%0 Journal Article
%T An Alternative Route for Synthesis of Chiral 4-Substituted 1-Arenesulfonyl-2-imidazolidinones: Unusual Utility of (4S,5S)- and (4R,5R)-4,5-Dimethoxy-2-imidazolidinones and X-Ray Crystallography
%A Ibrahim A. Al-Swaidan
%A Amer M. Alanazi
%A Adel S. El-Azab
%A Alaa A.-M. Abdel-Aziz
%J Journal of Chemistry
%D 2013
%I Hindawi Publishing Corporation
%R 10.1155/2013/349519
%X An unusual synthesis of (S)-1-arenesulfonyl-4-(1-adamantyl)-2-imidazolidinones 15a每d and (R)-1-arenesulfonyl-4-tert-butyl-2-imidazolidinones 19a每d has been developed from trans-1-apocamphanecarbonyl-4,5-dimethoxy-2-imidazolidinones 6 and 7 as chiral synthons. Diastereomerically pure trans-1-apocamphanecarbonyl-4,5-dimethoxy-2-imidazolidinones 6 and 7 were successfully subjected to regioselective reduction using bulky organocuprates that afforded 1-apocamphanecarbonyl-5-methoxy-2-imidazolidinones 10 and 11. This new finding was used for synthesis of chiral 4-substituted 2-imidazolidinones 15a每d and 19a每d through the corresponding intermediates 13 and 17 by treatment with steric bulky tert-butylcuprate or 1-adamantylcuprate. 1. Introduction Methods involving the use of heterocyclic chiral auxiliaries have been very successful for a wide range of asymmetric transformations [1每5]. Chiral 2-imidazolidinones [4, 5] have been described as chiral auxiliaries for use in diastereocontrolled reactions and a number of enantiopure 2-imidazolidinones [6每8]. The most direct route for synthesis of 2-imidazolidinones is from the corresponding 1,2-diamines via carbonylation with phosgene or its synthetic equivalents [9]. The application of the 2-imidazolidinones in asymmetric synthesis requires that it should be readily available on a useful scale and preferably in both enantiomeric forms. A route to obtain optically active 4-tert-butyl-2-imidazolidinones 3 and 4-(1-adamantyl)-2-imidazolidinones 4 from a 2-imidazolidinone heterocycle has been described. The method involves the conversion of 4-methoxy-2-imidazolidinones 1, using organocuprates (tert-butylcuprate, 1-adamantylcuprate, phenylcuprate, and benzylcuprate), into 4-alkyl- and 4-aryl-derivatives 2, followed by optical resolution through either a stoichiometric or catalytic process (Scheme 1) [10]. It was also reported that (4S,5S)- and (4R,5R)-1-apocamphanecarbonyl-4,5-dimethoxy-2-imidazolidinones (DMIm 6, 7) are good candidates as chiral synthons. (DMIm 6, 7) could be used for the chiral synthesis of 1,2-diamino acids 8, sterically congested 1,2-diamines 9 [11] (Scheme 2), and for synthesis of biological active molecules [12, 13]. Scheme 1: General method for optical resolution of 4-substituted 2-imidazolidinones. Scheme 2: The utility of DMIm 6 and 7 for the synthesis of 1,2-diamino acids 8 and -symmetric 1,2-diamines 9. 2. Results and Discussion We now describe the conversion of (4S,5S)-1-apocamphanecarbonyl-4,5-dimethoxy-2-imidazolidinone 6 and (4R,5R)-1-apocamphanecarbonyl-4,5-dimethoxy-2-imidazolidinones 7
%U http://www.hindawi.com/journals/jchem/2013/349519/