Tert-Butyl Nitrite-initiated C-N Bond Cleavage of 1-Nitromethyl-N-aryltetrahydroisoquinolines: Synthesis of Furoxans with N-NO Skeleton

A series of furoxan derivatives with N-nitroso groups were synthesized in good yields by TBN initiated radical sp³ C-N bond cleavage of 1-nitromethyl-N-aryltetrahydroisoquinolines. This reaction grafts the biologically important furoxan skeleton and N-nitroso group into on molecule, greatly improving the molecular complexity in one step transformation. The mechanistic study shows that this reaction is mediated by the in situ generated α-carbonyl nitrile oxide, which is afforded by TBN promoted C-N bond cleavage.

Selective C(sp3 )-N Bond Cleavage of N,N-Dialkyl Tertiary Amines with the Loss of a Large Alkyl Group via an SN 1 Pathway

Polar disconnection of the C(sp³ )-N bond of N,N-dialkyl-substituted tertiary amines via ammonium species conventionally favored the loss of the smaller alkyl group by an S_N 2 displacement, while selective C(sp³ )-N bond cleavage by cutting off the larger alkyl group is still underdeveloped. Herein, we present a novel Pd⁰ -catalyzed [2+2+1] annulation, proceeding through an alkyne-directed palladacycle formation and consecutive diamination with a tertiary hydroxylamine by cleaving its N-O bond and one C(sp³ )-N bond, for the rapid assembly of tricyclic indoles in a single-step transformation. Noteworthy, experimental results indicated that large tert-butyl and benzyl groups were selectively cleaved via an S_N 1 pathway, in the presence of a smaller alkyl group (Me, Et, ⁱ Pr). Under the guidance of this new finding, tricyclic indoles bearing a removable alkyl group could be exclusively obtained by using a (α-methyl)benzyl/benzyl or tert-butyl/2-(methoxycarbonyl)ethyl mixed amino source.

N-Atom Deletion in Nitrogen Heterocycles

Excising the nitrogen in secondary amines, and coupling the two residual fragments is a skeletal editing strategy that can be used to construct molecules with new skeletons, but which has been largely unexplored. Here we report a versatile method of N-atom excision from N-heterocycles. The process uses readily available N-heterocycles as substrates, and proceeds by N-sulfonylazidonation followed by the rearrangement of sulfamoyl azide intermediates, providing various cyclic products. Examples are provided of deletion of nitrogen from natural products, synthesis of chiral O-heterocycles from commercially available chiral β-amino alcohols, formal inert C-H functionalization through a sequence of N-directed C-H functionalization and N-atom deletion reactions in which the N-atom can serve as a traceless directing group.

Recent Advances in the Pd-Catalyzed Coupling of Arylhydrazines and Ammonium Salts via C-N Bond Cleavage

Both arylhydrazines and quaternary ammonium salts are readily accessible or commercially available chemicals that show versatile reactivity in Pd-catalyzed coupling reactions via C-N bond cleavage. A tremendous array of coupling reactions involving reaction partners such as organoborons, aryl silanes, alkenes, alkynes, arylation or alkylation reagents in C-H functionalization and carbonylation reactions are summarized, in which arylhydrazines or quaternary ammonium salts function as aryl or alkyl donors. This account mainly focuses on recent advances in Pd-catalyzed coupling reactions with arylhydrazines or quaternary ammonium salts via C-N bond cleavage, including mechanistic elucidations.

Photoinduced C(sp3 )-N Bond Cleavage Leading to the Stereoselective Syntheses of Alkenes

Herein we report a versatile Mizoroki-Heck-type photoinduced C(sp³ )-N bond cleavage reaction. Under visible-light irradiation (455 nm, blue LEDs) at room temperature, alkyl Katritzky salts react smoothly with alkenes in a 1:1 molar ratio in the presence of 1.0 mol % of commercially available photoredox catalyst without the need for any base, affording the corresponding alkyl-substituted alkenes in good yields with broad functional-group compatibility. Notably, the E/Z-selectivity of the alkene products can be controlled by an appropriate choice of photoredox catalyst.

Organozinc-Mediated Direct C-C Bond Formation via C-N Bond Cleavage of Ammonium Salts

We report a direct cross-coupling reaction between diarylzinc (Ar₂ Zn) and aryltrimethylammonium salts (ArNMe₃⁺ ⋅^- OTf) in the presence of LiCl, via C-N bond cleavage. The reaction takes place smoothly upon heating in THF without any external catalyst, enabling an efficient and chemoselective formation of biaryl products. Mechanistic studies indicate that the reaction proceeds through a single electron transfer route.