One-pot Diels–Alder cycloaddition/gold(I)-catalyzed 6-endo-dig cyclization for the synthesis of the complex bicyclo[3.3.1]alkenone framework

Abstract

SummaryThe rapid synthesis of bicyclo[m.n.1]alkanone cores possessing quaternary carbon centers adjacent to a bridged ketone represents a significant synthetic challenge. This type of architectural feature is embedded in various complex biologically active compounds such as hyperforin and garsubellin A. Herein, we report a highly diastereoselective one-pot Diels–Alder reaction/Au(I)-catalyzed carbocyclization to generate bicyclo[3.3.1]alkanones in yields ranging from 48–93%.

Modular Total Syntheses of Hyperforin, Papuaforins A, B, and C via Gold(I)-Catalyzed Carbocyclization

“…Previous work from our group revealed that bicyclic ketone framework 10 can be easily synthesized through a 6- endo dig gold­(I)-catalyzed carbocyclization of 1,5-enyne 7 using catalyst 8 (Scheme ). , Taking advantage of this method, we delineated a blueprint in which the bicyclo[3.3.1]­nonenone core 11 could serve as a central intermediate for the construction various PPAPs, including 1 – 4 via late-stage functionalization at C1 and C3. However, we took early cognizance that the formation of carbon–carbon at C1 bond adjacent to a quaternary carbon center (C8) might be challenging.…”

Research Progress of Polycyclic Polyprenylated Acylphloroglucinols

“…The concise total syntheses of hyperforin ( 422 ) and its analogues, papuaforins A–C ( 478 – 480 ), were accomplished in 17 steps by Barriault and Bellavance (Scheme ). They provided a strategy of short and scalable synthesis of densely substituted PPAP scaffolds with a bicyclo[3.3.1]-nonane core through a gold­(I)-catalyzed 6-endo-dig carbocyclization of cyclic enol ethers for late-stage functionalization. − First, a selective 6- endo-dig carbocyclization of silyl enol ethers to alkynes was achieved by modulating the steric and electronics properties of the ancillary ligand on the cationic gold complex. Starting from commercially available ketone 470 , a careful orchestration of stereospecific allylation, alkylation, and aldol reactions (from 471 to 474 ) installed the functional groups at C-5, C-7, and C-8.…”

Silver and gold

“…4 One major group of gold(I) compounds used for catalysis are complexes with 2-biphenyl-phosphine-derivatives. Cationic Au(I) complexes with JohnPhos can be used to form bicyclo [3.3.1]alkenone frameworks, 5 or bicyclo[3.2.1]octadienes 6 as well as for cyclisation of polyenynes resulting in large aromatic systems. 7 Derivatives with t Bu-or i Pr-groups on the biphenyl-moiety in these gold(I) compounds were shown to catalyse the formation of bicyclic structures from 1,7-enynes, 8 the reaction of trans-stilbene with cycloheptatriene to form cyclopropanes 9 as well as the formation of pyrenes from 2,6-dialkynylbiphenyls.…”

“…For complexes with acetonitrile and benzonitrile MLCT emissions were observed, while cinnamonitrile complexes only show nonradiative transitions. 88 Supramolecular structures due to argentophilic interactions and p-stacking have a strong influence on the emission of [(AgL) 2 (3,5-(CF 3 ) 2 Pz)] + [Ag 5 (3,5-(CF 3 ) 2 Pz) 6 (CH 3 CN)] À , with L being a tridentate triazine-based ligand. 89 Ag 2 complexes with H 2 dpzpda show p-p* IL or inter-ligand charge-transfer transitions, depending on the anions and solvents used, for [Ag 2 (ClO 4 ) 2 -(H 2 dpzpda) 2 ](DMF) 2 the two-photon absorption and emission were measured and discussed.…”