Nucleophilic attack rhodium compounds

Secondary amines can be added to certain nonactivated alkenes if palladium(II) complexes are used as catalysts The complexation lowers the electron density of the double bond, facilitating nucleophilic attack. Markovnikov orientation is observed and the addition is anti An intramolecular addition to an alkyne unit in the presence of a palladium compound, generated a tetrahydropyridine, and a related addition to an allene is known.Amines add to allenes in the presence of a catalytic amount of CuBr " or palladium compounds.Molybdenum complexes have also been used in the addition of aniline to alkenes. Reduction of nitro compounds in the presence of rhodium catalysts, in the presence of alkenes, CO and H2, leads to an amine unit adding to the alkene moiety. An intramolecular addition of an amine unit to an alkene to form a pyrrolidine was reported using a lanthanide reagent. 

Reaction 7.34 involves a metal-carbene intermediate, while reaction 7.35 involves nucleophilic attack by the diazo compound to the coordinated alkene. With a rhodium-porphyrin catalyst direct spectroscopic evidence has been obtained for the carbene pathway (see Section 2.5.2). 

Heterofunctionalized derivatives can be prepared following the same methodology. In the case of esters and halides, rhodium(II) acetate dimer must be employed as catalyst instead of copper compounds.After transformation of the acetoxymethyl group of 7 (X = OAc) into an ester functionality, these compounds are valuable precursors of highly functionalized bi-cyclo[1.1.0]butanes since nucleophilic attack on the keto group takes place under very mild conditions. Thus, the t> /o-bicyclo[1.1.0]butane-l,2,3-tricarboxylic ester is obtained from 3-oxo-tricyclo[2.1.0.0 - ]pentane-l, 5-dicarboxylic esters upon treatment with methanol at 20 °C for three hours. 

The cobalt carbonyls are prepared by the disproportionation reaction of [Co2(CO)g] in the presence of Lewis bases or by the reduction of cluster cobalt carbonyls with the alkali metals. The iridium compounds are obtained during reduction of [Ir4(CO)i2] with sodium in ether solution. The rhodium carbonyls are usually synthesized by reduction of [Rh2Cl2(CO)4] or [RhClg] " with carbon monoxide in basic medium or by nucleophilic attack of bases on the carbonyl group of carbonyl clusters (see preparation of [M4(CO)i2] and [M6(CO)i6]). 

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