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Relevant academic research and scientific papers

Synergetic Catalysis for One-pot Bis-alkoxycarbonylation of Terminal Alkynes over Pd/Xantphos?Al(OTf)3 Bi-functional Catalytic System

Tandem bis-alkoxycarbonylation of alkynes allows for the preparation of 2-substituted succinates from alkynes and nucleophile alcohol via two successive alkoxycarbonylation with advantages of 100 % atomic economy and simplified one-pot operation. Herein, the one-pot tandem bis-alkoxycarbonylation of alkynes was accomplished over the bi-functional catalytic system containing Xantphos-modified Pd-complex and Lewis super-acid of Al(OTf)3. It was found that, via the synergetic catalysis, the involved Xantphos-modified Pd-complex was responsible for the activation of CO and the alkynes through coordination to Pd-center while Al(OTf)3 was in charge of the activation of the alcohol to facilitate the formation of [Pd?H]+ active species. The in situ high-pressure FT-IR analysis, coupled with 1H/13C NMR spectral characterizations, confirmed that the introduced Al(OTf)3 with intensive oxophilicity (via acid-base pair interaction) was able to activate nucleophilic MeOH to be a reliable proton-donor (i. e. hydride-source) to warrant the formation and stability of [Pd?H]+ species upon the oxidation of Pd0 by H+ (Pd0+H+→[PdII?H]+). Over the developed bi-functional catalytic system, the yields of the target diesters were obtained in the range of 36～86 % in this sequence with the wide substrate scope.

Selective Palladium-Catalyzed Carbonylation of Alkynes: An Atom-Economic Synthesis of 1,4-Dicarboxylic Acid Diesters

A class of novel diphosphine ligands bearing pyridine substituents was designed and synthesized for the first time. The resulting palladium complexes of L1 allow for chemo- and regioselective dialkoxycarbonylation of various aromatic and aliphatic alkynes affording a wide range of 1,4-dicarboxylic acid diesters in high yields and selectivities. Kinetic studies suggest the generation of 1,4-dicarboxylic acid diesters via cascade hydroesterification of the corresponding alkynes. Based on these investigations, the chemo- and regioselectivities of alkyne carbonylations can be controlled as shown by switching the ligand from L1 to L3 or L9 to give α,β-unsaturated esters.

Co-catalysis over a bi-functional ligand-based Pd-catalyst for tandem bis-alkoxycarbonylation of terminal alkynes

A bi-functional ligand (L1) containing a diphosphino fragment and sulfonic acid group (-SO3H) enabled PdCl2(MeCN)2 to efficiently catalyze the tandem bis-alkoxycarbonylation of terminal alkynes to produce aryl-/alkyl-substituted succinate (α,ω-diesters). It was found that the -SO3H incorporated in L1 indispensably assisted the Pd-catalyst in accomplishing this tandem reaction via intramolecular synergic effects. Co-catalysis over the L1-based Pd-catalyst was not due to the physical mixture of Xantphos and MeSO3H. In situ FTIR analysis verified that the formation and stability of Pd-H active species were facilitated by the presence of L1. The formation of stabilized diacylpalladium intermediate (F) was the critical driving force for the second-step methoxycarbonylation. DFT calculation was carried out to optimize the geometric structure of F, which indicated that the developed intramolecular O?H hydrogen bonds were an important structural feature to stabilize F. In addition, the L1-based Pd-catalyst could be recycled successfully for at least 3 runs in the ionic liquid [Bmim]NTf2 without obvious activity loss and detectable metal leaching.

Selective aryl α-diimine/palladium-catalyzed bis-alkoxycarbonylation of olefins for the synthesis of substituted succinic diesters

Aryl α-diimine derivatives have been used, for the first time, as efficient new ligands for the palladium-catalyzed oxidative bis-alkoxycarbonylation reaction of olefins. The most active catalyst was formed in situ from bis(9-anthryl)-2,3-dimethyl-1,4-dia

Synthesis of 2-Arylsuccinates by Oxidative 1,2-Aryl Migration of 3-Aroylpropionic Acids or 5-Arylfuran-2(3H)-ones with Thallium(III) Nitrate

Treatment of 3-aroylpropionic acids (1) with thallium(III) nitrate causes smooth 1,2-aryl migration to give dimethyl 2-arylsuccinates (2) in good yields.Similar transformation of 5-arylfuran-2(3H)-ones (3) with thallium(III) nitrate to 1-methyl 2-arylsucc