Piperazine, ligand

Additional methods of late for the direct introduction of the NH2 moiety using aqueous ammonia are also available, with each made possible by the choice of ligand. Aryl bromides and iodides (but not chlorides) react in hot (120 C) ammonium hydroxide in the presence of Cul (10 mol%) to afford anilines in good yields, so long as a piperazine ligand was present (shown below) in its absence, no... 

Classic A/-heterocychc ligands, eg, bipyridyl (bipy), terpyridyl, imidazole, pyrazine, phenanthroline, piperazine (including alkyl- and aryl-substituted derivatives), and polypyrazol-l-yl-borates (bis, tris, and tetra), have all been found to coordinate Th(IV) chlorides, perchlorates, and nitrates. The tripodal hydrotris(pyrazolyl)borates, HBPz, have been used to stabilize organometaHic complexes (31). Bis-porphyrin Th(IV) "sandwich" complexes have been... 

Maldotti (96) studied the kinetics of the formation of the pyrazine-bridged Fe(II) porphyrin shish-kebab polymer by means of flash kinetic experiments. Upon irradiation of a deaerated alkaline water/ethanol solution of Fe(III) protoporphyrin IX and pyrazine with a short intense flash of light, the 2 1 Fe(II) porphyrin (pyrazine)2 complex is formed, but it immediately polymerizes with second-order kinetics. This can be monitored in the UV-Vis absorption spectrum, with the disappearance of a band at 550 nm together with the emergence of a new band due to the polymer at 800 nm. The process is accelerated by the addition of LiCl, which augments hydrophobic interactions, and is diminished by the presence of a surfactant. A shish-kebab polymer is also formed upon photoreduction of Fe(III) porphyrins in presence of piperazine or 4,4 -bipyridine ligands (97). 

Hsin, L.-W., Dersch, C.M., Baumann, M.H. et al. (2002) Development of long-acting dopamine transporter ligands as potential cocaine-abuse therapeutic agents chiral hydroxyl-containing derivatives of l-[2-[bis (4-fluorophenyl)methoxy]ethyl]-4-(3-phenylpropyl)piperazine and l-[2-(diphenylmethoxy)ethyl]-4-(3-phe-nylpropyl)piperazine. Journal of Medicinal Chemistry, 45 (6), 1321-1329. 

In contrast to Bosman et al., who only found metal complexation in the periphery of polypropylene imine) dendrimers, Tomalia and co-workers reported on the incorporation of copper ions into the interior of PAMAM dendrimers judging from EPR and UV/Vis studies [220, 221]. Metal binding in the dendrimer interior has also been observed for dendrimers carrying multiple ligands for metal complexation within their framework such as crown-ethers [222, 223] (Cs(I)-complexes), piperazine [224] (Pd(II)- and Cu(II)-complexes) or triazocyclononane [225] (Cu(II)- and Ni(II)-complexes). In most cases addition of the metal-salt to the dendrimer led to the formation of 1 1 complexes. 

The method lends itself nicely to the construction of enantiomerically enriched tri- and tetrasubstituted piperazines such as 23, substances that prove useful as ligands in enantioselective synthesis, such as that illustrated in Eq. (11) [20],... 

Fisher, M. J., Backer, R. T., Collado, L, et al. (2005) Privileged structure based ligands for melanocortin receptors—substituted benzylic piperazine derivatives. Bioorg. Med. Chem. Lett. 15, 4973-4978. 

A. Fleaid, K.L. Locker, A.M. MacLeod, D. Morrison, C.R. Moyes, D. O Connor, A. Pike, M. Rowiey, M.G.N. Russell, B. Sohal, J.A. Stanton, S. Thomas, FI. Verrier, A.P. Watt, J.L. Castro, Fluorination of 3-(3-(piperidin-1-yl)propyl)indoles and 3-(3-(piperazin-1-yl) propyl)indoles gives selective human 5-FITid receptor ligands with improved pharmacokinetic profiles, J. Med. Chem. 42 (1999) 2087-2104. 

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