Ligand-Controlled Product Selectivity in Gold-Catalyzed Double Cycloisomerization of 1,11-Dien-3,9-Diyne Benzoates

Abstract

ABSTRACT:A synthetic method to prepare tricyclic bridged heptenones and hexenones from gold(I)-catalyzed double cycloisomerization of 1,11-dien-3,9-diyne benzoates is described. A divergence in product selectivity was achieved by fine-tuning the steric nature of the ligand of the Au(I) catalyst. In the presence of [MeCNAu(JohnPhos)] + SbF6-(JohnPhos = (1,1'-biphenyl-2-yl)-ditert-butylphosphine) as the catalyst, tandem 1,3-acyloxy migration/metallo-Nazarov cyclization/1,6-enyne addition/Cope rearrangement of the substrate was found to selectively occur to afford the bridged heptenone adduct. In contrast, changing the Au(I) catalyst to [MeCNAu(Me4tBuXPhos)] + SbF6-(Me4tBuXPhos = di-tert-butyl(2',4',6'-triisopropyl-3,4,5,6-tetramethyl-[1,1'-biphenyl]-2-yl)phosphine) was observed to result in the 1,11-dien-3,9-diyne benzoate undergoing a more rapid tandem 1,3-acyloxy migration/metallo-Nazarov cyclization/[4 + 2]-cyclization pathway to give the bridged hexenone derivative.

Regio‐ and Site‐selective Molecular Rearrangements by Homogeneous Gold Catalysis

“…While, the sterically encumbered Me 4 ButylXphos ligand directs the reaction to a tandem 1,3-acyloxy migration/metallo-Nazarov cyclization/[4 + 2] cyclization, a less hindered JohnPhos ligand directs a tandem 1,3-acyloxy migration/metallo-Nazarov cyclization/1,6-enyne cyclization/Cope rearrangement. [175] Therefore, by modulating the steric properties of auxiliary diphenylphosphines ligated with the gold-metal centre granted access to a regiodivergent route for bridged cyclohexanone 112 and cycloheptenone adducts 113. Another revelation of 1,3-selective acyloxy shift from the same team is witnessed during the Au(I)-catalyzed tandem 1,3-acyloxy migration/double cyclopropanation of 1,ene-4,n-diyne esters to molecularly complex tetracyclodecene and tetracycloundecene frameworks as single regio and diastereoisomer.…”

“…These molecular systems initially undergo Au(I)‐activated selective 1,3‐ester shift to afford a common intermediate 111 and the regiochemistry of further cyclization (5‐ exo ‐ dig vs 6‐ endo ‐ dig ) was dictated by the steric nature of the auxiliary ligand (Scheme 27). While, the sterically encumbered Me 4 ButylXphos ligand directs the reaction to a tandem 1,3‐acyloxy migration/metallo‐Nazarov cyclization/[4+2] cyclization, a less hindered JohnPhos ligand directs a tandem 1,3‐acyloxy migration/metallo‐Nazarov cyclization/1,6‐enyne cyclization/Cope rearrangement [175] . Therefore, by modulating the steric properties of auxiliary diphenylphosphines ligated with the gold‐metal centre granted access to a regiodivergent route for bridged cyclohexanone 112 and cycloheptenone adducts 113 .…”

Synthesis of N‐Fused Seven‐Membered Indoline‐3‐ones via a Palladium‐Catalyzed One‐Pot Insertion Reaction from 2‐Alkynyl Arylazides and Cyclic β‐Diketones

“…Intramolecular cyclization of azide group to the activated alkyne led to the formation of complex B . Then the α‐imino palladium carbene C generated in situ by releasing the N 2 could be trapped by TsOH to afford the complex D , which followed by protodemetalation to form 1 H ‐indole‐3‐sulfonate E . [13b] Basic conditions produce the 2‐phenyl‐3 H ‐indol‐3‐one G via 1,3‐Ts shift of E and further reductive desulfonation of α‐amino sulfone F .…”

A ligand-directed divergent catalytic approach to establish structural and functional scaffold diversity

“…Gold(I)-mediated cycloisomerization reactions of 1, n -enynes ( n =5–7) are efficient molecular rearrangements that often pass through cyclopropyl gold carbene intermediates 13 14 15 16 , whose reactivity can be influenced by the properties of the ligands in the gold complex and by their substitution pattern 17 18 19 . Therefore, a wealth of gold and other coinage metal-catalysed transformations to generate distinct molecular scaffolds has been reported in recent years 20 21 22 23 24 25 26 27 28 29 . For gold(I)-catalysed transformations numerous different ligands, such as phosphines, phosphites, heterocyclic carbenes, halides and others are readily available.…”