Fluorinated aryl alcohols

Reaction of the partially fluorinated aliphatic aromatic ketone 22 with bromotrifiuoromethane/ tris(diethylamino)phosphane leads to formation of the tertiary aryl alcohol 23. ° ... 

Scheme 4.11 DKR of fluorinated aryl alcohols with Backvall s catalyst.

R F, R R or/and r5= F, CF3 Scheme 8.17 Enz3miatic DKR of fluorinated aryl alcohols with Backvall s catatyst. 

The asymmetric synthesis of chiral fluoroorganic compounds plays an important role in the development of medicines, agrochemicals, and materials due to the influence of fluorine s unique properties. In this context, Bogar and Backvall investigated the DKR of various fluorinated aryl alcohols, in 2007. As shown in Scheme 8.17, a series of chiral fluorinated acetates were produced in remarkably high yields and enantioselectivities by using a combination of CALB with Backvall s catalyst in the presence of isopropenyl acetate as the acyl donor at room temperature. 

Recently, a MW-promoted procedure for one-pot, two-step conversion of aryl alcohols to aryl fluorides via aryl nonafluorobutylsulfonates (ArONf) was reported (Scheme 44). Moderate to good yields were achieved by this MW-assisted palladium-catalyzed fluorination sequence. The in situ conversion of aryl alcohols to aryl nonaflates using CsF as base, followed by the MW heated (180 °C) fluorination, catalyzed by [Pd2(dba)3] (dba= dibenzyhdeneacetone) andt-BuBrettPhos [2-(di-ter<-butylphosphino)-2, 4 6 -triisopropyl-3,6-dimethoxy-l,T-biphenyl], allowed full conversion after 30—60 min reaction. ... 

Bogar K, Backvall J-E. High-yielding metalloenzymatic dynamic kinetic resolution of fluorinated aryl alcohols. Tetrahedron Lett. 2007 48 5471-5474. 

Recently, Wannberg et al. (2013) reported an easy and two step method for conversion of aryl alcohols to aryl fluoride using nonafluorobutylsulfonates (ArONf) as a reagent by one-pot procedure to give moderate to good yield (41-85%) at ISO C in 30 min under microwave-assisted heating. This fluorination reaction is palladium-catalyzed. 

The phosphazene backbone has a particularly high resistance to thermal treatment and to homolytic scission of the -P=N- bonds, possibly due to the combination of the high strength of the phosphazene bond and its remarkable ionic character [456]. As a consequence, the onset of thermal decomposition phenomena (as detected, for instance, by TGA) are observed at considerably high temperatures for poly[bis(trifluoroethoxy)phosphazene], [NP(OCH2CF3)2]n [391, 399, 457], for phosphazene copolymers substituted with fluorinated alcohols of different length [391, 399, 457], for polyspirophosphazenes substituted with 2,2 -dihydroxybiphenyl groups [458], and for poly(alkyl/aryl)-phosphazenes [332]. 

Several fluorinated aryl ethers 134 were prepared from the reaction of the 11,12/3-oxirane 133 <1994TL2129> with substituted benzyl alcohols (Equation 13 Table 8) <1995JME4120>. 

Cesium fluoroxysulfate in acetonitrile medium at 35 C converts primary alcohols and alkyl and aryl aldehydes into acid fluorides in high yields.i" Hammett correlation analysis of the fluorination of various benzene-substituted aldehydes gives the reactivity constant31 q = —0.38. It has been shown that solvent polarity plays an extremely important role in the conversion of aldehydes into fluorides the conversion is almost quantitative in acetonitrile, but completely stopped in dichloromethane, hexane or tetrahydrofuran. The presence of ni-... 

Both aromatic and aliphatic fluoroformates 7 can be readily prepared from phenols or alcohols and carbonyl difluoride and treated with sulfur tetrafluoride without isolation. Hydrogen fluoride evolved in the reaction of hydroxy compounds with carbonyl di fluoride serves as a catalyst for the consecutive reaction with sulfur tetrafluoride.15<)-162 This provides a general, convenient, direct synthesis of aryl and alkyl trifluoromethyl ethers 5 from phenols and alcohols. When the intermediate fluoroformate 7 is isolated prior to treatment with sulfur tetrafluoride, at least one mole equivalent of hydrogen fluoride is necessary to promote the fluorination reaction. 159 163 Representative examples of the conversion of hydroxy compounds 6 into trifluoromethyl ethers 5 via intermediate fluoroformates 7 are given (for other examples 7 -> 5, see Houben-Weyl, Vol. E4, pp 628. 629). 

Various benzophenones and aryl alkyl ketones substituted with a fluorine atom on the ortho position were effectively converted into the corresponding alcohols with high to excellent enantioselectivities in the presence of the optically active ketoim- inatocobalt(II) complexes (14). The combination of o-F substituent and a modified lithium borohydride reagent contributed to the high yield and high enantioselectivity (88-96% ee).316... 

Primary alcohols and their silylated derivatives are selectively fluorinated by tetraalkyl-ammonium fluorides in the presence of an aryl- or alkylsulfonyl fluoride, in a one-pot reaction. 

NaHCOs, and methanesulfonic anhydride.Dimethyl sulfoxide in 48% HBr oxidizes benzylic alcohols the aryl aldehydes.Note that Swern oxidation of molecules having alcohol moieties, as well as a disulfide, leads to the ketone without oxidation of the sulfur. Sulfoxides other than DMSO can be used in conjunction with oxalyl chloride for the oxidation of alcohols,including fluorinated sulfoxides and a polymer-bound sulfoxide. ... 

Fluorinated methyl aryl ethers. The facile rearrangement of oxygenated benzyl derivatives effected by XeFa to give fluorinated methyl ethers, i.e., benzyl alcohols to fluoromethyl aryl ethers and benzaldehydes to difluoromethyl aryl ethers, may involve the formation of fluoroxy intermediates and thence oxaspirobenzenium ions. 

The reaction of the acetate with secondary amines gives various amines with different alkyl and aryl groups, including amino alcohols. Two amines. 13 and 14, with fluorinated alkyl groups have been applied for enantioselective hydrosilylation of alkenes. with considerable success38 (Sections D.4.3. and D.9.). 

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