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Ethers are among the most important chemicals in organic synthesis, the pharmaceutical industry, agrochemical production, and material science. C–O bond formation via substitution is one of the most widely used strategies for ether formation. However, known methods usually employ transition-metal and bases to facilitate the process. In this work, we describe the base- and transition-metal-free ether formation via alcohol and phenol-participated substitution. The protocol allows access to a large number of ethers with enyne functional moieties, and features mild reaction conditions, high efficiency, and good regio- and stereoselectivities. The reaction could be readily scaled up, and the products could be used in a range of further transformations.

Transition‐metal‐catalysed reactions of cyclic ethynylethylene carbonates have been intensively studied because of their robustness in new bond formation and diversified molecule construction. Known reaction modes usually involve a substitution step occurring at either the propargylic or terminal alkyne positions. Here, we report an unprecedented reaction pattern in which cyclic ethynylethylene carbonates first undergo a rearrangement to release allenal intermediates, which subsequently react with diverse nucleophiles to furnish synthetically useful allylic and propargylic allenols, phosphorus ylides, and cyclopropylidene ketones through an addition process rather than a substitution pathway. The products enable various further transformations, and mechanistic studies and theoretical calculations reveal that the reaction does not proceed via a semipinacol type [1,2]‐hydride shift, but through base‐mediated deprotonation as the key step to induce the rearrangement. [ABSTRACT FROM AUTHOR]

A unique cascade sequence of vinylogous Michael addition‐Michael addition‐oxa‐Michael addition using dienone substrates was reported for the first time, achieving the rapid construction of 5/6/5 fused ring compounds in good yields with good to high stereoselectivities under mild conditions. Enantioenriched polycyclic rings can be obtained with high level of enantioselectivity by the stereodivergent resolution using ruthenium‐catalyzed transfer hydrogenation. The protocol provides a concise approach for the construction of the related fused ring substances. [ABSTRACT FROM AUTHOR]

2‐Hydroxy‐2,3‐dihydronaphthalene‐1,4‐diones (HDNDs) are ubiquitous in natural products and bioactive molecules, but the rapid asymmetric construction of such scaffolds remains a significant challenge to date. Reported herein is the rapid construction of the above key units via carbene‐catalyzed benzoin reaction. The resolution technique of divergent reaction on racemic mixture (divergent RRM) was employed, affording both isomers of HDNDs in a one‐step fashion. Disubstituted substrates afford products with two contiguous quaternary stereocenters. A series of highly selective transformations on the products can be realized, and mechanistic studies indicate that the benzoin reaction is much faster than the racemization process and the aldol reaction. [ABSTRACT FROM AUTHOR]