ChemInform Abstract: Chiral Bis(imidazolidine)pyridine—Cu(OTf)₂: Catalytic Asymmetric Endo‐Selective [3 + 2] Cycloaddition of Imino Esters with Nitroalkenes.

Abstract

A new bis(imidazolidine)pyridine ligand is easily synthesized in a single condensation of 2,6‐pyridyl bisaldehyde and optically active diphenylethylenediamine.

Recent Advances of Catalytic Asymmetric 1,3-Dipolar Cycloadditions

“…154 Arai and co-workers reported highly endoselective [3+2] cycloaddition catalyzed by Cu(OTf) 2 /chiral bis(imidazolidine)pyridine 92 complex (Scheme 104). 155 The imidazolidine moiety of the ligand was important to promote the reaction as the use of Cu(OTf) 2 /pybox gave only a trace amount of the product. It is also noteworthy that trisubstituted nitroalkenes were also applicable in this reaction.…”

Additive Effects on Asymmetric Catalysis

“…In the copper-catalyzed asymmetric endo-selective [3 + 2] cycloaddition of imino esters with nitroalkenes, Arai et al observed that the basic additives played a remarkable role on the reactivity and selectivity (Scheme 202). 439 In the absence of an additive, the reaction afforded the product in rather low yield (18%) and selectivity (endo:exo 83:17 and 51% ee). With the assistance of a base like Cs 2 CO 3 , the yield was greatly increased to 96%, the ratio of endo:exo to 99:1, and ee to 99%.…”

Stereodivergent Catalysis

“…The chiral Cu(OTf) 2 /bis(imidazoline)pyridine 786 complex has been used as catalyst in the unusual endo-selective 1,3-DC of imino esters with β-nitroalkenes providing nitroprolinates endo-778 with high de and ee (Scheme 302). 669 However, the complex formed by imidazoline-aminophenol (IAP) ligand 662 and Ni(OAc) 2 catalyzes the formation of exo'-adducts 787, which possess a 2,5-trans configuration, in good de and excellent ee. 670 These two chiral ligands are derived from (1S,2S)-1,2-diphenylethanediamine as a chiral starting material.…”