Polymer-supported chiral Lewis acids as asymmetric catalysts for diels-alder reactions of methacrolein with cyclopentadiene

Chiral 1,3,2-oxazaborolidines in asymmetric synthesis: recent advances

“…The catalysis of the Diels ± Alder reaction by 1,3,2-oxazaborolidines covalently bound to a polymeric matrix is also possible. 231,232…”

“…158 Several approaches to the synthesis of immobilised oxazaborolidines are known. First, the reaction of chloromethylated crosslinked polystyrene with amino alcohols containing phenol-type linkers (particularly, with tyrosine derivatives 156,231,236,237 ) yields the immobilised amino alcohol 183, its reaction with BH 3 . THF affords the immobilised oxazaborolidine 184.…”

“…Homogeneous dendrimeric catalysts seem promising, since their application gives higher values of ee than the heterogeneous polymeric systems. 254 The use of immobilised catalysts of the type 187 in enantioselective Diels ± Alder reactions, 231,232 aldol condensation 242 and for addition of diethylzinc to aldehydes has been described. 247 VI.…”

Polymer-supported synthesis

“…The lactonisation was achieved by treatment of the polymer-bound substrate with 12 and was accompanied by liberation from the chiral polymer auxiliary which was freed for recycling. Chiral Lewis acids have also received attention recently and Itsuno et al, who have been very active in the use of chiral polymers, have now reported the first polymer-supported systems [92]. These immobilised species were prepared by reaction of borane with polystyrene resins functionalised with chiral species such as amino alcohols, diols and N-sulphonylamino acids.…”

Asymmetric Diels−Alder Reaction of Methacrolein with Cyclopentadiene Using Polymer-Supported Catalysts: Design of Highly Enantioselective Polymeric Catalysts

“…Although a number of chiral catalysts have been demonstrated for enantioselective Diels−Alder reactions in solution systems, polymer-supported catalysts for the reaction have not been utilized extensively. During our study of polymer-assisted asymmetric synthesis, , we investigated various polymer-supported chiral catalysts for Diels−Alder reactions and found that polymers possessing chiral oxazaborolidinone units showed satisfactory selectivity and reactivity. − In this study, several polymer-supported catalysts of chiral oxazaborolidinone having different cross-linking structures were prepared and used for the Diels−Alder reaction of methacrolein with cyclopentadiene. We found that the cross-linking structure greatly affected the performance of the polymeric catalyst.…”