| Popis: |
In Chapter 1, a general introduction to the reaction of rhodium-catalyzed hydroformylation of olefins is presented with its broad utility in organic synthesis, reaction mechanism, and a brief review of the current advances in ligand development. In Chapter 2, new tetraphosphoramidite ligands have been designed and synthesized. These ligands have been applied in the rhodium-catalyzed regioselective hydroformylation of various functionalized allyl, vinyl, and styrene derivatives. Remarkable high linear selectivity was obtained. The rhodium/tetraphosphoramidite catalyst system is highly effective to produce linear aldehydes from functionalized allyl derivatives with substituents containing heteroatoms such as O, N, Si and halogens either directly adjacent to or at distance to the allyl group. For vinyl derivatives, the ligand is highly linear selective for acrylic derivatives, styrene, vinyl pyridines and vinyl phthalimide. The catalyst system makes it possible to prepare Cn (n ≥ 3) functionalized terminal aldehydes from readily available vinyl and allyl derivatives by hydroformylation with high linear selectivity and efficiency. The electronic effects on catalyst activity and regioselectivity by both ligands and styrene derivatives have been studied with Hammett plots. For the substituent changes in ligands, with the increase of Hammett constant σp, the linear selectivity increases but the catalyst activity decreases. For the substituent changes in styrenes, with the increase of σp, the linear selectivity decreases but the catalyst activity increases. In Chapter 3, new class of tetraphosphine ligands has been developed and applied in the rhodium-catalyzed regioselective hydroformylation of terminal and internal olefins. The steric and electronic effects of substituents on tetraphosphine have also been studied. The high linear selectivity (above 97% for 1-octene and 1-hexene) at high temperature (140 oC) showing by those tetraphosphine ligands is remarkable considering the commonly observed low linear selectivity under similar reaction conditions when bisphosphine analogues were used. The rhodium/tetraphosphine catalyst system is also highly effective for the isomerization and hydroformylation of 2-alkenes to form linear aldehydes. Greater than 95% linear selectivity and up to 94% yield of the total aldehydes were obtained for 2-pentene, 2-hexene and 2-octene. |
