Oxetanes, fluorinated

Fluorinated oxetanes, oxolanes and oxanes were prepared by several authors [189-194],... 

Harris and Coffman [189] obtained fluorinated oxetanes from aldehydes, ketones or acid fluorides according to the reaction ... 

A series of water-dispersible, surface-active poly(fluorinated oxetane)s was prept sd by ring-opening polymerization of fluorinated oxetane monomers using Lewis acid catalysis <02L5993>. 

Patent Fluorinated Oxetane Derivatives and Production Process Thereof... 

Table 8. Fluorinated Oxetanes by [2 -(- 2]-Cycloaddition Reactions of Carbonyl Compounds with Fluorinated Alkenes...

Four-membered heterocydes are easily formed via [2+2] cycloaddition reac tions [63] These cycloaddition reactions normally represent multistep processes with dipolar or biradical intermediates The fact that heterocumulenes, like isocyanates, react with electron-deficient C=X systems is well-known [77d] Via this route, p lactones are formed on addition of ketene derivatives to hexafluoroacetone [777, 77S] The presence of a trifluoromethyl group adjacent to the C=N bond in quinoxalines, l,4-benzoxazin-2-ones, l,2,4-tnazin-5-ones, and l,2,4-tnazm-3,5-diones accelerates [2+2] photocycloaddition processes with ketenes and allenes [106] to yield the corresponding azetidine derivatives Starting from olefins, fluorinated oxetanes are formed thermally and photochemically [779, 720] The reaction of 577-1,2-azaphospholes with fluonnated ketones leads to [2+2] cycloadducts [727] (equation 27)... 

Preparation of F-oxetane (1), disclosed in the patent by Kauck and Simons in 1952, was the first report on synthesis of fluorinated oxetane. It was obtained from parent hydrocarbon by electrochemical fluorination in anhydrous HF and isolated as nonflammable, water-insoluble, colorless gas with boiling point of —38°C. Much later, a direct fluorination by fluorine gas was employed to convert 2,2,3,3-tetra-fluorooxetane (2) into F-oxetane (1) or 2,2,3,3,4-pentafluorooxetane (Scheme 2.1). Varying the conditions of the fluorination, each of the two can be obtained as the major product. 

Formation of the four-membered ring of fluorinated oxetanes as for their hydrocarbon congeners is normally accomplished by one of the two general approaches the cyclization of y-substituted alcohols or [2 + 2] cycloaddition reaction. 

Alcohols with a good leaving group in the y-position can be cyclized into oxetanes. This approach was successfully applied to the synthesis of fluorinated oxetanes either by electrophilic cyclization of 2-perfluoroalkyl 1,3-diols in concentrated sulfuric acid or by nucleophilic ring closure of fluorinated y-chloro" or y-fluoro alcohols under action of a strong base (see Scheme 2.2). The ease of intramolecular cyclization is influenced by the nucleophilicity of alkoxy group and the best yields are obtained for tertiary alcohols. 

By far the most important method of preparation of fluorinated oxetanes is [2 + 2] cycloaddition that can either be photoinitiated (Paterno-Buchi reaction) or result from electrophilic condensation. 

Bissell and Fields reported that very low yields (<3%) of fluorinated oxetanes of type 3 from radical addition of acetaldehyde to perhalogenated ethylenes can be achieved, while the major (but still low yield) products were the ketones of type 4 (Scheme 2A) ... 

Fluorinated oxetanes can be obtained in decent yield through an electrophilic [2 + 2] cycloaddition of carbonyl compounds and fluoroolefins. The formation of oxetane 2 was first reported by Weinmayr in 1963. The reaction of TFE with paraformaldehyde... 

At the same time, even highly fluorinated oxetanes are able to react with electrophiles. For example, the reaction of F-(2,2-dimethyloxetane) 11 with HF/ SbFs leads to high-yield formation of C2F5C(CF3)20H. " ... 

The high hydrophobic surface is a consequence of the segregation effect of the fluorinated oxetane which, due to its low surface energy, migrates towards the air interface and concentrates in the outermost layer. 

Finally different fluorinated containing HBP were synthesizied starting fix)m different fluorinated oxetanes [49] and employed as additives. As observed for the other hydroxyl containing HBP, they internet with the polymeric carbocation through a chain transfer mechanism inducing an increase in the final epoxy conversion [50], High gel content values (>96%) for the photoeured films confirm that the HBP additive is tightly crosslinked to the polymeric network. 

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