Hydroformylation-acetalization intermolecular

If platinum catalysts are used no additives are required, probably because of the Lewis acidity ofplatimun [74]. 

Catalytic systems such as [Rh(n-S(CH)2NMe2)(cod)]/PPh3, which are anchored to a sulphonic exchange resin by protonation of the amino group, converts 115 into 116 under hydroformylation conditions and witii methanol as the solvent [76]. In a similar reaction the catalytic system [Rh(p-SCH2NH3)(C00H]2 (OTf)2, in the presence of ethyl orthoformate, converts terpenes into acetals [77]. 

Unexpectedly, the 3,4,6-tri-O-benzyl-D-glucal gave only the methyl a-glycoside 121 under the hydroformylation-acetalization conditions. In fact, there are two electrophilic reagents in competition for the nucleophilic alkene, the rhodium complex and the proton. When the alkene is deactivated (R=Ac) the coordination of rhodium is preferred and the hydroformylation-acetalization takes place. But when it is not deactivated (R=Bn) the acidic proton reacts faster than rhodium and methanol is added. 

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