2.6- Bis piperazine

An efficient, practical solid-phase synthesis of a variety of bis-hetero-cyclic compounds was developed starting from resin-bound orthogonally protected lysine (Fig. 10). Tetraamines 36 were synthesized by exhaustive reduction of resin-bound tetraamides 35. Cyclization with different commercially available bifunctional reagents such as cyanogen bromide, thio-carbonyldiimidazole, carbonyldiimidazole, and oxalyldiimidazole yielded the corresponding bis-heterocyclic compounds bis-cyclic guanidines 37,39 bis-cyclic thioureas 38, bis-cyclic ureas 39, and bis-diketopiperazines 40, respectively.40 Reduction of compounds 40 led to bis-piperazines 41. 

Variable-temperature Raman spectra of aqueous solutions containing Cd(OH2)6 show vCdOe bands at 235 cm and 185 cm , assigned to Cg and t2g modes respectively. The IR spectra of cadmium(II) bis(acetylacetonate) and its bis-piperazine adduct show that vCdO decreases on the additional coordination of the V-donor. 2... 

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