Enantioselective assembly of multi-layer 3D chirality

Abstract

The first enantioselective assembly of sandwich-shaped organo molecules has been achieved by conducting dual asymmetric Suzuki-Miyaura couplings and nine other reactions. This work also presents the first fully C-C anchored multi-layer 3D chirality with optically pure enantiomers. As confirmed by X-ray diffraction analysis that this chiral framework is featured by a unique C2-symmetry in which a nearly parallel fashion consisting of three layers: top, middle and bottom aromatic rings. Unlike the documented planar or axial chirality, the present chirality shows its top and bottom layers restrict each other from free rotation, i.e., this multi-layer 3D chirality would not exist if either top or bottom layer is removed. Nearly all multi-layered compounds showed strong luminescence of different colors under UV irradiation, and several randomly selected samples displayed aggregation-induced emission (AIE) properties. This work is believed to have broad impacts on chemical, medicinal and material sciences including optoelectronic materials in future.

Asymmetric Catalytic Approach to Multilayer 3D Chirality

“…The synthesis of double‐layer reactants ( 6 a – i ) (Scheme 2) was started from the treatment of 4,7‐dibromo‐2,1,3‐benzothiadiazole ( 4 ) with bis(pinacolato)diboron under in situ catalytic systems involving KOAc as a base additive and (1,1‐bis(diphenylphosphino)ferrocene) dichloropalladium (II) as the catalyst in 1,4‐dioxane to give 4,7‐bis(4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolan‐2‐yl)benzo[c][1,2,5]thiadiazole ( 5 ) [27] . 1‐Bromo‐8‐arylnaphthalenes ( 3 a – i ) were synthesized by conducting the Suzuki‐Miyaura cross‐coupling between 1,8‐dibromo‐naphthalene ( 1 ) and arylboronic acids ( 2 a – i ) which are either directly purchased or readily synthesized by following literature procedures [22b,27] . The Suzuki‐Miyaura coupling of 1‐bromo‐8‐arylnaphthalenes ( 3 a – i ) with 4,7‐bis(4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolan‐2‐yl)benzo[c][1,2,5]thiadiazole ( 5 ) led to the formation of double‐layered reactants ( 6 a – i ) in an overall chemical yields arranging from 47 % to 68 % (see Supporting Information).…”

“…We also established the C−C bond‐based multilayer 3D chirality by conducting double Suzuki‐Miyaura cross‐couplings [27] with its asymmetric induction controlled by chiral auxiliaries (Scheme 1a, ii) [22b] . This work would be the first enantioselective synthesis of sandwich‐shaped organic molecules controlled by asymmetric aromatic interactions.…”

“…Interestingly, when these aromatic diamines are protected with various carbonyl groups, luminescence colors can be changed from gold to deep blue under UV irradiation. These multilayer 3D chiral molecules presented strong aggregation‐induced emission (AIE) [22b] . Furthermore, some of the above products displayed macro chirality that can be directly visualized by the naked eyes without an aid of any microscopic devices.…”

Multi‐Layer π‐Stacked Molecules as Efficient Thermally Activated Delayed Fluorescence Emitters

“…Notably, the device based on DM-BD2 realizes a larger increase in EQE than DM-Bm, because dual donors in the sandwich conformation play a better role in holding a parallel face-to-face D/A/D conformation which can further restrict the free motion of each layer to prevent energy loss. [28] In comparison, DM-BD1 actually has a slighter conformation change with respect to D/A interaction as compared to DM-B, but the EQE is still increased, attributed to the shorter D/A distance caused by the additional donor. These device features reveal that such multi-layer molecules with confined and compact D/A/D are favored to realize highly efficient devices.…”

Organocatalytic Enantioselective Construction of Chiral Azepine Skeleton Bearing Multiple‐Stereogenic Elements

“…Thedefined structure of chiral molecules bearing multiple stereogenic elements holds aspecial place in the development of bioactive compounds,advanced materials and asymmetric catalytic systems,w hose absolute and relative configurations are both critically important for their inherent properties. [1] To date,an umber of asymmetric catalytic strategies have been developed for the construction of multi-stereogenic chiral centers, [2] and af ew atroposelective protocols of multiaxis, [3,4] multihelical [5] and multiplanar [6] systems have been recently explored (Figure 1a). However,t ot he best of our knowledge,c atalytic enantioselective approaches installing more than three types of stereochemical elements into different sites of as ubstrate within as ingle step are intrinsically challenging and have not been reported.…”