S-Chirogenic Auxiliaries

Aldrich ChemFiles 2005, 5.4, 8.

Aldrich ChemFiles 2005, 5.4, 8.

2-Methyl-2-propanesulfinamide (Ellman Sulfinamide)

Developed by Ellman, these chiral sulfinamides have found widespread use in diastereoselective alkylations, the synthesis of protected chiral amines, the Strecker synthesis of α-alkyl α-amino acids, and the preparation of novel ligands for asymmetric Lewis acid catalysis. In 2001, Ellman et al. reported on an example of a Lewis acid catalyzed Diels–Alder reaction using a chiral bis(sulfinyl)imidoamidine copper complex, readily synthesized in a straightforward and modular synthesis starting from (R)-(+)-2-methyl-2-propanesulfinamide. Extremely high enantio- and diastereoselectivities were achieved with a range of substrates (Scheme 17).1


Scheme 17

The application of chiral P,N-sulfinyl imine ligands in Ir-catalyzed hydrogenation of olefins using (R)-(+)-2-methyl-2-propanesulfinamide as starting material was demonstrated by the same author. Enantioselectivities of up to 94% were observed (Scheme 18).2


Scheme 18

Very recently, Weix et al. reported on the diastereoselective Rh(I)-catalyzed addition of arylboronic acids to N-tert-butanesulfinyl aldimines readily prepared from (R)-(+)-2-methyl-2-propanesulfinamide (Scheme 19).3 The chiral sulfinyl group is easily cleaved from the addition products under mildly acidic conditions. Thus, this method provides access to highly enantiomerically enriched α-branched secondary amines.


Scheme 19


S-Methyl-S-phenylsulfoximine

Chiral sulfoximines have shown to be versatile compounds for asymmetric synthesis.4 Most of today’s chemistry involving chiral sulfoximines can be reduced to a small number of key intermediates. Sigma-Aldrich is pleased to announce one of these “key” sulfoximines, available in both enantiomeric forms as precursor materials for the modular preparation of S-chirogenic ligands for asymmetric synthesis.

In 2003, Bolm et al. introduced a new class of C1-symmetric monosulfoximine ligands derived from (R)-(–)-S-methyl-S-phenylsulfoximine for enantioselective hetero-Diels–Alder reactions. Under optimized conditions, cycloadducts could be obtained in excellent diastereo- and enantioselecitivities (Scheme 20).5


Scheme 20

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Materials

     

References

  1. (a) Backes, B. J. et al. J. Org. Chem. 1999, 64, 5472; (b) Borg, G. et al. Tetrahedron Lett. 1999, 40, 6709; (c) Davis, F. A. et al. J. Org. Chem. 2000, 65, 8704; (d) Owens, T. D. et al. J. Am. Chem. Soc. 2001, 123, 1539.
  2. Schenkel, L. B.; Ellman, J. A. et al. J. Org. Chem. 2004, 69, 1800.
  3. Weix, D. J. et al. J. Am. Chem. Soc. 2005. 127, 1092.
  4. Reggelin, M.; Zur, C. Synthesis 2000,1.
  5. Bolm, C. et al. Chem. Comm. 2003, 2826.

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