Decarbonylative coupling reaction

Decarbonylation of the acylmetal intermediates has been extended to a variety of carbon-carbon forming reactions. For example, Li et al. reported decarbonylative addition reactions of aromatic aldehydes to alkynes (Scheme 7.17) [24] and acrylates [25]. An oxidative decarbonylative coupling reaction of aromatic aldehydes with 2-arylpyridines was promoted by a rhodium catalyst (Scheme 7.18) [26]. Carboxylic acid derivatives were also employed for analogous carbon-carbon bond-forming reactions through decarbonylation [27]. 

Andrus and Liu exploited a Pd(NHC) decarbonylative Heck coupling reaction in the total synthesis of resveratrol [59], The catalyst was formed in situ with Pd(OAc), and IPr HCl. 

The synthetic potential of palladium-mediated cross-coupling reactions (Heck, Suzuki, Stille, Sonogashira, Buchwald-Hartwig) led to the search for a practical synthesis of p-[ F]fluoroiodo- and p-[ F]fluorobromobenzene. p-[ F]Fluoroio-dobenzene (G, X = iodine) can be obtained in poor yield from p F]fluoride and a trimethylammonium precursor (P7). p-p F]Fluorobromobenzene can be prepared in a more reproducible way from 5-bromo-2-nitrobenzaldehyde (radiochemical yields > 70%). The synthesis involves a two-step procedure radiofluorination (F for NO2 substitution), then a catalysed decarbonylation [190,191]. Also very efficient is the one-step reaction of p F]fluoride with a suitable diaryliodonium salt (P6) giving >70% radiochemical yield [192-194]. 

Several copper(I)-catalyzed coupling reactions of alkynes or diynes with Co3 clusters proceed with the deposition of insoluble black materials which have v(CO) spectra typical to those of the CCo3(CO)g clusters described above.438 Similar products were obtained when HCsCMgBr was used. Thermal decomposition of 286 at 100 °C gives conducting aggregates, which continue to show v(CO) absorptions and are soluble in non-aqueous solvents.480 The conductivity appears to be associated with partial decarbonylation and formation of granular microcrystalline materials. 

Various Pd-catalyzed carbonylation reactions have often been referred to as carbonyla-tive cross-coupling reactions (Scheme 4). However, these reactions involving the formation of two C—C bonds with incorporation of CO clearly display a pattern of chemical transformation that is different from Scheme 1. So, these reactions are discussed in Parts VI and VIII. On the other hand, Pd-catalyzed acylation with acyl halides and related derivatives are examples of the reaction represented by Scheme 1, where is acyl, and they are therefore discussed in this Part (Sect. III.2.12.1), even if CO may be used to prevent decarbonylation. 

Other reactions such as alkane dehydrogenation [159, 160], decarbonylation reactions [161], cyclization of alkynoic acids [162,163], three-component coupling reactions of boronic acids, allenes and imines [164], fluorenone synthesis by sequential reactions of 2-bromobenzaldehydes with arylboronic acids [165], and hydrosilylation reactions [166, 167] using cyclometalation compounds as their catalysts have also been reported. 

Some methods based on decarbonylation reactions promoted by nickel complexes have also been developed. Thus, coupling reactions proceeding through acylnickel(II) complexes lead to carbonyl compounds resulting from partial decarbonylation of the starting acid chloride (Eq. or related derivatives. On the other hand. 

Aroyl chlorides undergo silylative decarbonylation to give arylsilanes by the reaction of disilanes. Oxidative addition of aroyl chlorides and decarbonylation are followed by transmetallation with disilane to generate (aryl)silylpalladium, and its reductive elimination gives arylsilanes. For example, neat trimellitic anhydride add chloride reacted with dichlorotetramethyldisilane at 145 °C to afford 4-(chlorodimethylsilyl)phthalic anhydride by decarbonylation and reductive elimination. Also, trimellitic anhydride add chloride was converted to biphenyltetracarboxylic anhydride at 165 °C in refluxing mesitylene by reaction of the disilane. Thus, decarbonylation-coupling of aroyl chlorides offers a good synthetic method of biaryls (Scheme 7). ... 

The rhodium(I) catalyst (COl Rhlacac) was found to promote the decarbonylative coupling of aromatic aldehydes with norbomene to generate new C-C bonds with high stereoselectivity (Scheme 22.5) [10]. The reaction took place through an oxidative addition of the aldehyde C-H... 

Stoner, C.E., Jr., and Brill, T.B. (1989) Thermal Decomposition of Energetic Materials 34. Decarbonylation, Decarboxylation and Coupling Reactions of Metal Propiolate Salts, M[02CC=CH] Inorganic Chemistry, in press. 

The reaction of fluorinated vinylstannane 23 with n-BuLi in THF at -78 C for 1 h followed by the addition of carbonyl compounds afforded the corresponding allyl alcohols 26 in good yields (Scheme 5). On the other hand, the Pd(0)-catalyzed cross-coupling reaction of perfluorocyclopentenylstannane 23 with benzyl chloro-formate in THF at reflux for 2 h proceeded smoothly to form the decarbonylated coupling product 27 in high yield. 

The application of a rhodium catalyst to decarbonylative and direct coupling reactions of cyclobutenones with 2-norbornene provides stereoselective access to fused cyclopentenes (Scheme 6.23). Argon atmosphere is crucial for this reaction to give fused cyclopentenes, while in the presence of carbon monoxide the reaction affords cyclohexenones by direct coupling [27]. 

Other sources for cross-coupling reactions are aldehydes and carboxylic acids after decarbonylation and decarboxylation, respectively, which can be reacted with aryl halides to form biaryls. The following Experimental Procedure illustrates the potential of this quite atom-economic reaction. In this case, a copper co-catalyst promotes both the decarboxylation and the cross-coupling. 

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