Synthesis of bis(benzoxazole) frameworks chiralized by planar chiral [2.2]Paracyclophane

[2.2]Benzoindenophane-Based Chiral Indenyl Ligands: Design, Synthesis, and Applications in Asymmetric C-H Activation

Development of chiral indenyl ligands for asymmetric C-H activation is a longstanding challenge, and extremely few successes have been achieved. In this paper, we describe a class of readily accessible, facilely tunable and user-friendly chiral indenyl ligands featuring a [2.2]benzoindenophane skeleton via a divergent synthesis strategy. The corresponding chiral indenyl rhodium catalysts were successfully applied in the asymmetric C-H activation reaction of O-Boc hydroxybenzamide with alkenes to give various chiral dihydroisoquinolone products (up to 97 % yield, up to 98 % ee). Moreover, the asymmetric C-H activation reaction of carboxylic acids with alkynes was also successfully accomplished, providing a range of axially chiral isocoumarins (up to 99 % yield, up to 94 % ee). Notably, this represents the first example of enantioselective transition metal catalyzed C(sp2)-H activation/oxidative coupling of benzoic acids with internal alkynes to construct isocoumarins. Given many attractive features of this class of indenyl ligands, such as convenient synthesis, high tunability and exclusive face-selectivity of coordination, its applications in more catalytic asymmetric C-H activation and in other asymmetric catalysis are foreseen.

The hamburger-shape photocatalyst: thioxanthone-based chiral [2.2]paracyclophane for enantioselective visible-light photocatalysis of 3-methylquinoxalin-2(1H)-one and styrenes

A new thioxanthone-based photocatalyst with a [2.2]paracyclophane skeleton and planar chirality has been developed. The catalyst has been successfully applied in the visible light-mediated enantioselective aza Paternò-Büchi reactions of quinoxalinone and styrenes to produce azetidines. The structures of the catalyst derivatives were unequivocally determined by their single crystal X-ray crystallography analysis.

Guerbet upgrading of ethanol to n-butanol using Ru(iii) catalysts under air

A series of in situ prepared Ru(iii) complexes supported by easily accessible N-donor organic pincer ligands were used as catalysts in the Guerbet upgrading reaction of ethanol under aerobic conditions.

Metal-to-Metal Distance Modulation by Ligand Design: A Case Study of Structure-Property Correlation in Planar Chiral Cyclophanyl Metal Complexes

Multinuclear metal complexes have seen tremendous progress in synthetic advances, their versatile structural features, and emerging applications. Here, we conceptualize Metal-to-Metal distance modulation in cyclophanyl metal complexes by bridging ligand design employing the co-facially stacked cyclophanyl-derived pseudo-geminal, -ortho, -meta, and -para constitutional isomers grafted with N-, O-, and P- containing chelates that allow the installation of diverse (hetero)metallic moieties in a distance-defined and spatially-oriented relation to one another. Metal-to-Metal distance modulation and innate transannular "through-space" π-π electronic interactions via the co-facially stacked benzene rings in cyclophanyl-derived complexes as well as their specific stereochemical structural features (element of planar chirality) are crucial factors that contribute to the tuning of structure-property relationships, which stand at the very center from the perspective of cooperative effects in catalysis as well as emerging material applications.