Catalytic, intermolecular
hydroaminoalkylation (HAA) of styrenes
provides a powerful disconnection for pharmacologically relevant γ-arylamines,
but current methods cannot utilize unprotected primary alkylamines
as feedstocks. Metal-catalyzed HAA protocols are also highly sensitive
to α-substitution on the amine partner, and no catalytic solutions
exist for α-tertiary γ-arylamine synthesis via this
approach. We report a solution to these problems using organophotoredox
catalysis, enabling a direct, modular, and sustainable preparation
of α-(di)substituted γ-arylamines, including challenging
electron-neutral and moderately electron-rich aryl groups. A broad
range of functionalities are tolerated, and the reactions can be run
on multigram scale in continuous flow. The method is applied to a
concise, protecting-group-free synthesis of the blockbuster drug Fingolimod,
as well as a phosphonate mimic of its
in vivo
active
form (by iterative α-C–H functionalization of ethanolamine).
The reaction can also be sequenced with an intramolecular
N
-arylation to provide a general and modular access to valuable
(spirocyclic) 1,2,3,4-tetrahydroquinolines and 1,2,3,4-tetrahydronaphthyridines.
Mechanistic and kinetic studies support an irreversible hydrogen atom
transfer activation of the alkylamine by the azidyl radical
and some contribution from a radical chain. The reaction is photon-limited
and exhibits a zero-order dependence on amine, azide, and photocatalyst,
with a first-order dependence on styrene.
We report a Chan–Lam
coupling reaction of benzylic and allylic
boronic esters with primary and secondary anilines to form valuable
alkyl amine products. Both secondary and tertiary boronic esters can
be used as coupling partners, with mono-alkylation of the aniline
occurring selectively. This is a rare example of a transition-metal-mediated
transformation of a tertiary alkylboron reagent. Initial investigation
into the reaction mechanism suggests that transmetalation from B to
Cu occurs through a single-electron, rather than a two-electron process.
A new approach combining virtual screening, 19F and STD NMR, and biochemical assays using hiPSC and targetting multiple pathways involving Aβ, PrPC and Tau provides a more effective strategy for Alzheimer's disease drug discovery than Aβ only approach.
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