Macrocycle thermodynamic

But in most macrocyclizations, thermodynamic control is not yet possible. These macrocyclizations have therefore been carried out under kinetic control, often using high dilution conditions. Typical reactions are the formation of lactams, for instance, in the second macro-cyclization during the synthesis of concave pyridines 1 by reaction of the macrocyclic diamines 8 with diacid dichIorides. or the reaction of calix[6]arene with... 

Lamb, J. D., Izatt, R. M., Christensen, J. J., Eatough, D. J. Thermodynamics and Kinetics of Cation-Macrocycle Interaction, in Coordination Chemistry of Macrocyclic Compounds (ed. Melson, G. A.), p. 145-217, New York, Plenum Press 1979... 

The palladium-catalyzed cyclization of compound 138 amply demonstrates the utility of the Stille reaction as a macrocyclization method (see Scheme 37). This efficient ring closure is just one of many examples disclosed by J.E. Baldwin and his group at Oxford.58 Interestingly, compound 138 can be employed as a stereoisomeric mixture of vinylstannanes because both stereoisomers converge on the same cyclized product. To rationalize this result, it was suggested that the configuration of the vinylstannane moiety is conserved in the cyclization, but that the macrocycle resulting from the (Z)-vinylstannane stereoisomer isomerizes to the thermodynamically favored trans product under the reaction condi-... 

Thermodynamics of cation-macrocyclic compound interaction. R. M. Izatt, D. J. Eatough and J. J. Christensen, Struct. Bonding (Berlin), 1973,16,161-189 (53). 

Izatt RM, Eatough DJ, Christensen JJ (1973) Thermodynamics of Cation-Macrocyclic Compound Interaction. 16 161-189... 

The 14-membered macrocycle 1,4,8,11-tetraazacyclotetradecane (cyclam or [14]aneN4), unlike cyclen, is capable of encircling most transition metal ions and in the case of Co111 the trans configuration is much preferred by comparison with the folded cis isomer. Electrochemical reduction of A,v-[Co(cyclam)(OI I)2]+ in 3M NaOH leads to rapid isomerization to the trans form, and the relative stabilities of the trans and cis isomers of the di- and trivalent complexes were determined from a thermodynamic cycle.702 This preference for trans orientation of the non-macrocyclic donors has enabled the isolation and investigation of many Co complexes without the complications of isomerization. Some novel examples include /r[Pg.61]

C-functionalization of azamacrocycles is in general more difficult to achieve than N-functional-ization. The latter has been developed to an extent that macrocycles carrying side chains with various ligating groups are accessible, and Ni11 complexes can be prepared with high selectivity and predisposition for high thermodynamic and kinetic stability. 

Both the AH° and -A.S ° values are quite large for the Ni11 complex (633) bearing a pendent hydroxyethyl arm.1595 If this complex is treated with a bidentate ligand that binds exclusively in a cis fashion, coordination forces the macrocycle to fold out of the plane to give a so-called cis folded product. Thermodynamic data for the binding of ethylenediamine to give (635)... 

Complexation of Cd with a series of polyamine macrocycles, but also related open-chain polyamines, comprising or attached to the 2,2 -bipyridine (bipy) and 1,10-phenanthroline (phen) moieties, has been studied by combined UV/vis spectrometry and potentiometry.24 Formation constants and distribution diagrams of the species present have been evaluated. As a result the thermodynamic stabilities, i.e., the formation constants, are lower for the bipy- and phen-contain-ing ligands than those for Cd complexes with aliphatic oligoaza macrocycles containing the same number of N donors. The probable reason is loss of flexibility of the ligands caused by the size and stiffness of the inserted heteroaromatic moieties. 

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