Asymmetric Allenophanes: Synthesis of a Tris‐meta‐allenophane and Tetrakis‐meta‐allenophane by Sequential Cross‐Coupling

Abstract

Around and around: A strategy based on sequential Pd‐catalyzed cross‐coupling reactions was applied for the asymmetric synthesis of new macrocyclic meta‐allenophanes composed of 18‐ or 24‐membered rings (see structures). The chiral components, tertiary propargyl alcohols and allene bridges, were assembled by a general enantioselective protocol, which involved a Sharpless epoxidation, an oxidation, and Sonogashira cross‐coupling.

All‐Carbon Scaffolds by Rational Design

“…7). [127] The circular dichroism (CD) spectra of the isolated enantiomer, recorded in hexanes, feature Cotton effects of moderate intensity [31: …”

“…7). [127] The circular dichroism (CD) spectra of the isolated enantiomer, recorded in hexanes, feature Cotton effects of moderate intensity [31: 263 nm (De $ 105 M À1 cm À1 ), (À)-32a: $265 nm (De $ 20 M À1 cm À1 ), (À)-32b: $270 nm (De $ 7 M À1 cm À1 )]. Clear proof for the enantiomeric purity of the target compounds was not provided and the absolute configuration of the used allene building blocks was only derived based on reaction mechanisms.…”

Oxidative allene amination for the synthesis of nitrogen-containing heterocycles

“…Despite the potential of allenes as convenient three-carbon synthons for the preparation of saturated stereotriads, they have been traditionally underutilized in this context. [37][38][39][40][41][42][43][44] However, we felt that their ready accessibility from well-established reactions, the rapid increase in recent methods for their enantioselective syntheses, and their unique axial chirality, make them ideally suited for this purpose. Our group has been engaged in efforts to rapidly elaborate chiral allenes into densely functionalized and stereochemically complex amine triads via oxidative allene amination strategies.…”

Conformational Stable Alleno‐Acetylenic Cyclophanes Bearing Chiral Axes

“…During the last years, we have been devoted to preparing and rationalizing the chiroptical properties of different chiral allenophanes. Chiral allenophanes and alleno‐acetylenic cyclophanes (cyclophanes bearing allene and allene‐acetylenic bridges, respectively) with helical chirality present a unique combination of electronic and geometric properties, which give rise to outstanding chiroptical responses. Herein we present our results regarding cyclophanes with four, two, or one aromatic units bridged by DEA 1 , namely, [7 4 ]‐, [14 2 ]‐, and [14 1 ]‐allenophanes, [7 4 ]‐ 2 , [14 2 ]‐ 3 , and [14 1 ]‐ 4 , respectively (Fig.…”