Difluorocarbene generation from

Finally, the addition of difluorocarbene (generated from FjClCCOjNa) to steroidal acetylenes has been achieved24-26 giving rise to exotic cyclopropenones bearing steroid systems as substituents, e.g. 19/20. 

Difluorocarbene, generated from fluorosulfonyldifluoroacetate, adds on double bonds and aromatic or vinylic ketones, affording fluorinated cyclopropanic ethers. ... 

In fluorinated agrochemicals, the difluoromethoxy group is less commonly encountered than the trifluoromethoxy group. The difluoromethoxy group is readily available from the reaction of a phenoxy group and difluorocarbene, generated from chlorodifluoromethane and a base (Fig. 27) [6,107-109]. 

The 5,7-diaryl-2-fluoro-47/-l,3-diazepines 391 have been synthesized from 3-aryl substituted 2/7-azirines 390 and difluorocarbene generated from CF2Br2 (Scheme 184). This reaction involves isomerization of the initial azirinium ylide 392 into a 2-aza-l,3-diene 393, which undergoes [4 + 2] cycloaddition with the starting azirine, followed by ring expansion of cycloadduct 394 and dehydrofluorination <2006TL639>. 

Precursor of difluorocarbene [before references]. In a study of the behavior of cholesterol to dihalocarbenes, a Syntex group6 found that dichlorocarbene does not add to the somewhat unreactive double bond of cholesterol but that the less bulky difluorocarbene, generated from sodium chlorodifluoroacetate, does add to give a difluorocyclopropane which was assigned the 5/3,6/3-orientation mainly on the basis... 

Difluorocarbene generated from HFPO (1) adds to thiocarbonyl compounds to give thiiranes, as illustrated in the section on oxiranes with the formation of thiirane 30. Tetrafluorothiirane (87) has been made in 30 0% yield from thiocarbonyl fluoride (86) by this method. ... 

Aziridines are commonly prepared from imine precursors. Carbene addition to the C=N bond is illustrated by the formation of aziridine 127 from imine 126. ° Difluorocarbene, generated from HFPO (1), also adds to imines such as 128 to give the highly fluorinated aziridine 129. In the presence of Lewis acids, diazo compounds react with imines to produce aziridines. Ethyl diazoacetate and imine 130 gave aziridine 131 in 93% yield, with a cis/trans ratio of 95 5. Chiral diazo compound 132 reacted with the aldimine precursor 133 to afford aziridine 134 in 81 % yield.The reaction displayed both high cis selectivity (>95 5) and excellent diasteroselectivity (94% de). Reductive removal of the chiral auxiliary gave the optically active hydroxymethylaziridine 135. 

Phase-transfer systems for generating fluorohalocarbenes from the corre spending haloforms are simple and effective with nucleophilic olefins [5J, 54 55, 56, 57, 58, 59] (Table 3 and equations 23 and 24), and the process was extended recently to difluorocarbene [60] Chlorofluorocarbene also can be generated from fluorotrichloromethane and utanium(O) produced in situ (T1CI4 + L1AIH4) Yields of gem-chlorofluorocyclopropanes range from excellent (85% for a. meth ylstyrene) to poor (12% for 1-hexene) [61]... 

It is well known that azomethine ylides, which are usually formed in situ, are very good substrates for 1,3-dipolar cycloadditions. The group of Novikov and Khlebnikov [328] generated such a 1,3-dipol by reaction of difluorocarbene formed from CBr2F2 (2-626) with the imine 2-627. Cycloaddition of the obtained 2-629 with an ac-... 

Difluorocarbene.1 This carbene can be generated from CF2Br2 by reaction with zinc in THF catalyzed by I2. This reagent should prove useful for the generation of difluorocyclopropanes. 

Hexafluorocyclopropane (7) is also a source of difluorocarbene under conditions similar to those used with hexafluoropropylene oxide. It is also possible to generate difluorocarbene from the explosive difluoro-3//-diazirine (8) thermally or by photolysis with UV light. Difluorocarbene can be generated from trimethyl(trifluoromethyl)tin (McjSnCFj) by heating at a temperature of 150 or at a lower temperature of 80 C in the presence of sodium iodide. ° ... 

Among the simple transient species of carbon and fluorine are included trifluoromethyl cation, CF3+, which has a very transient existence trifluoromethyl anion, CF3, which is stable at low temperature and can be generated from CF3TMS (trimethylsilyltrifluoromethane) CF3-, a free radical available from irradiation of CF3I and difluorocarbene, CF2 , which exists as a ground-state singlet. 

Difluorocarbene can be generated from trimethyl(trifluoromethyl)tin (Me3SnCF3) by heating at a temperature of 150 C2n or at a lower temperature of 80 C in the presence of sodium iodide.2021... 

Other electrophiles that react with in situ-generated perfluorocarbanions in elude epoxides [226] equation 47), carbon dioxide [227] (equation 47) acyl halides [228, 229, 230, 20, 232, 233] (equation 48), fluoroformates [23d] car bonyl fluonde [23S, 236, 237] hexafluorothioacetone (generated from its dimei) [238] (equation 48), an a-fluoroalkylamine f2J9] (equation 48), cyanuric fluoride [240], and reactive alkyl halides [247, 242 243, 244, 245] (equation 49) Interestingly, an in situ-generated carbanion will also react with dibromodifluoromethane ia a mechanism involving difluorocarbene [246] (equation 50)... 

Dihalocarbenes generated from haloforms and strong bases e.g. alkoxides) or from haloforms and alkali metal hydroxides under phase transfer conditions " or organomeicuiytrihalomethanes, add to azomethines to yield 2,2-dihaloaziridines (49 equation 30). The following carbenes have been used for such purposes dichlorocarbene, " dibromocarbene, " difluorocarbene, bromochlorocar-bene and bromofluorocarbene. The addition of dihalocarbenes to azoxybenzene or azobenzene affords dihaloaziridines e.g. 50 equation 31) among other products. 

The initial experiments that indicated that difluorocarbene ligands could be generated from trifluoromethyl groups were reported by Reger who abstracted fluoride ions from compounds like CpMo(CO)3CF3 with strong Lewis acids. The CpMo(CO)3CF2+ ion produced,... 

COFj is generated from PTFE in air, both by pyrolysis [1166,1247,1285,1382,1794, 2149,2167], and by exposure to ionizing radiation [647,790]. A possible scheme for the formation of COF by PTFE pyrolysis is indicated beiow, involving homolytic fission of the polymer chain, fragmentation to eliminate difluorocarbene, and its subsequent oxidation to COFj [1382,2149] ... 

The reaction of norbornadiene with fluorochlorocarbene (generated from sodium dichloro-fluoroacetate in diglyme at 140 °C) and difluorocarbene [from phenyl(trifluoromethyl)mercury and sodium iodide at 80 °C] gave, in addition to 1,2-addition products, 1,5-addition products 1 and 2 resulting from a linear homocheletropic reaction. ... 

In order to test this effect, difluoromethyl perfluoroalkanesulfonates have been synthesized and investigated. Difluoromethyl triflate was synthesized earlier from the insertion of difluorocarbene, generated by photolysis of difluorodiazirine into the O—H bond of triflic acid114 (equation 94). By using HCF2S03H as a difluorocarbene precursor, difluoromethyl perfluoroalkanesulfonate can be obtained in 30-50% yields115 (equation 95). 

Generated from HFPO, difluorocarbene reacts with a wide variety of unsaturated compounds, both fluorinated and unfluorinated. It can react stereospecifically, as illustrated with the chloro-l,2-difluoroethylenes. 

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