Difluoromethylene dimerization

Isocyanides react with fluorine [75 to yield difluoromethylene imines, which tend to dimerize In an inert solvent, imines accept fluorine fioin trifluoromethyl hypofluorite [76, 77] (equation 11)... 

The addition of primary amines to fluoroolefins under anhydrous conditions yields imines The hexafluoropropene dimer, perfluoro-2-methyl-2-pcntcne, and ten butylamine react to yield a mixture of two compounds m a 9 4 ratio [4] (equation 3) rather than just the major keteiiimme-imine, as previously reported [5] It IS claimed that this result is possible by means of isomerization to the terminally unsaturated difluoromethylene isomer prior to nucleophilic attack Secondary amines add to fluoroolefins under anhydrous conditions to give fluonnated ternary amines m good yields If the fluoroolefin is added to the amine without cooling the reaction mixture, or if an excess of the secondary armne is used, there is a tendency toward dehvdrofluonnation of the ternary amine The products... 

The behavior of strained,/Zuorimiret/ methylenecyelopropanes depends upon the position and level of fluorination [34], l-(Difluoromethylene)cyclopropane is much like tetrafluoroethylene in its preference for [2+2] cycloaddition (equation 37), but Its 2,2-difluoro isomer favors [4+2] cycloadditions (equation 38). Perfluoromethylenecyclopropane is an exceptionally reactive dienophile but does not undergo [2+2] cycloadditions, possibly because of stenc reasons [34, 45] Cycloadditions involving most possible combinations of simple fluoroalkenes and alkenes or alkynes have been tried [85], but kinetic activation enthalpies (A/f j for only the dimerizations of tetrafluoroethylene (22 6-23 5 kcal/mol), chlorotri-fluoroethylene (23 6 kcal/mol), and perfluoropropene (31.6 kcal/mol) and the cycloaddition between chlorotnfluoroethylene and perfluoropropene (25.5 kcal/mol) have been determined accurately [97, 98] Some cycloadditions involving more functionalized alkenes are listed in Table 5 [99. 100, 101, 102, 103]... 

Diphenylallene affords a dimer characterized as 1-diphenylmethyl-ene-2-methylene-3,3-diphenylcyclobutane 18>. 1, l-Difluoro-3,3-bis (triflu-oromethyl)allene gives at 90 °C a mixture of at least seven compounds thought to be dimers and trimers 1 L). 1,1-Difluoroallene dimerizes to both the 3,3,4,4-tetrafluoro and l-difluoromethylene-2-methylene-3,3-difluoro-cyclobutane Z6>. Perfluoro-l,2-pentadiene reacts at 20 °C to produce three dimers, including 22% of a l,2-bis(difluoromethylene)cyclobutane and 63% of a l-fluoroperfluoroethylmethylene-2-difluoromethylene cycloadduct 10>. l,l-Dichloro-3,3-dimethylallene gives a mixture of dimers 25>. 

Difluoromethylene(trifluoromethyl)phosphane (216), available most conveniently by thermolysis of the stannylphosphane (215), dimerizes and trimerizes on warming from a cold trap to give the... 

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