Metal-Free, One-Pot, Sequential Protocol for Transforming α,β-Epoxy Ketones to β-Hydroxy Ketones and α-Methylene Ketones
摘要:
A new sequential, one-pot protocol for transforming 1,3-disubstituted 2,3-epoxy ketones to beta-hydroxy ketones and alpha-methylene ketones has been developed. Reaction of epoxy ketones with boron trifluoride etherate ((BF3OEt2)-O-.) generates the cationic intermediates by regioselective epoxide ring opening and an acyl shift. Then, a treatment of these cations with 2-aryl-1,3-dimethylbenzimidazolines (DMBIH) results in formation of 1,2-disubstituted 3-hydroxy ketones. DMBIH serves as a hydride donor in the second step of this process. Finally, the beta-hydroxy ketones can be converted to 1,2-disubstituted 2-methylene ketones by treatment with methanesulfonic acid or a combination of methanesulfonyl chloride and triethylamine. Importantly, the sequential steps involved in formation of the alpha-methylene ketone products can be carried out in one pot.
α,β-Unsaturated ketones were obtained from alkylphenylketene and aroyl chloride via decarbonylation reaction in the presence of catalytic amounts of tetrakis(triphenylphosphine) palladium.
A novel enantioselective protonation protocol that is triggered by reductive cross coupling of olefins is reported. When under cooperative photoredox and chiral hydrogen-bonding catalytic conditions and using a terminal reductant, various α-branched vinylketones with diverse vinylazaarenes could provide important enantioenriched azaarene derivatives containing tertiary stereocenters at their remote
Azidation of alkenes is an efficient protocol to synthesize organic azides which are important structural motifs in organic synthesis. Enantioselective radical azidation, as a useful strategy to install a C–N3 bond, remains challenging due to the inherently instability and unique structure of radicals. Here, we disclose an efficient enantioselective radical carboazidation and diazidation of α,β-unsaturated
作者:Zhenhua Zhang、Yiyang Liu、Mingxing Gong、Xiaokun Zhao、Yan Zhang、Jianbo Wang
DOI:10.1002/anie.200906349
日期:2010.2.1
On the move: A palladium‐catalyzed reaction of aryl iodides, diazo compounds or N‐tosylhydrazones, and carbon monoxide affords β‐oxo esters or ketones/enones (see scheme; DCE=1,2‐dichloroethane). The products are delivered with high efficiency through the title sequence.
Formal Enone α-Arylation via I(III)-Mediated Aryl Migration/Elimination
作者:Bruna S. Martins、Daniel Kaiser、Adriano Bauer、Irmgard Tiefenbrunner、Nuno Maulide
DOI:10.1021/acs.orglett.1c00251
日期:2021.3.19
A formal enone α-arylation is described. This metal-free transformation relies on the I(III)-mediated skeletal reorganization of silyl enol ethers and features mild conditions, good yields, and high stereoselectivities for β-substituted enones.