Enantioselective solvent-free Robinson annulation reactions

Rajagopal, D. ; Narayanan, R. ; Swaminathan, S. (2001) Enantioselective solvent-free Robinson annulation reactions Journal of Chemical Sciences, 113 (3). pp. 197-213. ISSN 0377-8444

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Related URL: http://dx.doi.org/10.1007/BF02704070


The enantioselective cyclization of the prochiral cyclic substrates1 to 7 and 26, can be carried out in theneat using S-proline as catalyst. The substrates18 to 22 and 27 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 triones 45 and 47 and also the racemic tricarbonyl compounds 54 to 57 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 of S-11 and S-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.

Item Type:Article
Source:Copyright of this article belongs to Indian Academy of Sciences.
Keywords:Enantioselective Annulation; Cyclization; S-Proline; S-Phenylalanine; D-Camphorsulphonic Acid
ID Code:70797
Deposited On:21 Nov 2011 05:11
Last Modified:18 May 2016 16:44

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