Fluoroolefin synthesis

Peterson fluoroolefination. Synthesis of the AlaiJ/[ Z)-CFC]-pro isostere (50) DPP IV inhibitors using the Peterson fluoroolefination reaction... 

Peterson fluoroolefination. Synthesis of 2-(2-amino-1-fluoro-propylidene)-cyclopentanecarbonitrile (55) as DPP IV inhibitors... 

Terminal Fluoroolefins. Synthesis and Application to Mechanism-Based Enzyme Inhibition ... 

Rozhkov IN, Stepanoff AA (1981) The second regular meeting of soviet-japanese fluorine chemists. Reductive coupling of fluoroolefins Synthesis of higher perfluorinated 1,3-dienes and allenes, Moscow, p 133... 

The research group of Shoichet [57, 59] also has demonstrated that using CO2 as a polymerization medium can improve the effectiveness of the propagation reaction over chain transfer reactions in fluoroolefin synthesis. Shoichet s... 

Nickel fluoride is used in marking ink compositions (see Inks), for fluorescent lamps (4) as a catalyst in transhalogenation of fluoroolefins (5), in the manufacture of varistors (6), as a catalyst for hydrofluorination (7), in the synthesis of XeF (8), and in the preparation of high purity elemental fluorine for research (9) and for chemical lasers (qv) (10). 

Table 18. Synthesis of Fluoroolefins via Reaction of Fluoromethylene-triphenylphosphorane with Carbonyl Compounds [49]...

Much of the recent effort m the study of perfluoroaliphatic lithium compounds IS concerned with vinyl or substituted fluorovinyl compounds. Modifications and extensions of the earlier research on the synthesis of trifluorovinyllithium provide many new fluorovmyllithium intermediates that react with numerous electrophiles to give novel and interesting fluoroolefinic compounds... 

Today microemulsions are used in catalysis, preparation of submicron particles, solar energy conversion, extraction of minerals and protein, detergency and lubrication [58]. Most studies in the field of basic research have dealt with the physical chemistry of the systems themselves and only recently have microemulsions been used as a reaction medium in organic synthesis. The reactions investigated to date include nucleophilic substitution and additions [59], oxidations [59-61], alkylation [62], synthesis of trialkylamines [63], coupling of aryl halides [64], nitration of phenols [65], photoamidation of fluoroolefins [66] and some Diels-Alder reactions. 

Since PTFE was first synthesized more than 50 years ago, fluoropolymers have been produced by radical polymerization and copolymerizaton processes, but without any functional groups, for several reasons. First, the synthesis of functional vinyl compounds suitable for radical polymerization is much more complicated and expensive in comparison with common fluoroolefins. In radical polymerization of one of the simplest possible candidates—perfluorovinyl sulfonic acid (or sulfonyl fluoride—there was not enough reactivity to provide high-molecular-weight polymers or even perfluorinated copolymers with considerable functional comonomer content. Several methods for the synthesis of the other simplest monomer—trifluoroacrylic acid or its esters—were reported,1 but convenient improved synthesis of these compounds as well as radical copolymerization with TFE induced by y-irradiation were not described until 1980.2... 

The polymerization of other fluoroolefins such as TFE with hexafluoropro-pylene (HFP), TFE with ethylene, and vinylidine difluoride - " further demonstrates the broad applicability of liquid and supercritical CO in the production and processing of fluorinated polymers. Many of the aforementioned advantages associated with CO2, including tunable solvent properties, integrated synthesis, separation and purification processes, negligible chain transfer in the presence of highly electrophilic species, and relative ease of recycling, make it an ideal solvent for fluoroolefm polymerization. 

Synthesis of funtionalized (Z)-fluoroalkene-type dipeptide isosteres (36) via Sml2-mediated reduction of y,y-difluoro-ot, -enoates 2.3.19. Reductive formation of fluoroolefins and subsequent conversion to diketopiperazine mimics (71). Nonpeptidic amide bond replacement... 

The synthesis and utility of fluoroolefin peptide isosteres has previously been reviewed [45], The fluoroolefin isostere preparations summarized below are organized by the synthetic method employed to introduce the fluoroolefin rather than by the dipeptide isostere formed. 

Bartlett etal. [14] described the synthesis of a series of fluoroolefin tripeptide isosteres Cbz-Glyi/r[(Z)-CF=CH]LeuXaa (Xaa = Gly, Ala, Leu, Phe, and NH2) (10) (Scheme 3) as the ground-state analog inhibitors of thermolysin. Treatment of acid (15) with ammonia gave 10e. The inhibitors 10a-d are formed by conventional amide acid coupling reactions of suitably protected amino acids followed by saponification with lithium hydroxide. 

