1187-13-9Relevant academic research and scientific papers
Ligand-controlled divergent dehydrogenative reactions of carboxylic acids via C–H activation
Wang, Zhen,Hu, Liang,Chekshin, Nikita,Zhuang, Zhe,Qian, Shaoqun,Qiao, Jennifer X.,Yu, Jin-Quan
, p. 1281 - 1285 (2021/12/10)
Dehydrogenative transformations of alkyl chains to alkenes through methylene carbon-hydrogen (C–H) activation remain a substantial challenge. We report two classes of pyridine-pyridone ligands that enable divergent dehydrogenation reactions through palladium-catalyzed b-methylene C–H activation of carboxylic acids, leading to the direct syntheses of a,b-unsaturated carboxylic acids or g-alkylidene butenolides. The directed nature of this pair of reactions allows chemoselective dehydrogenation of carboxylic acids in the presence of other enolizable functionalities such as ketones, providing chemoselectivity that is not possible by means of existing carbonyl desaturation protocols. Product inhibition is overcome through ligand-promoted preferential activation of C(sp3)–H bonds rather than C(sp2)–H bonds or a sequence of dehydrogenation and vinyl C–H alkynylation. The dehydrogenation reaction is compatible with molecular oxygen as the terminal oxidant.
Synthesis of Cyclopentenones through Rhodium-Catalyzed C-H Annulation of Acrylic Acids with Formaldehyde and Malonates
Yu, Shuling,Hong, Chao,Liu, Zhanxiang,Zhang, Yuhong
supporting information, p. 5054 - 5059 (2021/07/20)
An efficient rhodium-catalyzed protocol for the synthesis of cyclopentenones based on a three-component reaction of acrylic acids, formaldehyde, and malonates via vinylic C-H activation is reported. Exploratory studies showed that 5-alkylation of as-prepared cyclopentenones could be realized smoothly by the treatment of a variety of alkyl halides with a Na2CO3/MeOH solution. Excess formaldehyde and malonate led to a multicomponent reaction that afforded the multisubstituted cyclopentenones through a Michael addition.
γ-C (sp3)-H bond functionalisation of α,β-unsaturated amides through an umpolung strategy
Futaki, Erika,Miyata, Okiko,Shinada, Tetsuro,Takeda, Norihiko,Ueda, Masafumi,Yasui, Motohiro
supporting information, p. 1563 - 1566 (2020/03/06)
The nucleophilic γ-phenylation and γ-alkylation of α,β-unsaturated amides have been developed. This umpolung reaction allows the regioselective introduction of phenyl and alkyl groups to a vinylketene N,O-acetal, which is generated in situ from an α,β-uns
2-Vinylcyclobutanones by Cycloaddition of Vinylketenes to Simple Olefins
Jackson, David A.,Rey, Max,Dreiding, Andre S.
, p. 2330 - 2341 (2007/10/02)
Selected -cycloadditions of three alkylvinylketenes 2 to one mono- and seven dialkyl-olefins 3 yielded eleven 2-alkyl-2-vinylcyclobutanones 4 (Tables 1 and 2).Three methods were compared, all involving in situ generation of the ketenes 2 by HCl-elimination from α,β-unsaturated acid chlorides 1; the most effective employed a large excess of olefin 3 and a high reaction temperature.The -cycloadditions were fully regio- and stereoselective with respect to the olefin 3, but less so with respect to the ketene 2, so that - where possible - two stereoisomers of 4 resulted, namely A and B, whose configurations were determined from their 1H-NMR spectra, mechanistic considerations and, in one case, 4f, by chemical correlation with a previously known cycloadduct 8.
