Primary aliphatic amines are important building blocks in organic synthesis due to the presence of a synthetically versatile NH2 group. N-functionalization of primary amines is well established, but selective C-functionalization of unprotected primary amines remains challenging. Here, we report the use of CO2 as an activator for the direct transformation of abundant primary aliphatic amines into valuable γ-lactams under photoredox and hydrogen atom transfer (HAT) catalysis. Experimental and computational studies suggest that CO2 not only inhibits undesired N-alkylation of primary amines, but also promotes selective intermolecular HAT by an electrostatically accelerated interaction between the in situ-generated negatively charged carbamate and the positively charged quinuclidinium radical. This electrostatic attraction overwhelms the inherent bond dissociation energies which suggest that HAT should occur unselectively. We anticipate that our findings will open up new avenues for amine functionalizations as well as selectivity control in HAT reactions.

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Direct α-alkylation of primary aliphatic amines enabled by CO 2 and electrostatics

A practical, catalytic entry to α,α,α-trisubstituted (α-tertiary) primary amines by C-H functionalisation has long been recognised as a critical gap in the synthetic toolbox. We report a simple and scalable solution to this problem that does not require any in situ protection of the amino group and proceeds with 100 % atom-economy. Our strategy, which uses an organic photocatalyst in combination with azide ion as a hydrogen atom transfer (HAT) catalyst, provides a direct synthesis of α-tertiary amines, or their corresponding γ-lactams. We anticipate that this methodology will inspire new retrosynthetic disconnections for substituted amine derivatives in organic synthesis, and particularly for challenging α-tertiary primary amines.

https://onlinelibrary.wiley.com/doi/epdf/10.1002/anie.202005294

Photocatalytic α‐Tertiary Amine Synthesis via C−H Alkylation of Unmasked Primary Amines

Regio- and Stereoselective Synthesis of Unsaturated Carbonyl Compounds Based on Ceric Ammonium Nitrate-Promoted Oxidative Addition of Trimethylsilyl Enol Ethers to Conjugated Dienes

We report the results of pump–probe optical Kerr effect (OKE) experiments performed on neat solutions of carbon tetrachloride, nitrobenzene, methyl methacrylate monomer, binary solutions of the squaraine dye indole squarylium, and the phthalocyanine dye silicon phthalocyanine-monomethacrylate, respectively, in carbon tetrachloride, and solid solutions of indole squarylium and phthalocyanine-monomethacrylate in poly(methyl methacrylate). Dispersion measurements of the dye solutions were performed in the visible one-photon resonant region of the dyes defined by their linear-absorption spectra. The dyes’ third-order molecular susceptibility response γxxxx(-ω2;ω1,-ω1, ω2) in this spectral region is markedly different, with R{γISQ}>0 and R{γSiPc}<0. Analysis of the dyes’ OKE response requires the inclusion of high-lying two-photon states and suggests that a purely electronic mechanism dominates their OKE response. The results are used to calculate the dyes’ off-resonant third-order molecular susceptibilities, which are well within the limits predicted by the Thomas–Reiche–Kuhn sum rule [
	 M. G.
	 Kuzyk
	 
	, Opt. Lett.25, 1183–1185 (2000)].

Absolute molecular optical Kerr effect spectroscopy of dilute organic solutions and neat organic liquids

Stereoselective Synthesis of (2S, 8S)‐2‐Benzyl Hexahydro‐pyrrodizin‐3‐one Starting from (L)‐Proline Based on Stereoselective Benzylation

Photocatalyzed Multiple Additions of Amines to α,β- Unsaturated Esters and Nitriles.

Photochemistry of Squaraine Dyes. Part 5. Aggregation of Bis(2,4- dihydroxyphenyl)squaraine (Ia) and Bis(2,4,6-trihydroxyphenyl) squaraine (Ib) and Their Photodissociation in Acetonitrile Solutions.

K. G. Thomas

Papers

Photocatalyzed Multiple Additions of Amines to α,β- Unsaturated Esters and Nitriles.

Photochemistry of Squaraine Dyes. Part 5. Aggregation of Bis(2,4- dihydroxyphenyl)squaraine (Ia) and Bis(2,4,6-trihydroxyphenyl) squaraine (Ib) and Their Photodissociation in Acetonitrile Solutions.

Photochemistry of Squaraine Dyes. Part 6. Solvent Hydrogen Bonding Effects on the Photophysical Properties of Bis(benzothiazolylidene) squaraines.