Cycloadditions of 1,1-difluoroallene. A novel probe of mechanism.

Dolbier, William R. Jr.; Piedrahita, Carlos Alberto Romero; Houk, K. N.; Strozier, Robert W.; Gandour, Ruth Wells

doi:10.1016/s0040-4039(01)91499-6

Cited by 19 publications

(7 citation statements)

References 16 publications

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“…The addition of hydrogen fluorine to allene (10), for instance, gives exclusively 2,2-difluoropropane [22], whereas the same reaction with tetrafluoroallene (12) gives 1,1,3,3,3,-pentafluoropropane quantitatively [22b] . There is also, as expected, a difference in the reactivity of the two rr-bonds in 1,l-difluoroallene (ll) [23]. II undegoes [2+4] cycloadditions with electron-rich dienes at the electron-deficient, non-fluorinated double bond.…”

Section: Creactionssupporting

confidence: 68%

“Push‐Pull” Substituted Allenes

Saalfrank¹

1985

Israel Journal of Chemistry

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The two prototype "push-pull"-substituted allenes (cyclopropenylidene) (cyclopentadienylidene)methane and (cyclopentadienylidene) (cycloheptatrienylidene)-methane remain unknown. Although (fluoren-9-ylidene) (dibenzo [a,d] cyclohepten-Svylldenejrnethane has been synthesized [3] the spectroscopic data show no significant carbene character. Allene 4 should, however, show considerable carbene character because of the gain in aromatic stabilization on going from allene 4 to carbene s.• A. SynthesisThe difficulties involved in synthesizing and isolating "push-pull"-substituted allenes have two main causes:(1) Normal allene syntheses [4] are totally unsuitable for donor/acceptor substituted allenes. These methods all require the presence of a nucleophile or an electrophile, which then reacts further with the initially formed allene.(2) "Push-pull" allenes are expected to show a strong tendency to dimerize as reactive groups of opposite polarity are part of one and the same molecule.If the non-enohzing ketones 6 are reacted with the

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Section: Creactionssupporting

confidence: 68%

“Push‐Pull” Substituted Allenes

Saalfrank¹

1985

Israel Journal of Chemistry

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“…Reaction of Difluoroallene with 1,3-Butadiene. 1,1-Difluoroallene (DFA) has been shown to react with a number of 1,3-dienes by competing [2 + 4] and [2 + 2] reactions, the Diels−Alder cycloaddition mechanism being presumably concerted, whereas the [2+2] cycloaddition apparently proceeds via a diradical intermediate. , …”

Section: Resultsmentioning

confidence: 99%

“…The aim of the current study was, first, to validate gas-phase 19 F NMR as a technique for making reliable kinetic measurements of second-order reactions and, second, to use the method to study the kinetics of the cycloaddition reactions of 1,1-difluoroallene with 1,3-butadiene, for which no kinetic data are available. , The latter reaction is of considerable kinetic and mechanistic interest because [2 + 2] and [2 + 4] cycloadditions, mechanistically quite distinct, are in competition with each other and, to our knowledge, no experimental kinetic data or activation parameters for allene cycloadditions are presently available …”

Section: Introductionmentioning

confidence: 99%

Bimolecular Kinetic Studies with High-Temperature Gas-Phase ¹⁹F NMR: Cycloaddition Reactions of Fluoroolefins

et al. 2001

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A gas-phase NMR kinetic technique has been used for the first time to obtain accurate measurements of rate constants of some bimolecular, second-order cycloaddition reactions. As a test of the potential use of this technique for the study of second-order reactions, the rate constants and the activation parameters for the cyclodimerization reactions of chlorotrifluoroethylene (CTFE) and tetrafluoroethylene (TFE) were determined in the temperature range 240-340 degrees C, using a commercial high-temperature NMR probe. Obtaining excellent agreement of the results with published data, the technique was then applied to the reaction of 1,1-difluoroallene with 1,3-butadiene, the results of which indicate that the use of gas-phase NMR for reaction kinetics is particularly valuable when a reagent is available only in small amounts and in cases where there are several competing processes occurring simultaneously. The major processes observed in this reaction are regioselective [2+2] and [2+4] cycloadditions, whose rates and activation parameters were determined [k2 = 9.3 x 10(6) exp(-20.1 kcal x mol(-1)/RT) L/mol(-1) x s(-1) and k3 = 1.2 x 10(6) exp(-18.4 kcal x mol(-1)/RT) L/mol(-1) x s(-)(1), respectively] in the temperature range 130-210 degrees C.

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“…Ll-Dlfluoroallene (DFA) is a very reactive dienophile which undergoes exclusive cyc1oaddition to l,3-dienes using its non-fluorine-substituted C 2-C 3 double bond [l] . Such behavior is in dramatic contrast to the general non-regiospecificity of the [2+2] reactions of DFA, where the major adducts are always contrarily those with the CF2 group in the ring [1,2] . to~C .Fl The regiospecificity of the [2+4] reactions of DFA was rationalized in terms of the FMO theory of concerted cyc1oadditions [3,4], recognizing that the LUMO of DFA is its C 2-C 3 1(* orbital [4].…”

mentioning

confidence: 68%

“…Indeed, OFA is apparently a very electron-deficient alkene, if its reactivity (i.e. with cyclopentadiene) (1] is to be considered a measure. Also to be kept in mind is the fact that allene itself apparently undergoes non-regiospecific cycloaddition to nitrone 13 [15] .…”

Section: Nitrile Oxide Cycloadditionmentioning

confidence: 99%

1,3‐Dipolar Cycloadditions of 1,1‐Difluoroallene, Nitrones, Nitrile‐Oxides and Carbonyl Ylides

Burkholder

1985

Israel Journal of Chemistry

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The 1,3‐dipolar cycloadditions of C,N‐diphenylnitrone, C‐phenyl‐N‐methylnitrone, triphenylnitrone, mesitylnitrile oxide and tetracyanocarbonyl ylide with 1,1‐difluoroallene (DFA) are reported and discussed with respect to regiochemistry. Each of the dipoles adds exclusively to the C2—C3, non‐fluorine‐substituted π‐bond of DFA. The nitrones all undergo regiospecific reactions while mesitylnitrile oxide does not. The results are discussed with respect to FMO theory and other factors which can give rise to regiochemical variation.

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Cycloadditions of 1,1-difluoroallene. A novel probe of mechanism.

Cited by 19 publications

References 16 publications

“Push‐Pull” Substituted Allenes

“Push‐Pull” Substituted Allenes

Bimolecular Kinetic Studies with High-Temperature Gas-Phase ¹⁹F NMR: Cycloaddition Reactions of Fluoroolefins

1,3‐Dipolar Cycloadditions of 1,1‐Difluoroallene, Nitrones, Nitrile‐Oxides and Carbonyl Ylides

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Cycloadditions of 1,1-difluoroallene. A novel probe of mechanism.

Cited by 19 publications

References 16 publications

“Push‐Pull” Substituted Allenes

“Push‐Pull” Substituted Allenes

Bimolecular Kinetic Studies with High-Temperature Gas-Phase 19F NMR: Cycloaddition Reactions of Fluoroolefins

1,3‐Dipolar Cycloadditions of 1,1‐Difluoroallene, Nitrones, Nitrile‐Oxides and Carbonyl Ylides

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Bimolecular Kinetic Studies with High-Temperature Gas-Phase ¹⁹F NMR: Cycloaddition Reactions of Fluoroolefins