Aldehydes chlorotris rhodium

Aldehydes, both aliphatic and aromatic, can be decarbonylated by heating with chlorotris(triphenylphosphine)rhodium or other catalysts such as palladium. The compound RhCl(Ph3P)3 is often called Wilkinson s catalyst.In an older reaction, aliphatic (but not aromatic) aldehydes are decarbonylated by heating with di-tert-peroxide or other peroxides, usually in a solution containing a hydrogen donor, such as a thiol. The reaction has also been initiated with light, and thermally (without an initiator) by heating at 500°C. 

Cyclopentanones Aluminum chloride. Chlorotris(triphenylphosphine)rhodium. Dichloroketane. N, N-Diethylaminopro-pyne. 1-Hydroxycyclopropanecarbox-aldehyde. Rhodium(II) carboxylates. 

Catalytic hydroacylation. Aldimines of 3-methyl-2-aminopyridine and aromatic aldehydes react with chlorotris(triphenylphosphine)rhodium(I) (1) in THF at 55 to afford products of imine C—H insertion (3). Aminals of 2-aminopyridine and aldehydes with a-hydrogens (4) similarly react with 1 to give 5 presumably, the aminals are in equilibrium with the corresponding imines under these conditions. These complexes undergo hydroacylation reactions with ethylene as illustrated for 2. The overall reaction can be performed with catalytic quantities of 1, as indicated for the reaction of 4. 

Palladium chloride and metallic palladium are useful for carbonylating olefinic and acetylenic compounds. Further, palladium is active for decarbonylation of aldehydes and acyl halides. Homogeneous decarbonylation of aldehydes and acyl halides and carbonylation of alkyl halides were carried out smoothly using rhodium complexes. An acyl-rhodium complex, thought to be an intermediate in decarbonylation, was isolated by the oxidative addition of acyl halide to chlorotris(triphenylphosphine)rhodium. The mechanisms of these carbonylation and decarbonylation reactions are discussed. 

Kampmeier, J. A., Harris, S. H., Mergelsberg, I. Intramolecular trapping of alkyl- and aryirhodium hydride intermediates in the decarbonylation of aldehydes by chlorotris(triphenylphosphine)rhodium. J. Org. Chem. 1984,49, 621-625. 

Chlorotris(triphenyIphosphine)rhodium, [(C Hs)3P]3RhCI. Mol. wt. 913.09 This organometallic complex is obtained as purple-red crystals by interaction of ethanolic solutions of RhCla-SHsO and a sixfold molar excess of triphenyl-phosphine. It catalyzes exceedingly rapid hydrogenation of double and triple bonds. Aliphatic aldehydes are decarbonylated to the corresponding paraffins according to the equation ... 

A number of metal complexes catalyze the hydrosilylation of various carbonyl compounds by triethylsilane. Stereoselectivity is observed in the hydrosilylation of ketones as in the reactions of 4-t-butylcyclohexanone and triethylsilane catalyzed by ruthenium, chromium, and rhodium metal complexes (eq 4). Triethylsilane and Chlorotris(triphenylphosphine)rho-dium(I) catalyst effect the regioselective 1,4-hydrosilylation of Q ,/3-unsaturated ketones and aldehydes. Reduction of mesityl oxide in this manner results in a 95% yield of product that consists of 1,4- and 1,2-hydrosilylation isomers in a 99 1 ratio (eq 5). This is an exact complement to the use of phenylsilane, where the ratio of respective isomers is reversed to 1 99. ... 

The best studied decarbonylation reagent is chlorotris(triphenylphos-phine)rhodium(I), RhCl(PPh3)3, which decarbonylates aldehydes and acyl and aroyl halides under mild conditions (i.e., thermally in solution at temperatures below 100°C). The reactions are stoichiometric and are summarized by Equations... 

Substituted v-butyrolactones can be prepared by reaction of aldehydes or ketones with tbe dianion (28), and direct condensation of symmetrical ketones with diethyl 2-oxomalonate provides a useful synthetic route to the butenolides (29). A number of initiators have been used previously to promote the free-radical addition of ketones to alkenes now transition-metal oxides have been shown to be effective. Pent-4-enal is cyclized to cyclopentanone by chlorotris(triphenylphos-phine)rhodium(i) through a non-radical pathway. ... 

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