No abstract

Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. AbstractThe Guanidinium catalysts 7a-e were prepared and applied to the phase transfer alkylation of glycinate Schiff's base 8 in 21-86% ee in addition to the phase transfer epoxidation of the chalcones 10a-e in 85-94% ee. The pK a values of 7a-d were determined to be in the range 13.2-13.9, which supports a standard phase transfer mechanism for these processes. The use of 7a and 7e as catalysts for the addition of nucleophiles in Michael addition reactions was investigated and both were found to be effective catalysts. A counterion effect was apparent in these reactions, however no enantiomeric enrichment of the adducts was observed.

Enantioselective syntheses Enantioselective syntheses O 0031Synthesis and Applications of C 2 -Symmetric Guanidine Bases. -The tetracyclic C 2 -symmetric guanidinium salts (I) are investigated as catalysts in different enantioselective reactions. In particular, (Ic) is an effective catalyst for phase-transfer reactions, e.g. benzylation of (VIII) or epoxidations of (XI). -(ALLINGHAM, M. T.; HOWARD-JONES, A.; MURPHY*, P. J.; THOMAS, D. A.; CAULKETT, P. W. R.; Tetrahedron Lett. 44 (2003) 48, 8677-8680; Dep. Chem., Univ. Wales, Gwynedd, Wales LL57 2UW, UK; Eng.) -Roy 10-026