1121775-76-5Relevant academic research and scientific papers
Two-Carbon Ring Expansion of Cyclobutanols to Cyclohexenones Enabled by Indole Radical Cation Intermediate: Development and Application to a Total Synthesis of Uleine
Leclair, Alexandre,Wang, Qian,Zhu, Jieping
, p. 1209 - 1215 (2022/01/19)
A single-electron transfer (SET) oxidation of indole or benzo[b]thiophene to a radical cation reverses the intrinsic polarity of these π-excessive bicyclic heteroarenes. Here we report an oxidative two-carbon homologation of cyclobutanols to cyclohexenones under a visible-light photoredox catalysis. 1-(Indol-2-yl)cyclobutan-1-ols are converted to 2,3,4,9-tetrahydro-1H-carbazol-1-ones, important structural motifs found in alkaloids and pharmaceuticals, with a broad substrate scope. A mechanistic study suggests that the reaction is initiated by an SET from an indole to an excited acridinium salt to generate the radical cation, which is followed by two consecutive 1,2-alkyl migrations and a rearomatization. Benzo[b]thiophene-substituted cyclobutanols are similarly converted to 2,3-dihydrodibenzo[b,d]thiophen-4(1H)-ones. A total synthesis of (±)-uleine featuring this ring-expansion process is documented.
Catalytic formal homo-Nazarov cyclization
De Simone, Filippo,Andres, Julien,Torosantucci, Riccardo,Waser, Jerome
supporting information; experimental part, p. 1023 - 1026 (2009/07/18)
The first catalytic method for the cyclization of vinyl-cyclopropyl ketones (formal homo-Nazarov reaction) is reported. Starting from activated cyclopropanes, heterocyclic, and carbocyclic compounds were obtained under mild conditions using Bronsted acid catalysts. Preliminary investigation of the reaction mechanism indicated a stepwise process.
