New chiral ligands bearing two N-heterocyclic carbene moieties at a dioxolane backbone. Gold, palladium and rhodium complexes as enantioselective catalysts
The first base-free catalyticWittigreaction utilizing readily available Bu3P (5 mol %) as an organocatalyst is reported. The initial Michael addition of the phosphine to a suitable acceptor substituted alkene ultimately results in the formation of an ylide which is subsequently converted with an aldehyde. The presented 1H NMR studies actually reveal evidence for the Michael addition and proposed
报道了利用容易获得的Bu 3 P(5mol%)作为有机催化剂的第一无碱催化Wittig反应。将膦最初加成到合适的受体取代的烯烃上的迈克尔最终加成最终形成叶立德,其随后被醛转化。提出的1 H NMR研究实际上揭示了迈克尔加成反应和拟形成的内鎓盐的证据。在优化的反应条件下,将各种马来酸酯和富马酸酯用芳族,杂芳族和脂族醛进行转化,以评估这种前所未有的反应的范围和局限性。值得注意的是,马来酸盐和富马酸盐以立体会聚的方式反应。以高达95%的分离产率和E获得了相应的产物/ Z选择性高达99:1。
Poly(methylhydrosiloxane) as a reductant in the catalytic base-free Wittig reaction
作者:Jan Tönjes、Lars Longwitz、Thomas Werner
DOI:10.1039/d1gc00953b
日期:——
catalytic, base-free Wittigreaction forming highly functionalized alkenes with PMHS as a terminal reductant and butylacetate as a green solvent. Poly(methylhydrosiloxane) (PMHS) is a non-toxic, enviromentally friendly, inexpensive and easy to handle reductant. However, the inherent low reactivity hampers its applicability in catalytic reactions, such as P(III)/P(V) redox cycling reactions. Most of these
New chiral ligands bearing two N-heterocyclic carbene moieties at a dioxolane backbone. Gold, palladium and rhodium complexes as enantioselective catalysts
Biscarbene ligands with two imidazolin-2-ylidene moieties at a chiral dioxolane backbone were used as ligands for gold, rhodium and palladium complexes. All new complexes showed varying degrees of enantioselectivity toward hydrogenation of prochiral alkenes with ees up to 95%.