meta-Substituted anilines were efficiently synthesized
via copper-catalyzed [1,3]-methoxy rearrangement of N-methoxyanilines followed by Michael addition of nucleophiles to
the in situ generated ortho-quinol imine. The present
reaction exhibits excellent applicability of para-substituents, such as vinyl, methylthio, ester, and bromo, and carbon
nucleophiles, such as 1,3,5-trimethoxybenzene, N-methylindole,
and dimethyl malonate. Thus, the present rearrangement can resolve
problems stemming from oxidation reactions, such as the use of stoichiometric
amounts of oxidants and low compatibility of electron-withdrawing
groups.
The [1,3]-alkoxy rearrangement reactions of N-alkoxyanilines were efficiently catalyzed by cationic N-heterocyclic carbene (NHC)-Cu catalysts in affording 2-alkoxyaniline derivatives in good to excellent yields with high functional group compatibility. For N-alkoxyanilines having an electron-withdrawing substituent at the meta-position, the alkoxy group selectively migrated to the more hindered ortho-position. In contrast, the alkoxy group migrated to the less hindered ortho-position for N-alkoxyanilines having an electron-donating substituent. Mechanistic studies suggest that the rearrangement reactions proceed via an intramolecular route.
Gold‐catalyzed reactions of alkynyl N‐sulfinylimines were used to produce the corresponding 2H‐azirines possessing sulfenyl and acyl groups at the 3‐position of the azirine ring in good to excellent yields. These reactions involved internal transfer of the sulfinyl oxygen atom to form a thiooxime intermediate tethered to an α‐oxo gold carbene moiety. Subsequent insertion of the carbene into the N−S bond resulted in ring construction.
Gold-catalyzed reactions between sulfenamides and terminal
alkynes
proceeded via cis-insertion of alkynes into the N–S
bond in sulfenamides, affording the corresponding β-sulfenylenamines
in yields up to 90%. Mechanistic studies revealed that the reactions
proceeded via nucleophilic attack of the sulfenamide nitrogen atom
on the π-activated alkyne, followed by tosylate-assisted intermolecular
transfer of the sulfenyl group.
A gold catalyst promotes the sequential cleavage of the S−O and N−S bonds of a sulfinyl group, leading to S‐functionalized azirines. As Itaru Nakamura et al. illustrate in their Communication on page 12248, the transformation is like making plastic models: A golden diagonal plier cuts these bonds, and the cut out parts are assembled into the product using an alkyne triple bond unit. Substituents in the product can be chosen from the kit as desired.
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