Ring closing and opening reactions leading to aza-polycyclic aromatic compounds

Abstract

A series of functionalized aza-polycyclic aromatic compounds were prepared by a superacid-promoted ring closing and opening reaction cascade. A reaction mechanism is proposed, which involves reactive dicationic intermediates. A key step in the conversions involves ipso protonation of an aryl group and elimination of an alkyl phenyl group.

Contemporary Carbocation Chemistry: Applications in Organic Synthesis

“…Although the phenyl group is not generally considered a good leaving group, ipso protonation generates the arenium ion 160 and benzene elimination occurs to give the chrysene aromatic ring system. A similar reaction may be accomplished with heterocyclic alcohols, such as pyridine 161 (Scheme ) . Ionization in superacid gives the dication 162 , and subsequent ring-closing and ring-opening steps lead to the functionalized benzo[ f ]quinoline ( 163 ).…”

Synthesis of dibenzosuberenone-based novel polycyclic π-conjugated dihydropyridazines, pyridazines and pyrroles

“…π-Conjugated polycyclic hydrocarbons (CPHs) containing polycyclic heteroaromatic molecules (PHAs) and aza-polycyclic ar-omatic hydrocarbons (aza-PAHs) have been attracting considerable attention as they are widespread in natural products, as well as in pharmaceuticals, agrochemicals, and organic materials. Among the π-CPHs, pyridazines and pyrroles have important roles [17][18][19][20][21][22].…”

Superelectrophiles in ring-forming reactions

“…A route to functionalized aza-polycyclic aromatic compounds has been described and the chemistry utilizes superelectrophilic carbocations. 22 The ring closing and opening cascade involves ionization of substrates such as alcohol 53 to give dication 54. This species undergoes cyclization to initially provide structure 55.…”