Radical annulations and cyclisations with isonitriles: the fate of the intermediate imidoyl and cyclohexadienyl radicals

Free‐Radical‐Mediated Multicomponent Coupling Reactions

“…Although the yield and product selectivity require further improvement, the three-component coupling reaction of azo-bis-isobutyronitrile (AIBN), phenylacetylene, and p-methoxyphenyl isonitrile proceeds to give a quinoxaline derivative (Scheme 6.9) [16]. Decomposition of AIBN gives a cyanopropyl radical, which adds to phenylacetylene to form a vinyl radical.…”

A new era for homolytic aromatic substitution: replacing Bu3SnH with efficient light-induced chain reactions

“…Mechanistic studies have shown that azo-initiator derived radicals [7][8][9][10][11][12] and/or oxygen 12-14 may be involved in the hydrogen atom abstraction from the intermediate cyclohexadienyl radical (Scheme 1). It is thus tempting for researchers to add large amounts of azo-initiator however this can result in the incorporation of the initiator derived radicals into the aromatic substitution products [15][16][17] or through radical combination to give non-aromatic products. 11 HAS of 3-indolylacyl radical onto pyridine occurs in moderate yield, and is accompanied by the product of incorporation of the 2-cyano-2-propyl radical onto the 2-position of indole due the use of stoichiometric amounts of AIBN (Scheme 3).…”

Radical and Radical–Ionic Multicomponent Processes

“…Heterocyclic compounds such as quinoxalines for example have been assembled using such processes based on isonitrile chemistry. [17] The addition of electron-deficient, heteroatom-centered radicals (PhS, PhSe, PhCO 2 ) to alkenes and alkynes have been described and subsequently used in intermolecular radical additions which may also be related to 3-CR processes. [18] These few examples illustrate the power of this simple and straightforward strategy to elaborate, with a high degree of convergence, functionalized and useful intermediates for organic synthesis starting from electron-deficient radical precursors.…”