Aliphatic aldehydes oxidative esterification

The simple cleavage of lactones 1 or 2 with alcohol and acid has not been reported. However, when 1 is treated with benzaldehyde diethyl acetal and hydrochloric acid, ethyl 3,5 4,6-di-0-benzylidene-L-gulonate (47) is formed in >90% yield.77,78 No other isomers were observed, and other acetals of benzaldehyde, as well as aliphatic aldehydes, afford similar products in good yield.77 D Addieco prepared36 similarly protected derivatives of L-gulonic acid by oxidation of l,3 2,4-di-0-ethylidene-D-glucitol (15), followed by esterification of the resulting acid with diazomethane. 

P,S -Unsaturated alcohols undergo an oxidative esterification with aliphatic aldehydes in the presence of an iridium(I) catalyst and potassium carbonate.330 Precoordination of the ene-alkoxide with iridium is proposed, followed by reaction with aldehyde. Although the ester yield is high, a mixture of unsaturated and saturated esters is typically obtained, except for secondary alcohols. 

Pincer-ligated iridium complexes have been used as homogeneous catalysts for the dehydrogenation of aliphatic polyalkenes to give partially unsaturated polymers. The catalyst appears to be selective for dehydrogenation in branches as compared with the backbone of the polymer.56 The mechanism shown in Scheme 1 has been suggested for an [IrCl(cod)]2-catalysed oxidative esterification reaction of aliphatic aldehydes and olefinic alcohols.57... 

The oxidative esterification of aldehydes in the presence of alcohols to produce saturated and unsaturated aliphatic esters has been developed at the Nippon Shokubai laboratories a great result is represented by the new synthesis of methylmethacrylate (MMA) from methacrolein, methanol and molecular oxygen, which allows yields up to 50 mol MMA (kg cat)" h" using supported bimetallic gold catalysts under relatively mild conditions (80 °C and 3 MPa) [7]. 

Selective oxidations of benzylic and aliphatic alcohols to aldehydes and esters, by O2 in the presence of the ligand Q, o -bis(di-f-butyl phosphino)-o-xylene or Bu"P(l-adamantyl)2 and the additive AgPFg in toluene and in the presence of various alcohols, were achieved using Pd(OAc)2 as the catalyst without the need for additional organic hydrogen acceptors. " In a parallel study, the [PdCl2(MeCN)2]-catalysed esterification of benzylic alcohols with methanol and various long-chain aliphatic alcohols in the... 

---