A synthesis of fused acenaphthopyrrolizines via the 1,3-dipolar cycloaddition reaction of azomethine ylides with acetylenic esters

An efficient synthesis of tetraalkyl 6a-hydroxy-3-alkyl-3H, 6aH-acenaphtho[1,2-g] pyrrolizine-1,2,5,6-tetra-carboxylates via the 1,3-dipolar cycloaddition reaction of azomethine ylides (generated in situ from alpha-amino acids and acenaphthylene-1,2-dione) with dialkyl acetylenedicarboxylates is described. When glycine was used instead of alanine, phenylalanine, valine, or isoleucine, dialkyl (E)-1'-(1,4-dialkoxy-1,4-dioxobut-2-en-2-yl)-2-oxo-1',5'-dihydro-2H-spiro [acenaphthylene-1,2'-pyrrole]-3',4'-dicarboxylates were obtained. The steric effects of the alpha-amino acids side chains may be responsible for their different behaviors.