A Rotaxane‐Based Switchable Organocatalyst

Abstract

Switch it on! The activity of an organocatalytic group incorporated within a rotaxane architecture can be controlled by switching the position of the macrocycle. The system was used to mediate the progress of the Michael addition of an aliphatic thiol to trans‐cinnamaldehyde.

A Cholesterol Containing pH‐Sensitive Bistable [2]Rotaxane

“…[12] Three permanent cationic units have been used most in this context: dialkylated 4,4Ј-bipyridinium ions as pioneered by J. F. Stoddart in the late 1990s [13] and more recently alkylated pyridinium ions as employed by S.-H. Chiu, [14] F. Coutrot, [15] T. Ogoshi, [16] and U. Lüning, [17] or alkylated triazolium ions as used by F. Coutrot, [18] Y. Liu, [19] C.-F. Chen, [20] P. D. Beer, [21] and D. A. Leigh. [22] Among these, the latter one is very appealing because the triazole unit can also act as a key structural element to actually synthesis the rotaxane by means of a copper-catalysed azide-alkyne cycloaddition (CuAAC). [23] Scheme 1.…”

Enantioselective Formation of 2‐Azetidinones by Ring‐Assisted Cyclization of Interlocked N‐(α‐Methyl)benzyl Fumaramides

“…Thus,s ynthetic compounds having either ar estricted void or matrix, which could emulate the behavior of enzymes,are highly demanding. [10,11] Thep resence of the mechanical bond [10a] imparts particular chemical properties to these systems,which have been applied as selective and/or switchable catalysts among others. These tailor-made systems can be easily tuned to enhance their catalytic features in as imilar way to that of other enzymatic structures.…”

“…[2] Besides the use of highly confined organocatalysts [3] or materials, [4] which are able to create the desired rigid space for the stabilization of the corresponding transition states,self-assembled capsules, [5] molecular cages, [6] and macrocycles [7] are in the spotlight. [11] Recently,w er eported the intramolecular cyclization of the N-benzyl fumaramide [2]rotaxanes 1 (Scheme 1). [8,9] Thec hemical activity of mechanically interlocked molecules has been under intense study in recent years.…”

Localized Template‐Driven Functionalization of Nanoparticles by Dynamic Combinatorial Chemistry

“…[1] Organic chemists can now synthesize molecules of almost arbitrary complexity [2] and design them to perform useful work at the nanoscale, including directional movement, [3] programmed synthesis of other molecules, [4] regulation of catalytic activity, [5] selfassembly, [6] and even self-replication. [7] However,i ti ss till very difficult to control the relative positioning of functional groups on the surface of nanoparticles,instark contrast to the elaborate control possible for their organic counterparts.…”