Perfectly regioselective acylation of a cardiac glycoside, digitoxin, via catalytic amplification of the intrinsic reactivity
摘要:
Organocatalytic regioselective acylation of digitoxin has been developed. This method provides the 4'''-O-manoacylate as the sole product without the concomitant formation of diacylates. The extremely high regioselectivity was assumed to be the result from the combined effects of the high intrinsic reactivity of C(4''')-OH and catalyst-promoted regioselective acylation of the same hydroxy group. (C) 2010 Elsevier Ltd. All rights reserved.
A Versatile, Practical, and Inexpensive Reagent, Pyridine-3-carboxylic Anhydride (3-PCA), for Condensation Reactions
作者:Setsuo Funasaka、Teruaki Mukaiyama
DOI:10.1246/bcsj.81.148
日期:2008.1.15
A highly useful method for the preparation of carboxylic esters and carboxamides from various carboxylic acids was established by using a novel condensing reagent, pyridine-3-carboxylic anhydride (3-PCA), in the presence of 4-(dimethylamino)pyridine as an activator. The reactions of various carboxylic acids with nucleophiles, such as alcohols or amines, afforded the corresponding carboxylic acids or carboxamides in good to high yields under mild conditions by using simple experimental procedure. In addition, it was confirmed that this protocol was applicable to a gram-scale synthesis and the by-products, including pyridine-3-carboxylic acid and pyridine-3-carboxylate (or pyridine-3-carboxamide) produced in situ, were easily removed by using a simple aqueous workup.
Enantioselective CuH-Catalyzed Reductive Coupling of Aryl Alkenes and Activated Carboxylic Acids
作者:Jeffrey S. Bandar、Erhad Ascic、Stephen L. Buchwald
DOI:10.1021/jacs.6b03086
日期:2016.5.11
A new method for the enantioselective reductive coupling of aryl alkenes with activated carboxylic acid derivatives via copper hydride catalysis is described. Dual catalytic cycles are proposed, with a relatively fast enantioselective hydroacylation cycle followed by a slower diastereoselective ketone reduction cycle. Symmetrical aryl carboxyclic anhydrides provide access to enantioenriched α-substituted
acylation of symmetrical carboxylic anhydrides has inherited limitation of reaction efficiency along with relatively poor reactivity. Traditionally, one equivalent carboxylic acid is generated during nucleophilic acylation of a symmetrical anhydride, which always limits the yield of final product to 50% or less. This is a major drawback, which discourages the use of anhydrides for laboratory or industrial
The one-step synthesis of aromatic acid anhydrides from aromaticcompounds such as benzene, toluene, anisole, chlorobenzene, furan, and thiophen has been carried out using carbonmonoxide, 1,2-dibromoethane, and palladium acetate.
New Synthesis of Biaryls<i>via</i>Rh-Catalyzed Decarbonylative Suzuki-Coupling of Carboxylic Anhydrides with Arylboroxines
作者:L. J. Gooßen、J. Paetzold
DOI:10.1002/adsc.200404190
日期:2004.12
cross-coupling of aromatic carboxylicanhydrides or acid chlorides with triarylboroxines has been achieved for the first time under decarbonylation, giving rise to the unsymmetrical biaryls rather than the expected diaryl ketones. This newdecarbonylative Suzuki coupling, catalyzed by a [Rh(ethylene)2Cl]2/KF system, can be applied to aromatic, heteroaromatic and vinylic carboxylicanhydrides, potentially opening