- Electrochemical Umpolung C-H Functionalization of Oxindoles
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Herein, we present a general electrochemical method to access unsymmetrical 3,3-disubstituted oxindoles by direct C-H functionalization where the oxindole fragment behaves as an electrophile. This Umpolung approach does not rely on stoichiometric oxidants and proceeds under mild, environmentally benign conditions. Importantly, it enables the functionalization of these scaffolds through C-O, and by extension to C-C or even C-N bond formation.
- Pastor, Miryam,Vayer, Marie,Weinstabl, Harald,Maulide, Nuno
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p. 606 - 612
(2022/01/12)
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- Rapid Oxidation Indoles into 2-Oxindoles Mediated by PIFA in Combination with n-Bu4NCl ? H2O
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We report the development of a rapid approach for directly converting indoles into 2-oxindoles promoted by HOCl formed in situ from the combination of (bis(trifluoroacetoxy) iodo)benzene (PIFA) and n-Bu4NCl ? H2O. The procedure is widely functional group tolerant and provides 2-oxindoles in up to 95% yield within 5 min. The potential applications of the developed methodology are demonstrated by the gram-scale preparation of 3-methyl-2-oxindole (11 a), the one-pot two-step syntheses of spiro-oxindoles 26 a and 26 b, and the formal synthesis of (-)-folicanthine (2). (Figure presented.).
- Liang, Peng,Zhao, Hang,Zhou, Tingting,Zeng, Kaiyun,Jiao, Wei,Pan, Yang,Liu, Yazhou,Fang, Dongmei,Ma, Xiaofeng,Shao, Huawu
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supporting information
p. 3532 - 3538
(2021/06/09)
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- B(C6F5)3-Catalyzed Direct C3 Alkylation of Indoles and Oxindoles
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The direct C3 alkylation of indoles and oxindoles is a challenging transformation, and only a few direct methods exist. Utilizing the underexplored ability of triaryl boranes to mediate the heterolytic cleavage of α-nitrogen C-H bonds in amines, we have developed a catalytic approach for the direct C3 alkylation of a wide range of indoles and oxindoles using amine-based alkylating agents. We also employed this borane-catalyzed strategy in an alkylation-ring opening cascade.
- Basak, Shyam,Alvarez-Montoya, Ana,Winfrey, Laura,Melen, Rebecca L.,Morrill, Louis C.,Pulis, Alexander P.
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p. 4835 - 4840
(2020/04/22)
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- Palladacycle-Phosphine Catalyzed Methylation of Amines and Ketones Using Methanol
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Methylation of amines and ketones with palladacycle precatalyst has been performed using methanol as an environmentally benign reagent. Various ketones and amines undergo methylation reaction to yield monomethylated amines or ketones in moderate to good isolated yields. Moreover, this protocol was tested for the chemoselective methylation of 4-aminobenzenesulfonamide. The scope of the reaction was further extended to the deuteromethylation of ketones.
- Mamidala, Ramesh,Biswal, Priyabrata,Subramani, M. Siva,Samser, Shaikh,Venkatasubbaiah, Krishnan
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p. 10472 - 10480
(2019/08/20)
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- Iron-Catalyzed Methylation Using the Borrowing Hydrogen Approach
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A general iron-catalyzed methylation has been developed using methanol as a C1 building block. This borrowing hydrogen approach employs a Kn?lker-type (cyclopentadienone)iron carbonyl complex as catalyst (2 mol %) and exhibits a broad reaction scope. A variety of ketones, indoles, oxindoles, amines, and sulfonamides undergo mono- or dimethylation in excellent isolated yields (>60 examples, 79% average yield).
- Polidano, Kurt,Allen, Benjamin D. W.,Williams, Jonathan M. J.,Morrill, Louis C.
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p. 6440 - 6445
(2018/07/25)
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- Synthesis of indolones via radical cyclization of N-(2-halogenoalkanoyl)- substituted anilines
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The radical reactions of N-(2-halogenoalkanoyl)-substituted anilines (anilides) of type 1 have been investigated under various conditions. Treatment of compounds 1a-1o with Bu3SnH in the presence of (2,2′-azobis(isobutyronitrile) (AIBN) afforded a mixture of the indolones (oxindoles) 2a-2o and the reduction products 5a-5o (Table 1). In contrast, the N-unsubstituted anilides 1p-1s, 1u, and 1v gave the corresponding reduction products exclusively (Table 1). Similar results were obtained by treatment of 1 with Ni powder (Table 2) or wth Et3B (Table 3). Anilides with longer N-(phenylalkyl) chains such as 6 and 7 were inert towards radical cyclization, with the exception of N-benzyl-2-bromo-N,2-dimethylpropanamide (6b), which, upon treatment with Ni powder in i-PrOH, afforded the cyclized product 9b in low yield (Table 4). Upon irradiation, the extended anilides 6, 7, 10, and 11 yielded the corresponding dehydrobromination products exclusively (Table 5).
