Enantioselective syntheses with titanium carbohydrate complexes. Part 7. Enantioselective allyltitanation of aldehydes with cyclopentadienyldialkoxyallyltitanium complexes was written by Hafner, Andreas;Duthaler, Rudolf O.;Marti, Roger;Rihs, Grety;Rothe-Streit, Petra;Schwarzenbach, Franz. And the article was included in Journal of the American Chemical Society in 1992.Reference of 93379-49-8 This article mentions the following:
The preparation, anal., and reactions of novel, highly stereoselective cyclopentadienyldialkoxyallyltitanium reagents, available in both enantiomeric forms, are described. Chiral monochlorotitanates are readily prepared from CpTiCl3 (Cp = cyclopentadienyl) or Cp*TiCl3 (Cp* = pentamethylcyclopentadienyl) and chiral 1,4-diols, which in turn are obtained from tartrate ester acetals by Grignard addition The resulting stable seven-membered titanacycles have been analyzed by 1H, 13C, and 49Ti NMR spectroscopy. The structures of two representatives, the complexes I (R = Cl, R1 = Ph, Me), are confirmed by x-ray diffraction. The allyl reagents are obtained from the chlorides by transmetalation with allyllithium, allylpotassium, or allyl Grignard compounds These reagents do not have to be isolated or purified for the ensuing reactions with aldehydes. Correlation of x-ray data and Ti NMR line widths with selectivity suggests that asym. distortion of the titanium coordination geometry could be essential for enantioface discrimination, rather than direct interactions of reactants with the chiral ligand. By variation of the ligand substituents, allyltitanates derived from chloride I (R = Cl, R1 = Ph) (with 2,2-dimethyl-α,α,α’,α’-tetraphenyl-1,3-dioxolane-3,4-dimethanol as the ligand) emerged as the most selective reagents. Excellent regio-, diastereo-, and enantioselectivities (usually ≥95% ee, ≥95% de) are obtained for reactions with various achiral and chiral aldehydes. The NMR spectra of the allyl and the crotyl complexes (R,R)-I (R = allyl, 2-butenyl, R1 = Ph) exhibit fast 1,3-shifts favoring the (E) isomer with titanium η1-bound to the unsubstituted allyl terminus. This equilibration, and also the equilibrations of other aryl-, alkoxy-, and silyl-substituted allyltitanium complexes, restricts this method to the preparation of branched regioisomers with the anti configuration. In the experiment, the researchers used many compounds, for example, ((4S,5S)-2,2-dimethyl-1,3-dioxolane-4,5-diyl)bis(diphenylmethanol) (cas: 93379-49-8Reference of 93379-49-8).
((4S,5S)-2,2-dimethyl-1,3-dioxolane-4,5-diyl)bis(diphenylmethanol) (cas: 93379-49-8) belongs to dioxole derivatives. Dioxoles, particularly fluorinated dioxoles, are used as co-monomers to make polymers that find use in forming protective coatings for chemical resistance. 1,3-Benzodioxole can be synthesized from catechol with disubstituted halomethanes.Reference of 93379-49-8
Referemce:
1,3-Benzodioxole – Wikipedia,
Dioxole | C3H4O2 – PubChem