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

Abstract

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.

Highly efficient palladium‐catalyzed hydroesterification of functionalized alkenes

“…This observation suggested that Al (OTf) 3 coordinated with the oxygen atom in the hydroxyl group and led to the cleavage of the O‐H bond in MeOH and the release of the proton. This process might facilitate the formation of the [Pd II ‐H] + reactive species 4,19,34 …”

“…Notably, compounds such as dimethyl succinate (DMS), dimethyl adipate, and other diesters have been the research hotspots in today's academia and industry 2,3 . Dimethyl succinate (DMS) can be used as a food mold inhibitor and biodegradable environmentally friendly plastic (PBS) 4–6 . Additionally, it can be used in the synthesis of miglitazone analogs, known for their therapeutic efficacy against type II diabetes 7 ; On the other hand, dimethyl adipate was the fundamental component in polyamide and polyester, finding applications in the manufacturing of plasticizers, lubricants, and nylons 8,9 …”

Transition-Metal-Catalyzed Carbonylative Multifunctionalization of Alkynes

“…Chatani et al reported a Rh-catalyzed carbonylative cyclization of internal alkynes with 2-bromophenylboronic acids leading to indenones (Scheme 11). 37 The regioselectivity of this reaction was largely determined by the electronic and steric hindrance of substituents on alkynes. In general, a bulky group and an electron-withdrawing group prefer to stay at the αposition of the indenones.…”

Palladium-catalyzed regio- and stereoselective alkoxycarbonylation of unsymmetrical internal alkynes toward α, β-unsaturated succinates

“…In addition, it also has a wide range of applications in industry (such as beverages, cosmetics) [32][33][34][35][36][37]. Accordingly, much effort has been devoted to developing new synthetic methods to establish such a structure (Scheme 1B) [38][39][40][41][42][43][44][45][46][47][48][49][50]. For example, Chatani and co-workers accomplished a Rh-catalyzed alkoxycarbonylation of internal alkynes to construct saturated succinates by using special alcohol, pyridine-2-ylmethanol [40].…”