Search results for "Tetraloop"

Stepwise synthesis and selective dimerisation of bis- and trisloop tetra-urea calix[4]arenes.

2008

Tetra-urea calix[4]arenes substituted with four mono- or bisalkenyl residues have been converted into bis- or tetraloop compounds by intramolecular olefin metathesis, with use of a tetratosylurea calix[4]arene as template. The same strategy has now been used to synthesise trisloop compounds and bisloop compounds with adjacent loops, completing the series of the loop-containing tetra-urea derivatives. A tetra-urea calix[4]arene of the AABB type, where A stands for a bisalkenyl- and B for a monoalkenyl-substituted urea unit, was used as precursor for the three loops. It was easily synthesised from a tetraamino calix[4]arene in which two adjacent amino groups were Boc-protected. The ABCB-type …

Multiple catenanes based on tetraloop derivatives of calix[4]arenes

2009

Abstract Four novel tetraarylurea calix[4]arenes ( 4a – d ) have been synthesized, substituted by ω-alkenyloxy residues in 3,5-positions of the arylurea residues. The eight alkenyl groups were pairwise connected by olefin metathesis and subsequent hydrogenation. The ring-closure reaction was carried out with heterodimers exclusively formed by 4 with a tetratosylurea calix[4]arene 1 , which serves as a template in this reaction step. The potential trans-cavity bridging is entirely suppressed in this way. Bis- and tetraloop calix[4]arenes cannot form dimers due to overlapping loops. However, they readily form heterodimers with open-chain tetraureas, as long as their urea residues can pass thr…

ChemInform Abstract: Multiple Catenanes Based on Tetraloop Derivatives of Calix[4]arenes.

2009

Topologically Novel Multiple Rotaxanes and Catenanes Based on Tetraurea Calix[4]arenes

2006

Calix[4]arenes bearing at their wide rim four urea residues easily form hydrogen bonded dimeric capsules. This has been used to preorganise alkenyl functions attached to these urea groups for their controlled connection via metathesis reaction. Multimacrocyclic tetraurea derivatives are thus obtained in excellent yields via heterodimers which are formed exclusively with tetratosylurea derivatives. Heterodimerisation of such bis- and tetraloop tetraureas leads analogously to multicatenanes, or to rotaxanes by stoppering. Huge macrocycles are detached from tetraloop derivatives by cleavage of the urea function.

Fine-Tuning the Dimerization of Tetraureacalix[4]arenes

2010

Calix[4]arenes substituted by four urea residues at their wide rim form hydrogen-bonded homo- and heterodimeric capsules in apolar solvents. If urea groups are covalently connected to loops or substituted by bulky residues, the dimerization may be restricted to those pairs in which the loops do not overlap and for which the residues are small enough to pass the loops. In the present study, we describe the dimerization properties of tetraureas with one, two (adjacent or opposite), three, or four loops and those bearing (additionally) up to four residues of different size: a = tolyl, b = 3,5-di-tertbutylphenyl, c = 4-propyloxy-3,5-di-(tert-butylphenyl)phenyl, and d=4-[tris-(4-tert-butylphenyl…

Rotaxanes and Catenanes Derived from Tetra-Urea Calix[4]arenes

2010

Calix[ 4] arenes, substituted by four urea groups at their wide rim, form dimeric capsules in apolar solvents, which are held together by a seam of intermolecular hydrogen bonds. The heterodimerisation of tetra-aryl and tetratosyl ureas was used to synthesize various derivatives, in which adjacent urea residues are connected to form two, three or four loops. The aliphatic connections were tied by olefin metathesis between adjacent alkenyl residues followed by hydrogenation. Heterodimers of tetra-alkenyl substituted tetra-ureas and bis- or tetraloop derivatives were converted analogously to multiple catenanes. Tetra[2]rotaxanes were obtained in a similar manner. In addition to the spectrosco…