Photoreactions of 4-(Tribromomethyl)-4-methyl-2,5-cyclohexadienone and Its Derivatives with Amines:  Radical Cyclization and Ring Expansion Reactions Promoted through Photoinduced Electron Transfer Processes

Hasegawa, Eietsu; Tamura, Y.; Suzuki, Kimihito; Yoneoka, and Akira; Suzuki, Toshio

doi:10.1021/jo990215v

Cited by 15 publications

(2 citation statements)

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“…Stereoselective synthesis of various types of heterocyclic compounds and ring expansion by reactions promoted through photoinduced SET by amines were also reported by the J. Cossy laboratory, E. Hasegawa laboratory, and Mattay laboratory. These reactions have been reviewed by J. Cossy. ,, …”

Section: Reductive Chemistrymentioning

confidence: 99%

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Single Electron Transfer in Radical Ion and Radical-Mediated Organic, Materials and Polymer Synthesis

et al. 2014

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Section: Reductive Chemistrymentioning

confidence: 99%

“…These reactions have been reviewed by J. Cossy. 776,780,781 3.5.2.2. Thermal-Induced Cyclization Reactions Mediated by Amine Donors.…”

Section: Thermal-and Photoinduced Set Mediated By Amine Donorsmentioning

confidence: 99%

Single Electron Transfer in Radical Ion and Radical-Mediated Organic, Materials and Polymer Synthesis

et al. 2014

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Synthesis of 3‐Aminotropones from N‐Boc‐Protected Furan‐2‐amine (=tert‐Butyl Furan‐2‐ylcarbamate; Boc=(tert‐Butoxy)carbonyl) by Cycloaddition Reactions and Subsequent Rearrangement

Montaña

Barcia

Kociok‐Köhn

et al. 2008

Helvetica Chimica Acta

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In memoriam Professor Xavier SolansThe 3-aminotropones (¼ 3-aminocyclohepta-2,4,6-trien-1-ones) 4 were prepared in two steps by i) a [4 þ 3] cycloaddition reaction between a conveniently substituted a,a'-dihalo ketone 1 and a furan-2amine derivative 2 functionalized at C(2) by a protected amino group (! 3), and ii) a base-induced molecular rearrangement of the cycloadduct 3 via cleavage of the O-bridge. A mechanism for the formation of 3-aminotropones is proposed on the basis of the initial deprotonation of the [(tertbutoxy)carbonyl]amino (BocNH) group of 3, followed by O-bridge opening, an acid -base equilibrium, and finally an alkoxyaluminate elimination to afford the conjugated stable troponoid system (Scheme 7).2. Results and Discussion. -Here, a versatile and short synthesis of 2-and/or 7substituted 3-aminotropones 4 is reported. Our synthetic methodology consists of only two steps: i) a [4 þ 3] cycloaddition reaction between an a,a'-dihalo ketone 1 and a furan derivative 2, functionalized at C(2) by a protected amino group, and ii) a rearrangement of the cycloadduct 3, via cleavage of the O-bridge, under basic conditions (Scheme 2) [23]. 2.1. [4 þ 3] Cycloaddition Reaction. The cycloadducts 3a -d were obtained by a [4 þ 3] cycloaddition reaction [24] between N-[(tert-butoxy)carbonyl]-protected furan-2amine 2 and an oxyallyl cation, generated in situ from a,a'-dibromo ketones 1a -d and a reducing metal (M 0 ) [25]. The halo ketones 1a -d were prepared in one step and in moderate to good yields from the corresponding commercial ketones, by bromination under PBr 3 catalysis [24a] [25a]. Aminated furan 2 was easily obtained in excellent yield from furan-2-carbonyl chloride and sodium azide in tert-butyl alcohol via a Curtius rearrangement [26]. The oxabicycles 3a -d were readily available in diastereoisomerically pure form from 1a -d and 2 after flash column chromatography [27]. 2.1.1. [4 þ 3] Cycloaddition Reaction Optimization. The [4 þ 3] cycloaddition reaction between 1a and 2 (Scheme 3) was broadly studied to optimize the reaction conditions and to improve the yield, the workup, and the isolation and purification processes of the products (see Table 1). Thus, it turned out that for the evaluated substrates, the highest yield was obtained by using [Fe 2 (CO) 9 ] as reducing agent in anhydrous MeCN (Entry 12). The reduction of a,a'-dihalo ketones with [Fe 2 (CO) 9 ] generates highly electrophilic oxyallyl cations due to the more or less covalent nature of the OÀFe bond (of the iron enolatoiron moiety). Since the bonding electron pair of the enolato O-atom is mostly localized in the covalent OÀFe bond, its contribution to the resonance stabilization of the positive charge of the oxyallyl cation is low, making it more electrophilic (reactive) for the capture by an electron-rich diene [24d]. When using a reducing metal or a metallic pair, except for [Fe 2 (CO) 9 ], the presence of NaI improved the reaction yields, due to the intermediate generation of diiodo ketones, which are formed in situ from dibromo ketone...

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Photoinduced electron-transfer reaction of α-bromomethyl-substituted benzocyclic β-keto esters with amines: selective reaction pathways depending on the nature of the amine radical cations

et al. 2012

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Photoreactions of 4-(Tribromomethyl)-4-methyl-2,5-cyclohexadienone and Its Derivatives with Amines: Radical Cyclization and Ring Expansion Reactions Promoted through Photoinduced Electron Transfer Processes

Cited by 15 publications

References 31 publications

Single Electron Transfer in Radical Ion and Radical-Mediated Organic, Materials and Polymer Synthesis

Single Electron Transfer in Radical Ion and Radical-Mediated Organic, Materials and Polymer Synthesis

Synthesis of 3‐Aminotropones from N‐Boc‐Protected Furan‐2‐amine (=tert‐Butyl Furan‐2‐ylcarbamate; Boc=(tert‐Butoxy)carbonyl) by Cycloaddition Reactions and Subsequent Rearrangement

Photoinduced electron-transfer reaction of α-bromomethyl-substituted benzocyclic β-keto esters with amines: selective reaction pathways depending on the nature of the amine radical cations

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