Formation of five- and six-membered heterocyclic rings under radical cyclisation conditions

Experimental and Computational Study of 6-exo and 7-endo Cyclization of Aryl Radicals Followed by Tandem SRN1 Substitution

“…Intramolecular addition of aryl radicals to double bonds has also been widely studied. , As shown in Scheme , the general synthetic strategy involves the generation of intermediate radical 1 , which rearranges to the exo -cyclic radical 2 by 5- exo ( n = 1) or 6- exo ( n = 2) cyclization. Radical 2 is then trapped with hydrogen donors to yield the reduced compounds 3-r , or with other reagents to obtain the substituted compound 3-s .…”

Regioselective 6-Endo Cyclizations of 2-Indolylacyl Radicals: Total Synthesis of the Pyrido[4,3-b]carbazole Alkaloid Guatambuine

“…Radical reactions have become an important tool for the construction of nitrogen heterocycles. , In this context, there are several reports in the literature concerning radical cyclizations upon tetrahydropyridines, most of them leading to structures with the nitrogen atom in the newly formed ring. , In our initial design there were two distinct ways to close the central carbocyclic ring, namely, a 6-endo cyclization of a 5-hexenoyl radical (1,2,5,6-tetrahydropyridine) or a 6-exo cyclization of a 6-heptenoyl radical (1,2,3,6-tetrahydropyridine). As the required starting substrates appeared to be more accessible from pyridine derivatives through conventional reductive protocols, we focused our attention on the first approach.…”

Modern Developments in Aryl Radical Chemistry

“…For intramolecular Meerwein reactions, compounds of type 1 can serve as attractive test systems for new initiators, reaction conditions, and trapping reagents, which are finally responsible for the substituent Y in the cyclized product 2 (Scheme 1) [16,17].…”