Deoxygenation of nitro and nitrosoaromatics by photolysis with t‐BuHgl/Kl. Regiochemistry of tert‐Butyl radical addition to nitrosoaromatics [1]

Glen A. Russell, Ching‐Fa ‐F Yao

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Abstract

Photolysis of nitroaromatics in the presence of t‐BuHgI/KI in Me2SO or DMF leads to products formed by t‐Bu addition to the nitroso compounds. Similar products are formed in the dark in the presence of K2S2O8. Nitroso or nitrobenzene is converted into N,O‐di‐tert‐butylphenylhydroxylamine by a process involving N‐tert‐butylphenylhydroxylamine as an intermediate. In the presence of PTSA and KI, N‐tert‐butylphenylhydroxylamine predominates in Me2SO, but in DMF, the phenylhydroxylamine is reduced to N‐tert‐butylaniline. In a similar fashion, o‐nitrosotoluene is converted into o‐MeC6H4N(Bu‐t)OBu‐t, o‐MeC6H4N(Bu‐t)OH, and o‐MeC6H4NHBu‐t. p‐Nitroso‐N,N‐dimethylaniline forms the N,O‐di‐tert‐butylated derivative in the absence of acid but in the presence of PTSA/KI yields p‐Me2NC6H4NHBu‐t. Excellent yields of the N,O‐di‐tert‐butylated arylhydroxylamines are formed in DMF from the nitroaromatics with para Me2N, OH, I, Br, Cl, and ortho Ph or PhNH substituents. Nitrobenzenes with p‐CHO, p‐PhCO, or p‐CN substituents are deoxygenated to the nitroso compounds which react with t‐Bu to form the tert‐butoxyamino radicals (ArṄOBu‐t). In Me2SO, the amino radicals react to form ArN(HgI)OBu‐t compounds which condense with the nitroso compounds to yield the azoxy compounds. With the p‐CN substituent, the azoxy compound is subsequently deoxygenated and tert‐butylated to yield p‐NCC6H4N(Bu‐t)NHC6H4CN‐p. In the presence of PTSA/KI, the amino radicals are reduced to p‐Y‐ArNHOBu‐t (Y = PhCO, CN). The compounds Y‐ArN(Bu‐t)OBu‐t undergo photochemical degradation to yield Y‐ArNHBu‐t with Y = p‐PhCO or p‐CN in a reaction that is inhibited by I. With PTSA/H2O/KI in Me2SO, p‐Me2NC6H4N(t‐Bu)OBu‐t is converted into 4‐(N‐tert‐butylimino)‐2,5‐cyclohexadien‐1‐one, p‐Me2NC6H4NHBu‐t, and p‐tert‐butylamino‐m‐tert‐butoxy‐N,N‐dimethylaniline. o‐MeC6H4N(Bu‐t)OH reacts with PTSA/KI to form o‐MeC6H4N(Bu‐t)H in DMF or a mixture of the aniline and 4‐(N‐tert‐butylimino)‐3‐methyl‐2,5‐cyclohexadien‐1‐one in Me2SO. In the absence of KI, only the cyclohexadienone is formed in Me2SO.

Original languageEnglish
Pages (from-to)433-444
Number of pages12
JournalHeteroatom Chemistry
Volume4
Issue number5
DOIs
Publication statusPublished - 1993 Oct

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ASJC Scopus subject areas

  • Chemistry(all)

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