A kinetically controlled Negishi palladium-catalyzed coupling reaction was used in a highly stereospecific synthesis of (E)- or (Z)-a-fluoro-a,/(-unsaturated ketone (29), an intermediate to the above described depsipeptides [54], Reaction of E/Z gem-bromofluoroolefin (30) and alkoxyvinylzinc species (31) yielded (Z)-29 in 70-99% yields. When the unreacted (Z) bromo, fluoroolefin was allowed to react in tetrahydrofuran (THF) under reflux, (E)-29 was formed in up to 98% yield (Scheme 9). 

As a prelude to the use of olefination reactions to introduce the fluoroolefin amide isostere, the synthesis of fluoroolefin analogs of CGP 49823 is described where a nonpeptidic amide bond was replaced with a fluoroolefin [55]. Comparison of the binding affinities of these analogs for the NK1 receptor enabled determination of the active conformation of the amide containing compound CGP 49823. It was otherwise not easy to establish that the syn orientation of the aromatic ring of the benzamide towards the 2-benzyl substituent was the active conformation (Scheme 10). 

Alai/r[(Z)-CF=C]-Pro containing N, 0-diacylhydroxamic acid type protease inhibitors have been prepared as shown in Scheme 18 [63,64], The synthesis is based upon the use of fert-butyl-a-fluoro-trimethylsilylacetate in a variation of the Peterson olefination procedure to construct the necessary functionalized fluoroolefin. Treatment of 51 with 4 equiv. of lithium diisopropylamide (LDA) and 6equiv. of chlorotri-methylsilane at 78°C formed 52 in 71% yield. The key step is the Peterson olefination reaction of the TBDMS-protected 2-(hydroxymethyl)cyclopentanone (53) with tert-butyl-a-fluoro-a-trimethylsilylacetate (52). The fluoroolefin product was obtained as a mixture of (Z) (E) isomers (54). Separation of the double-bond isomers by column chromatography provided (Z) isomer (54) in 43% yield. Further... 

Strategies centered on reductive introduction of the fluoroolefin via a geminal difluoro allylic array have been reviewed [66]. In an introductory example to this synthetic approach, Okada et al. [67] developed a completely stereoselective synthesis of Z)-2,5-syn 2-alkyl-4-fluoro-5-hydroxy-3-alkenoic acids through the Cu(l)-mediated allylic substitution reaction of trialkylaluminum with the (E)-4,4-difluoro-5-hydroxyallylic alcohol derivative (61) (Scheme 21). Reaction... 

T. Allmendinger, E. Felder, E. Hungerbuehler, Fluoroolefin dipeptide isosteres. II. Enantioselective synthesis of both antipodes of the Phe-Gly dipeptide mimic. Tetrahedron Lett. 31 (1990) 7301-7304. 

The potential utility of peptides as therapeutics with clinical applications is limited by its metabolic instability or poor transmembrane mobility. Consequently, the preparation of metabolically stable peptide analogs that can either mimic or block the function of natural peptides or enzymes is an important area of medicinal chemistry research. Synthesis of fluoroolefin amide isosteres, its incorporation in peptidomimetics, and the influence of that isosteric substitution on the inhibition of several enzymes such as peptidyl prolyl isomerases, dipeptidyl peptidase IV, and thermolysin is described. Moreover, protein folding and activity... 

The synthesis of chlorine (I) and bromine (I) trifluoromethanesulfonates (triflates) was reported by DesMarteau. Stability and reactivity of these materials are similar to those of perfluoroalkyl hypohalites. Both compounds readily react at low temperature with a variety of fluoroolefins. Based on NMR analysis of the products of adding CF3S020X to pure cis- or trans-isomers of 1, 2-difluoroethylene, it was concluded that the reaction proceeds as syn-addition [35]. This statement was later criticized [18], since the assignment of stereoisomers was found to be incorrect. According to [18], addition of CF3S020X to haloolefins, as well as reactions of ClF, BrF and IF proceed as anti-addition via cyclic halonium cationic intermediates. 

The first publication on addition of BrOS02F to several fluoroolefins, which appeared in 1966 [103], was followed by a communication on the reaction of chlorine and bromine fluorosulfate with HFP [97]. This initiated the appearance of a number of papers on the use of halogen fluorosulfates in fluoroorganic synthesis. Most of these publications came from Professor Fokin s group in the former Soviet Union. 

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