Fluorinated Lactones

Section 2.2 mainly reviews the papers on novel fluorinated organic solvents, which include fluorinated lactones, fluorinated linear carboxylates, fluorinated cyclic carbonates, fluorinated linear carbonates, fluorinated monoethers, fluorinated diethers, and others. The physicochemical properties of typical fluorinated compounds are summarized in comparison with nonfluorinated counterparts. 

The reaction of perfluoroalkyl iodides with alkenes affords the perfluoro-alkylated alkyl iodides 931. Q.a-Difluoro-functionalized phosphonates are prepared by the addition of the iododifluoromethylphosphonate (932) at room temperature[778], A one-electron transfer-initiated radical mechanism has been proposed for the addition reaction. Addition to alkynes affords 1-perfluoro-alkyl-2-iodoalkenes (933)[779-781]. The fluorine-containing oxirane 934 is obtained by the reaction of allyl aicohol[782]. Under a CO atmosphere, the carbocarbonylation of the alkenol 935 and the alkynol 937 takes place with perfluoroalkyl iodides to give the fluorine-containing lactones 936 and 938[783]. 

Fluorinated lactone rings are al.so opened by fluoride ion to give alkoxides that can he trapped by electrophiles [280] (equation 62). 

Results of fluorination of lactones with sulfur tetrafluoride depend on the ring size. y-Butyrolactone undergoes ring cleavage to give y-fluorobutyryl fluoride, which IS further fluormated to 1,1,1,4-tetrafluorobutane. The six-membered 1,4-di-... 

When 1,2-0-isopropylidene- (285) or -benzylidene-a-D-glucofuranur-ono-6,3-lactones or 1,2-0-isopropylidene- -L-idofuranurono-6,3-lactone (288) were treated with DAST, 5-deoxy-5-fluoro-6,3-lactones 287 and 290 and 3,6-anhydro-6,6-difluorofuranoses 403 and 404 were formed in good total yield [287 403 = 13 58 (71 %) 290 404 = 2 3 (75%)]. As these products did not undergo further fluorination, an OH-5-assisted mechanism was proposed. 

Halogen substitution is expected to increase the electrophilicity of the carbenes, and in particular lh with four fluorine substituents is expected to be highly electrophilic and of unusual reactivity. All the carbenes le-g could be matrix-isolated by irradiation of their corresponding quinone diazides 2 in argon at 8-10 K.24 68,62 Again, the thermal reaction in (Vdoped matrices results in the formation of quinone oxides 7, which show the expected photochemical rearrangement to the spiro dioxiranes 8 and finally lactones 9. 

Trifluoromethyl)trimethylsilane has been prepared by a modification5 of the procedure originally published by Ruppert.4 The optimized yield is 75%. Other less convenient methods are also available for its preparation. (Trifluoromethyl)trimethylsilane acts as an in situ trifluoromethide equivalent under nucleophilic initiation and reacts with a variety of electrophilic functional groups. Carbonyl compounds such as aldehydes, ketones and lactones react rather readily5 7 with (trifluoromethyl)trimethylsilane under fluoride initiation. The reagent also reacts with oxalic esters,8 sulfonyl fluorides,9 a-keto esters,10 fluorinated ketones,11 and... 

The author next tried to stabilize the PGI2 structure by introducing second fluorine atom to the 7-position. However, it had been unknown to make such a difluorovinyl ether unit in the literature. We studied difluorination and Wittig reaction as key steps in the synthetic route of the target difluoro-PGl2 from the Corey lactone. After searching the difluorination reaction, it was found that fluorination with A/-fluorobenzenesulfonimide in the presence of potassium bis(trimethylsilyl) amide and manganese dibromide effectively provided the desired difluoride (Table 7) [106]. 

The synthesis of AFP-07 is shown in Scheme 9 [107], The enone 59 prepared from the Corey lactone was reduced with aluminum reagent and protected with f-butyidimethylsilyl chloride. Fluorination of the lactone 60 under the standard conditions gave the difluorolactone 61. The carbonyl group of the difluorolactone... 

In continuation of previous work, the reactions of gibberellin A, and Aj with neutral manganese dioxide have been examined. The products include those of decarboxylation and of lactonization on to C-15. The full paper describing the interesting bridgehead C-13 fluorination of gibberellins with fluoramine has appeared. ... 

Addition to carbonyl group by a nucleophile is commonplace. However, a-lactones undergo alcoholysis with formation of a-alkoxy carboxylic acids [144]. The acceptor role of the carbonyl is restored in the bistrifluoromethyl-a-lactone [145]. It may also be considered that the a-carbon is reluctant to become an acceptor because of the fluorine atoms. 

Difluorocyclopentadiene was prepared via a pyrolysis reaction the difluoro-methylene centre was installed (Eq. 119) using a DAST fluorination [318]. A fluorobutenolide building block was prepared by a Wadsworth-Emmons reaction of isopropylidene glyceraldehyde removal of the ketal protecting group led to the formation (Eq. 120) of the unsaturated lactone in acceptable overall yield... 

Fluorination of dichloromaleic anhydride proceeds at 300 C to give mainly cyclic products, difluoro lactone (28) and tetrafluoro ether (29) together with the isomeric 2,3-dichlorohexa-fluorobul-2-ene (30) in ratios depending on the reaction time. The lactone 28 is evidently an intermediate in this reaction. 21... 

Cyclic tetrafluoro ethers are also the main or sole products of the sulfur tctrafluoridc fluorination of phthalic and pyromellitic acids, or their anhydrides, possessing two bulky ortho substituents (e.g., CF3. N02, Br. Cl or even Me). These substituents create steric crowding which pushes two neighboring carboxylic acid groups towards each other and forces cyclization acid anhydrides and difluoro lactones are the intermediates and they may be isolated from reactions carried out under sufficiently mild conditions. Thus, reaction of 3,6-bis(trifluoromcthyl)bcn-zcnc-1,2-dicarboxylic acid (4) with sulfur tctrafluoridc at ambient temperature results in dehydration to give exclusively the corresponding cyclic anhydride 5 at 60"C a mixture of the anhydride 5, 3,6-bis(trifluoromethyl)phthaloyI difluoride (6) and 3,3-difluoro-4,7-bis(trifluoro-methyl)isobenzofuran-l(3//)-one (7) is obtained, but at 200"C the final product, 1,1,3,3-tct-rafluoro-4,7-bis(trifluoromethyl)-l,3-dihydroisobenzofuran (8), is formed as the sole product.137... 

The reagent was used to prepare the a-(difluoromethylene)-y-lactone (1). Grignard and alkyllithium reagents react with 1 with replacement of one or both fluorines.2... 

A systematic study of the impact of geminal a-fluorine substitution upon the rate of decarboxylation of /1-lactones has included investigation of die thermolysis of a,a-difluoro /1-lactones, to give CO2 and 1,1-difluoroalkenes, in die gas phase and in solution.48 The gas-phase results have been interpreted, with reference to ab initio calculations on the fluoro- and non-fluormated /1-lactone systems, in terms of a probable concerted, asynchronous, non-polar mechanism. However, a polar mechanism which probably involves formation of an intermediate zwirterion has been invoked to explain the solvent dependence observed. 

The fluorinations of a-phenylsulfanyl esters and lactones with DFIT are noteworthy, since a-fluorinations of aliphatic esters and lactones, or their silyl ketene... 

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