365-00-4Relevant academic research and scientific papers
Enolization rates control mono-: Versus di-fluorination of 1,3-dicarbonyl derivatives
Rozatian, Neshat,Beeby, Andrew,Ashworth, Ian W.,Sandford, Graham,Hodgson, David R.W.
, p. 10318 - 10330 (2019/11/20)
Fluorine-containing 1,3-dicarbonyl derivatives are essential building blocks for drug discovery and manufacture. To understand the factors that determine selectivity between mono- and di-fluorination of 1,3-dicarbonyl systems, we have performed kinetic studies of keto-enol tautomerism and fluorination processes. Photoketonization of 1,3-diaryl-1,3-dicarbonyl derivatives and their 2-fluoro analogues is coupled with relaxation kinetics to determine enolization rates. Reaction additives such as water accelerate enolization processes, especially of 2-fluoro-1,3-dicarbonyl systems. Kinetic studies of enol fluorination with Selectfluor and NFSI reveal the quantitative effects of 2-fluorination upon enol nucleophilicity towards reagents of markedly different electrophilicity. Our findings have important implications for the synthesis of α,α-difluoroketonic compounds, providing valuable quantitative information to aid in the design of fluorination and difluorination reactions.
Chemoselective Mono- And Difluorination of 1,3-Dicarbonyl Compounds
Cui, Ying,Jiao, Jingchao,Ma, Xiantao,Rao, Weihao,Tang, Lin,Yang, Zhen,Zhou, Qiuju,Zhou, Yuqiang,Zou, Guodong
, (2019/08/26)
By altering the amount of Selectfluor, the highly selective mono- and difluorination of 1,3-dicarbonyl compounds has been achieved, affording a variety of 2-fluoro- and 2,2-difluoro-1,3-dicarbonyl compounds in good to excellent yields. The reaction can be readily performed in aqueous media without any catalyst and base, which features practical and convenient fluorination. Importantly, a gram-scale reaction, transformation of 2-fluoro-1,3-diphenylpropane-1,3-dione to 4-fluoro-1,3,5-triphenyl-1H-pyrazole, and chlorination and bromination of 1,3-dicarbonyl compounds are realized to further exhibit its synthetic utility.
Translating solid state organic synthesis from a mixer mill to a continuous twin screw extruder
Cao, Qun,Howard, Joseph L.,Crawford, Deborah E.,James, Stuart L.,Browne, Duncan L.
supporting information, p. 4443 - 4447 (2018/10/17)
A study on the translation of a solid-state synthetic reaction from a mechanochemical mixer-mill to a continuous twin-screw extruder is discussed herein. The study highlights some considerations to be made and parameters to be tested in the context of a model fluorination reaction, which is the first organic fluorination to be attempted using extrusion. Upon optimization, which features the first use of grinding auxiliary solids to enable effective synthetic extrusion, the difluorination reaction was successfully translated to the extruder, leading to a 100-fold improvement in Space Time Yield (STY); 29 kg m-3 day-1 in a mixer mill to 3395 kg m-3 day-1 in a twin screw extruder.
Switching Chemoselectivity: Using Mechanochemistry to Alter Reaction Kinetics
Howard, Joseph L.,Brand, Michael C.,Browne, Duncan L.
supporting information, p. 16104 - 16108 (2018/11/23)
A reaction manifold has been discovered in which the chemoselectivity can be altered by switching between neat milling and liquid assisted grinding (LAG) with polar additives. After investigation of the reaction mechanism, it has been established that this switching in reaction pathway is due to the neat mechanochemical conditions exhibiting different kinetics for a key step in the transformation. This proof of concept study demonstrates that mechanochemistry can be used to trap the kinetic product of a reaction. It is envisaged that, if this concept can be successfully applied to other transformations, novel synthetic processes could be discovered and known reaction pathways perturbed or diverted.
SelectfluorTMon a PolyHIPE Material as Regenerative and Reusable Polymer-Supported Electrophilic Fluorinating Agent
Kawada, Kosuke,Okano, Koji,Iskra, Jernej,Krajnc, Peter,Cahard, Dominique
supporting information, p. 584 - 589 (2017/02/23)
The first recyclable polymer-supported electrophilic fluorinating agent was prepared by reaction of molecular fluorine with the triethylenediamine motif that is grafted onto a poly(4-vinylbenzyl chloride-co-divinylbenzene) polyHIPE material. The resulting
Controlling reactivity through liquid assisted grinding: The curious case of mechanochemical fluorination
Howard, Joseph L.,Sagatov, Yerbol,Repusseau, Laura,Schotten, Christiane,Browne, Duncan L.
