Activation of acrylate-moiety by strain and fluoroalkyl substitution in 4-chloro-3,3,4-trifluoro-methoxycarbonyl cyclobutene

Catalytic Cyclopropanation of Fluorine‐Containing Alkenes and Dienes with Diazomethane and Methyl Diazoacetate

“…Scheme 1 It should be noted that, in contrast to compounds 1 and 7, some non-fluorinated cyclobutenes with endocyclic double bonds undergo catalytic cyclopropanation with diazomethane and ethyl diazoacetate. [12Ϫ14] The formal cyclopropanation of endocyclic double bonds of fluorinated cyclobutene derivative has occurred in reactions with ethyl diazoacetate and phenyldiazomethane in the absence of catalysts, [15] but this process could be a result of 1,3-dipolar cycloaddition and deazotation reactions.…”

“…[12Ϫ14] The formal cyclopropanation of endocyclic double bonds of fluorinated cyclobutene derivative has occurred in reactions with ethyl diazoacetate and phenyldiazomethane in the absence of catalysts, [15] but this process could be a result of 1,3-dipolar cycloaddition and deazotation reactions.…”

“…Scheme 5 Note that the signal of the CF 2 group of one of the isomers appeared in the 19 F NMR spectrum as a broadened singlet, whereas the corresponding signal of the other isomer appeared as two broadened doublets with the geminal spinϪspin coupling constant J FF ϭ 257 Hz. The dehydrochlorination of compound 14 in the presence of tBuOK in THF resulted in the formation of an isomer of methyl 3,4,4-trifluorobicyclo[4.1.0]hept-2-ene-7-carboxylate (15). The trans configuration of the cyclopropane unit in compound 15 was attributed from 1 H NMR spectral data.…”