1) Where R, = Aliphatic or Aromatic groups R 2 = Η Resorcinarenes are interesting for their receptor properties and as building blocks for large supramolecular assemblies of a fascinating architecture /5,19-21/. The bridging of hydroxy 1 groups of resorcinarenes leads to cavitands, bowl shaped species serving as synthetic receptors and able to assembly into capsules 122-217.In this review, selected examples of resorcinarenes are described, showing their synthetic approaches and reactivity as well as formation of complexes, host-guest systems and capsules. The preparation of mono-and multi-layers of resorcinarenes, promising for their applications, is also presented.
SYNTHESISResorcinarenes can be obtained in high yields via simple, one step procedures without using templates or high dilution techniques.A) Most cases involve the acid-catalyzed condensation reaction between resorcinol and aliphatic or aromatic aldehydes /10,11,28/.Weinelt and Schneider studied the reaction mechanism of the acidcatalyzed condensation reaction between resorcinol and acetaldehyde in methanol / HCl /29/.The electrophile stems not directly from the aldehyde but from its rapidly 156 Brought to you by | Purdue University Libraries Authenticated Download Date | 5/28/15 12:51 PM Y.K. Agrawal andR.N. Patadia Reviews in Analytical Chemistry 157 Brought to you by | Purdue University Libraries Authenticated Download Date | 5/28/15 12:51 PM Vol. 25, No. 3, 2006 Resorcinarenes and their Analytical ApplicationsThe ratio of the conformation of (10) is 3 : 2 mixture of boat isomer (all cis): diamond isomer ( cis.cis.trans).* Another high yield synthesis of resorcinarenes (13) involves the lewis acid catalyzed condensation tetramerization of 1,3-dimethoxy benzene (11) with isovalaraldehyde (12) /30/. Different types of lewis acids like SOCl 2 , POCl 3 , A1C1 3 , SiCl 2 Me 2 , SiClMe 3 , SnCl 4 had been used. Amongst these lewis acids, only SnCl 4 catalyses this reaction selectively and promotes the formation of the crown conformer (rccc) in high yield (85%).* When 2,4-dimethoxy benzyl alcohol (14) was treated with trifluoroacetic acid (5% in CHC1 3 ), resorcinarene (10) was obtained in 95 % yield /31/.The product is separated using reverse phase silica gel column HPLC.Measurements of steady state spectra and decay time of pyrene fluorescence of the (21) revealed that they form two types of excimer. * The synthesis of resorcinarene (22) was carried out by acid-catalyzed condensation of resorcinol with aldehydes, catalyzed by ytterbium (III) triflate nonahydrate {[Yb(H 2 0) 9 ](0Tf) 3 } /34/. * New ytterbium complexes with resorcinarene (121-127) containing methoxycarbonyl, methyldiethyl amino groups and bromine as the substituents in the resorcinol ring and methyl or phenyl substituents in the macroring were synthesized /85,86/.
