Diastereo- and regioselectivity in Diels–Alder reaction of [1,4,2]diazaphospholo[4,5-a]pyridines
作者:Raj K. Bansal、Konstantin Karaghiosoff、Neelima Gupta、Neelam Gandhi、Surendra K. Kumawat
DOI:10.1016/j.tet.2005.08.045
日期:2005.10
[1,4,2] Diazaphospholo[4,5-a]pyridines undergo diastereoselective Diels-Alder reaction at the >C=P-functionality with 2,3dimethylbutadiene and isoprene in the presence of sulfur or selenium. The reaction with isoprene occurs regioselectively. On carrying out the reaction with diene in presence of methyl iodide, the initially formed [2+4] cycloadduct is methylated regioselectively at the sigma(2), lambda(3)-nitrogen. The results of the DFT calculations of the Diets-Alder reaction with isoprene are in accord with the observed regioselectivity. The relative stabilities of the two transition structures have been explained on the basis of NBO analysis. (c) 2005 Elsevier Ltd. All rights reserved.