Highly oxidized graphene oxide as carbocatalyst for the multicomponent synthesis of triazoloquinazolines

• Main Author: Ebajo, Virgilio D., Jr.
• Format: text
• Language: English
• Published: Animo Repository 2019
• Subjects: Graphite; Organic compounds—Synthesis; Chemistry
• Online Access: https://animorepository.dlsu.edu.ph/etd_doctoral/1446; https://animorepository.dlsu.edu.ph/cgi/viewcontent.cgi?article=2497&context=etd_doctoral
• Institution: De La Salle University

The Brønsted acidity of graphene oxide (GO) materials has shown promising activity in organic synthesis. However, the roles and functionality of Lewis acid sites remain elusive. Herein, we report a carbocatalytic approach utilizing both Brønsted and Lewis acid sites in GOs as heterogeneous promoters in a series of multicomponent synthesis of triazoloquinazolinone compounds. The GOs possessing the highest degree of oxidation, also having the highest amounts of Lewis acid sites, enable optimal yields (up to 95%) under mild and non-toxic reaction conditions (85oC in EtOH). The results of FT-IR spectroscopy, temperature-programmed decomposition mass spectrometry, and X-ray photoelectron spectroscopy identified that the apparent Lewis acidity via basal plane epoxide ring-opening, on top of the saturated Brønsted acidic carboxylic groups, is responsible for the enhanced carbocatalytic activities involving Knoevenagel condensation pathway. Recycled GO can be effectively regenerated to reach 97% activity of fresh GO, supporting the recognition of GO as pseudocatalyst in organic synthesis.