993-22-6Relevant articles and documents
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Moss,R.A.,Schueler,P.E.
, p. 5792 - 5798 (1974)
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Photocatalytic Hydroaminoalkylation of Styrenes with Unprotected Primary Alkylamines
Askey, Hannah E.,Grayson, James D.,Tibbetts, Joshua D.,Turner-Dore, Jacob C.,Holmes, Jake M.,Kociok-Kohn, Gabriele,Wrigley, Gail L.,Cresswell, Alexander J.
supporting information, p. 15936 - 15945 (2021/10/12)
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 itsin vivoactive form (by iterative α-C-H functionalization of ethanolamine). The reaction can also be sequenced with an intramolecularN-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.
The challenge of palladium-catalyzed aromatic azidocarbonylation: From mechanistic and catalyst deactivation studies to a highly efficient process
Miloserdov, Fedor M.,McMullin, Claire L.,Belmonte, Marta Martinez,Benet-Buchholz, Jordi,Bakhmutov, Vladimir I.,Macgregor, Stuart A.,Grushin, Vladimir V.
supporting information, p. 736 - 752 (2014/03/21)
Azidocarbonylation of iodoarenes with CO and NaN3, a novel Heck-type carbonylation reaction, readily occurs in an organic solvent-H 2O biphasic system to furnish aroyl azides at room temperature and 1 atm. The reaction is catalyzed by Xantphos-Pd and exhibits high functional group tolerance. The catalyst deactivation product, [(Xantphos)PdI2], can be reduced in situ with PMHS to Pd(0) to regain catalytic activity. In this way, the catalyst loading has been lowered to 0.2% without any losses in selectivity at nearly 100% conversion to synthesize a series of aroyl azides in 80-90% isolated yield on a gram scale. Alternatively, the ArCON3 product can be used without isolation for further transformations in situ, e.g., to isocyanates, ureas, benzamides, and iminophosphoranes. A detailed experimental and computational study has identified two main reaction pathways for the reaction. For both routes, Ar-I oxidative addition to Pd(0) is the rate-determining step. In the presence of CO in excess, the Ar-I bond is activated by the less electron-rich Pd center of a mixed carbonyl phosphine complex. Under CO-deficient conditions, a slightly lower energy barrier pathway is followed that involves Ar-I oxidative addition to a more reactive carbonyl-free (Xantphos)Pd0 species. Mass transfer in the triphasic liquid-liquid-gas system employed for the reaction plays an important role in the competition between these two reaction channels, uniformly leading to a common aroyl azido intermediate that undergoes exceedingly facile ArCO-N 3 reductive elimination. Safety aspects of the method have been investigated.
