Study and application of graphene oxide in the synthesis of 2,3-disubstituted quinolinesviaa Povarov multicomponent reaction and subsequent oxidation

Abstract

Graphene oxide is exploited as a heterogeneous, metal-free and sustainable catalyst for the three-component Povarov reaction and subsequent oxidation. The multistep synthesis can also be performed as a one-pot procedure.

Graphene‐Oxide Mediated Chemodivergent Ring‐Opening of Cyclobutanols

“…From 2D { 1 H}‐ 13 C HETCOR experiments [ 20 ] (Figure 3, co‐processed for denoising) [ 21 ] we observed, in both cases ( Conditions A and B ), the emergence of correlation peaks between the 13 C signals at δ 20—30 and the 1 H signals in the δ 0—2 region, commonly associated with the presence of aliphatic carbon units (C—C sp 3 ). [ 22 ] The massive change after the reaction of the aromatic region intensity ‐ 13 C at δ 130 ‐ is strongly suggestive of the presence of protons near the aromatic C=C‐(sp 2 ) domains of GO and, again, the 2D { 1 H}‐ 13 C HETCOR experiment can be used to clarify this aspect: in the bottom panel of Figure 3 we reported the 2D { 1 H}‐ 13 C signals of GO after subjection to Conditions B acquired with a longer cross‐polarization contact time, which allowed us to observe couplings at longer range. Here the correlation between aromatic carbons ( 13 C at δ 130) and aliphatic protons ( 1 H at δ 0) becomes apparent.…”

Ball milled glyco-graphene oxide conjugates markedly disrupted Pseudomonas aeruginosa biofilms

“…13 C MAS ssNMR spectra allow us to monitor the different functionalities present on the GO surface, monitoring either the effective presence of the monosaccharides on the GO surface or the transformation in GO upon the ball milling process. [59][60][61][62] In Fig. 3, we report the comparison of the 13 C 1D Cross-Polarization MAS spectra (CP-MAS) for glyco-GO conjugates 1-3 and GObm.…”

Synthesis of α‐Imino Amidines and 2,3‐Diamino Indolenines Using a One‐Pot Graphene Oxide‐Catalyzed Process

“…Based on our experimental findings, we suppose that GO promotes the Ugi-type reaction acting both as Brønsted acid and as a Lewis acidic carbenium catalyst, as previously reported for other MCRs involving amines and aldehydes. [7] For what concerns the oxidation step, we have performed other experiments with the aim to investigate the reusability of GO. α-Amino amidine 1 g was used as model compound and subjected to the oxidation reaction under the optimized conditions.…”

“…In view of our continued efforts in the development of new synthetic methodologies using MCRs, [6] and following our recent interest on the use of graphene oxide (GO) as a heterogeneous catalyst for MCRs, [7] we planned to use GO for the synthesis of α ‐amino amidines 1 via this Ugi‐type reaction. Contrary to what expected, the reaction between aldehydes, isocyanides and 2 equivalents of aromatic amines in the presence of GO, provided a mixture of α ‐amino amidines 1 and α ‐imino amidines 2 , as the result of an Ugi‐type reaction and a partial C−N bond oxidation.…”