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Microwave‐Promoted Synthesis of N ‐Heterocycles by Tandem Imination/Annulation of γ‐ and δ‐Ketoalkynes in the Presence of Ammonia
Author(s) -
Alfonsi Maria,
Dell'Acqua Monica,
Facoetti Diego,
Arcadi Antonio,
Abbiati Giorgio,
Rossi Elisabetta
Publication year - 2009
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.200900014
Subject(s) - annulation , chemistry , tandem , regioselectivity , intramolecular force , ammonia , organic chemistry , combinatorial chemistry , medicinal chemistry , catalysis , materials science , composite material
The synthesis of 3‐substituted 1‐methylpyrrolo[1,2‐ a ]pyrazines and 3‐substituted isoquinolines was achieved by the intramolecular cyclisation of 2‐acetyl‐1‐propargylpyrroles and 2‐alkynylbenzaldehydes, respectively, in the presence of ammonia under microwave heating. The tandem imination/annulation of 2‐alkynylbenzaldehydes was easily accomplished under standard conditions, while TiCl 4 was used to achieve pyrrolo[1,2‐ a ]pyrazines. The reaction mechanism and the regioselectivity were discussed on the basis of theoretical calculations and spectroscopic data. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)