[3,3]‐Sigmatropic Rearrangements of Naphthyl 1‐Propargyl Ethers: para‐Propargylation and Catalytic Asymmetric Dearomatization

Abstract

The para-Claisen rearrangement of aryl 1propargyl ethers involves two-step [3,3]-sigmatropic rearrangements and dearomatization process, which has high activation barriers and is of challenge. Here we discovered thermal para-Claisen rearrangement of naphthyl 1-propargyl ethers, and it enabled the formation of formal para-CÀ H propargylation products upon rearomatization. Chirality transfer occurred if optically active propargyl ethers were employed, leading to the construction of aryl/propargyl-containing stereogenic centers. Moreover, catalytic asymmetric dearomatization of naphthyl 1-propargyl ethers with different substitution at para-position gave access to benzocyclohexenones bearing all-carbon quaternary stereocenters. The reaction was accelerated by a chiral N,N'-dioxide/Co(OTf) 2 complex catalyst to achieve high yields (up to 98 %) and high enantioselectivities (up to 93 % ee). The DFT calculations and experimental results provided important clues to clarify the para-Claisen rearrangement process as well as the chiral induction and remote delivery.

Gold(I)-Catalyzed Dearomatization–Allenene Reaction for the Construction of Polycycles with Excellent Diastereoselectivity

“…This is of interest as 16 contains a stereogenic quaternary α-carbonyl carbon atom. [28,[38][39] Structural analysis of 16 was performed by NOESY spectroscopy and comparison with the calculated structure (Figure S17). This article is protected by copyright.…”

“…This is of interest as 16 contains a stereogenic quaternary carbonyl carbon atom. 28,38,39 In a next step, we wanted to investigate the gold(I)-catalyzed reaction of 1-naphthyl propargyl ether 7 with alkynes 5 (Scheme 4a). For this purpose, we studied the reaction with 1-phenyl-1-pentyne and [JohnPhosAu(NCMe)]SbF 6 as catalyst in chloroform in an NMR experiment.…”

Merging Johnson–Claisen and Aromatic Claisen [3,3]-Sigmatropic Rearrangements: Ytterbium Triflate/2,6-Di-tert-butylpyridine Catalytic System

“…Notable tandem sequences employed in synthesis are oxy-Cope/Claisen/ene (wiedemannic acid), cationic aza-Cope/Mannich (gelsemin), , Ireland–Claisen/Cope (isocyclocitrinol), double Johnson–Claisen (morphine), double Overman rearrangements (agelastatin A), and others . In recent years, a number of novel promising cascades waiting for application in construction of complex natural products have emerged: Winstein/Overman, Cope/Winstein, Claisen/Cope rearrangement of propargylic ethers, and multiple sequential Overman rearrangement . In general, the idea of tandem sigmatropic rearrangement could be outlined as a migration of the double bond across the carbon skeleton upon utilization of neighboring functionalities, which opens vast possibilities for synthetic planning.…”

Cobalt(II)-Catalyzed Enantioselective Propargyl Claisen Rearrangement: Access to Allenyl-Substituted Quaternary β-Ketoesters

“…Later in 2017, Sun, You, and co-workers reported a highly efficient synthesis of 3-allenyloxindoles via asymmetric propargyl Claisen rearrangement with the Sc­(OTf) 3 -PyBox L3 complex as the catalyst (Scheme c) . The enantioselective para -Claisen rearrangement of naphthyl 1-propargyl ethers that employed the Co­(OTf) 2 - N , N ′-dioxide complex as a chiral catalyst, delivering dearomatized benzocyclohexenones bearing all-carbon quaternary stereocenters in excellent yields was also reported by Feng and co-workers later in 2022 . Recently, we developed a chiral tridentate imidazoline-pyrroloimidazolone pyridine (PyIPI) ligand and applied it for enantioselective dearomative [3 + 2] annulation of indoles with aminocyclopropanes .…”