Preparation of Substituted Phenanthridines from the Coupling of Aryldiazonium Salts with Nitriles: A Metal Free Approach

Abstract

A transition metal free approach for the synthesis of substituted phenanthridines from the coupling reaction of aryldiazonium tetrafluoroborates with nitriles has been developed. This operationally simple protocol proceeds through a substitution of aryldiazonium with nitriles followed by an intramolecular arylation to provide the corresponding phenanthridines in moderate to excellent yields.

Palladium‐Catalyzed Selective Aryl Ring C–H Activation of N‐Acyl‐2‐aminobiaryls: Efficient Access to Multiaryl‐Substituted Naphthalenes

“…Among the studied conditions, a notable minor by‐product, 9,10‐diphenyl phenanthrene 3a′ , was isolated in less than 6% yield under certain conditions (entries 2 and 13). Moreover, trace amounts of a by‐product, 6‐phenylphenanthridine ( 3t ), were isolated through oxidative cleavage of diphenylacetylene (entries 6 and 7; see the Supporting Information, Figures S61 and 62 for spectral data). Our examination of the various experimental conditions revealed that the following conditions provided the maximum yield: Pd(OAc) 2 (10 mol%) as the catalyst, NaOAc (50 mol%) as the additive, and Cu(OAc) 2 (0.2 equiv.…”

“…Moreover, trace amounts of a byproduct, 6-phenylphenanthridine (3t), [13] were isolated through oxidative cleavage of diphenylacetylene (entries 6 and 7; see the Supporting Information, Figures S61 and 62 for spectral data). NaOAc played a crucial role in product formation because of its possible potential in stabilizing the relevant Pd(II) intermediates during the reactions.…”

Leaving Groups in Metal‐Free Arylations: Make Your Choice!

“…Phenyl radicals can be generated by simple heating the diazonium salts. This strategy have been adopted in the synthesis of phenanthridines starting from 2-phenylbenzenediazonium salt and nitriles at 120°C [82] and in the carbohydroxyarylation of styrenes in water mixture as solvent. [83] Under thermal conditions aryl radicals can be also generated by treating aryldiazonium salts with a base (e.g.…”

Base‐Promoted Aerobic Oxidation/Homolytic Aromatic Substitution Cascade toward the Synthesis of Phenanthridines

“…[7] Cascade annulation of nitriles with biphenyls containing diazo or hypervalent iodine is also reported. [8] All these methods (Scheme 1a), although widely studied, suffer from the limited scope and practicality due to the elaborated synthesis of starting biphenyl derivatives.…”

“…[6] Another popular approach is the photolysis or oxidant-induced cyclization of oxime, imine or nitrile derivatives via the formation of iminyl radical. [8] All these methods (Scheme 1a), although widely studied, suffer from the limited scope and practicality due to the elaborated synthesis of starting biphenyl derivatives. [8] All these methods (Scheme 1a), although widely studied, suffer from the limited scope and practicality due to the elaborated synthesis of starting biphenyl derivatives.…”