- Synthesis of functionalized γ-lactones via a three-component cascade reaction catalyzed by consecutive N-heterocyclic carbene systems
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Two consecutive N-heterocyclic carbene (NHC) catalytic systems were combined in a one-pot cascade reaction for the assembly of aromatic aldehydes and 2-haloenals into a structurally complex γ-lactone backbone. To our knowledge, this is the first report of NHC-catalyzed [3 + 2] annulation of α,β-unsaturated acylazoliums with 1,2-bisnucleophiles.
- Zhao, Qian,Han, Bo,Wang, Biao,Leng, Hai-Jun,Peng, Cheng,Huang, Wei
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- Desyl and phenacyl as versatile, photocatalytically cleavable protecting groups: A classic approach in a different (visible) light
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A highly efficient, catalytic strategy for the deprotection of classical phenacyl (Pac) as well as desyl (Dsy) protection groups has been developed using visible light photoredox catalysis. The deliberate use of a neutral two-phase acetonitrile/water mixture with K3PO4 applying catalytic amounts of [Ru(bpy)3](PF6)2 in combination with ascorbic acid is the key to this truly catalytic deprotection of Pac- and Dsy-protected carboxylic acids. Our mild yet robust protocol allows for fast and selective liberation of the free carboxylic acids in very good to quantitative yields, while only low catalyst loadings (1 mol %) are required. Both Pac and Dsy, easily introduced from commercially available precursors, can be applied for the direct protection of carboxylic acids and amino acids, offering orthogonality to a great variety of other common protecting groups. We further demonstrate the general applicability and versatility of these formerly underrated protecting groups in combination with our catalytic cleavage conditions, as underscored by the gained high functional group tolerance. Moreover, this method could successfully be adapted to the requirements of solidphase synthesis. As a proof of principle for an efficient visible light, photocatalytic linker cleavage, a Boc-protected tripeptide was split off from commercially available brominated Wang resin.
- Speckmeier, Elisabeth,Zeitler, Kirsten
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- Lipophilic NHC assisted one-pot synthesis of syncarpamide analogues in aqueous medium
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Lipophilic NHC catalysis in aqueous medium was reported for the synthesis of biologically relevant (a)symmetrically substituted and unsymmetrically substituted syncarpamide analogues. All the reported reactions were performed in the absence of any expensive metal salts or additives. A diverse array of syncarpamide analogues was obtained in good yields. Lipophilic NHC catalysis was also extended to chemoselective transesterification reactions.
- Suresh, Pavithira,Selva Ganesan, Subramaniapillai
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p. 6257 - 6261
(2019/04/25)
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- ANIONIC ACTIVATION BY FLUORIDE ION IN SOLID-LIQUID SYSTEMS. SYNTHESIS OF 3 (2H)-FURANONES AND 2 (5H)-FURANONES.
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The evolution of 2-acyloxy 2-methyl 3-oxobutanamides 1 and 2-acyloxy 3-oxo 2,3-diphenylpropanamides 13 under anionic activation by cesium fluoride was studied.The fluoride ion is an efficient base for the heterocyclization of 1 into 3 (2H)-furanones and 2 (5H)-furanones, but the hydrolysis of the ester group lowered the selectivity of the reaction.However, the cleavage of 13 into the esters 14 and the cyclization of 3-benzoyloxy 3-methyl 2-butanone into bullatenone are very selective.
- Sebti, S.,Foucaud, A.
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p. 1361 - 1368
(2007/10/02)
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