Chromenone‐Fused Pyrrolizines and Pyrrolizine Analogues of Lamellarins: Expanding the Lamellarin Family

• DOI: 10.1002/ejoc.202301230
• Publication Date: 2024-01-09T07:48:38Z
• Authors: Stefania M. Scalz...; Garreth L. Morgans; Robin Klintworth; Charles B. de Koning; Manuel A. Fernandes; Willem A. L. van ...; Joseph P. Michael
• Keywords: Pyrrolidine; Pyrrole; Isoquinoline

Abstract Several N ‐ethoxycarbonylmethyl enaminones, prepared by Eschenmoser sulfide contraction between ‐(ethoxycarbonylmethyl)pyrrolidine‐2‐thione and various ortho ‐oxygenated phenacyl halides, underwent cyclisation to give ethyl 6‐aryl‐2,3‐dihydro‐1 H ‐pyrrolizine‐5‐carboxylates upon microwave heating with silica gel in xylene. With enaminones made from ‐hydroxyphenacyl not only did dihydropyrrolizine formation take place, but spontaneous lactonisation also occurred 9,10‐dihydrochromeno[4,3‐ b ]pyrrolizin‐6(8 )‐ones. Bromination Suzuki‐Miyaura arylation of these chromenopyrrolizines at the free C−H site on pyrrole ring afforded four analogues lamellarin alkaloids which a pyrrolidine replaces isoquinoline system fused polycyclic core. The product 11‐(3,4‐dimethoxyphenyl)‐2,3‐dimethoxy‐9,10‐dihydrochromeno[4,3‐ )‐one, particular, is congener well‐known G trimethyl ether. Preliminary results pertaining an extension chromenone‐fused indolizines are reported.