Substrate-Induced Diastereoselectivity in Rhodium-Catalyzed Hydroformylation

The object of this Ph.D. thesis is an investigation on the substrate-controlled diastereoselectivity in rhodium-catalyzed hydroformylation of open-chain chiral substrates. Some cases of 1,3- and 1,2-asymmetric induction are reported starting from chiral vinyl- and allyl- alkenes and carrying out the hydroformylation reaction with an unmodified rhodium catalyst. Vinyl olefins containing an alkoxy group showed an exceptional 1,3-asymmetric induction (97/3) when a phenyl ring is linked to the stereogenic center. C-allylglycosides showed different levels of diastereoselectivity depending on the structure of the sugar-ring and the highest level of 1,3-asymmetric induction has been obtained in the case of the ƒÑ-C-allyl-glucoside, which gave 70% d.e. A different level of 1,2-asymmetric induction was observed in both chiral allylpyrroles and allylbenzenes as the steric hindrance of the alkyl chain was varied, providing diastereomeric excesses also up to 70%. Two different pyrrolylalkenes with an acetyl group linked to the ƒÒ-position of the pyrrole ring were also examined and an 8-hydroxy-5,6,7,8-tetrahydroindolizine was obtained via a complete 1,3-asymmetric induction in a domino process under oxo conditions. Theoretical investigations have also been employed in an effort to cast light on the reaction mechanism.