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    • Keywords


      Enantioselective annulation; cyclization; S-proline; S-phenylalanine; d-camphorsulphonic acid

    • Abstract


      The enantioselective cyclization of the prochiral cyclic substrates1 to7 and26, can be carried out in theneat using S-proline as catalyst. The substrates18 to22 and27 could not be cyclized with S-proline but could be cyclized with a mixture of S-phenylalanine and d-camphorsulphonic acid. The enantioselective cyclization of prochiral acyclic triones45 and47 and also the racemic tricarbonyl compounds54 to57 could also be carried out in theneat using S-proline as catalyst. The optically active enediones obtained in the above cyclizations could also be obtained directly from 1,3-diones or 2-hydroxymethylene cycloalkanones in a one-pot reaction with methyl vinyl ketone (MVK) and S-proline in the absence of solvents.13C NMR studies of the one-pot synthesis ofS-11 andS-14 reveal that the annulations involve initial formation of an acid-base complex followed by a Michael reaction and then an enantioselective cyclization. Such enantioselective cyclizations probably occur on the surface of S-proline crystals.

    • Author Affiliations


      D Rajagopal1 R Narayanan1 S Swaminathan1

      1. Department of Organic Chemistry, University of Madras, Guindy Campus, Chennai - 600 025, India
    • Dates

  • Journal of Chemical Sciences | News

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