An Efficient Approach to Pyrroles and <i>N</i><b>-Bridgehead Pyrroles by Propargylation/Cycloamination of 4-Amino-1-azabutadiene Derivatives</b>
作者:José Barluenga、Miguel Tomás、Vladimir Kouznetsov、Angel Suárez-Sobrino、Eduardo Rubio
DOI:10.1021/jo951887y
日期:1996.1.1
The thermal cycloamination of several propargyl-substituted 4-amino-1-azabutadienes 2 leading to 3-functionalized pyrroles 4-6 is described. Derivatives of pyrrolizidines 9 and indolizidines and azaazulenes 11-13 are synthesized directly from cyclic imines 7 and 10, respectively, in a multistep process that involves metalation with LDA, addition of a nitrile, carbanion trapping with propargyl bromide, and cycloamination. In all cases the more substituted imine nitrogen is involved in the cyclization reaction; such an experimental finding is supported by theoretical calculations.