- Insertion reactions of alkenes with diterpenoid chromium aminocarbenes
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Insertion reactions of electron-deficient alkenes with chromium aminocarbenes derived from podocarpic acid generally give aryl ketone products derived from ring opening of an aminocyclopropane and subsequent enamine hydrolysis, the exception being alkenyl sulphones which give products derived from insertion of the carbene into the β-CH bond of the alkene. Increasing steric hindrance due to the substituents on the aminocarbene nitrogen appears to result in higher yields of the insertion products. However, other factors such as stabilisation of the intermediate tetracarbonylaminocarbene may explain why morpholinocarbenes give superior yields of the insertion products. Propenoic acid, propenal or nitropropene give a 13-formyl-substituted diterpenoid. Electron-rich alkenes do not undergo insertion reactions with these aminocarbenes at 110°C.
- Woodgate, Paul D.,Sutherland, Hamish S.
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- Ag2CO3-mediated direct functionalization of alkyl nitriles: Facile synthesis of γ-ketonitriles through nitrile alkylation of enol acetates
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Direct C(sp3)-H functionalization of alkyl nitriles is a low toxic and facile route to nitrile-containing compounds. In this research, the Ag2CO3-mediated nitrile methylenation of enol acetates is developed to prepare γ-ketonitriles through the direct C(sp3)-H oxidative functionalization of acetonitrile. A radical pathway is proposed, and acetonitrile serves both as solvent and CN-containing radical source.
- Cheng, Pi,Wang, Wei,Wang, Lin,Zeng, Jianguo,Reiser, Oliver,Liang, Yun
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p. 1408 - 1412
(2019/05/06)
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- Copper-Catalyzed Decarboxylative Oxyalkylation of Alkynyl Carboxylic Acids: Synthesis of ?-Diketones and ?-Ketonitriles
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A novel copper-catalyzed decarboxylative oxyalkylation of alkynyl carboxylic acids with ketones and alkylnitriles via direct C(sp3)-H bond functionalization to construct new C-C bonds and C-O double bonds was developed. This transformation is featured by wide functional group compatibility and the use of readily available reagents, thus affording a general approach to ?-diketones and ?-ketonitriles. A possible mechanism is proposed.
- Li, Yi,Shang, Jia-Qi,Wang, Xiang-Xiang,Xia, Wen-Jin,Yang, Tao,Xin, Yangchun,Li, Ya-Min
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supporting information
p. 2227 - 2230
(2019/03/26)
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- Light-Driven Vitamin B12-Catalysed Generation of Acyl Radicals from 2-S-Pyridyl Thioesters
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Acyl radicals are invaluable intermediates in organic synthesis, however their generation remains challenging. Herein, we present an unprecedented light-driven, cobalt-catalysed method for the generation of acyl radicals from readily available 2-S-pyridyl thioesters. The synthetic potential of this methodology was demonstrated in the Giese-type acylation of activated olefins in the presence of heptamethyl cobyrrinate. This vitamin B12 derivative proved to be the most efficient catalyst in the studied process. The developed method features broad substrate scope (38 examples), good functional group tolerance, and mild reaction conditions. Moreover, it is easily scalable (illustrated on a 20-fold scale-up procedure), enabling its preparative use. Mechanistic studies revealed that the reaction proceeds via a radical pathway with the key steps involving the formation of an acyl-vitamin B12 complex and subsequent photolysis of the Co?C bond. (Figure presented.).
- Ociepa, Micha?,Baka, Oskar,Narodowiec, Jakub,Gryko, Dorota
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supporting information
p. 3560 - 3565
(2017/10/24)
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- Tert-Butyl Hypofluorite - An Electrophilic tert-Butoxylation Agent
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tert-Butyl hypofluorite, t-BuOF, easily synthesized from Z-BuOH and F2, is a unique source of the novel electrophilic tert-butoxylium moiety t-BuO+. It was added to several benzylic double bonds to form vicinal fluoro-tert-butoxide derivatives. Not surprisingly, this bulky reagent is quite sensitive to steric hindrance. The process is electrophilic in nature, but since the reaction is relatively slow (20-60 min) formation of various radical species can take place, forming eventually several distinct byproducts. t-BuOF was also reacted with a number of enols, producing the corresponding α-tert-butoxy ketone derivatives in moderate to good yields. The best results were obtained with benzylic enol derivatives.
- Ben-David, Iris,Mishani, Eyal,Rozen, Shlomo
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p. 4632 - 4635
(2007/10/03)
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