Carbon–Nitrogen Bond Formation Through Cross-Dehydrogenative Coupling Reactions

N-Alkylation of Amines by C1-C10 Aliphatic Alcohols Using A Well-Defined Ru(II)-Catalyst. A Metal-Ligand Cooperative Approach

A Ru(II)-catalyzed efficient and selective N-alkylation of amines by C1-C10 aliphatic alcohols is reported. The catalyst [Ru(L^1a)(PPh₃)Cl₂] (1a) bearing a tridentate redox-active azo-aromatic pincer, 2-((4-chlorophenyl)diazenyl)-1,10-phenanthroline (L^1a) is air-stable, easy to prepare, and showed wide functional group tolerance requiring only 1.0 mol % (for N-methylation and N-ethylation) and 0.1 mol % of catalyst loading for N-alkylation with C3-C10 alcohols. A wide array of N-methylated, N-ethylated, and N-alkylated amines were prepared in moderate to good yields via direct coupling of amines and alcohols. 1a efficiently catalyzes the N-alkylation of diamines selectively. It is even suitable for synthesizing N-alkylated diamines using (aliphatic) diols producing the tumor-active drug molecule MSX-122 in moderate yield. 1a showed excellent chemo-selectivity during the N-alkylation using oleyl alcohol and monoterpenoid β-citronellol. Control experiments and mechanistic investigations revealed that the 1a-catalyzed N-alkylation reactions proceed via a borrowing hydrogen transfer pathway where the hydrogen removed from the alcohol during the dehydrogenation step is stored in the ligand backbone of 1a, which in the subsequent steps transferred to the in situ formed imine intermediate to produce the N-alkylated amines.

TEMPO-Promoted Mono- and Bisimidation of Tertiary Anilines: Synthesis of Symmetric and Unsymmetric N-Mannich Bases

A TEMPO-promoted method was developed for the synthesis of symmetric bis-N-Mannich bases via sequential activation of two α,α'-amino C(sp³)-H bonds of N,N-dimethylanilines under mild conditions. This methodology was further extended for monoimidation of α-amino-functionalized methylanilines to give unsymmetric N-Mannich bases in good to high yields. Several control experiments were performed, and the coupling reaction outcomes indicated that the oxoammonium (TEMPO⁺) species is involved in the reaction.

CuII/H-USY as a regenerable bifunctional catalyst for the additive-free C–H amination of azoles

The use of the bifunctional Cu^II/H-USY catalyst for the direct amination of azoles under air and without additives has been disclosed.

Selective Reductive Elimination at Alkyl Palladium(IV) by Dissociative Ligand Ionization: Catalytic C(sp3 )-H Amination to Azetidines

A palladium(II)-catalyzed γ-C-H amination of cyclic alkyl amines to deliver highly substituted azetidines is reported. The use of a benziodoxole tosylate oxidant in combination with AgOAc was found to be crucial for controlling a selective reductive elimination pathway to the azetidines. The process is tolerant of a range of functional groups, including structural features derived from chiral α-amino alcohols, and leads to the diastereoselective formation of enantiopure azetidines.