- Nishio, Takehiko,Iseki, Kyoko,Araki, Norihito,Miyazaki, Takenori
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- Photochemical reactions of N-(2-halogenoalkanoyl) derivatives of anilines
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The photochemical reactions of 2-substituted N-(2-halogenoalkanoyl) derivatives 1 of anilines and 5 of cyclic amines are described. Under irradiation, 2-bromo-2-methylpropananilides 1a-e undergo exclusively dehydrobromination to give N-aryl-2-methylprop-2-enamides (= methacrylanilides) 3a-e (Scheme 1 and Table 1). On irradiation of N-alkyl- and N-phenyl-substituted 2-bromo-2-methylpropananilides 1f-m, cyclization products, i.e. 1,3-dihydro-2H-indol-2-ones (= oxindoles) 2f-m and 3,4- dihydroquinolin-2(1H)-ones (= dihydrocarbostyrils) 4f-m, are obtained, besides 3f-m. On the other hand, irradiation of N-methyl-substituted 2- chloro-2-phenylacetanilides 1o-q and 2-chloroacetanilide 1r gives oxindoles 2o-r as the sole product, but in low yields (Scheme 3 and Table 2). The photocyclization of the corresponding N-phenyl derivatives 1s-v to oxindoles 2s-v proceeds smoothly. A plausible mechanism for the formation of the photoproducts is proposed (Scheme 4). Irradiation of N-(2-halogenoalkanoyl) derivatives of cyclic amines 5a-c yields the cyclization products, i.e. five- membered lactams 6a, b, and/or dehydrohalogenation products 7a,c and their cyclization products 8a,c, depending on the ring size of the amines (Scheme 5 and Table 3).
- Nishio, Takehiko,Asai, Hidenori,Miyazaki, Takenori
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p. 1475 - 1483
(2007/10/03)
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- Reactions of Diarylnitrenium Ions with Electron Rich Alkenes: An Experimental and Theoretical Study
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Photolysis of N-(diphenylamino)-2,4,6-trimethylpyridinium tetrafluoroborate (1a) and N-[bis(4-methylphenyl)amino]-2,4,6-trimethylpyridinium salt (1b) gives products attributable to diarylnitrenium ion (Ar2N+, 2). The major products of these reactions include products from nucleophilic addition of various π-nucleophiles (e.g. electron rich alkenes) to the ortho and para positions of one of the phenyl rings. Nanosecond and EPR spectroscopy show that radicals also form. These radicals are thought to give rise to the diarylamines isolated as minor products from the photolysis of la and 1b. In addition to the para addition products and Ph2NH, N-phenylindoles and N-phenylindolinones are isolated when silyl enol ethers and silyl ketene acetals are used as trapping agents, respectively. The indoles and indolinones are generated from initial addition of the nucleophile to the ortho position on 2 followed by cyclization of the resulting intermediate. A product resulting from N addition of the nucleophile to 2 is isolated only when silyl ketene acetals are used. A number of electronic sturcture calculations at different levels of molecular orbital and density functional theory were carried out on Ph2N+. There do not seem to be effects associated with either the charge distribution or the LUMO that would strongly influence ortho/para/N selectivity in nucleophilic trapping. Laser flash photolysis on la provides absolute rate constants for the nucleophilic addition of various alkenes to Ph2N+. These fall in the range of 109-1010 M-1 s-1 and correlate with the oxidation potential of the alkene. From these data it is clear that the more easily oxidized the alkene the faster it will react with Ph2N+.
- Moran, Ricardo J.,Cramer, Christopher,Falvey, Daniel E.
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p. 2742 - 2751
(2007/10/03)
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- β-carboline derivative
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Disclosed are β-carboline derivatives represented by the formula: STR1 wherein R1 represents hydrogen atom, a lower alkyl group, a lower alkoxy group or hydroxy group; R5 represents hydrogen atom, or R1 and R5 a
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- Ring expansion of benzocyclic ketones via transient alkoxyl radicals: The side chain incorporation approach
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Radical cyclisation onto carbonyl groups followed by β-sission of the resulting alkoxy radicals provides a method for the one-carbon ring expansion of benzocyclic ketones. The radicals are generated by Bu3SnH reduction of bromomethyl moieties α
- Bowman, W. Russell,Westlake, Paul J.
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p. 4027 - 4038
(2007/10/02)
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