Carbonylation of allylic compounds

Ruthenium-catalyzed carbonylations of allylic compounds [62] were described in Chapter 11. Here, ruthenium-catalyzed carbonylative cyclization of allylic carbonates with alkenes, not alkynes, which offers a new route to cyclopentenones is revealed [63]. Treatment of allyl methyl carbonate with 2-norbornene in the presence of 2.5 mol% [RuCl2(CO)3]2 and 10 mol% Et3N in THE at 120°C for 5 h under 3 atm of carbon monoxide gave the corresponding cyclopentenone, exo-4-methyltri-cyclo[5.2.1.0 ]dec-4-en-3-one, in 80% yield with high stereoselectivity exo 100%) (Eq. 5.37). 

The carbonylation of allylic compounds by transition metal complexes is a versatile method for synthesizing unsaturated carboxylic acid derivatives (Eq. 11.22) [64]. Usually, palladium complexes are used for the carbonylation of allylic compounds [65], whereas ruthenium complexes show characteristic catalytic activity in allylic carbonylation reactions. Cinnamyl methyl carbonate reacts with CO in the presence of a Ru3(CO)i2/l,10-phenanthroline catalyst in dimethylformamide (DMF) to give methyl 4-phenyl-3-butenoate in excellent yield (Eq. 11.23) [66]. The regioselectivity is the same as in the palladium complex-catalyzed reaction. However, when ( )-2-butenyl methyl carbonate is used as a substrate, methyl ( )-2-methyl-2-butenoate is the major product, with the more sterically hindered carbon atom of the allylic group being carbo-nylated (Eq. 11.24). This regioselectivity is characteristic of the ruthenium catalyst [66]. 

The transition metal-catalyzed carbonylation of allylic compounds has been developed as a simple extension of carbonylations of benzylic derivatives. In this respect nickel cyanide has been used as a catalyst precursor for carbonylation of allyl... 

Unsaturated esters are prepared by the carbonylation of allylic compounds under various conditions depending on the leaving groups. Carbonylation of allylic chlorides proceeds under two-phase (liquid-solid) and mild conditions (room temperature, 1 atm of CO in the presence of K2CO3 in EtOH) using ligandless Pd catalyst. Ethyl 4-phenyl-3-butenoate was obtained from cinnamyl chloride in 94% yield [143]. Allylic carbonates are reactive and their carbonylation proceeds under mild neutral conditions [144]. 

Carbonylation of allylic compounds in alcoholic solvent gives p,y-unsaturated esters, however, these substrates are far less reactive to palladium-catalyzed carbonylation than aryl or alkenyl halides." In general, a large positive pressure of carbon monoxide is necessary to drive these reactions forward. 

Coupling of allylic compounds. Bauld found that allyl and cinnamyl acetates react with nickel carbonyl to give biallyl and bicinnamyl in moderate yields. 

In the past decade much effort in organoindium chemistry has been devoted to study of carbonyl allylation and aUylindation of carbon-carbon multiple bonds with allylic indium reagents. Apart from the conventional transmetalation of allyl-lifhium or aUyl Grignard reagents with indium(III) halides, a method widely used for preparation of allyhndium(III) compounds is the oxidative addition of metallic indium or indium(I) iodide to aUyhc substrates [3, 6]. Transmetalation of allylstan-nane with indium(III) chloride also gives allylindium(III) [7]. Allylindium(I) was recently prepared by transmetalation of allylmercury with metallic indium in water this compound is regarded as an intermediate in the allylation of carbonyl compounds in aqueous media [8]. A new method of preparation of allylic in-dium(III) reagents - reductive transmetalation of a 7r-allylpalladium(ll) complex with indium(I) salts has been reported this enables the use of a wide variety of allylic compounds and solvents [9]. 

Coupling of allylic compounds [1, 722-723, before references] revision and extension. Bauld s observation of the coupling of allylic acetates by Ni(CO)4 cited in ref. 12 was preceded by the discovery of Webb and Borcherdt14 (du Pont) in 1951 that nickel carbonyl in methanol effects coupling of allylic chlorides in excellent yield, for example ... 

COUPLING OF ALLYLIC COMPOUNDS Dimethylcopperlithium. Iron. Nickel carbonyl. Trimethylironlithium. GRIGNARD REAGENTS Thallium(I)-bromide. 

Carbonylation. Homologation of allylic compounds, stitching of an alkene with an... 

Less reactive allylic alcohols are carbonylated under harsh conditions. However, carbonylation of allylic alcohols proceeds smoothly in the presence of phenol as a nucleophile. Phenyl 4-phenyl-3-butenoate (374) was obtained in 80 % yield from cinnamyl alcohol under 5 atm of CO at 100 °C. The carbonylation may proceed by the formation of allyl phenyl ether, which is a reactive compound [145]. Allyl alcohol was carbonylated under high pressure of CO2 (50 atm) and CO (50 atm) in dioxane to provide 2-butenoic acid as the main product and 3-butenoic acid as the minor product at 110°C. Presumably monoallyl carbonate 375 is generated from... 

In the presence of main group organometallic compounds, ketones are obtained. Carbonylation of allylic ester 382 with alkylzinc reagent afforded the ketone 383 in high yield [149]. Carbonylation of allyl chloride 384 in the presence of tin hydride afforded the -unsaturated aldehyde 385 via hydrogenolysis of acylpalladium intermediate [150]. 

Other organic processes facilitated by metal carbonyl clusters include a palladium carbonyl catalysed Diels-Alder reaction the selective reduction of aromatic nitro compounds using rhodium and ruthenium phosphine-carbonyls aza- and oxa-carbonylations of allyl phosphates by rhodium carbonyls Michael reactions of alkoxy-alkenones using iron... 

Palladium-catalyzed carbonylation of allylic and propargylic compounds offers a potential tool of one-carbon homologation. Particularly, pd-catalyzed carbonylation of propargylic compounds further provides synthetically valuable transformations because of the high reactivity of the intermediary allenyl esters. 

J. Tsuji and J. Kiji, in Transition Metals for Organic Synthesis, Vol. 1, M. Beller and C. Bolm, Eds., Wiley-VCH, Weinheim, 1998, 68-78. Palladium-Catalyzed Carbonylation of Allylic and Propargylic Compounds. 

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