New Cascade 2-Indolylacyl Radical Addition−Cyclization Reactions

Free‐Radical‐Mediated Multicomponent Coupling Reactions

“…In the following reaction (Scheme 6.25), a cycloheptanone fused to an indanol skeleton is prepared via a three-component reaction [44]. The sequential addition of an acyl radical to two molecules of methyl acrylate followed by a 7-endo-type radical addition account for the annulation.…”

Furan ring opening ‐ indole ring closure: Synthesis of furo[2′,3′:3,4]‐cyclohepta[1,2‐b]indolium chlorides

“…Among examples of the intramolecular cyclization leading to the formation of carbocyclic fragment of azaazulenes the following should be mentioned: the carbenoid insertion [14], the cascade addition-cyclization reaction of indolyl radicals generated from phenyl selenoesters [15] and intramolecular cyclization of indolylborates [16]. A convenient approach to the carbocycle construction is provided by the intramolecular condensation of corresponding indole derivatives in the PPA medium or under the treatment with (CF 3 CO) 2 O in the presence of BF 3 [17].…”

The Mechanism of Bu3SnH‐Mediated Homolytic Aromatic Substitution

“…A large and growing number of Bu 3 SnH-mediated cyclization reactions which proceed in modest to good yields [1][2][3][4][5][6] involve intramolecular homolytic aromatic substitution of arenes and heteroarenes. These and similar intermolecular reactions proceed by addition of the initial radicals RC, generated by Bu 3 SnC radicals, to the aromatic rings (ArH) to yield intermediate substituted cyclohexadienyl radicals ArRHC 1.…”

“…For cyclization onto indoles, [6] products from the addition of Me 2 CCCN from AIBN breakdown to the p radicals have been isolated and shown to undergo elimination to give the aromatic product.…”

“…It appears therefore that the predominant, although probably not the sole, reaction sequence [6,13] for processes initiated by azo compounds (R' À N = N À R') is given by Equations (6)-(9)…”