Acylpalladium derivatives reactions

Carboxylic acid chlorides and chloroformate esters add to tetrakis(triphenylphosphine)palladium(0) to form acylpalladium derivatives (equation 42).102 On heating, the acylpalladium complexes can lose carbon monoxide (reversibly). Attempts to employ acid halides in vinylic acylations, therefore, often result in obtaining decarbonylated products (see below). However, there are some exceptions. Acylation may occur when the alkenes are highly reactive and/or in cases where the acylpalladium complexes are resistant to decarbonylation and in situations where intramolecular reactions can form five-membered rings. 

Negishi E, Makabe H (2002) Reactions of Acylpalladium Derivatives with Enolates and Related Amphiphilic Reagents. In Negishi E, de Meijere A (eds) Handbook of Organopalladium Chemistry for Organic Synthesis. Wiley, New York, p 2455... 

Tsuji, J. Other reactions of acylpalladium derivatives palladium-catalyzed decarbonylation of acyl halides and aldehydes. Handbook of Organopaiiadium Chemistry for Organic Synthesis 2002, 2, 2643-2653. 

First, coordinatively unsaturated active palladium catalyst, PdL2, is produced via dissociation of the ligands, which then reacts with acyl halide to give the acylpalladium intermediate. Since deinsertion of CO of the acylpalladium derivatives may occur simul-taneously, the next step, transmetallation (so-called metathesis), is the most crucial for the efficiency of the overall reaction. A variety of organometallic compounds, such as boron, aluminum, copper, zinc, mercury, silicon, tin, lead, zirconium, and bismuth, are used as the partner in this coupling reaction without loss of CO. In this section, the important features of the cross-coupling reactions of a variety of organometallic compounds with acyl halides and related electrophiles are discussed. 

VI.2.1 Reactions of Acylpalladium Derivatives with Oxygen, Nitrogen, and Other Group 15,16, and 17 Atom Nucleophiles... 

VI.2.3 Reactions of Acylpalladium Derivatives with Enolates and Related Amphiphilic Reagents... 

In view of the facile reactions of acylpalladium derivative with a wide variety of groups 14-17 atom nucleophiles discussed in Sects. VI.2.1 and VI.2.2, it might readily be expected that acylpalladium derivatives should react with enolates, which can, in principle, serve as amphiphilic 0 and/or C nucleophiles (Scheme 1). Somewhat surprisingly, these reactions had not been reported until 1986. 

Also in 1986, intermolecular versions of the reaction of putative acylpalladium derivatives with the enolates derived from malonic esters and a few ketones were independently reported, Two different courses of reaction were observed with malonate esters (Scheme 3). However, both involve selective C-acylation. In cases where the C-acylation products, which are /S-keto diesters, still contain an acidic /3 C—H bond, they will further react with acylpalladium derivatives as 0-enolates rather than C-enolates, as detailed in the following section. 

B. INTERMOLECULAR REACTIONS OF ACYLPALLADIUM DERIVATIVES WITH ENOLATES... 

The original investigation by Kobayashi and Tanaka delineated the courses of reaction of acylpalladium derivatives with malonates (Scheme 3 and Table 1). On the other... 

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