2.2- Dichloro-1 -phenylethanol

Hydrogenation of 1-phenylethanone in the presence of a bis(/j4-norbornadiene)dichloro-dirhodium/(S.S)-4,5-bis(diphenvlphosphinomcthy])-2,2-dimethyl-1,3-dioxolane, [Rh(nbd)CI]2/ (Diop), catalyst gives a 64% yield of (S)-l-phenylethanol in 80% ee7. Typically, a substrate,/ rhodium catalyst ratio of 100 1 and, within the catalyst, a rhodium/ligand ratio of 1 1.1 is used. 

A soln. of dichloromethyllithium in THF treated with Ti(OPr-/)4 at —70°, equimolar amounts of benzaldehyde and acetophenone in THF added dropwise at —78°, and allowed to warm to room temp, within 12 h - 2,2-dichloro-l-phenylethanol. Y 81%. There was no chemoselectivity in the absence of Ti(IV), but ketones did react at higher temp. F.e. and syntheses via Cl3CTi(OPr-/)4Li and (Cl2CH)3MnLi s T. Kauffmann et al., Angew. Chem. Intern. Ed. 27, 943-4 (1988). 

Obtained by DDQ oxidation of l-(3,5-dichloro-4-hydroxy-phenyl)-2-phenylethanol in dioxane at r.t. 

Figure 1 CSEARCH data she howing the C NMR spectral data of 2,2-dichloro-l-phenylethanol...

Figure 2 Comparison of the C NMR spectra of 2,2-dichloro-l-phenylethanol, 2,2,2-trichloro-l-phenylethanol, and 2,2-dichloro-l-(o-chloro-phenyl)ethanol showing the substituent-induced chemical shift variations...

In Figure 3 the estimation has been performed for 2,2-dichloro-l-phenylethanol using the HOSE code technique over a one- to four-bond sphere, showing the necessity of taking into account at least the three-bond sphere in order to get reliable results. From practical experience it can be concluded that for chemical shift estimation of an sp carbon a three-bond sphere is necessary in order to include y-effects, whereas for sp carbons a four-bond sphere usually gives acceptable results, because this includes also pnrn-substituents within aromatic systems. For some rare cases a correlation up to a six-bond sphere may be necessary the alternative is the visual inspection of the distribution of the chemical shift values of the reference spectra in order to select the correct entries... 

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