Oxidative Coupling of O-Silyl and O-Alkyl Enethers:  Application of the Novel Annulation Sequence to the Synthesis of Fluorinated Naphthaldehydes and Naphthyl Ketones

Facile and Efficient Synthesis of Hydrophenanthren‐1(2H)‐ones and Naphtho[2,1‐c]furan‐3(1H)‐ones by a Palladium‐Catalyzed Aryne Annulation Strategy

“…Polysubstituted naphthalenes, including hydrophenanthren‐1(2 H )‐ones and naphtho[2,1‐ c ]furan‐3(1 H )‐ones, are not only the fundamental structural unit of biologically active compounds, but also building blocks in organic synthesis 1,2. Therefore, considerable efforts have been devoted to develop efficient methods for their preparation 2c–g,3. According to the literature, unsubstituted hydrophenanthren‐1(2 H )‐one can be easily obtained by Friedel–Crafts‐type cyclization of 4‐(naphthalen‐1‐yl)butanoic acid derivatives; also, starting from naphtho[2,1‐ c ]furan‐1,3‐dione, unsubstituted naphtho[2,1‐ c ]furan‐3(1 H )‐ones can be furnished conveniently 2e,4.…”

Cyclizations of Silyl Enol Ether Radical Cations − The Cause of the Stereoselectivity

“…[18] Reversible anodic oxidation during fast-scan cyclovoltammetric experiments provided strong evidence for the formation of radical cations. [19] One-electron oxidation with chemical oxidants has been performed using cerium ammonium nitrate (CAN), [19,20] tetranitromethane, [21] and xenon difluoride, [22] respectively. Furthermore, photoinduced electron transfer (PET) has been applied successfully; [23Ϫ29] all transient species in the electron transfer process between chloranil and several silyl enol ethers have been investigated thoroughly by time resolved spectroscopy.…”

“…[20,30] They assigned the radical cation 6 to be the reactive intermediate for the cyclization reaction, because the cyclization mode was completely 6-endo selective (8), in contrast to the results from the atom transfer reaction, which proceeded via the α-carbonyl radical 7 (Scheme 2). Scheme 2 The influence of the reaction medium and, especially, its nucleophilic character is decisive for the mesolytic SiϪO cleavage, as has been pointed out by Schmittel [19] and Kochi.…”

“…(1.73 g, 7.33 mmol) and 3-ethoxycyclopent-2-enone(20) [64Ϫ67](1.11 g, 8.80 mmol) after purification by column chromatography (cyclohexane/EtOAc, 90:10) and kugelrohr distillation. NMR experiments:1 H, H/H-COSY, APT, HMQC.…”

A Facile Approach to Alkyl- and Aryl-Substituted 3-Furylphosphonates Based on Ceric Ammonium Nitrate-Promoted Radical Reactions

“…4 More recently, alkylated 3-furylphosphonates were prepared in satisfactory yields either by a multi-step procedure based on the addition of homoallylic phosphonates to nitriles, 5 or by a-acylation of phosphonoketals followed by acid catalyzed Pall-Knorr cyclization of the resulting phosphonosubstituted 1,4-dicarbonyl compounds. 6 Relying on our experience in the ceric ammonium nitrate (CAN)-promoted carbon-carbon bond-formation reactions, 7 we decided to investigate a radical approach to substituted 3-furyl phosphonates. Ba³czewski has already used a-phosphonyl carbon-centred radicals to synthesize several polyfunctionalized long-chain phosphonates by Bu 3 SnH/Et 3 B/O 2 -promoted reductive addition of iodoalkylphosphonates to alkenes.…”