Carbonylative Stille coupling

Chiral oxazolines Stille carbonylative coupling,4 Pd-catalyzed carbonylative coupling of Inflates of ketones and phenols with chiral amino alcohols provides )3-hydroxy amides, which cyclize to chiral oxazolines when treated with thionyl chloride. 

When the above reaction is performed under an atmosphere of carbon monoxide, CO insertion occurs with the concomitant formation of two sigma carbon carbon bonds to give a ketone as product. This reaction is referred to as the Stille carbonylative coupling reaction (see equation 2 below). 

Scheme 31. Catalytic cycle for the Stille reaction carbonylative coupling.

Palladium(0)-catalyzed coupling reactions - i. e. the Heck and Sonogashira reactions, the carbonylative coupling reactions, the Suzuki and Stille cross-coupling reactions, and allylic substitutions (Fig. 11.1) - have enabled the formation of many kinds of carbon-carbon attachments that were previously very difficult to make. These reactions are usually robust and occur in the presence of a wide variety of functional groups. The reactions are, furthermore, autocatalytic (i.e. the substrate regenerates the required oxidation state of the palladium) and a vast number of different ligands can be used to fine-tune the reactivity and selectivity of the reactions. 

Scheme 6 Carbonylative Stille cross-coupling of vinyl halides, triflates, and sulfonyl chlorides.

Vaska s complex ([IrCl(CO)(PPh3)2]) also catalyzed the carbonylative coupling of diynes, which provided bicyclic cyclopentadienones (Scheme 11.23) [35]. Due to the instability of the products, the substrates are limited to symmetrical diynes with aromatic groups on their termini nonetheless, this reaction still serves as the catalytic and practical procedure for the synthesis of cyclopentadienones, which are anti-aromatic with a 47t system and serve as active synthetic intermediates. 

Another approach developed by the Vogel group relies on a carbonylative Stille cross-coupling between stannylated glucal derivative 410 and enol triflate 412 derived from isolevoglucosenone [152] (O Scheme 80). 

When the Stille reaction is carried out under a CO atmosphere, the carbonylative coupling proceeds in a manner similar to that described for the Suzuki reaction namely, carbonyl insertion into the Pd-C bond of the oxidative addition complex. Transmetalation, followed by ds-trans-isomerization and reductive elimination, generates the ketone product. " ... 

A concise synthesis of photoactivatable 4-benzoyl-L-phenylalanines and related peptides was described by G. Ortar et al. using a carbonylative Stille cross-coupling as the key step. Surprisingly, when the coupling was attempted with tyrosine triflate derivatives, it proved to be unsuccessful. However, 4-iodo-phenylalanine derivatives reacted smoothly under standard conditions to give the corresponding 4-benzoyl derivatives. 

Pd-catalyzed Stille carbonylative cross-coupling Pd-catalyzed coupling of organostannanes and alkenyl-or aryl halides and CO to form ketones. 436... 

Gyorkos, A. C., Stille, J. K., Hegedus, L. S. The total synthesis of ( )-epi-jatrophone and ( )-jatrophone using palladium-catalyzed carbonylative coupling of vinyl triflates with vinyl stannanes as the macrocycle-forming step. J. Am. Chem. Soc. 1990,112, 8465-8472. 

Ketones can be obtained by coupling of acid chlorides with organostannanes or by carbonylative couplings. The first reaction is one of the older and more general Stille coupling reactionsi i 122 and continues to be used under essentially the original conditions.1 3... 

This alternative to the Friedel-Crafts reaction, extensively developed by Stille and coworkers, is particularly important, since the reaction conditions are essentially neutral, and so provides a method for acylation of compounds containing an acid-sensitive functionality which would preclude the use of the Friedel-Crafts reaction. Reaction temperatures are often below 100 C, and high (1000-fold) turnovers of the catalyst have been achieved. Solvents employed include chloroform, toluene, and, on occasions, HMPA. Some reactions have been carried out under an atmosphere of carbon monoxide to prevent excessive decarbonylation of the acyl palladium intermediate. Indeed, carbonylative coupling of alkenylstannanes with allyl halides in the presence of carbon monoxide ca. 3 atm or greater 1 atm =101 kPa) offers an alternative to the Friedel-Crafts acylation, ketones being formed by the reaction of the stannane with the acyl species formed by carbon monoxide insertion into the allyl palladium intermediate. ... 

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