Acetylenes, perfluoroalkyl

Perfluoroalkylation of olefins and acetylenes occurs in low yields when perfluoroalkylcopper reagents are heated with alkenes or acetylenes in DMSO [226, 237, 238, 239]. Undine derivatives react similarly [240]... 

Perfluoroalkylation of perfluoroalkylethylenes and addition of perfluoroalkyl iodides to olefins or acetylenes are catalyzed by copper metal [238, 239] Similar copper-catalyzed addition of iododifluoroacetates to olefins has been observed [241]... 

Examples of perfluoroalkyl iodide addition to the triple bond include free radical addition of perfluoropropyl iodide to 1 -heptyne [28] (equation 21), thermal and free radical-initiated addition of lodoperfluoroalkanesulfonyl fluorides to acetylene [29] (equation 22), thermal addition of perfluoropropyl iodide to hexa-fluoro 2 butyne [30] (equation 23), and palladium-catalyzed addition of per-fluorobutyl iodide to phenylacetylene [31] (equation 24) The E isomers predominate in these reactions Photochemical addition of tnfluoromethyl iodide to vinylacetylene gives predominantly the 1 4 adduct by addition to the double bond [32] Platinum catalyzed addition of perfluorooctyl iodide to l-hexyne in the presence of potassium carbonate, carbon monoxide, and ethanol gives ethyl () per fluorooctyl-a-butylpropenoate [JJ] (equation 25)... 

Similarly, low-temperature photolysis of 4,5,6-fluorosubstituted 1,2,3-tna zines results in the elimination of nitrogen, but the product composition depends on the substituents When the substituents are fluonne atoms, the intermediate product IS a four-membered, mtrogen-contaming ring that quickly dimenzes When all the substituents are perfluoroalkyl groups, the pyrolysis results in a mixture perfluoroalkyl acetylenes and perfluoroalkyl cyanides [79] (equations 48 and 49). 

Migration of the perfluoromethylthio group occurs in perfluoroalkyl acetylenic thiol esters and substituted Mmethylpyrroles [78, 79] (equation 18)... 

The values presented in Table 2 depict the variation of C = C re-bond strength with increasing fluorination and are consistent with the differences in reactivity associated with differing degrees of fluorination.3 Fluorination also destabilizes allenes and acetylenes.20 22 Similarly, per-fluoroalkyl groups destabilize C = C bonds. Note, however, that perfluoroalkyl groups can lend kinetic stabilization to strained molecules.3... 

Approaches that represent a type (ii) synthesis of 277-pyran-2-ones include the self-condensation of 1,3-dicarbonyl compounds, the reaction of cyclopropanones with pyridinium enolbetaines and the reaction of activated methylene groups with acetylenic esters <1984CHEC, 1996CHEC-II>. 4-Perfluoroalkyl-6-aryl-pyran-2-ones are formed by the reaction of the phosphonium salts 631 with 2-perfluoroalkynoates (Equation 254) <1999JFC(95)135, 1998JFC(91)99>. Dimedone reacts with dimethyl acetylenedicarboxylate to afford the pyran-2-one 632 in excellent yield (Equation 255) <2003PS2627>. 

Hetaryl-substituted perfluoroalkyl(aryl)acetylenes, reactions with heterocycles 91UK1005. 

Perfluoroalkyl iodides RFI also add to olefins and acetylenes in presence of transition metal complexes674,675 as well as with free-radical initiators676. A typical example is the addition of perfluorooctyl iodide to phenylacetylene (equation 90). 

With acetylenes containing perfluoroalkyl groups (CF3, C4F9) as substituents, cis and trans isomers of the bis(difluoroamino) compound could be isolated in good yield, but rearrangement took place at a higher temperature. 

Benzimidazoles, 2,3-dihydro-, by Nu addition at C-2, 56, 203 Benzimidazole, 2-fluoro-, 59, 272 Benzimidazole, 1-methyl-, ring expansion to chloroquinoxalines, 59, 305 Benzimidazole, l-methyl-2-(5 -methyl-2 -thienyl)-, bromination, 57, 319 Benzimidazole 3-oxides, chloro-deoxygenation, 59, 270 Benzimidazoles, 2-perfluoroalkyl-, 60, 25 Benzimidazoles, 2-(l-pyridinio)-, 60, 204 Benzimidazoles, 2-(2-pyridinioethyl)-, elimination reactions, 60, 246 Benzimidazoles, tetrafluoro-, 59, 14 Benzimidazole-2-carboxylic ester 3-oxide, 7-nitro-5-trifluoromethyl-, 60, 17 Benzimidazolium salts, l-amino-3-alkyl-, reaction with activated acetylenes, 56, 138... 

Perfluoroalkynylcopper reagents can be prepared by metathesis reactions with the zinc or cadmium reagent (e.g., formation of 6) or by treatment of terminal (perfluoroalkyl)acetylenes with copper(I) chloride/ammonium hydroxide. Perfluoroalkynylcopper reagents react with... 

Perfluoroalkylcopper reagents couple with 1-iadoacetylenic derivatives to give the expected perfluoroalkyl-substituted acetylenes [226] (equation 153) The coupling reaction is complicated by formation of the diyne from competitive exchange processes... 

The allylstannylation of aryl(perfluoroalkyl)acetylenes with (3-(methoxycarbonyl)allylstannanes does not require any activator (Scheme 5.7.9), where addition of a catalytic amount of AIBN shortens the reaction time without a decrease in yield. 

The less stable trifluoromethyl zinc compounds [48] can be used as a source of nucleophilic trifluoromethyl fragments either in the isolated form or generated in situ by sonication of perfluoroalkyl iodides with zinc in DMF or THF. Zinc perfluoroorganyls find application in Barbier-type reactions [49], palladium-catalyzed cross-coupling reactions [50], or hydroperfluoroalkylations of acetylenes or olefins [51] (Scheme 2.119). 

In addition to the arenes, enolates, and other nucleophiles depicted in Scheme 2.142, FITS reagents are also reactive in the perfluoroalkylation of unactivated alkenes, alkadienes [19], and acetylenes [20] (Scheme 2.146). In contrast with olefin perfluoroalkylation by means of perfluoroalkyl bromides or iodides (Section 2.2.1), this reaction does not follow a free radical mechanism but proceeds via cationic intermediates which can be either trapped by addition of nucleophiles or nucleophilic solvents or quenched by -deprotonation with a base (Scheme 2.147). 

A mechanism taking either an ionic or a radical path, depending on the solvent, is assumed for the reaction of perfluoroalkyl iodonium reagents with acetylenes [20], leading to a variety of addition or substitution products (Table 2.3 and Scheme 2.148). 

Scheme 2.148 Proposed mechanism for the reaction of perfluoroalkyl iodonium reagents with different acetylene derivatives [20].

Syntheses of several other perfluoroalkyl or perfluorocycloalkyl-pyridazines are reported. With acetylenic compounds, for example with hexafluorobut-2-yne, tetrafluoropyridazine is alkylated in the presence of fluoride ion at position 4 (186), but in addition a bicyclic derivative (187) was isolated. ... 

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