Synthetic Methods for Fluorinated Olefins

Yanai, Hikaru; Taguchi, Takeo

doi:10.1002/ejoc.201100495

Cited by 164 publications

(46 citation statements)

References 119 publications

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“…In the area of fluoroorganic chemistry, 9 we 10,11 and others 12 have been involved in modular synthesis of variously functionalized fluoroolefins 10,13 using Julia-Kocienski approach. 14 The effect of fluorine atom incorporation on pharmaceuticals is well established.…”

Section: Introductionmentioning

confidence: 99%

E- or Z-Selective synthesis of 4-fluorovinyl-1,2,3-triazoles with fluorinated second-generation Julia–Kocienski reagents

et al. 2015

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A highly modular approach to N-substituted 4-(1-fluorovinyl)triazoles is described. In situ desilylation and Cu-catalyzed ligation reaction of TMS-protected α-fluoropropargyl benzothiazole sulfone with aryl, alkyl, and metallocenyl azides furnished second-generation Julia-Kocienski reagents in good to excellent yields. Condensation reactions of these reagents with aldehydes can be tuned to yield E or Z-alkenes selectively. Under mild conditions with DBU as base, reactions of aldehydes furnished E-alkenes as the major isomer. On the other hand, in condensations with LHMDS as base and in appropriate solvents, both aldehydes and ketones reacted to yield fluoroalkenes with Z-selectivity. Stereochemical assignment to E/Z olefins obtained in the reaction of a ketone with two Julia reagents was performed via X-ray crystallographic analysis and comparisons of NMR data. The method allows efficient and ready diversification of N1-substituent and substituents at the double bond.

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Section: Introductionmentioning

confidence: 99%

E- or Z-Selective synthesis of 4-fluorovinyl-1,2,3-triazoles with fluorinated second-generation Julia–Kocienski reagents

et al. 2015

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“…1,2 While a wide variety of methods have been developed to access different classes of monofluoroalkenes, modular synthesis and stereoselective synthesis remain outstanding challenges. 3 Moreover, traditional chromatographic techniques, including preparative HPLC, often fail to separate E and Z isomers of monofluoroalkenes, highlighting the importance of stereoselective methods. 4 …”

mentioning

confidence: 99%

“…[1,2] While aw ide variety of methods have been developed to access different classes of monofluoroalkenes,m odular synthesis and stereoselective synthesis remain outstanding challenges. [3] Moreover, traditional chromatographic techniques,including preparative HPLC,o ften fail to separate E and Z isomers of monofluoroalkenes,t hus highlighting the importance of stereoselective methods. [4] Hu and co-workers have recently developed aJ ulia-Kocienski olefination procedure which utilizes as elective decomposition strategy of sulfinate intermediates to isolate the E and Z isomers by extraction (Scheme 1).…”

mentioning

confidence: 99%

“…Additionally,t his protocol required the synthesis of anew olefination reagent for each derivative,an impediment to modularity which is inherent to olefination strategies for monofluoroalkene synthesis. [3] As an alternative,C ao and co-workers have recently reported an ickelcatalyzed Suzuki-type coupling of boronic acids and difluorostyrenes,w hich afforded monofluorostilbenes stereoselectively (Scheme 1). [5] They proposed that the reaction proceeds through oxidative addition of the alkene CÀFb ond, [6,7] followed by cross-coupling with an aryl boronic acid.…”

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confidence: 99%

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Palladium‐Catalyzed Defluorinative Coupling of 1‐Aryl‐2,2‐Difluoroalkenes and Boronic Acids: Stereoselective Synthesis of Monofluorostilbenes

2016

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The palladium-catalyzed defluorinative coupling of 1-aryl-2,2-difluoroalkenes with boronic acids is described. Broad functional group tolerance arises from a redox-neutral process via a Pd(II) active species that is proposed to undergo a β-fluoride elimination to afford the products. The monofluorostilbene products were formed with excellent diastereoselectivity (≥50:1) in all cases, which is critical, as traditional chromatographic techniques often fail to separate monofluoroalkene isomers. As a demonstration of this method’s unique combination of reactivity and functional group tolerance, a Gleevec© analogue using a monofluorostilbene as an amide isostere was synthesized.

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“…as a relatively novel class of melt processable fluoropolymers have been used as key materials in the fields of medicinal chemistry, chemical biology, and materials sciences because the introduction of fluorine into the molecular architecture dramatically changes the physical/chemical properties of polyolefins. 94 In the last decade, these materials have been also successfully used for die drool elimination as documented in a number of patents. 86,[95][96][97][98][99][100][101] However, even if the extruded product is composed of fluoropolymers, for example, FEP (tetrafluoroethylene/hexafluoropropylene) copolymer and PFA (tetrafluoroethylene/perfluoro(alkyl vinyl ether)) copolymer die drool can occur due to high melting temperature difference (around 45 • C) between these two copolymers, high shearing conditions phase separation, and sloughing off of copolymer particles.…”

Section: Molecular Architecturementioning

confidence: 99%

Historical Review of Die Drool Phenomenon in Plastics Extrusion

Musil

Zatloukal

2014

Polymer Reviews

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Die drool phenomenon is defined as unwanted spontaneous accumulation of extruded plastics on die exit face(s) of extrusion die during plastics extrusion process. Such accumulated material builds up on die exit face(s) and frequently or continually sticks onto the extruded product and by this way reduces the quality of the product. When the die drool appears, the extrusion process must be shut down and the die exit face(s) must be manually cleaned, which is time consuming as well as money consuming.Die drool has been observed from the beginning of plastics extrusion and the first published remark about it was made in 1946. For a long time it was considered as only an engineering problem and even if a wide range of suppressing ideas based on modification of extrusion dies, plastics materials, and processing conditions have already been patented, its source remained unclear. During the last few years, a number of experimental as well as theoretical research papers focusing on its fundamental nature have been published. Nowadays, die drool is considered as a fundamental rheological phenomenon.The force which drives the building up of extruded plastics on die exit face(s) is negative pressure (suction) occurring in the die exit edge(s) region where the free surface of the extruded plastics is created. Moreover, two different die drool types (external and internal) exist. The formation mechanisms of external/internal die drool are based on negative pressure occurring in the die exit region together with deformation of free extrudate surface/material separation wherever inside the extrusion equipment, respectively. From the processing point of view, the internal die drool is much more problematic than the external one, primarily due to a higher build up rate and compact shapes of the accumulated drool mass. Two theories of internal die drool formation mechanism based on wall slip theories (flow-induced molecular weight fractionation and stress-induced cohesive chain disentanglement) have been recently proposed and tested.In this historically ordered review, breakthrough works in the field of die drool research are presented, many ways to suppress it are shown, techniques for its quantitative evaluation and experimental methods for its analytical investigation are introduced, external and internal die drool types are explained, and theories of external as well as internal die drool formation mechanism are presented and discussed in depth, which

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Synthetic Methods for Fluorinated Olefins

Cited by 164 publications

References 119 publications

E- or Z-Selective synthesis of 4-fluorovinyl-1,2,3-triazoles with fluorinated second-generation Julia–Kocienski reagents

E- or Z-Selective synthesis of 4-fluorovinyl-1,2,3-triazoles with fluorinated second-generation Julia–Kocienski reagents

Palladium‐Catalyzed Defluorinative Coupling of 1‐Aryl‐2,2‐Difluoroalkenes and Boronic Acids: Stereoselective Synthesis of Monofluorostilbenes

Historical Review of Die Drool Phenomenon in Plastics Extrusion

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