Group 15 imides macrocyclic

A useful method to synthesize ten and fourteen-membered ring imides 346 involved an initial condensation of macrocyclic -ketoestes 343 with alkyl or aryl isocyanates and carbodiimides, respectively, in the presence of a base [68]. After a nucleophilic attack of the enolate on the isocyanate C, the resultant amide N anion 344 induced a ring closure by addition to the keto group. Then, the intermediately formed four-membered ring 345 underwent a fragmentation... 

Initial cyclizadons were effected by the addition of an enamine to an imidate ester, both groups being suitably located by ligand coordination.263 An analogous process can be carried out on a thioimidate but a sulfide is formed and removal of sulfur with consequent ring contraction yields the corrin (100).264 These two complementary routes can be effected with different metal ions, nickel(II), palladium(II) and cobalt(III) in the first route, zinc(II) in the second. Removal of zinc ions easily provides the free corrin macrocycle. These two routes are summarized in Scheme 64. The sulfide contraction route was used in the Eschenmoser-Woodward total synthesis of vitamin Bn-265... 

A miscellany of papers dealing with the potency of the thioureido neighbouring group in nucleophilic substitution processes, the complexing ability of thioureas towards macrocyclic polyethers, and the cycloaddition reactions of thiocarbamoyl isothiocyanates (190) with ketens, ketenimines, imines, isocyanates, carbodi-imides, and isonitriles also deserve attention. 

Photo-Fries products are also formed upon irradiation of pyridine [68, 69], indole [70, 71], and carbazole [72] derivatives. In the case of imides, only one of the acyl groups tends to migrate [73-76] however, macrocyclic imides give rise to photoproducts diacylated at the aromatic ring [77]. 

The covalently linked dinuclear (salen)Al complex 24 and the macrocyclic cyclooctene-supported salen-AlCl catalyst 25 were applied in the asymmetric Michael addition of cyanide to a,p-unsaturated imides (Scheme 19.20). The Jacobsen group found that the covalently linked catalyst 24 had several orders of magnitude greater reactivity than the mononuclear analogue [S,S)-Al(salen) ent-3, and the enantioselectivities were comparable.In the... 

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