A Supramolecular Chiral Auxiliary Approach: "Remote Control" of Stereochemistry at a Hierarchically Assembled Dimeric Helicate. Issue 10 (2nd February 2016)

• Record Type: Journal Article
• Authors: Van Craen, David; Albrecht, Markus; Raabe, Gerhard; Pan, Fangfang; Rissanen, Kari
• Is Part Of: Chemistry. Volume 22:Issue 10(2016)
• Page Start: 3255
• Page End: 3258
• Publication Date: 2016-02-02
• Subjects: Diels–Alder reaction -- helicates -- lithium -- self-assembly -- titanium; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201600158
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: Dimeric hierarchically‐assembled titanium(IV) helicates are in solvent‐dependent equilibrium with the corresponding monomers. Statistically formed mixtures of such complexes bearing chiral stereocontrolling ligands and achiral diene‐substituted ligands show high diastereoselectivity and reasonable enantioselectivity in the Diels–Alder reaction with maleimides if the reaction proceeds with the dimer but not with the monomer. Thus, solvent dependent switching between the monomer and dimer enables on/off switching of the enantioselectivity. Abstract : Far but not too far : A chiral auxiliary as well as an achiral reacting unit are statistically introduced in a hierarchically formed helicate. The Diels–Alder reaction with maleimides proceeds with moderate enantioselectivity with the dimer, whereas it is nearly switched off with the monomer (see scheme).