Coupling of acyl halides

Decarbonylative cross coupling of acyl halides.8 This unusual reaction is observed on coupling aroyl chlorides with alkyl(phenyl)acetyl chlorides in the pres-... 

An interesting coupling of acyl halide with Michael acceptors involves an organo-metallic intermediate and photochemical step as well as an electroreduction. The electrochemical reduction, however, is used to reduce the intermediate cobalt oxidation state [115]. 

Palladium-catalyzed cross-coupling of acyl halides with organometallic reagents of zinc and tin is a convenient synthetic route to ketones and aldehydes. Typical examples are shown in eq (85) and (86) [116,117]. 

Pd-catalyzed coupling of acyl halides with organometallic reagents is a useful synthetic method of ketones. The alkylzinc reagent 127, prepared from the corresponding alkyl iodide with Zn/Cu couple, was coupled with the acid chloride 128 to give the ketone 129 in 50 % yield and used for the total synthesis of amphidinolide T14 [55]. 

There are several alternative methods for the formation of acylsilanes these include the reaction of silyl cuprates with acid halides, palladium-assisted coupling of acyl halides with hexamethyldisilane, the reaction of thiopyridyl esters with tris(trimethylsilyl)aluminum in the presence of Cu salts, and the hydroboration of trimethylsilyl-substituted alkynes. While all of these procedures are complementary, the method involving the title corqtound provides an easy, inexpensive route to acylsilanes. 

Tributylstannyl)-3-cyclobutene-1,2-diones and 4-methyl-3-(tributylstan-nyl)-3-cyclobutene-l,2-dione 2-ethylene acetals undergo the palladium/copper-catalyzed cross coupling with acyl halides, and palladium-catalyzed carbon-ylative cross coupling with aryl/heteroaryl iodides [45]. The coupling reaction of alkenyl (phenyl )iodonium triflates is also performed by a palladium/copper catalyst [46],... 

An intermediate acylnickel halide is first formed by oxidative addition of acyl halides to zero-valent nickel. This intermediate can attack unsaturated ligands with subsequent proton attack from water. It can give rise to benzyl- or benzoin-type coupling products, partially decarbonylate to give ketones, or react with organic halides to give ketones as well. Protonation of certain complexes can give aldehydes. Nickel chloride also acts as catalyst for Friedel-Crafts-type reactions. 

Treatment of acyl halides (3) with Sml2 provides 1,2-diketones (4) via the coupling of acyl radicals, which are sp2 carbon-centered radicals (eq. 2.2). Generally, aromatic acid halides are more reactive than aliphatic acid halides. 

Benzyl ketones. Ni(0) is a useful catalyst for coupling of benzyl halides with acyl halides to form benzyl ketones, AK-HjCOR, in 40-85% yield.-... 

The mechanism of palladium-catalyzed coupling of organic halides with tetrasubstituted organotins has been widely studied by Stille and a general understanding of the mechanism is critical to further developments in this area. The use of other organometallics in palladium-catalyzed acylation will follow this discussion, as well as further examples where this method has been used. 

Acylstannanes will couple with acyl halides to give mixtures of mono- and diketones, but decarbonylation can be prevented by an atmosphere of CO, when the diketone is the predominant product.48... 

The present methods for the preparation of N acyl a arylenamides include (i) reductive acylation of ketoximes with iron metal [2] or phosphines [3] in the presence of acyl chlorides or acyl anhydrides (Method A) (ii) metal catalyzed coupling of vinyl halides [4], triflates [5], or tosylates [6] with amides (Method B) (iii) reaction of imine intermediates derived from nitriles with acyl chlorides or anhydrides (Method C) [7] and(iv) Pd catalyzed coupling ofaryl tosylates with N acyl vinylamines (MethodD) [8]. 

Similar methodology is used for the coupling of alkenyl halides and triflates with 1) alkenyl-, aryl-, or alkynylstannanes, 2) alkenylzinc species, or 3) arylboron species. This methodology is applied in the synthesis of cephalosporin derivatives (eq 7), and can be used for the introduction of acyl and vinylogous acyl equivalents (eq 8). 

The coupling of diazonium halides with suitable halogenated activated methylene groups is an excellent method of synthesis of a variety of acyl and aroyl hydrazidoyl halides. This method has been used by Favrel and by Dieckmann and Platz to synthesize the acetyl derivative (IV). 

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