Palladium-Catalyzed Synthesis of 1-Azaazulenes from Cycloheptatrienylmethyl Ketone <i>O</i>-Pentafluorobenzoyl Oximes

Kitamura, Masaya; Chiba, Shunsuke; Saku, Osamu; Narasaka, Koichi

doi:10.1246/cl.2002.606

“…To further illustrate this point, regiochemically pure 7‐isopropyl‐2,4‐dimethylazulene ( 15 )18a (a naturally occurring isomer of guaiazulene ( 2 )),15b 1‐chloro‐3‐methylazulene ( 16 a ),18b and the phenylazulenes 16 b 18c and 16 c 18d have also been efficiently prepared, thereby demonstrating four distinctly different substitution options as well. Finally, acetoxy and aza derivatives 17 a 18e and 17 b 18f are examples of novel azulenes that are readily prepared with this methodology.…”

Section: Methodsmentioning

confidence: 99%

Approach to the Blues: A Highly Flexible Route to the Azulenes

Carret

¹

,

Blanc

²

,

Coquerel

³

et al. 2005

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“…[41] Particularly, in the presence of nBu 4 NCl, the pyridine was obtained as a major product. [44] This amino-Heck reaction could be applied to prepare a wide range of heterocycles. Scheme 14. Isoquinolines were prepared by the 6-exo cyclization of O-allyl acetophenone oxime derivatives (Scheme 15).…”

Section: Radical Cyclizationmentioning

confidence: 99%

Amination with Oximes

Narasaka

¹

,

Kitamura

²

2005

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The SN2 reaction has been well recognized not to occur at sp2 carbons, while such an SN2‐type substitution reaction was found to proceed readily at the sp2 nitrogen of oximes. Ab initio MP2 calculations show that the activation energy of the nucleophilic substitution at sp2 nitrogen is almost same as that of the Beckmann rearrangement. By the intramolecular SN2‐type reaction at the oxime nitrogen, various aza‐arenes and cyclic imines, such as quinolines, aza‐spiro compounds, and dihydropyrroles, can be synthesized. Intermolecular substitution of oximes with organometallic reagents also proceeds, and electrophilic amination of Grignard reagents is accomplished by the use of 4,4,5,5‐tetramethyl‐1,3‐dioxolan‐2‐one O‐(phenylsulfonyl)oxime. Anion radicals generated by one‐electron reduction of oxime derivatives act as iminyl radical equivalents. That is, the intramolecular C–N bond formation of γ,δ‐unsaturated or β‐aryl oximes is induced by a single electron transfer to give various pyrroles, quinolines, and carbolines, in which phenols, hydroquinones, or copper reagents can be used as electron donors. A photo‐induced radical process is also applied to the transformation of γ,δ‐unsaturated oximes to dihydropyrroles. Oxidative addition of oximes to palladium(0) complexes generates alkylideneaminopalladium(II) species, which are utilized as key intermediates in carbon–nitrogen bond formation. Various aza‐heterocycles, including pyrroles, pyridines, isoquinolines, spiroimines, and aza‐azulenes, are synthesized from O‐(pentafluorobenzoyl)oximes having olefinic moieties via the intramolecular Heck‐type reaction (amino‐Heck reaction) by treatment with a catalytic amount of a Pd0 complex. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

show abstract

“…To further illustrate this point, regiochemically pure 7‐isopropyl‐2,4‐dimethylazulene ( 15 )18a (a naturally occurring isomer of guaiazulene ( 2 )),15b 1‐chloro‐3‐methylazulene ( 16 a ),18b and the phenylazulenes 16 b 18c and 16 c 18d have also been efficiently prepared, thereby demonstrating four distinctly different substitution options as well. Finally, acetoxy and aza derivatives 17 a 18e and 17 b 18f are examples of novel azulenes that are readily prepared with this methodology.…”

Section: Methodsmentioning

confidence: 99%