Conversion of O‐Propargyl β‐enones to 2‐Allylidene 1,3‐Diones and Furan Derivatives via [3,3]‐Sigmatropic Rearrangement

Abstract

An efficient synthetic protocol was developed for the formation of 2‐allylidene 1,3‐diones in very good yields via [3,3]‐sigmatropic rearrangement of O‐propargyl β‐enones. Good yields of highly functionalized substituted furan derivatives were synthesized from O‐propargyl β‐enones under gold‐catalysis via intramolecular cycloisomerisation.

Gold Catalysis and Furans: A Powerful Match for Synthetic Connections

“…A [3,3]-sigmatropic rearrangement/1,3-H shift to 2-allylidene-1,3-diones 62, starting from propargyl vinyl ether 61, was featured as the first step in the tandem synthesis of 3-acyl furans 63, in which the second step was a gold-catalyzed cycloisomerization (Scheme 20). 33 The synthesis of 2-acyl-3-iodobenzo [b]furans 66 was accomplished by gold-catalyzed rearrangement of 2-(iodoethynyl)aryl esters 64 through insertion of a gold vinylidene intermediate 65, formed upon a gold-assisted 1,2-iodine shift, 34 into the C-O bond of the acyl group (Scheme 21). The methodology was applied to the latestage functionalization of (S)-naproxen, affording the corresponding furan 68 with conservation of its enantiomeric purity.…”