A Novel Access to Ionone‐Type Compounds: (E)‐4‐oxo‐β‐ionone and (E)Oxo‐β‐irone via metal‐catalyzed intramolecular reactions of α‐diazo ketones with furans

Abstract ( E )‐5‐Demethyl‐4‐oxo‐β‐ionone ( 2 ), (E)‐4‐oxo‐β‐ionone ( 3 ), ( E )‐4‐oxo‐β‐irone ( 4 ), and the five‐membered ring analogs 36 – 41 were synthesized by a novel, convergent route starting from 2‐methylfuran ( 1 ). A recently discovered, intramolecular reaction of 2‐(diazoacyl)furans, catalyzed by dirhodium tetraacetate, leading to dienediones served as key step, thereby testing its utility in natural‐product synthesis for the first time.