Regioselectivity of Pyrrole Synthesis fromm Diethyl Aminomalonate and 1,3-Diketones: Further Observations

Article abstract of DOI:10.1021/jo00227a009

1,3-Diketones 1 react with diethyl aminomalonate (2) in boiling acetic acid to afford ethyl 2-pyrrolecarboxylates 6.Considerable regioselectivity was noted for the following classes of diketone: 2-acylcyclohexanones 10a,b , 2-acylcyclopentanones 10c,d pyrroles 13a,b>, 1-phenyl-2-alkyl-1,3-alkanediones 17a-d , 3-phenyl-2,4-hexanedione (21a) , 1-phenyl-3-alkyl-2,4-alkanediones 24a,b , and 2,2-dimethyl-3,5-alkanediones 29a,b .The yields varied with the structural class, decreasing with increased steric hindrance.The product structure correlated with the structure of the enolized diketones in the case of the 2-acylcycloalkanones studied.