1- Decene dihydroxylation

Fig. 11 Partitioning scheme for IMOMM calculations of the dihydroxylation of a styrene and b 1-decene by 0s04-(DHQD)2PYDZ. Alkenes highlighted in black...

We have recently broadened those investigations to study the origin of the enantioselectivity in the dihydroxylation of terminal aliphatic n-alkenes. The dihydroxylation of the series from propene to 1-decene was studied by means of the IMOMM method [97]. Experimental studies on propene, 1-butene, 1-pentene, 1-hexene and 1-decene showed that the reaction was enantioselec-tive in all cases, leading to the R product. Moreover, the results show a dependence of the enantioselectivity on the chain length it sharply increases from propene to 1-pentene, and after that the enantioselectivity remains practically constant for 1-hexene and 1-decene. The explanation for this dependence of the enantioselectivity with the chain length remained elusive. On the other hand, the -stacking interactions that were found to be critical for styrene cannot be responsible for the observed enantioselectivity for these terminal aliphatic n-alkenes because they do not have aromatic rings. 

Fig. 8. Eyring plot of the asymmetric dihydroxylation of 1-decene using different ligands...

The study was broadened by the same authors to the investigation of the origin of the enantioselectivity in the dihydroxylation of terminal aliphatic n-alkenes. The dihydroxylation of the series from propene to 1-decene was studied by means of the IMOMM method [71]. Experimental studies on propene,... 

For example, in the presence of ligand 34 and iV-ethylpyrrolidone at conversions of 80 to 90%, the enantioselectivity with respect to /ran -stilbene was found to be 80% to tran -methylstyrene, 85% to trans-5-decene, 42% and to styrene, 60%. In using monomethyl ether modified with phthalazine 35 as a ligand and potassium ferrocyanide as an oxidant, the enantioselectivity with respect to the same substrates reached almost 100% [71]. A similar result was also obtained in ethyl trans -cinnamate dihydroxylation [72]. 

In order to improve the enantioselectivity in the AD of aliphatic alkenes, the two dihydroquinidine-derived polymers 275 and 276 were prepared by radical copolymerization of the corresponding monomers with hydroxyethyl methacrylate and ethylene glycol dimethacrylate as crosslinking agent (Scheme 112) [172], These two polymers 275 and 276 exhibited enhanced enantioselectivities (88 and 86% vs 75% with polymer 274) for the dihydroxylation of two aliphatic alkenes, 1-decene and 5-decene compared to those observed... 

Despite the slow hydrolysis of the sterically hindered Os(VI) glycolate, trans-5-decene reacted smoothly to give the corresponding diol. This result is especially impressive since addition of stoichiometric amounts of hydrolysis aids is usually necessary in the dihydroxylation of most internal alkenes in the presence of other oxidants. 

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