Unusual radical ipso-substitution reaction of an aromatic methoxy group induced by tris(trimethylsilyl)silane-AIBN or SmI2

Tanaka, Tetsuaki; Wakayama, Ryutaro; Maeda, Shinichiro; Mikamiyama, Hidenori; Maezaki, Naoyoshi; Ohno, Hiroaki

doi:10.1039/b003742g

Cited by 15 publications

(10 citation statements)

References 12 publications

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“…Several aromatic homolytic substitution reactions have been facilitated by reduction using SmI 2 to yield initial radicals. 135,136 The conditions are important, as shown in the example in Scheme 37. 135 In the absence of a proton source, the intermediate spirocyclic radical has time to undergo a neophyl rearrangement and rearomatise.…”

Section: Cyclisation Using Redox Reagentsmentioning

confidence: 99%

Synthesis using aromatic homolytic substitution—recent advances

2007

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This critical review aims at presenting recent developments in intramolecular aromatic homolytic substitution which has become one of the common methodologies in modern synthesis. The application of Bu3SnH-mediated cyclisations have proved especially useful. The critical review illustrates the mechanistic considerations required for planning synthetic applications and a wide range of synthetic protocols and natural product syntheses are shown. The latest evidence for the mechanisms involved in aromatic homolytic substitution are presented. (152 references).

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Section: Cyclisation Using Redox Reagentsmentioning

confidence: 99%

Synthesis using aromatic homolytic substitution—recent advances

2007

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“…Recently, we found that a radical ipso substitution reaction of the aromatic methoxy group is effectively promoted by samarium(II) to afford cyclized products such as 6 (Scheme ) . The detailed investigation revealed that addition of HMPA to the reaction mixture dramatically changes the cyclization mode: thus, treatment of 5 with SmI 2 in the presence of HMPA and i -PrOH yielded a condensed ring, 7 , bearing a cyclohexadienyl moiety as a diastereomeric mixture .…”

Section: Introductionmentioning

confidence: 99%

Samarium(II)-Promoted Radical Spirocyclization onto an Aromatic Ring

et al. 2003

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Samarium(II)-mediated spirocyclization onto an aromatic ring was achieved by the reaction of methyl 4-(4-oxoalkyl)benzoates with SmI(2) in the presence of i-PrOH and HMPA, yielding methyl 1-alkyl-1-hydroxyspiro[4.5]dec-6-ene-8-carboxylates in moderate to high yields. Utilizing this chemistry, spiro[3.5] and -[5.5] systems, and sterically congested spiro[4.5] systems, were easily synthesized. For the successful conversion, appropriate activation of the aromatic ring has proven to be extremely important: while an ester or amide functionality on the aromatic ring can promote the spirocyclization, a sulfonamide substituent causes ortho cyclization.

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“…7 Recently, we have reported that treatment of 4 with SmI 2 yields ipso-substituted product 5 (Scheme 2). 8 The detailed investigation of this reaction revealed that addition of HMPA to the reaction mixture dramatically changes the cyclisation mode: thus, treatment of 4 with SmI 2 in the presence of HMPA 9 and i-PrOH yielded a condensed ring 6 bearing a cyclohexadienyl moiety as a diastereomeric mixture (8+1). 10 Considering that the ketyl radical attacks at the para-position of the ester group of 4, we expected that the radical spirocyclisation onto an aromatic ring could be possible when using benzoates such as 7 bearing an oxoalkyl group at the para-position to the ester group.…”

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confidence: 99%