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Abstract
The formation of novel indolo-macrocyclic imines derived from N,N -diindolylxylene dialdehydes has been investigated. The xylene linkage between two indole units was found to contribute to the rigidity of the systems, and allows the selective condensations of N,N -diindolylxylene dialdehydes with diamino compounds. N,N -Diindolylxylene-3,3 -dialdehyde underwent cyclization only with 1,2-diaminoethane to afford an 18-membered cyclic diimine while N,N -diindolylxylene-7,7 -dialdehyde was only able to form a 19-membered cyclic diimine with 1,3-diaminopropane. Both kinds of imines could be reduced to the corresponding macrocyclic amines, by reductions with sodium borohydride.
Novel calix[3]indoles have been synthesized via two different strategies of acid-catalyzed addition reactions. In the first method, the indolo 2,7-dimethanols were cyclized with bis-indoles under acidic conditions. In the second method, bis-indole-3,3 -dimethanols were cyclized with active indoles. Attempts to synthesize macrocyclic structures containing more than four indole units via stepwise acid-catalyzed addition reactions failed due to the fact that the methylene linkages between the indole units were not stable under acidic conditions.
Tin(IV) chloride catalyzed oxidative coupling reactions were found to give novel 2 ,7-biindolyls and 2,2 -biindolyls. An investigation of the mechanism of this unusual bi-aryl coupling reaction was carried out. Through optimization of conditions it was found that in the mixture of dichloromethane and nitromethane, tin(IV) chloride could form tin-indole intermediates with active indoles and under mild heat a series of novel biindolyls can be obtained in moderate yield.
Further investigations of the reactivity of the new biindolyls and syntheses of biindolyl based macrocycles were carried out. The N,N -substitution of biindolyls gave the pyrrolophenanthridone analogues. The formylation of biindolyls gave mono- and di-formyl biindolyls, which were subsequently condensed with different diamino compounds to afford various 1:1 and 2:2 macrocyclic imines. Reduction of the di-formyl biindolyl gave the biindolyl dimethanol which could yield two different types of semi-calix[4]indoles in one-pot and stepwise manners. Oxidation reactions of biindolyls produced an indorphyrin with related tetraindolyl macrocycles in moderate yields. Different molecular shapes as well as the related supramolecular chemistry of tetraindolyl macrocycles were further investigated via X-ray crystallography studies.