A Serendipitous Synthesis: SiO2‐HNO3 Mediated Oxidative Aromatization and Regioselective Nitration of 1,3,5‐Trisubstituted‐4,5‐Dihydro‐1H‐Pyrazoles

Bhatia, Rimpy; Kadyan, Kulbir; Duhan, Meenakshi; Devi, Meena; Singh, Rahul; Kamboj, Ramesh C.; Kumar, Parvin

doi:10.1002/slct.201902285

Cited by 5 publications

(1 citation statement)

References 71 publications

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“…A serendipitous discovery [14][15][16][17][18] led to a new, somewhat more flexible scaffold. We attempted to generate 4a 1 (Figure 6), stabilized by a cation-π interaction, as a characterizable species.…”

Section: Scaffold IImentioning

confidence: 99%

Through‐Space, Lone‐Pair Promoted Aromatic Substitution: A Relay Mechanism Can Beat Out Direct Activation

Kazim

Feng

Vemulapalli

et al. 2023

Chemistry A European J

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We report a detailed experimental and theoretical analysis of through‐space arene activation with halogens, tetrazoles and achiral esters and amides. Contrary to previously assumed direct activation through σ‐complex stabilization, our results suggest that these reactions proceed by a relay mechanism wherein the lone pair‐containing activators form exothermic π‐complexes with electrophilic nitronium ion before transferring it to the probe ring through low barrier transition states. Noncovalent interactions (NCI) plots and Quantum Theory of Atoms in Molecules (QTAIM) analyses depict favorable interactions between the Lewis base (LB) and the nitronium ion in the precomplexes and the transition states, suggesting directing group participation throughout the mechanism. The regioselectivity of substitution also comports with a relay mechanism. In all, these data pave the way for an alternate platform of electrophilic aromatic substitution (EAS) reactions.

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