Fluorinated aldehydes

The best carbonyl components for these reactions are highly electrophilic compounds such as glyocylate, pyruvate, and oxomalonate esters, as well as chlorinated and fluorinated aldehydes. Most synthetic applications of the carbonyl-ene reaction utilize Lewis acids. Although such reactions may be stepwise in character, the stereochemical outcome is often consistent with a cyclic TS. It was found, for example, that steric effects of trimethylsilyl groups provide a strong stereochemical influence.28... 

The kinetics of deuterium isotope exchange between diphenyl phosphine and t-butylthiol have been studied by H n.m.r. spectroscopy.274 A negative temperature coefficient was observed for the reaction of a perf1uoroalky1 phosphite with a fluorinated aldehyde.275 The kinetics for the reaction of alcohols with phosphoryl trichloride bore strong similarities to those of carboxylic acid derivatives.276 An interesting report desribed the solvolysis of ary 1 hydroxymethyl-phosphonates. It was shown that a phosphoryl group does not prevent carbocation formation on an immediately adjacent carbon atom.277... 

It is difficult to prepare fluorinated aldehydes from the corresponding alcohols. The reason is that the initially formed aldehyde is usually immediately oxidized to a carboxylic acid. When the oxidation is only partially successful, then there is also the difficulty of separating the aldehyde from the starting alcohol. The oxidation of benzylic alcohols having a fluorinated... 

The a-hydroxy peroxides 2 obtained by the above reaction can be used as oxidizing agents for perfluorinated or highly fluorinated aldehydes to transform them also to a-hydroxy peroxides.186... 

Scheme 6 Synthesis of a Trifluoromethyl Ketone by Reaction of an Organometallic Reagent with a Simple Fluorinated Aldehyde 281...

Aldehydes. Fluorinated aldehydes are unknown. It has been observed that the reduction of a fluoro acid yields the alcohol directly, and also that the oxidation of a fluoro alcohol does not stop short of the acid.88... 

The (S)-proline-catalyzed Mannich reactions of aldehyde donors and N-PMP-protected imines of fluorinated aldehyde, such as CF3CHO, C2F5CHO, and PI1CF2CHO, were also used for the expedient synthesis of fluorinated aminoalco-hols [81]. 

Fluorinated aldehydes, where the fluorine is located a to the carbonyl or more remotely. 

Fluorinated aldehydes, where the fluorine is located a to the carbonyl42 or more remotely, undergo olefination reactions cleanly,43 45 e.g. reaction to give 36 and 37 45... 

Aluminum has exceedingly high affinity toward fluorine, as is evident from the bond strengtlis in several metal-fluorine diatomic molecules Al-F, 663.6 6.3 Li-F, 577 21 Ti-F, 569 34 Si-F, 552.7 2.1 Sn-F, 466.5 13 and Mg-F, 461.9 5.0 kJ mol [33]. This characteristic feature can be used for chelation-controlled aldol reaction of fluorinated aldehydes with KSA. Thus, in the presence of a stoichiometric amount of MesAl, 2-fluorobenzaldehyde reacts smoothly with KSA 10 to give aldol 11 with high anti selectivity. Other Lewis acids and non-fluorinated aldehydes lead to less stereoselectivity (Scheme 10.6) [34]. 

The more convenient reagent DAST can also be used to fluorinate aldehydes and some ketones in high yields (Scheme 2.65). The reaction does not work for sterically hindered ketones or for esters or anhydrides, even under harsh conditions. 

Figure 7.18 Synthesis of 2-fluoroalkylquinolines by reaction of fluorinated aldehydes and anilines.

The same complex type was employed in an impressive synthesis of fluorinated aldehydes (Scheme 13) [42]. In this reaction, a preformed cationic complex in the presence of the nucleophilic fluoride source AgHFa enables access to unprecedented reactivity. While yields and enantiomeric excesses are not satisfactory, this reaction bears enormous potential and devises new mechanistic pathways for future development of the field. 

REACTIONS OF ANIONIC POLY(ALKYL/ARYLPHOSPHAZENES) WITH CARBON DIOXIDE AND FLUORINATED ALDEHYDES AND KETONES... 

