Full control over multiple competing coupling sites would enable straightforward access to densely functionalized compound libraries. Historically, the site selection in Pd0‐catalyzed functionalizations of poly(pseudo)halogenated arenes has been unpredictable, being dependent on the employed catalyst, the reaction conditions, and the substrate itself. Building on our previous report of C−Br‐selective functionalization in the presence of C−OTf and C−Cl bonds, we herein complete the sequence and demonstrate the first general arylations and alkylations of C−OTf bonds (in <10 min), followed by functionalization of the C−Cl site (in <25 min), at room temperature using the same air‐ and moisture‐stable PdI dimer. This allowed the realization of the first general and triply selective sequential C−C coupling (in 2D and 3D space) of C−Br followed by C−OTf and then C−Cl bonds.
We report a remote
functionalization strategy, which allows the Z-selective
synthesis of silyl enol ethers of (hetero)aromatic
and aliphatic ketones via Ni-catalyzed chain walking from a distant
olefin site. The positional selectivity is controlled by the directionality
of the chain walk and is independent of thermodynamic preferences
of the resulting silyl enol ether. Our mechanistic data indicate that
a Ni(I) dimer is formed under these conditions, which serves
as a catalyst resting state and, upon reaction with an alkyl bromide,
is converted to [Ni(II)-H] as an active chain-walking/functionalization
catalyst, ultimately generating a stabilized η3-bound
Ni(II) enolate as the key selectivity-controlling intermediate.
We report a new air-stable Pd I dimer, [Pd(m-I)(PCy 2 t Bu)] 2 , which triggers E-selective olefin migration to enamides and styrene derivatives in the presence of multiple functional groups and with complete tolerance of air. The same dimer also triggers extremely rapid CÀC coupling (alkylation and arylation) at room temperature in a modular and triply selective fashion of aromatic C À Br, C À OTf/OFs, and C À Cl bonds in poly(pseudo)halogenated arenes, displaying superior activity over previous Pd I dimer generations for substrates that bear substituents ortho to CÀOTf.
We herein disclose the use of tetramethylammonium fluoride (TMAF) as a direct and selective methylating agent of a variety of amides, indoles, pyrroles, imidazoles, alcohols, and thiols. The method is characterized by operational simplicity, wide scope, and ease of purification. Our computational studies suggest a concerted methylation −deprotonation as the preferred reaction pathway.
Full control over multiple competing coupling sites would enable straightforward access to densely functionalized compound libraries. Historically, the site selection in Pd0‐catalyzed functionalizations of poly(pseudo)halogenated arenes has been unpredictable, being dependent on the employed catalyst, the reaction conditions, and the substrate itself. Building on our previous report of C−Br‐selective functionalization in the presence of C−OTf and C−Cl bonds, we herein complete the sequence and demonstrate the first general arylations and alkylations of C−OTf bonds (in <10 min), followed by functionalization of the C−Cl site (in <25 min), at room temperature using the same air‐ and moisture‐stable PdI dimer. This allowed the realization of the first general and triply selective sequential C−C coupling (in 2D and 3D space) of C−Br followed by C−OTf and then C−Cl bonds.
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