Two complementary and efficient strategies have been developed for the regiospecific synthesis of unsymmetrical indolopyrrolocarbazoles (IPCs) mono-N-substituted with a pentacycle. A halogen in position 2 of the intermediate bisindolylmaleimides 3a−e allows a selective Mitsunobu coupling by exploiting the increased acidity of the 2-chloro-substituted indole nitrogen. It also promotes an easier cyclization of bisindolylmaleimides 4a−e and 7b−e to IPCs. Alkylation of the 2-unsubstituted indole-3-carboxamides 2a,b and further processing to the corresponding IPCs gives access to the opposite regioisomers.
Regiospecific synthesis of mono-N-substituted indolopyrrolocarbazoles / W. Froehner, B. Monse, T. Braxmeier, L. Casiraghi, H. Sahagun, P. Seneci. - In: ORGANIC LETTERS. - ISSN 1523-7060. - 7:21(2005 Oct 13), pp. 4573-4576.
Regiospecific synthesis of mono-N-substituted indolopyrrolocarbazoles
P. SeneciUltimo
2005
Abstract
Two complementary and efficient strategies have been developed for the regiospecific synthesis of unsymmetrical indolopyrrolocarbazoles (IPCs) mono-N-substituted with a pentacycle. A halogen in position 2 of the intermediate bisindolylmaleimides 3a−e allows a selective Mitsunobu coupling by exploiting the increased acidity of the 2-chloro-substituted indole nitrogen. It also promotes an easier cyclization of bisindolylmaleimides 4a−e and 7b−e to IPCs. Alkylation of the 2-unsubstituted indole-3-carboxamides 2a,b and further processing to the corresponding IPCs gives access to the opposite regioisomers.Pubblicazioni consigliate
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