Two series of new polyphosphazenes were prepared by derivatization of preformed poly(methylphenylphosphazene), [Me(Ph)PN]p. This Involved Initial deprotonatlon of part of the methyl substituents with n-BuLi followed by treatment of the intermediate anion with carbon dioxide or with fluorinated aldehydes or ketones. With appropriate workup procedures, either carboxylic acid, ester, carboxylate salt, or fluorinated alcohol derivatives were obtained. These reactions and the characterization of the products are discussed In this paper. Related derivatization reactions are also discussed. 

The simplest fluorinated aldehydes, fluoral, known to undergo polymerization instantaneously in the presence of amines, failed to undergo effieient MBH reaction with ethyl acrylate and acrylonitrile. However, pentafluoro-benzaldehyde could provide good yields of MBH adduct 135. Alternatively, unsubstituted and -substituted [a-(ethoxycarbonyl)vinyl] aluminium 136 reacts with perfluoroalkyl and aryl aldehydes 134 to provide the fluorinated MBH adducts 135 in good to excellent yields (Scheme 1.59). °... 

In then article on intramolecular fluorine migration via four-member cychc transition states Nguyen et al analysed p values at BCPs in transition states of fluorinated aldehydes and acychc ketones reactants at the B3LYP/6-31G // B3LYP/6-31G level. 

A hierarchical integration of nanoscale textures by macromolecular building, is obtained in this way by grafting a newly designed highly fluorinated aldehyde and the last layer of amino-functionalized silica particles is then hydrophobized, creating a monomolecular layer via the formation of an imine function (Figure 28). 

A synthesis of this type was first successfully carried out by Machleidt and Wessendorf (1964), who reacted the fluorinated aldehydes (440) and (441) with the C5 phosphonate (166) to obtain a mixture of the 13E and 13Z ethyl esters (442) and (443). At that time, it was not possible to separate this mixture into the individual isomers. 

Fluorinated aldehydes are prepared in high yield by reaction of readily available acid chlorides with trialkylsilanes in the presence of Pd/C catalyst. Since no solvent is used, simple separation from by-product chlorosilane provides pure aldehyde. Previously reported syntheses are inconvenient, not easily amenable to scale-up, or require separate dehydration steps. Polymerization reactions of these aldehydes are described. Aluminum and titanium alkoxides initiate polymerization by a coordination mechanism. With selected examples, polymerization and appropriate end-capping affords soluble, high molecular weight polyacetal stable to ca. 300 ° C. 

We have found that fluorinated aldehydes can be prepared conveniently and in high yield by reaction of readily available fluorinated acid chlorides with triall lsilanes in the presence of a supported palladium catalyst (eq. 1) 1). Previously reported laboratory methods for preparing fluorinated... 

Aldehyde purity can be of critical importance some of the reactions of fluorinated aldehydes are adversely affected by the presence of small amounts of precursor acid chloride or aldehyde hydrate. For example, some of the catalysts used for polymerization (vide infraf are effectively deactivated by small amounts (0.1-0.5%) of aldehyde hydrate. We have not examined medium effects in the silane/acid chloride reaction, but the high reactivity of the fluorinated aldehydes can lead to unexpected results. For example, fluorinated aldehydes and acid chlorides condense rapidly in THF to afford esters of the form RfC(0)0CHCIR f. In contrast, this reaction is very slow in CHCI3. Fortunately, esters of this type are usually not significant products under our preferred reduction conditions. The aldehydes described here are quite reactive and can undergo spontaneous... 

FARNHAM AND ZANE Fluorinated Aldehydes and Their Polymers... 

The literature on fluorinated aldehydes and their polymers, although relatively sparse, has been reviewed (5). A reading of this review and the original literature citations reveals that much remains to be learned about this area most of the polymerization studies were carried out with CF3CHO which offers difficult handling problems along with rather intractable polymer. Some mechanistic speculation has been advanced but critical evaluation appears minimal. Longer chain or substituted fluorinated aldehydes have received less attention. 

Reactions of hydrocarbon acid chlorides with silicon hydrides in the presence of palladium have been reported (Citron, J. D., J. Org. Chem. 1969, 34, 1977). Significant reactivity differences are usually found in comparisons of hydrocarbon- and fluorocarbon-substituted carbonyl substrates, and the fluorinated aldehydes discussed in this chapter further exemplify this trend. 

A1(0CH2CF3)3, polymerization of fluorinated aldehyde, 214 Anion(s), polyfluorinated. See Polyfluorinated anions Anion basicity scale, dimethyltin(IV) cation, 352-354... 

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