Rhodium acetate allylic oxidation

Another route to the diol monomer is provided by hydroformylation of allyl alcohol or allyl acetate. Allyl acetate can be produced easily by the palladium-catalyzed oxidation of propylene in the presence of acetic acid in a process similar to commercial vinyl acetate production. Both cobalt-and rhodium-catalyzed hydroformylations have received much attention in recent patent literature (83-86). Hydroformylation with cobalt carbonyl at 140°C and 180-200 atm H2/CO (83) gave a mixture of three aldehydes in 85-99% total yield. 

Allylic oxidation.2 t-Butyl hydroperoxide (0.5 equiv.) in acetic acid in the presence of catalytic amounts of this Rh30 complex (1) oxidizes cycloalkenes to a,/ -enones and the corresponding allylic acetates in the ratio of 6-7 1. Other rhodium complexes are less effective. Allylic alcohols (but not the acetates) are oxidized by this reaction to a,/ -enones. 

A combination of rtiodium(III) chloride with silver acetate, and treatment of rhodium(II) acetate in acetic acid solution with ozone, are two methods for generation of the (is-oxotrimetal-acetato complex of rhodium [Rhs0(0Ac)6 2O)3]0Ac. This RhsO complex was found to effect catalytic allylic oxidation of alkenes efficiently to give the corresponding a -unsaturated carbonyl compounds in the presence of a reoxidant such as r-butyl hydroperoxide, although in disappointing yield (equation 44). 

Vinylogs of benzylic alcohols, e.g. cinnamyl alcohol, undergo easy saturation of the double bond by catalytic hydrogenation over platinum, rhodium-platinum and palladium oxides [39] or by reduction with lithium aluminum hydride [609]. In the presence of acids, catalytic hydrogenolysis of the allylic hydroxyl takes place, especially over platinum oxide in acetic acid and hydrochloric acid [39]. 

The isomerization of allyl ethers to 1-propenyl ethers, which is usually performed with potassium tert-butoxide in dimethyl sulfoxide, can also be carried out under milder conditions using tris(triphen-ylphosphine)rhodium chloride,208 and by an ene reaction with diethyl azodicarboxylate,209,210 which affords a vinyl ether adduct. Removal of an O-allyl group may be achieved by oxidation with selenium dioxide in acetic acid,211 and by treatment with N-bromosuccinimide, followed by an aqueous base.201,212... 

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