Photocatalytic Generation of N‐Centered Hydrazonyl Radicals:  A Strategy for Hydroamination of β,γ‐Unsaturated Hydrazones

Abstract

A visible-light photocatalytic generation of N-centered hydrazonyl radicals has been accomplished for the first time. This approach allows efficient intramolecular addition of hydrazonyl radical to terminal alkenes, thus providing hydroamination and oxyamination products in good yields. Importantly, the protocol involves deprotonation of an N-H bond and photocatalytic oxidation to an N-centered radical, thus obviating the need to prepare photolabile amine precursors or the stoichiometric use of oxidizing reagents.

Light on Unsaturated Hydrocarbons – “Gotta Heterofunctionalize Them All”

“…Com- Scheme 5. The hydroamidation of benzamide derivatives reported by Chen. pared to those in their previous work, [17] the hydrazones can be substituted differently on the phenylsulfonyl ring (23). Aromatic and alkyl hydrazones were well tolerated, as shown in examples 20, 21, and 22.…”

“…[17] In their work, they were able to perform hydroamination reactions of sulfonohydrazone derivatives with pendant alkenes in an intramolecular fashion. Indeed, starting from readily synthesized sulfonohydrazone derivatives, they found that Ru(bpy) 3…”

“…This method presents good functional-group compatibilities and yields of up to 88 %, as shown in Scheme 3. Several N-tosylhydrazones can serve as efficient starting materials in this reaction such as alkyl tosylhydrazones (17), benzyl tosylhydrazones (18), or differently substituted phenyl tosylhydrazones (15, 16, and 19).…”

Olefin difunctionalizations via visible light photocatalysis

“…47 The reaction of allyl hydrazone with TEMPO was performed in the presence of Ru(bpy) 3 Cl 2 and sodium hydroxide to afford cyclic products in 56-95% yields. The N-centered radical could be generated through oxidation of nitrogen anion which is generated by deprotonation of the hydrazone.…”

Photocatalytic Dehydrogenative Cross‐Coupling of Alkenes with Alcohols or Azoles without External Oxidant

“…[5] Alkenes can also serve as redox compounds,and the resulting radical cations can be generated by removal of as ingle electron from an eutral parent compound. [5] Alkenes can also serve as redox compounds,and the resulting radical cations can be generated by removal of as ingle electron from an eutral parent compound.…”