Chiral Diols

Aldrich ChemFiles 2007, 7.9, 13.

Apart from numerous examples using TADDOLs in metal-catalyzed asymmetric reactions, Rawal recently reported that TADDOLs could be used as Brønsted acid organocatalysts in highly stereoselective hetero-Diels–Alder reactions.1 The reaction of an electron-rich diene with benzaldehyde using 10 mol % TADDOL (395242) provides the dihydropyrone as a single stereoisomer (Scheme 1).

Scheme 1

The α-amination of carbonyl compounds has also been accomplished by using the 1-naphthyl TADDOL derivative as a Brønsted acid catalyst (Scheme 2).2 The reaction of different enamines with nitrosobenzene gave exclusively the N-regioisomers in a highly enantioselective manner.

Scheme 2

A highly enantioselective addition of cyclohexenone to different aldehydes (asymmetric Morita–Baylis–Hillman reaction) catalyzed by octahydro-BINOL-derived Brønsted acid (669172) was reported by Schaus (Scheme 3).3 Important for achieving high enantioselectivity were both the partial saturation and substitution at the 3,3’-positions of the BINOL derivative.

Scheme 3

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  1. Huang, Y.; Unni, A. K.; Thadani, A. N.; Rawal, V. H. Nature 2003, 424, 146.
  2. Guo, H.-M.; Cheng, L.; Cun, L.-F.; Gong, L.-Z.; Mi, A.-Q.; Jiang, Y.-Z. Chem. Commun. 2006, 429.
  3. McDougal, N. T.; Schaus, S. E. J. Am. Chem. Soc. 2003, 125, 12094.

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