supporting information, p. 2798 - 2802 (2017/07/24)
We have identified an example of a mechanochemically milled organic reaction where liquid-assisted grinding controls the selectivity, such a phenomenon has not been reported/observed before. It was found that upon milling dibenzoylmethane with Selectfluor in the absence of any solvent, a 3:1 ratio of monofluorinated:difluorinated product was observed. Whereas, addition of 0.125 mL of acetonitrile (～10% of the total volume of materials present) to the ground reaction mixture afforded 50:1 selectivity. Furthermore, this phenomenon is applicable to a small range of diketone substrates thus far explored. Additionally, we have demonstrated that difluorination can be achieved by simply switching from adding acetonitrile to addition of sodium carbonate. Most notable, in the latter case, is the reduced reaction time compared to a conventional solvent approach, 2 hours in the mill and 24 hours in the flask.
A Route to α-Fluoroalkyl Sulfides from α-Fluorodiaroylmethanes
Lin, Ya-Mei,Yi, Wen-Bin,Shen, Wan-Zhao,Lu, Guo-Ping
supporting information, p. 592 - 595 (2016/02/18)
α,α-Difluorodiaroylmethane can be used as a nucleophilic difluoromethylation reagent for generating α-thioaryl-α,α-difluoroacetophenones (Ar1COCF2SAr) and difluoromethylthiolated arenes (ArSCF2H) under transition-metal-free conditions. The reaction selectivity is mainly dependent on temperature. The method has also been extended to the synthesis of α-thioaryl-α-monofluoroacetophenones using α-monofluorodibenzoylmethane. Moreover, the benzoyl cation derived from α,α-difluorodibenzoylmethane can react with nucleophiles to afford the desired products in a one-pot process.
2,2-Difluoro-1,3-diketones as gem-Difluoroenolate Precusors for Asymmetric Aldol Addition with N-Benzylisatins
Qian, Jinlong,Yi, Wenbin,Huang, Xin,Jasinski, Jerry P.,Zhang, Wei
, p. 2811 - 2816 (2016/09/13)
2,2-Difluoro-1,3-diketones are introduced as gem-difluoroenolate precursors for the first example of an organocatalytic asymmetric aldol addition with N-benzylisatins to form 3-difluoroalkyl-3-hydroxyoxindoles. (Figure presented.).
Apparent electrophilic fluorination of 1,3-dicarbonyl compounds using nucleophilic fluoride mediated by PhI(OAc)2
Nash, Toby J.,Pattison, Graham
supporting information, p. 3779 - 3786 (2015/06/16)
The apparent electrophilic fluorination of 1,3-dicarbonyl compounds using Et3N·3HF as a nucleophilic fluoride source is reported. This reaction requires PhI(OAc)2 as oxidant and can be conducted safely in standard laboratory glassware. Alternative selectivity compared to Selectfluor was observed in some cases. This approach may reduce our reliance on difficult-to-handle fluorine gas and expensive electrophilic fluorinating agents derived from elemental fluorine. Mechanistic analysis related to the active fluorinating species and fluoride/acetate exchange is presented. The apparent electrophilic fluorination of 1,3-dicarbonyl compounds using Et3N·3HF mediated by the in-situ formation of PhIF2 from PhI(OAc)2 is reported. This can be performed safely in standard laboratory glassware, and this approach may reduce our reliance on difficult-to-handle fluorine gas and expensive electrophilic fluorinating agents derived from elemental fluorine.
Preparation of iodonium ylides: Probing the fluorination of 1,3-dicarbonyl compounds with a fluoroiodane
Geary, Gemma C.,Hope, Eric G.,Singh, Kuldip,Stuart, Alison M.
, p. 16501 - 16506 (2015/03/04)
The isolation of iodonium ylide 8, from the reaction of fluoroiodane 1 with ethyl 3-oxo-3-phenylpropanoate 5 in the presence of potassium fluoride, provides strong evidence that 1,3-dicarbonyl compounds undergo an addition reaction with fluoroiodane 1 to form an iodonium intermediate which can be deprotonated to generate an iodonium ylide. In the presence of TREAT-HF, however, the iodonium intermediate reacts to form the 2-fluoro-1,3-dicarbonyl product and we propose that fluoroiodane 1 simulates electrophilic fluorination via an addition/substitution mechanism. Further evidence to support this mechanism was obtained by successfully reacting the isolated iodonium ylide 8 with TREAT-HF, hydrochloric acid, acetic acid and p-toluenesulfonic acid to form the 2-fluoro-, 2-chloro-, 2-acetyl- and 2-tosyl-1,3-ketoesters respectively. This journal is
