Double carbonylation reactions

Alkenyl bromides or iodides having phenyl substituent(s) on the vinyl group can be doubly carbonylated to the corresponding a-ketoamides 13 [29]. This latter derivative is formed as a consequence of the reductive elimination of the palladium complex 12 

Ammonia Equivalent for the Palladium-Catalyzed Preparation oT N-Unsubstituted a,P-Unsaturated Amides 

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Pd-catalyzed double carbonylation reactions are rare due to the inefficiency of formation of bis-carbonylation products. Addition of bulky tricyclohexylphosphine to the normal carbonylation system greatly facilitated the formation of the double carbonylation product. Subjecting 4-iodopyridine 199 to such conditions afforded primarily 4-pyridylglyoxylic acid derivative 200, which was not easily attainable via classical synthetic methods [159]. The monoamide 201 was isolated as a minor by-product. 

Similarly, cyclizative tandem double-carbonylation reactions of 4-pentenyl iodide under irradiation conditions, is boosted by the addition of a catalytic amount of palladium complexes [72]. When performed in the presence of diethylamine, the carbonylation provided a triply carbonylated a,<5-diketo amide as the major product along with the doubly carbonylated y-keto amide (Scheme 6.48). Experimental evidence supports the interplay of two reactive species, radicals and organopalladium... 

In the case ofo-methylbenzyl bromide (22), a substantial amount (34%) of an alkylated phenylpyruvic acid derivative (24) was formed along with the anticipated phenylacetic acid (23) (34). This novel double carbonylation reaction (to give 27) was later observed to a variable, but minor, ex-... 

Depending on the catalyst system and the reaction conditions, especially at elevated CO pressure it is possible to obtain selectively double carbonylation reactions to 1-keto carboxylic derivatives [25]. Recent mechanistic investigations have shown that double CO insertion into the palladium-carbon bond does not occur directly instead, the terminal step of double carbonylation is generally a coupling reaction between metal-bonded acyl, alkoxycarbonyl or amidocarbonyl groups and CO. 

Nickel cyanide catalyzes the PTC carbonylation of vinyl halides to a,y9-unsat-urated acids [141]. A similar reaction involving 2-bromo-l-phenyl-l,3-butadiene gives the a-ketolactone (60%) and dienoic acid (15 %) (the former results from the double carbonylation reaction (eq. (11)) [142]), possibly proceeding via a nickel metallacycle [143]. 

The cobalt and PTC carbonylation of dienes and trienes give acylated products [147]. Cyclohexa-1,3-diene is transformed to 1-acetylcyclohexa-1,3-diene and a mixture of isomeric diacylated cyclohexadienes. 1-Vinylcyclohexene and other substituted dienes are acylated at the dienic moiety to give the tranj -isomers of the corresponding dienones [153]. Carbonylation of a-vinylcinnamic acid in the presence of nickel cyanide gives a-ketolactone, resulting from a decarboxylation-double carbonylation reaction [154]. 

Another example was reported by Ryu and coworkers, who examined the use of tributylgermyl hydride for cyclizative double carbonylation reactions (Scheme 6)... 

Recently developed palladium-catalysed double carbonylation reactions provide a convenient method for introducing two reactive carbonyl groups into organic substrates. This reactivity has been exploited in syntheses of isatin and quinoline derivatives (Scheme 56).79... 

Oxamides, dialkyl oxalate esters, and oxamic add esters can be prepared by Pd-catalyzed double carbonylation of secondary amines and alcohols via incorporation of two molecules of carbon monoxide into amines and/or alcohols. Pd-catalyzed double carbonylation reactions of amines in the absence or presence of alcohol were reported earlier to give ox-amides and oxamic acid ester.t i t Selective formation of oxamides has been achieved by double carbonylation of secondary amines in the presence of iodide ion and dioxygen catalyzed by Pd(OAc>2 (Eq. 

H. DOUBLE CARBONYLATION REACTIONS PROMOTED BY OTHER TRANSITION METAL COMPLEXES... 

As we mentioned in Sect. A, the first catalytic double carbonylation reaction was found to take place by using cobalt carbonyl complex as catalyst. In fact, there are a few other transition metals that can promote the double carbonylation process in addition to palladium complexes. The following is a brief description of the double carbonylation process promoted by transition metals other than palladium. 

H.i. Double Carbonylation Reactions Catalyzed by Cobalt Complexes... 

The mechanism of the Co-catalyzed double carbonylation reaction of benzylic compounds has been proposed as shown in Scheme 12 to involve the formation of enolic intermediate, which undergoes the subsequent insertion of carbon monoxide followed by nucleophilic The proposed mechanism can circumvent the difficulty in-... 

A short review of the double carbonylation reaction used to form a-ketoamides and -esters at Pd centres has appeared. 55 insertion of alkenes into the Pd-C bond of [Pd(COMe)(NCMe)dppe]+ readily forms the metallacycles [P[Pg.261]

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