Development of .BETA.-keto ester and malonate chemistry Palladium-catalyzed new reactions of their allylic esters

Abstract

Introduction.Palladium is now regarded as the most versatile metal among a number of transition metals used for organic synthesis.1) We started research on organopalladium chemistry in early 1960s, and discovered carbon-carbon bond formation by using palladium complexes for the first time. Since then we have carried out extensive studies on organopalladium. One topic of these studies is palladium-catalyzed reaction of allylic compounds via π-allylpalladium complexes. Among a number of new catalytic reactions discovered in this area, synthetically useful catalytic reactions of allyl β-keto carboxylates and malonates via palladium enolates are summarized in this review. The first palladium-mediated carbon-carbon bond formation. At first we investigated the possibility of carbon-carbon bond formation by using palladium complexes. When we treated the stable PdCl 2 complex of cyclooctadiene (COD) 1 with diethyl malonate in ether in the presence of sodium carbonate at room temperature, a facile carbopalladation occurred to give the new stable complex 2. This reaction is the first example of carbopalladation of an alkene in palladium chemistry, resulting in the carbon-carbon bond formation. The palladium-carbon σ-bond in the complex 2 is stabilized by coordination of π-olefin bond. By the treatment of the complex 2 with a base, malonate anion was generated and attacked the palladium-carbon bond, affording the bicyclo[6. Abstract: During extensive studies on π-allylpalladium chemistry, we have developed classical β-keto ester and malonate chemistry to a new generation by discovering a variety of palladium-catalyzed reactions of their allylic esters. Palladium enolates are generated from allyl β-keto esters after decarboxylation and undergo the following transformations; a) reductive elimination to provide α-allyl ketones, b) elimination of β-hydrogen to give α, β-unsaturated ketones, c) formation of α-methylene ketones, d) hydrogenolysis to give ketones, e) aldol condensation, and f) Michael addition. Allyl malonates and cyanoacetes undergo similar reactions. Results of these studies, including several applications carried out by other researchers are summarized.

Coupling Photocatalysis and Substitution Chemistry to Expand and Normalize Redox-Active Halides

“…Our working mechanism of the reaction is shown in Scheme . The reaction begins with absorption of a blue photon to give strongly oxidizing Ir­(III)* [Ir*­(III)/Ir­(II) = 1.21 V vs SCE in CH 3 CN], followed by reductive quenching by the amine , (NR 3 ≈ 0.50 V vs SCE). , This is supported by Stern–Volmer analysis ( 5a ). Next, the reduced Ir­(II) undergoes SET to collidinium salt 1h , (Ir­(II/III) = −1.37 V vs SCE; estimated E 1/2 = −1.27 V vs SCE in DMF), giving collidinium radical I and completing cycle A.…”

Total Synthesis of Peloruside A through Kinetic Lactonization and Relay Ring‐Closing Metathesis Cyclization Reactions

“…Attempts to effect hydrolysis or dealkylation and decarboxylation of the methyl ester analogue of 21 into 3 were compromised by competitive β elimination of PMB‐OH. We solved this complication by use of the allyl ester 21 , which could be smoothly decarbalkoxylated with [Pd(PPh 3 ) 4 ] (HCO 2 H, Et 3 N) 36. The nonbasic conditions associated with this conversion of nitrile into methyl ketone render this strategy applicable to other base‐sensitive nitrile substrates.…”

Transition Metal-Catalyzed Decarboxylative Allylation and Benzylation Reactions

“…4a,32 Specifically, it was found that [Cp*RuCl] 4 and bipyridine formed an effective catalyst for decarboxylative allylation (Scheme 8). The bipyridine (bpy) was found to be an essential ligand as it helped form the active monomeric catalyst from the tetrameric precatalyst.…”

“…In addition, studies of decarboxylative allylations have shown that there are several mechanisms for decarboxylative coupling that do not necessarily follow the simplified rubric shown in Scheme 1. While several accounts have been published on this topic in the last several years, 4 none has done so in the comprehensive manner of this review which covers relevant publications through August 2010.…”