76671-56-2Relevant articles and documents
Planar chiral [2.2]paracyclophane-based bisoxazoline ligands: Design, synthesis, and use in cu-catalyzed inter- and intramolecular asymmetric O-H insertion reactions
Kitagaki, Shinji,Murata, Shunsuke,Asaoka, Kisaki,Sugisaka, Kenta,Mukai, Chisato,Takenaga, Naoko,Yoshida, Keisuke
, p. 1006 - 1014 (2018/10/08)
Centrally chiral bisoxazolines connected directly to a planar chiral [2.2]paracyclophane backbone were synthesized and evaluated as asymmetric ligands in Cu-catalyzed intermolecular ethanolic O-H insertion reactions of α-diazo esters. The reactivities and enantioselectivities of Cu complexes of the synthesized bisoxazoline ligands were lower than those of ligands without central chirality. However, planar chiral [2.2] paracyclophane-based bisoxazoline ligands with an inserted benzene spacer that had a sterically demanding isopropyl substituent showed good enantioselectivities in inter- and intramolecular aromatic O-H insertion reactions, without the aid of central chirality.
Asymmetric O–H insertion reaction of carbenoids catalyzed by chiral bicyclo bisoxazoline copper(I) and (II) complexes
Le Maux, Paul,Carrié, Daniel,Jéhan, Philippe,Simonneaux, Gérard
, p. 4671 - 4675 (2016/07/18)
Chiral copper(I) and (II)-bicyclobisoxazoline complexes were found to catalyze the insertion of α-diazocarbonyl compounds into O–H bonds of alcohols. The insertion reactions of various α-diazopropionates proceeded with moderate yields (40–90%) and high enantioselectivities (up to 92% and 94% with copper(I) and copper(II)-catalysts, respectively). A predominant effect on the enantiocontrol of the reaction was observed when copper(I) and (II)-catalysts were associated with NaBARF and molecular sieves (4??).
Advances and mechanistic insight on the catalytic Mitsunobu reaction using recyclable azo reagents
Hirose, Daisuke,Gazvoda, Martin,Ko?mrlj, Janez,Taniguchi, Tsuyoshi
, p. 5148 - 5159 (2016/07/29)
Ethyl 2-arylhydrazinecarboxylates can work as organocatalysts for Mitsunobu reactions because they provide ethyl 2-arylazocarboxylates through aerobic oxidation with a catalytic amount of iron phthalocyanine. First, ethyl 2-(3,4-dichlorophenyl)hydrazinecarboxylate has been identified as a potent catalyst, and the reactivity of the catalytic Mitsunobu reaction was improved through strict optimization of the reaction conditions. Investigation of the catalytic properties of ethyl 2-arylhydrazinecarboxylates and the corresponding azo forms led us to the discovery of a new catalyst, ethyl 2-(4-cyanophenyl)hydrazinecarboxylates, which expanded the scope of substrates. The mechanistic study of the Mitsunobu reaction with these new reagents strongly suggested the formation of betaine intermediates as in typical Mitsunobu reactions. The use of atmospheric oxygen as a sacrificial oxidative agent along with the iron catalyst is convenient and safe from the viewpoint of green chemistry. In addition, thermal analysis of the developed Mitsunobu reagents supports sufficient thermal stability compared with typical azo reagents such as diethyl azodicarboxylate (DEAD). The catalytic system realizes a substantial improvement of the Mitsunobu reaction and will be applicable to practical synthesis.
