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[摘要]：A new route to bilanes and porphyrins bearing four distinct meso substituents was studied to elucidate the scope and gain entry to previously inaccessible compds. The route entails (i) synthesis of a 1-bromo-19-acylbilane by acid-catalyzed condensation of a intramol. cyclization of the 1-bromo-19-acylbilane in the presence of a metal salt (MgBr2, 3 mol equiv) and a nonnucleophilic base (DBU, 10 mol equiv) in a noncoordinating solvent (toluene) at 115?exposed to air to afford the corresponding magnesium(II) porphyrin. Two sets of bilanes were initially prepd. to explore substituent effects. In the first set, all bilanes vary only in the nature of the substituent at the 10-position. In the second set, all bilanes vary only in the nature of the substituent attached to the acyl unit (the 20-position). The substituents examd. at the 10- and 20-positions include alkyl, aryl (electron-rich, electron-deficient, hindered), heteroaryl, ester, or no substituent (-H). The bilanes were obtained in 35-87% yield, and the target porphyrins in up to 60% yield. Further study of the scope focused on bilanes and porphyrins bearing three heterocyclic substituents (o-, m-, p-pyridyl) or four alkyl groups (Et, Pr, Bu, pentyl), in which case microwave irradn. was used for the porphyrin-forming step. Altogether, 17 bilanes and 19 porphyrins were prepd. and characterized. In summary, the new route provides access to meso-substituted bilanes and porphyrins for which access is limited via other methods. |
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