Organic halides formylation

Formylation reactions of organic halides, palladium-catalyzed, 26 330, 331 Fouling, 26 378... 

Baillargeon, V. P., Stille, J. K. Palladium-catalyzed formylation of organic halides with carbon monoxide and tin hydride. J. Am. Chem. Soc. 1986, 108,452 61. 

A more versatile palladium-catalyzed formylation of organic halides takes place using tributyltin hydride and carbon monoxide (equation 7). The reaction works for a variety of substrates — aryl, benzyl and vinyl iodides, vinyl triflates and allyl halides. Reaction conditions are mild (1-3 bar CO, 50 °C), and a variety of functional groups can be tolerated. With unsymmetrical allyl halides formylation is regio-selective, taking place at the less-substituted allylic position with retention of geometry at the allylic double bond. 

Hydroxymethylation. Organic halides undergo radical carbonylation and in the presence of NaBHjCN the formyl group is reduced in situ. 

In a useful application, Kahne and Gupta reported the radical hydroxymethyla-tion (formylation and in situ reduction) of organic halides, including sugar derivatives, using a catalytic amount of triphenylgermyl hydride in the presence of so-... 

A variety of carbonyl compounds can be prepared, using tin hydride as a radical mediator. Table 1 illustrates examples of radical formylation of several organic halides. The reaction can be applied to aromatic formylation [18] but not to stable radicals such as allyl, benzyl, alkoxymethyl, a-cyanoalkyl, and a-acylalkyl radicals. 

Alkyl halides do not fonnylate due to the propensity of the palladium species to undergo /3-hydride ehmination. The conversion of organic halides containing a /3-hydride to the methyl ketone was reported using tetramethyltin, but no mention of formylation has followed to the best of our knowledge. " Methyl alcohol was converted to acetaldehyde using a mixed catalyst system of CO and hi an earher report the acylpalladium... 

Formate salts [69] or formic add under conditions converting them electrodiemically into formate [70,71], sUyl, and tin hydrides have been also explored to perform formylations of organic halides/triflates under lower pressure of carbon monoxide. Acetic formic anhydride has been used as a source of carbon monoxide for the conversion of aryl iodides in conjunction with RsSiH [72]. The palladium-catalyzed formylation of a wide variety of vinyl iodides and triflates with tin hydride and carbon... 

Staab introduced azolides as versatile reagents in organic synthesis. The reaction of carbonyldiimid-azolide with carboxylic acids produces imidazolides under mild conditions which can be converted by the action of hydrogen halides to acid halides in high yield (equation 20). The method does not even require the isolation of the imidazolides, but can be carried out as a one-pot synthesis. The possibility of carrying out this reaction at low temperatures allows the preparation of temperature sensitive compounds. Formyl chloride, which decomposes at -40 °C, has been prepared in this way. 

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