- Cross-Dehydrogenating Coupling of Aldehydes with Amines/R-OTBS Ethers by Visible-Light Photoredox Catalysis: Synthesis of Amides, Esters, and Ureas
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A straightforward synthesis of amides, ureas, and esters is reported by visible-light cross-dehydrogenating coupling (CDC) of aldehydes (or amine carbaldehydes) and amines/R-OTBS ethers by photoredox catalysis. The reaction is found to be general and high yielding. A plausible mechanistic pathway has been proposed for these transformations and is supported by appropriate controlled experiments.
- Pandey, Ganesh,Koley, Suvajit,Talukdar, Ranadeep,Sahani, Pramod Kumar
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- Ester Formation via Symbiotic Activation Utilizing Trichloroacetimidate Electrophiles
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Trichloroacetimidates are useful reagents for the synthesis of esters under mild conditions that do not require an exogenous promoter. These conditions avoid the undesired decomposition of substrates with sensitive functional groups that are often observed with the use of strong Lewis or Br?nsted acids. With heating, these reactions have been extended to benzyl esters without electron-donating groups. These inexpensive and convenient methods should find application in the formation of esters in complex substrates.
- Mahajani, Nivedita S.,Meador, Rowan I. L.,Smith, Tomas J.,Canarelli, Sarah E.,Adhikari, Arijit A.,Shah, Jigisha P.,Russo, Christopher M.,Wallach, Daniel R.,Howard, Kyle T.,Millimaci, Alexandra M.,Chisholm, John D.
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p. 7871 - 7882
(2019/06/27)
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- Zn-Catalyzed tert-Butyl Nicotinate-Directed Amide Cleavage as a Biomimic of Metallo-Exopeptidase Activity
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A two-step catalytic amide-to-ester transformation of primary amides under mild reaction conditions has been developed. A tert-butyl nicotinate (tBu nic) directing group is easily introduced onto primary amides via Pd-catalyzed amidation with tert-butyl 2-chloronicotinate. A weak base (Cs2CO3 or K2CO3) at 40-50 °C can be used provided that 1,1′-bis(dicyclohexylphosphino)ferrocene is selected as ligand. The tBu nic activated amides subsequently allow Zn(OAc)2-catalyzed nonsolvolytic alcoholysis in tBuOAc at 40-60 °C under neutral reaction conditions. The activation mechanism is biomimetic: the C3-ester substituent of the pyridine in the directing group populates the trans-conformer suitable for Zn-chelation, C=Oamide-Zn-Ndirecting group, and Zn-coordinated alcohol is additionally activated as a nucleophile by hydrogen bonding with the acetate ligand of the catalyst. Additionally, the acetate ligand assists in intramolecular O-to-N proton transfer. The chemoselectivity versus other functional groups and compatibility with challenging reaction partners, such as peptides, sugars, and sterols, illustrates the synthetic applicability of this two-step amide cleavage method. The tBu nic amides do not require purification before cleavage. Preliminary experiments also indicate that other weak nucleophiles can be used such as (hetero)arylamines (transamidation) as exemplified by 8-aminoquinoline.
- Wybon, Clarence C. D.,Mensch, Carl,Hollanders, Charlie,Gadais, Charlène,Herrebout, Wouter A.,Ballet, Steven,Maes, Bert U. W.
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p. 203 - 218
(2018/01/17)
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- Esters of benzoic, 5-arylisoxazole-3-carboxylic and 4,5- dichloroisothiazole-3-carboxylic acids
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The method of synthesis was developed of esters of benzoic, 2-chlorobenzoic, 5-phenylisoxazole-3-carboxylic, 5-tolylisoxazole-3-carboxylic, and 4,5-dichloroisothiazole-3-carboxylic acids with some aliphatic and substituted aromatic alcohols. The latter were obtained by reduction of aldehydes used in perfumery.
- Dikusar,Potkin,Zhukovskaya,Murashova,Petkevich,Kletskov,Zolotar',Chepik
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p. 1179 - 1185
(2014/08/05)
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- Inhibitory effects of benzyl benzoate and its derivatives on angiotensin II-induced hypertension
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Hypertension is a lifestyle-related disease which often leads to serious conditions such as heart disease and cerebral hemorrhage. Angiotensin II (Ang II) plays an important role in regulating cardiovascular homeostasis. Consequently, antagonists that block the interaction of Ang II with its receptors are thought to be effective in the suppression of hypertension. In this study, we searched for plant compounds that had antagonist-like activity toward Ang II receptors. From among 435 plant samples, we found that EtOH extract from the resin of sweet gum Liquidambar styraciflua strongly inhibited Ang II signaling. We isolated benzyl benzoate and benzyl cinnamate from this extract and found that those compounds inhibited the function of Ang II in a dose-dependent manner without cytotoxicity. An in vivo study showed that benzyl benzoate significantly suppressed Ang II-induced hypertension in mice. In addition, we synthesized more than 40 derivatives of benzyl benzoate and found that the meta-methyl and 3-methylbenzyl 2′-nitrobenzoate derivatives showed about 10-fold higher activity than benzyl benzoate itself. Thus, benzyl benzoate, its derivatives, and benzyl cinnamate may be useful for reducing hypertension.
- Ohno, Osamu,Ye, Mao,Koyama, Tomoyuki,Yazawa, Kazunaga,Mura, Emi,Matsumoto, Hiroshi,Ichino, Takao,Yamada, Kaoru,Nakamura, Kazuhiko,Ohno, Tomohiro,Yamaguchi, Kohji,Ishida, Junji,Fukamizu, Akiyoshi,Uemura, Daisuke
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experimental part
p. 7843 - 7852
(2009/04/11)
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