Synthesis and properties of guanidine cocatalysts prepared by cycloaddition reactions

Barešić, Luka (2023) Synthesis and properties of guanidine cocatalysts prepared by cycloaddition reactions. Doctoral thesis, Sveučilište u Zagrebu, Prirodoslovno-matematički fakultet.

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Abstract

As part of this dissertation, methods for the synthesis of new polycyclic guanidines were developed. The influence of the guanidine structure and the type of dienophile on the success of the cycloaddition reaction and the possible role of protons as a protective group were investigated. Maleic acid derivatives give a mixture of exo and endo products regardless of the synthetic methods employed. The cycloaddition of furfuryl-guanidine to dimethyl acetylenedicarboxylate produces the target products together with three- or tetracyclic derivatives in good yields. Aza-Michael addition as a side reaction caused by the nucleophilicity of anions is also explained. Reaction mechanisms were investigated by DFT quantum chemical calculations. The cocatalytic activity of the new compounds was tested in aldol reaction catalyzed by (S)- proline. An increase in the selectivity and yield of the reaction was observed, with the best result of 98:2 diastereoisomer ratio, with an enantiomeric excess of >99.5% and a yield of 97% at 0 °C. The best cocatalyst was tested in the Knoevenagel reaction where a poor activity, significantly lower than for 1,5,7-triazabicyclo[4.4.0]dec-1-ene, was observed.

Item Type:

Thesis (Doctoral thesis)

Uncontrolled Keywords:

aza-Michael; catalysis; cycloaddition; DFT; guanidine

Subjects:

NATURAL SCIENCES
NATURAL SCIENCES > Chemistry
NATURAL SCIENCES > Chemistry > Organic Chemistry

Divisions:

Division of Organic Chemistry and Biochemistry

Projects: