Synthesis of Bisloop Tetra-urea

A mixture of tetra-urea 5 (Y=C5H11 m = 9) (0.050g, 0.0261 mmol) and bisloop compound 8 (Y = C5Hu n = 20) (0.0510g, 0.0274mmol) in benzene (60mL) was 

A solution of 3,5-di-(7-octenyloxy)benzoic add (1.47g, 3.92mmol), diphenylpho-sphorylazide (1.19 ml, 4.31 mmol), and triethylamine (0.436ml, 4.31 mmol) in toluene (79 ml) was stirred for 2 h at 55 °C. Tetraamino calix[4]arene (0.500 g, 0.654 mmol) was added, and the mixture was stirred for 2h at 85 °C. Then the solvent was evaporated, and the residue was triturated with methanol. The crude product thus obtained was purified by column chromatography (silica gel, ethyl acetate/hexane, 1 20) followed by reprecipitation from methanol/dichloromethane, which gave the desired tetra-urea 6 (Y = C5Hn m = 6) (0.714g, 48% yield) as a colorless powder. 

1 Sauvage, J.-P. and Dietrich-Buchecker, C. (1999) Molecular Catenaries, Rotaxanes and Knots, Wiley-VCH, Weinheim. 

33 A similar dimerization was recently observed for thiocalix[4]arenes substituted by four CMPO-residues. 

41 For self-assembled monolayers of heterodimers with 3, see Xu, S., Podoprygorina, G., Bohmer, V., Ding, Z., Rooney, D., Rangan, C. and Mittler, S. (2007) Org. Biomol. Chem., 5, 558—568. 

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