64261-57-0Relevant academic research and scientific papers
C5-Disubstituted Meldrum's Acid Derivatives as Platform for the Organocatalytic Synthesis of C3-Alkylated Dihydrocoumarins
Martzel, Thomas,Annibaletto, Julien,Levacher, Vincent,Brière, Jean-Fran?ois,Oudeyer, Sylvain
, p. 995 - 1000 (2019)
C5-disubstituted Meldrum's acid precursors were shown to be a useful platform for the synthesis of an array of 3-alkylated dihydrocoumarins with up to 93:7 er, thanks to an enantioselective domino cyclization-decarboxylative-protonation reaction triggered by an unprecedented benzhydryl-derived cupreine organocatalyst. This cyclization sequence was extended to an emerging organocatalytic decarboxylative-chlorination reaction in the presence of trichloroquinolinone and by means of a bifunctional cinchona derived Br?nsted base which gave rise to the formation of dihydrocoumarins (up to 79:21 er) with a tertiary chlorinated stereocenter. (Figure presented.).
Pd-Catalyzed Decarboxylative Asymmetric Protonation of Sterically Hindered α-Aryl Lactones and Dihydrocoumarins
James, Jinju,Akula, Ramulu,Guiry, Patrick J.
, p. 3138 - 3149 (2018/08/01)
Pd-catalyzed decarboxylative asymmetric protonation (DAP) has been developed for sterically hindered α-aryl lactone and dihydrocoumarin substrates. Optimization studies were conducted using δ-lactone- and dihydrocoumarin-derived α-aryl, β-oxo-allyl esters with 2,4,6-trimethoxyphenyl as the aryl substituent. In the absence of a chiral P,N-ligand, (1R,2S)-(?)ephedrine, a cheap and readily available chiral proton donor, induced enantioselectivities of up to 92% ee and 88% ee with lactone and dihydrocoumarin substrates, respectively. Bulky aryl groups containing di-ortho substitutions and naphthyl groups gave the highest enantioselectivities of up to 92% and 86%, respectively. A stereochemical rationale is proposed to explain the preferred sense of asymmetric induction. (Figure presented.).
Organocatalytic annulation of aldehydes and o-quinone methides: A facile access to dihydrocoumarins
Zhou, Ding,Mao, Kaizhe,Zhang, Jian,Yan, Bingliang,Wang, Wei,Xie, Hexin
, p. 5649 - 5652 (2016/11/29)
A [4+2] annulation of aldehydes and o-quinone methides catalyzed by a secondary amine is developed. This process leads to biologically important dihydrocoumarins in moderate to good yields after oxidation. In addition, the employment of a chiral secondary amine catalyst allows access to optically active dihydrocoumarins with up to 64% ee.
A General and mild catalytic α-alkylation of unactivated esters using Alcohols
Guo, Le,Ma, Xiaochen,Fang, Huaquan,Jia, Xiangqing,Huang, Zheng
supporting information, p. 4023 - 4027 (2015/03/30)
Catalytic α-alkylation of esters with primary alcohols is a desirable process because it uses low-toxicity agents and generates water as the by-product. Reported herein is a NCP pincer/Ir catalyst which is highly efficient for α-alkylation of a broad scope of unactivated esters under mild reaction conditions. For the first time, alcohols alkylate unactivated α-substituted acyclic esters, lactones, and even methyl and ethyl acetates. This method can be applied to the synthesis of carboxylic acid derivatives with diverse structures and functional groups, some of which would be impossible to access by conventional enolate alkylations with alkyl halides. In a pinch: An NCP pincer/iridium catalyst is highly efficient for the α-alkylation of unactivated esters using alcohol under mild reaction conditions. The reaction is simple, clean, and scalable (1-10 mmol), and the scope with respect to the ester is wide.
N-Heterocyclic carbene-catalyzed enantioselective annulations: A dual activation strategy for a formal [4+2] addition for dihydrocoumarins
Lee, Anna,Scheidt, Karl A.
, p. 3407 - 3410 (2015/03/18)
A highly efficient asymmetric formal [4+2] annulation for the synthesis of dihydrocoumarins has been developed via an in situ activated NHC catalysis. Both electrophilic and nucleophilic species are generated in situ simultaneously whereby acyl imidazoles facilitated rapid formation of an NHC-enolate intermediate to afford the [4+2] dihydrocoumarin adducts.
