Novel calix[4]cryptands: “Mappemonde II” and “Mill II”

Two novel calix[4]cryptands were synthesized from 1,3‐alternate calix[4]bis‐azacrown. “Mappemonde II” consists of one 1,3‐calix[4]bis‐azacrown wrapped by a benzo‐crown ether loop. “Mill II” is composed of two 1,3‐calix[4]bis‐azacrowns linked by two benzo‐crown ether strands.     

“Truncated” Pagodanes — Synthesis of Functionalized [1.1.1.1] and [1.1.1.0] Pagodanes

“Truncated” [1.1.1.1] pagodanes like the [1.1.0.0] and [0.0.0.0] homologues3 and 4 (E_Str = 146.1 – 171.5 kcal mol^?1, MM2) are potential precursors of unusual unsaturated homoconjugated radical cations and σ-bishomoaromatic dications. Attempts are presented toward the synthesis of 3 - starting out from [1.1.1.1] pagodane-4,9-dione 9 and diaza [2.2.1.1] pagodadiene 11 by cycloelimination (unsuccessful) and by Favorskii-type ring contraction methodologies. Control experiments with the model diketone 19 documented the limitations for α,α′-difunctionalization of 9 as the prerequisite for one-pot double Favorskii-type ring contraction. A de novo synthesis for such α,α′-disubstituted derivatives of 9(54) was not sufficiently expeditious to open a practical access to 3. Sequential double bridgehead hydroxylation of 9, successfully practized with model 19, similarly suffered from inherent cage effects and allowed only limited yields of [1.1.1.0] pagodanone 10, the intermediate on the way to 3.     

From Packed “Sandwich” to “Russian Doll”: Assembly by Charge‐Transfer Interactions in Cucurbit[10]uril

As the host possessing the largest cavity in the cucurbit[n]uril (CB[n]) family, CB[10] has previously displayed unusual recognition and assembly properties with guests but much remains to be explored. Herein, we present the recognition properties of CB[10] toward a series of bipyridinium guests including the tetracationic cyclophane known as blue box along with electron‐rich guests and detail the influence of encapsulation on the charge‐transfer interactions between guests. For the mono‐bipyridinium guest (methylviologen, MV ²⁺), CB[10] not only forms 1:1 and 1:2 inclusion complexes, but also enhances the charge‐transfer interactions between methylviologen and dihydroxynaphthalene ( HN ) by mainly forming the 1:2:1 packed “sandwich” complex (CB[10] ? 2 MV ²⁺ ?HN ). For guest 1 with two bipyridinium units, an interesting conformational switching from linear to “U” shape is observed by adding catechol to the solution of CB[10] and the guest. For the tetracationic cyclophane‐blue box, CB[10] forms a stable 1:1 inclusion complex; the two bipyridinium units tilt inside the cavity of CB[10] according to the X‐ray crystal structure. Finally, a supramolecular “Russian doll” was built up by threading a guest through the cavities of both blue box and CB[10].