972 [9] Other types of fluonne-substi-tuted 1,3-dipoles were virtually unknown until only recently However, largely because of the efforts of Tanaka s group, a broad knowledge of the chemistry of tnfluoromethyl-substituted nitrile oxides, nitnle imines, nitnle ylides, and nitrones has been accumulated recently... 

Dream reactions can be performed using chemical micro process engineering, e.g., via direct routes from hazardous elements [18]. The direct fluorination starting from elemental fluorine was performed both on aromatics and aliphatics, avoiding the circuitous Anthraquinone process. While the direct fluorination needs hours in a laboratory bubble column, it is completed within seconds or even milliseconds when using a miniature bubble column. Conversions with the volatile and explosive diazomethane, commonly used for methylation, have been conducted safely as well with micro-reactors in a continuous mode. 

The conversion of diazo compounds into gm-difluoroalkenes is an attractive route to the synthesis of these compounds (Scheme 7.105) [168]. The reactions are catalyzed by a catalytic amount of copper salt with an equimolar amount of cesium fluoride as an additive. It is noteworthy to point out the copper loading in this example is significantly lower than other copper-catalyzed fluorinations. In general, diaryl diazomethanes bearing electron-donating groups afforded lower yields than electron-deficient arenes. 

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