Monoloop compounds

As shown in Section 5.5, bisloop or tetraloop tetra-ureas (8, 9) do not form homodimers, while monoloop compounds (e.g., 15) form selectively only one homodimer. These selectivities may be summarized as follows ... 

Molecular models suggest that such a P -connection between remote alkenyl residues in a dimer is possible. To check whether it really occurs under the conditions of the metathesis reaction, we synthesized the monoloop tetra-urea compounds 16, in which one of the non-cyclic urea residues is substituted by a bulky group which cannot penetrate the loop (Scheme 5.18). (The synthesis is analogous to that of 15, introducing in the final two steps the bulky residue first.). 

Scheme 5.23 Self-sorting of open (1), monoloop (15 with tolyl urea residues), and bisloop (8) tetra-ureas. The addition of bisloop compound 8 converts the mixture of three dimers 1-1, 1-15, and 15-15 into a mixture of only two dimers, 1 -8 and 15-15, the only possibility to have all tetra-ureas assembled in a dimer.

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See also in sourсe #XX -- [ ]

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