Synthesis of β-acetoxy alcohols by PhI(OAc)<sub>2</sub>-mediated metal-free diastereoselective β-acetoxylation of alcohols
作者:Chun-Yang Zhao、Liang-Gui Li、Qing-Rong Liu、Cheng-Xue Pan、Gui-Fa Su、Dong-Liang Mo
DOI:10.1039/c6ob01203e
日期:——
β-Acetoxy alcohols can be synthesized in good yields with excellent diastereoselectivity from tertiary alcohols through PhI(OAc)2-mediated metal-free β-acetoxylation. Mechanistic studies showed that the β-acetoxylation process might undergo dehydration and sequential highly regioselective and diastereoseletive dioxygenation. Gram scale and diverse useful scaffolds could be prepared via this β-acetoxylation
Thiazol-2-ylidene Catalysis in Intramolecular Crossed Aldehyde-Ketone Benzoin Reactions
作者:Dieter Enders、Oliver Niemeier
DOI:10.1055/s-2004-831306
日期:——
Intramolecular crossedaldehyde-ketone benzoin-type reactions catalyzed by nucleophilic carbenes, easily generated from commercially available thiazolium salts as precatalysts, are described. Five- and six-membered cyclicacyloins are obtained in moderate to good yields. Depending on the structure of the aldehyde-ketone substrate, an interchange of the alcohol and ketone function of the resulting acyloin
etherate as a Lewis acid, acetophenone and benzophenone derivatives bearing a prenyl (or a related) side chain in ortho-position were shown to undergo intramolecular carbonyl―olefin metathesis, in the absence of any transition-metal catalyst. The cationic cyclization process is supposed to proceed via an oxetane intermediate, which fragments to give the cyclization product (indene or 1,2-dihydronaphthalene)
Copper-Catalyzed Intramolecular Aldehyde–Ketone Nucleophilic Additions for the Synthesis of Chromans Bearing a Tertiary Alcohol Motif
作者:Chenghao Zhu、Wenbo Jiang、Da Ma
DOI:10.1021/acs.joc.3c02365
日期:2024.1.19
The synthesis of chroman-3-ol derivatives via intramolecular nucleophilic additions has been established. Aldehydes can be used as alkyl carbanion equivalents viareductive polarity reversal which is facilitated by a copper catalyst and N-heterocyclic carbene ligand under mild conditions. The key to success is the difference in reaction activity between aldehydes and ketones. Finally, this methodology
Modified Chiral Triazolium Salts for Enantioselective Benzoin Cyclization of Enolizable Keto-Aldehydes: Synthesis of (+)-Sappanone B
作者:Hiroshi Takikawa、Keisuke Suzuki
DOI:10.1021/ol070929p
日期:2007.7.1
Asymmetric synthesis of (+)-sappanone B (1), a natural product with a 3-hydroxy chromanone structure, was achieved via enantioselective benzoin cyclization by using a modified Rovis catalyst and triethylamine. This catalyst enabled the successful benzoin cyclization of readily enolizable keto-aldehydes.