| dc.description.abstract | 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. | en |
