Development and applications of phosphorus ligands in Rhodium-catalyzed hydroformylation and hydrogenation.

摘要

Transition metal-catalyzed homogeneous catalysis is one of the key tools of modern synthetic chemistry. Generally, variation of the steric bulk and electronic properties of the ligands is one of the most efficient methods to improve catalytic performance of an organometallic complex. This dissertation mainly focuses on the design and synthesis of efficient phosphorus ligands and the exploration of their applications in rhodium-catalyzed hydroformylation and asymmetric hydrogenation.;Asymmetric hydroformylation has attracted much attention as an atom economic method to convert olefins into enantiomerically pure aldehydes. Although a number of chiral phosphorus ligands have been developed for this challenging transformation, only a few of them can give practicable enantioselectivities (> 90% ee). We report the synthesis of a new family of hybrid phosphine-phosphoramidite ligands. Their applications in Rh-catalyzed asymmetric hydroformylation afforded up to 99 % ee for styrene derivatives, 98 % ee for vinyl acetate derivatives and 96 % ee allyl cyanide, which represents the best result up to date. The relationship between the substituent and the enantioselectivity of the ligands was investigated by systematic variation on the ligand structure, which was successfully rationalized by Herrmann's theoretical model with CAChe MM2 calculation.;The further application of phosphine-phosphoramidite ligands family in the rhodium-catalyzed asymmetric hydroformylation of a variety of allylic substrates achieved very high enantioselectivities (up to 99 % ee) and reactivities (up to 9700 turnover number) under mild conditions. To the best of our knowledge, this is the first example of applying N-allylamides and N-allylsulfonamides in asymmetric hydroformylation, which provides an alternative catalytic route to beta2-amino aldehydes, acids, and alcohols for pharmaceutical and synthetic chemistry.;To increase the linear-selectivity in hydroformylation of olefins, especially the more accessible internal olefins, a new strategy for ligand design was developed by using tetraphosphorus ligands with multiple chelating modes to enhance chelating ability and regioselectivity. Based on this concept, two types of tetraphosphorus ligands, tetraphosphoramidite ligands and tetraphosphine ligands, were designed and synthesized. With tetraphosphoramidite ligand, the highest regioselectivity ever reported in the hydroformylation of both internal olefins and terminal olefins were achieved. Tetraphosphine ligands exhibited remarkably improved high temperature performance in the hydroformylation of terminal olefins.;Although P-stereogenic ligands have achieved excellent enantioselectivities in asymmetric hydrogenation, their development is still limited due to their synthetical difficulties. A new highly electron-donating, P-stereogenic bisphospholane ligand (named as ZhangPhos) was developed, which can be synthesized practically and highly enantioselectively from a commercially available chiral reagent. ZhangPhos exhibited extremely high enantioselectivities (up to 99 % ee) and reactivities (up to 50 000 TON) for rhodium-catalyzed hydrogenation of a wide range of functionalized olefin derivatives.