Dynamic Kinetic Resolution of Azlactones by Bifunctional Thioureas with alpha-Trifluoromethyl or Methyl Groups
Por:
Jimenez, I, Eddy, Cantu-Reyes, Margarita, Flores-Ramos, Miguel, Roman-Chavarria, Carlos A., Diaz-Salazar, Howard, Hernandez-Rodriguez, Marcos
Publicada:
21 oct 2022
Categoría:
Organic chemistry
Resumen:
The asymmetric ring opening of azlactones via dynamic kinetic resolution
(DKR) is investigated by contrasting thioureas incorporating 1-arylethyl
substituents against their more acidic trifluoromethylated analogs. All
the catalysts under study outperform Takemoto's thiourea because of the
inclusion of an additional chiral center. However, the difference in
yield and selectivity between the fluorinated and non-fluorinated
catalysts is minimal. We explain this observation by analysis of
calculated transition states. Our findings show that the hydrogen bond
(HB) between the NH linked to the 1-arylethyl and the negatively charged
oxygen in the benzyloxy ion is the longest in the HB network, whereas
the HB between the ammonium group and the same oxygen atom is the
shortest. Thus, the substituents and the HB donor ability of this chiral
fragment attached to the thiourea are not important in the reaction.
Filiaciones:
Cantu-Reyes, Margarita:
Jimenez, Eddy, I , Univ Nacl Autonoma Mexico, Inst Quim, Dept Quim Organ, Ciudad Univ, Del Coyoacan 04510, Cdmx, Mexico
Flores-Ramos, Miguel:
Jimenez, Eddy, I , Univ Nacl Autonoma Mexico, Inst Quim, Dept Quim Organ, Ciudad Univ, Del Coyoacan 04510, Cdmx, Mexico
Roman-Chavarria, Carlos A.:
Jimenez, Eddy, I , Univ Nacl Autonoma Mexico, Inst Quim, Dept Quim Organ, Ciudad Univ, Del Coyoacan 04510, Cdmx, Mexico
Diaz-Salazar, Howard:
Jimenez, Eddy, I , Univ Nacl Autonoma Mexico, Inst Quim, Dept Quim Organ, Ciudad Univ, Del Coyoacan 04510, Cdmx, Mexico
Hernandez-Rodriguez, Marcos:
Jimenez, Eddy, I , Univ Nacl Autonoma Mexico, Inst Quim, Dept Quim Organ, Ciudad Univ, Del Coyoacan 04510, Cdmx, Mexico
|