Synthesis of cyclic dimer

Template oligomer synthesis was described by Bohmer and Kammerer. Using p-cresyl-formaldehyde oligomers as a frame of the template, esters of aminoacids were prepared. The reaction, which may be considered as a model of a template reaction, was studied in its simplest form, based on the synthesis of cyclic dimers. The process can be represented by the following set of reactions (R - carbobenzoxy group) ... 

As we were interested in the synthesis of cyclic dimers 8 due to larger cavity sizes of such macrocycles, we elaborated their synthesis via N,N -di(dichlorophenyl)polyamines 6 obtained in situ from 2.2 equiv. of dichlorobromobenzene 4 and 1 equiv. of corresponding polyamine 2 (Scheme 3). Compoimds 6 were obtained in 85-90% yields, the reaction with the second... 

Then we decided to compare two approaches to the synthesis of cyclic dimers 41 which were described above. The first, via intermediate N,N -bis(bromobiphenyl) substituted polyamines 42 and 44, was complicated by the formation of linear oligomers 43 and 45 (Scheme 19). In the case of 3,3 -dibromobiphenyl 39 Xanthphos proved to be more efficient than BINAP due to its ability to suppress iV,iV-diaiylation of primary amines. The yields of target ( clodimers 38 and 41 were shown to be strongly dependent on the nature of polyamines, and the reactions also gave rise to by-products like cyclotetramers, cyclohexamers and linear oligomers. The attempts to use intermediate linear derivatives 42 and 44 in situ were unsuccessful. 

Synthesis of cyclic dimers 50 was conducted using two approaches via diarylated derivatives 51 and via bis(polyamine)substituted naphthalenes 54 which were used in situ (Scheme 22). The first route was less efficient due to the formation of by-products 52 and 53 in notable amounts. The second route is more convenient and affords better yields of cyclodimers 50. 

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