Supramolecular catalysis water

CDs are cyclic oligosaccharides comprised of a-l,4-linked glucopyr-anose units (37- 0). The following properties make CDs attractive components in organic chemistry and supramolecular catalysis/ enzyme mimics in particular (i) CDs are water soluble (ii) their hydrophobic cavity can host a variety of lipophilic guest molecules ... 

Aldehydes have been allylated with allyltributyltin, using supramolecular catalysis in acidic water at 60°C.196 Using j3-cyclodextrin as catalyst with all species at a 1 mmol level, high yields were obtained in a few hours. The catalyst, which can be recycled effectively, hydrogen bonds the aldehyde oxygen within the cavity. 

The use of cyclodextrins14 has provided the ability to conduct the Strecker reaction with TMSCN in water via supramolecular catalysis involving reversible guest-host interactions. Activation of imine 16 by complexation with the hydroxyl groups present in cyclodextrins was found to work best with p-cyclodextrin. This chemically green reaction could be applied to ketones as well as aldehydes. 

R. Sridhar, B. Srinivas, K. Surendra, N. S. Krishnaveni, K. R. Rao, Synthesis of j8-hydroxy selenides using benzeneselenol and oxiranes under supramolecular catalysis in the presence of /3-cyclodextrin in water, Tetrahedron Lett, 2005, 46, 8837-8839. 

M. S. Raddey, B. Srinivas, R. Sridhar, M. Narender, K. R. Rao, Highly regioselective thiolysis of oxiranes under supramolecular catalysis involving j8-cyclodextrin in water, J. Mol. Catal. A. Chem., 2006, 255, 180-183. 

Khalili B, Jajarmi P, Efiekhari-Sis B, Hashemi MH (2008) Novel one-pot, three-component synthesis of new 2-alkyl-5-aryl-(fH)-pyrrole-4-ol in water. J Org Chem 73 2090-2095 Murthy SN, Madhav B, Kumar AV, Rao KR, Nageswar YVD (2009) Multicomponent approach towards the synthesis of substituted pyrroles under supramolecular catalysis using P-cyclodextrin as a catalyst in water under neutral conditions. Helv Chim Acta 92 2118-2124 Pan L, Bi X, Liu Q (2013) Recent developments of ketene dithioacetal chemistry. Chem Soc Rev 42 1251-1286... 

This review is dedicated to the synthesis of water-soluble cryptophanes and of the closely related hemicryptophane derivatives that were developed more recently. The study of their binding properties with different species and some peculiar properties related to their chiral structure are also described. A particular attention is given to xenon-cryptophane complexes since, as above mentioned, these complexes have played a major role in the development of water-soluble cryptophane derivatives. We describe in a concise manner the different approaches, which have been reported in the literature to introduce hydrophilic moieties onto the cryptophane structure. Finally, we report some physical properties of the water-soluble cryptophane complexes. This mainly concerns the study of their binding properties with neutral molecules or charged species. The preparation of enantiopure cryptophanes has also contributed to the development of this field. Indeed, it was stressed that cryptophanes exhibit remarkable chiroptical and binding properties in water [11]. These properties are also described. The last part of this review is devoted to hemicryptophane derivatives, which are closely related to the cryptophane structure and which allow the functionalization of the inner space of the molecular cavity. These show a renewed interest in their applications in chiral recognition and supramolecular catalysis. 

Water-Soluble Metal Hemicryptophane Complexes Towards Supramolecular Catalysis in Water... 

This short compilation of the recent literature results convincingly demonstrates the usefulness of water-soluble supramolecular complexing agents in biphasic aqueous organometalHc catalysis. Due to their availability, cyclodextrins play a major role in this field. Thinking of the relatively low price of these chemicals (a few per kg in 1998 [2]) their use on a larger scale can also be envisaged in fine chemicals production. 

Roelfes s supramolecular assembly is one of the most efficient enan-tioselective catalysts for aqueous Michael additions. The DNA template approach has also been used for enantioselective Friedel-Crafts reactions in water, with outstanding results in terms of conversion and enantioselectivities (110). All these results confirm the impressive potential of DNA-based enantioselective catalysis. 

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