Visible light-mediated formal alkylation and [4+1]-cycloaddition strategies of silyl enol ethers with aryldiazoacetates.

A reaction sequence of visible light-mediated cyclopropanation/acid-promoted ring-opening is described for the formal alkylation of silyl enol ethers with aryldiazoacetates. Under the same conditions, the Danishefsky's diene can react with aryldiazoacetates to afford [4+1]-cycloaddition adducts. Key mechanistic aspects are proposed based on experimental evidence and DFT calculations.

Friedel-CraftsType Arylation Strategy for the Conversion of Alkyl 2-((Diphenoxyphosphoryl)oxy)-2-arylacetates to α,α-Diaryl Esters.

An arylation strategy allowing the conversion of alkyl 2-((diphenoxyphosphoryl)oxy)-2-arylacetates to α,α-diaryl esters is reported. This transformation can be promoted by TfOH when the starting organic phosphates do not carry -alkoxy groups on their aryl rings, but it does not require any additives when such groups are present. These alkyl 2-((diphenoxyphosphoryl)oxy)-2-arylacetates can be readily accessed from the insertion of diphenyl phosphate into aryldiazoacetates.

An -Robinson Annulation Strategy for the Synthesis of Fused Bicyclic Amides: Synthesis of (±)-Coniceine and Quinolizidine.

An -Robinson annulation strategy is described using a NaOEt-catalyzed conjugate addition of cyclic imides onto vinyl ketones, followed by a TfOH-mediated intramolecular aldol condensation to afford densely functionalized fused bicyclic amides. The potential use of these amides in the synthesis of alkaloids is demonstrated by the sequential conversion of appropriate precursors to (±)-coniceine and quinolizidine in two additional steps, thus allowing their preparation in overall 40 and 44% yields, respectively.

Visible light-mediated photolysis of organic molecules: the case study of diazo compounds.

Considering the recent rapid advancement of synthetic technologies promoted by visible light in the last 15 years, the use of photocatalysts has been rightfully justified based on the fact that organic molecules generally do not absorb visible light. However, an increasing number of different classes of organic molecules is being identified as actually directly absorbing in this region of the electromagnetic spectrum. Among them, diazo compounds are possibly one of these classes whose chemistry has been more explored so far.

H-F bond insertions into α-diazo carbonyl compounds.

A reaction for H-F bond insertion into α-diazo carbonyl compounds is reported. The protocol describes a simple reaction setup employing commercially available HF·pyr (Olah reagent) as the fluorine source. The method is rapid and practical, and allows access to a broad range of α-fluorinated carbonyl compounds in generally good yields.

Visible-Light-Mediated Strategies to Assemble Alkyl 2-Carboxylate-2,3,3-Trisubstituted β-Lactams and 5-Alkoxy-2,2,4-Trisubstituted Furan-3(2H)-ones Using Aryldiazoacetates and Aryldiazoketones.

Two new visible-light-mediated strategies are described starting from aryldiazoacetates. The first approach describes their reaction with azides to afford the corresponding imines, and then reaction with aryldiazoketones produces alkyl 2-carboxylate-2,3,3-trisubstituted β-lactams. The second approach describes the reaction with sulfoxides to afford the corresponding sulfoxonium ylides, followed by reaction with aryldiazoketones to produce 5-alkoxy-2,2,4-trisubstituted furan-3(2H)-ones.

A Selective C-C Bond Cleavage Strategy Promoted by Visible Light.

A new visible-light-promoted reaction between aryldiazoacetates and 1,3-diketones allows good yields and selectivities for C-C bond insertions, leading to the corresponding 1,4-dicarbonyl compounds. This transformation is straightforward and highly practical. It tolerates air and moisture and does not require the use of any metals.

Catalytic Friedel-Crafts Alkylation of Electron Rich Aromatic Derivatives with α-Aryl Diazoacetates Mediated by Brønsted Acids.

The catalytic protonation of aryl diazoacetates by strong Brønsted acids, followed by a Friedel-Crafts alkylation reaction with electron rich aromatic compounds, is reported. The reaction provided in a direct fashion 24 geminal diarylacetates in yields of ≤92%.

Synthesis of Oxazinanones: Intramolecular Cyclization of Amino Acid-Derived Diazoketones via Silica-Supported HClO Catalysis.

A Brønsted acid catalyzed intramolecular cyclization of -Cbz-protected diazoketones, derived from α-amino acids, is described. The reaction proceeds under metal-free conditions and is promoted by ecofriendly silica-supported HClO as the catalyst and methanol as the solvent. This transformation enables the short synthesis of various 1,3-oxazinane-2,5-diones under mild reaction conditions and in good yields (up to 90%).

α,α-Alkylation-Halogenation and Dihalogenation of Sulfoxonium Ylides. A Direct Preparation of Geminal Difunctionalized Ketones.

A one-pot alkylation-halogenation of ketosulfoxonium ylides in the presence of alkyl halides is described. The method furnishes several gem-difunctionalized haloketones (an alkyl and F, Cl, Br, or I) in good yields. Replacing alkyl halides with a mixture of electrophilic halogen species and various halide anions led to gem-dihalogenated ketones containing a combination of the same or two different halogens.