Allenes difluoro

Ethyl chlorodifluoroacetate has been used in a silicon-induced Reformatsky-Claisen reaction of allyl chlorodifluoroacetates in the presence ot zinc as a route to 2,2-difluoro unsaturated acids [( S] (equahon 58) When this methodology is applied to chlorodifluoropropargylic esters, the corresponding allenic esters are formed [SS]... 

Fluorinated allenes are especially reactive in cycloadditions because of their highly strained double bonds [118, 119] 1,1-Difluoro- and 1-fluoroallene readily undergo both [2+2] and [4+2] cycloadditions [118 124] (equations 50-52) Exten sive studies of stereochemistry and regioselectivity show that cyclobutane forma-... 

Because the fluorine substituents both inductively and hyperconjugatively withdraw electron density from the C(2)-C(3) tt bond, the LUMO is located there, and Diels-Alder reactions take place exclusively with this bond [25] 1,1 -Difluoro allene and fluoroallene reaet readily with a large selection of cyclic and acyclic dienes, and acyclic dienes, [2+2] cycloadditions compete with the Diels-Alder processes As shown in the example in equation 79, a significantly different regiochemistry is observed for the [2+4] cycloaddition compared with the [2+2]... 

Allene has been prepared recently [17b] in a similar manner by adding 260 gm (2.34 moles) of 2,3-dichloropropene dropwise over a 2-3 hr period to a refluxing mixture of400 ml of 95 % ethanol, 80 ml of water, and 300 gm (4.6 gm-atoms) of zinc dust. The allene is trapped and purified in a manner similar to 1,1-difluoro-allene. 

Whereas the lithium enolates of acetate and propionate esters of difluoroallylic alcohols are known to fragment rapidly, methoxy- and benzyloxy-acetates have been found151 to form chelated enolates which undergo a smooth [3,3]-sigmatropic rearrangement as their silyl ketene acetals to afford highly functionalized difluoro compounds (see Scheme 33). Allenic silyl ketene acetals (117) have been used152 to prepare 2-substituted methyl 3,4-dienoates (118). 

Difluoro(methylene)cyclopropanes have been obtained in modest yields from allene by difluorocarbene addition.61 The difluorocyclopropane moiety proved stable upon... 

Diphenylallene affords a dimer characterized as 1-diphenylmethyl-ene-2-methylene-3,3-diphenylcyclobutane 18>. 1, l-Difluoro-3,3-bis (triflu-oromethyl)allene gives at 90 °C a mixture of at least seven compounds thought to be dimers and trimers 1 L). 1,1-Difluoroallene dimerizes to both the 3,3,4,4-tetrafluoro and l-difluoromethylene-2-methylene-3,3-difluoro-cyclobutane Z6>. Perfluoro-l,2-pentadiene reacts at 20 °C to produce three dimers, including 22% of a l,2-bis(difluoromethylene)cyclobutane and 63% of a l-fluoroperfluoroethylmethylene-2-difluoromethylene cycloadduct 10>. l,l-Dichloro-3,3-dimethylallene gives a mixture of dimers 25>. 

With 1-phenylsulfinylallene, the residual double bond is found mainly at the 5-position in the cycloadduct (85SC663), whereas nitrogen-substituted allenes afford mainly 4-methylene-substituted isoxazolines [90JCS(P1)533 91JCS(P1)1843]. The regioselectivity of addition to 1-fluoro- and 1,1-difluoro-allene depends on the nitrile oxide and is thought to reflect the... 

Allene can be hydrofluorinated with anhydrous hydrogen fluoride to give 2,2-difluoro-propane (4) in 50% yield,... 

The 17)3-hydroxy-17a-difluorocyclopropenyl steroid (66) reacted with the fluorinating reagent 2-chloro-l,l,2-trifluorotriethylamine to give the trifluoro-methylallene (67) and other minor products. Formic acid hydrolysis of the difluoro-compound (66) gave the cyclopropenone (68), which reacted with 2-chloro-l,l,2-trifluorotriethylamine to give the allenic acid fluoride (69). Possible mechanisms are discussed. " ... 

The reactions of perfluoroisobutene with sodium salts of malonic esters are difficult to control, owing to rearrangement and base catalysed cyclization, but when the complex BFs NEts is used as HF acceptor, condensation is readily controlled (see Scheme 15 and p. 99) and yields of up to 50% of allene (39) obtained. Antimony pentaliuoride catalyses the electrophilic addition of acid fluorides to 1,1-difluoro- and trifluoro-ethylene. Propiophenones, PhCO CHX-CFs (X = H or F), are obtained from benzoyl fluoride, but with acetyl fluoride, further condensation occurs, and trifluoroethylene yields the jS-diketone, CF3-CHF-CO-CH2Ac. ... 

J. L. Allen, S.-D. Han, P. D. Boyle, W. A. Henderson, J. Power Sources 2011, 196, 9737-9742. Crystal structure and physical properties of lithium difluoro(oxalato)borate (LiDFOB or LiBF20x). 

Allene has the structural formula H2C=C=CH2. Do all of the atoms lie in the same plane Would you predict that 1,3-difluoro-allene, HFC=C=CHF, exists as an enantiomeric pair of substances or as a single optically inactive substance ... 

Allen, J.L., Boyle, P.D. and Henderson, W.A., Lithium difluoro(oxalato)borate tetramethylene sulfone disolvate, Acta Crystallogr. E67, m533 (2011). 

Phenyl-3,3-biphenylene-allene dimer, 40B, 142 C1HH30F2, anti-1,2-Difluoro-3,4,5,6,7,8-hexaphenyltricyclo-[4.2.0.02-5]octa-3,7-diene, 27, 786 C60H80O4 0.5 C4H10O, 3,3a ,5,5 -Tetra-t-butyl-2 -(3,5-di-t-butyl-4-hydroxyphenyl)-7 -[1 (3,5-di-t-butyl-4-hydroxyphenyl)ethylidene]-3a ,4 ,7 7a -tetrahydrospiro[cyclohexa-2,5-diene-1,1 -[IHjindene]- 4,4 -dione diethyl ether solvate, 46B, 110... 

Han S-D, Allen JL, Boyle PD, Henderson WA (2012) Delving into the properties and solution stiucture of nitrile-lithium difluoro(oxalato)borate (LiDFOB) electrolytes for Li-ion batteries. ECS Trans 41 47-51. doi 10.1149/1.4717962... 

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