The Development of New Classes of Enantioselective Hydrogen Bond Donor Catalysts for Organic Synthesis Based upon Werner Complexes
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In this dissertation, the development of highly effective, chiral monofunctional and bifunctional hydrogen bond donor catalysts based on cobalt(III) Werner complexes and their applications in enantioselective catalysis have been described. Furthermore, a protocol was developed to extend this chemistry into the fluorous media. Section 1 provides an overview of the hydrogen bond mediated organocatalysis and the scope of Werner complexes as hydrogen bond donors. Section 2 describes the fundamental stereochemical features of the trication [Co(en)3]3+ (en = ethylenediamine). Interactions between the trication, counter anions, and solvates are analyzed and a systematic nomenclature is developed. Section 3 provides highly diastereoselective syntheses of variety of diastereopure salts Λ- and Δ-[Co((S,S)-NHv2CHArCHArNHv2)v3]^3+ 2X–X'– (Ar = Cv6Hv5, vCv6Hv4n-Bu, 4- Cv6Hv4Cl, 4-Cv6Hv4CFv3, 4-Cv6Hv4OCHv3, ɑ-naphthyl, ß-naphthyl, 2-Cv6Hv4OBn; X/X' = Cl/BArvf (BArvf = B(3,5-Cv6Hv3(CFv3)v2)v4), PFv6/BArf, BF4/BArf, PhBF3/BArf, Cl/BArf20 (BArvf20 = B(Cv6F5)4), BArf/BArf, BArf20/BArvf20, BFv4/BFv4, PFv6/PFv6) and probes their properties. Sections 4 and 5 provide detail applications of the lipophilic salts of Λ- or Δ- [Co((S,S)-dpen)v3]^3+ ((S,S)-dpen = (S,S)-1,2-diphenylethylenediamine) in enantioselective addition reactions. Under optimized conditions, Λ-[Co((S,S)-dpen)v3]^3+ 3BFv4– catalyzes the Michael addition of dialkyl malonate to nitroalkenes in the presence of Et3N, affording adducts in up to 98% yields and 96% ee. Interestingly, Δ-[Co((S,S)- dpen)v3]^3+ 2Cl–BArvf20– is superior for the additions of cyclic ß-ketoesters to azodicarboylate diesters (up to 99% yields and >99% ee). Section 6 describes efficient syntheses of tris(hydrochloric acid) salts of chiral triamines Hv2NCH((CHv2)nNMe2)CHv2NHv2 (n = 1-4) from commercial starting materials in overall yields of 38-18%. Section 7 highlights syntheses of bifunctional catalysts and their applications in additions of dialkyl malonates to nitroalkenes. Racemic [Co(en)v2Ov2CO]^+ Cl^– and enantiopure (S)-[Hv3NCH((CH2)nNHMe2)CHv2NHv3]^3+ 3Cl^– (n = 1-4) are combined (water/ charcoal/100 °C) to give [Co(en)v2((S)-Hv2NCH((CHv2)vnNMev2H)CHv2NHv2)]4^+ 4Cl^–. The cobalt diastereomers (Δ/Δ)are separated via chiral Sephadex columns. Reactions with NaOH and Na^+ BArvf^– give the catalysts Λ- or Δ-[Co(en)v2((S)-Hv2NCH- ((CHv2)nNMev2)CHv2NHv2)]^3+ 3BArvf^–. Under optimized condition, Λ-[Co(en)v2((S)- Hv2NCH((CHv2)v3NMev2)CHv2NHv2)]^3+ 3BArvf^– gives addition products up to 98% yield and 99% ee. Section 8 describes an optimized procedure for the synthesis of highly fluorous Na^+ B(3,5-Cv6Hv3((CFv2)5CFv3)v2)v4– and its application in transporting polycations into fluorous media.
Ghosh, Subrata Kumar (2017). The Development of New Classes of Enantioselective Hydrogen Bond Donor Catalysts for Organic Synthesis Based upon Werner Complexes. Doctoral dissertation, Texas A & M University. Available electronically from