Ketones, diazo fluorination

Diazoketones react with trifluoromcthyl hypofluorite to give a mixture of a,a-difluoro ketones and o-fluoro-a-trifluoromethoxy ketones [70, 71] With elemental fluorine, two fluorine atoms replace the nitrogen in both diazoketones and unactivated diazo eompounds [70, 72, 73] (equation 9)... 

Polyfluoroalkyl- andperfluoroalkyl-substituted CO and CN multiple bonds as dipolarophiles. Dmzo alkanes are well known to react with carbonyl compounds, usually under very mild conditions, to give oxiranes and ketones The reaction has been interpreted as a nucleophilic attack of the diazo alkane on the carbonyl group to yield diazonium betaines or 1,2,3 oxadiazol 2 ines as reaction intermediates, which generally are too unstable to be isolated Aromatic diazo compounds react readily with partially fluorinated and perfluorinated ketones to give l,3,4-oxadiazol-3-ines m high yield At 25 °C and above, the aryloxa-diazolines lose nitrogen to give epoxides [111]... 

Diazoalkanes, diazoketones, and diazoacetates can be fluorinated at 0 C with the loss of nitrogen by treatment with 70 % hydrogen fluoride/pyridine (a,a-hydrofluorinations) in 30-95 % yield.31 133 Furthermore, diazo ketones and diazoacetates when N-halosuccinimide is additionally introduced into the hydrogen fluoride medium.133... 

Functional groups containing the C = N bond, such as hydrazones, oximes and diazo compounds, can also be used in the synthesis of fluorinated derivatives and these reactions are the subject of this section. The reaction products in these procedures are usually the corresponding g cw-difluoromethylene compounds. Since oximes and hydrazones arc obtained from aldehydes and ketones, these reactions can be considered as an alternative to the direct transformation of a carbonyl group into the difluoromethylene group. As indicated in Section... 

The reaction of diazo compounds with an electrophilic fluorinating reagent, tri-fluoromethyl hypofluorite. has also been studied (Tabic 8, entries 9 13). ° The reactions are carried out at — 70 C using trichlorofluoromethane as solvent and mixtures of g /n-difluoro compounds and fluoro(trifluoromethoxy) derivatives are obtained. Although conversion is generally complete, the yields of isolated products are low, due to their difficult separation. In some cases (entries 9, 11, and 12), ketones and epoxides arc formed as byproducts. Consequently, this method is not a useful alternative for the preparation ofgcw-difluoro compounds. 

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