- Site-selective monotitanation of dialkynylpyridines and its application for preparation of highly fluorescent π-conjugated oligomers
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(Chemical Equation Presented) Reaction of Ti(O-i-Pr)4/2i-PrMgCl reagent with 2,n-bis[(trimethylsilyl)ethynyl]pyridines, where n is 3, 4, 5, and 6, or with 3,4-bis[(trimethylsilyl)-ethynyl]pyridines, proceeded with excellent site-selectivity to afford the corresponding monotitanated complex. Synthetic application of the reaction was demonstrated by an efficient preparation of π-conjugated oligomers having pyridine and enyne units alternately, which possess intense blue fluorescence emission.
- Takayama, Yuuki,Hanazawa, Takeshi,Andou, Tomohiro,Muraoka, Kenji,Ohtani, Hiroyuki,Takahashi, Mizuki,Sato, Fumie
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- Synthesis of "acetylene-expanded" tridentate ligands
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Synthetic routes to four new tridentate ligands with large cavities have been developed. Each ligand features two halides at the termini of the molecules that could be used for further elaboration of the system. Such compounds are ideal for encapsulating organoiodide guests using charge-transfer interactions.
- Holmes, Brian T.,Pennington, William T.,Hanks
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- Deprotonative metalation of chloro- and bromopyridines using amido-based bimetallic species and regioselectivity-computed CH acidity relationships
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A series of chloro- and bromopyridines have been deprotometalated by using a range of 2,2,6,6-tetramethylpiperidino-based mixed lithium-metal combinations. Whereas lithium-zinc and lithium-cadmium bases afforded different mono- and diiodides after subsequent interception with iodine, complete regioselectivities were observed with the corresponding lithium-copper combination, as demonstrated by subsequent trapping with benzoyl chlorides. The obtained selectivities have been discussed in light of the CH acidities of the substrates, determined both in the gas phase and as a solution in THF by using the DFT B3LYP method.
- Snegaroff, Katia,Nguyen, Tan Tai,Marquise, Nada,Halauko, Yury S.,Harford, Philip J.,Roisnel, Thierry,Matulis, Vadim E.,Ivashkevich, Oleg A.,Chevallier, Floris,Wheatley, Andrew E. H.,Gros, Philippe C.,Mongin, Florence
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experimental part
p. 13284 - 13297
(2012/02/03)
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- Homoleptic zincate-promoted room-temperature halogen-metal exchange of bromopyridines
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Homoleptic lithium tri- and tetraalkyl zincates were reacted with a set of bromopyridines. Efficient and chemoselective bromine-metal exchanges were realized at room temperature with a substoichiometric amount of nBu 4ZnLi2·TMEDA reagent (1/3 equiv; TMEDA=N,N,N′,N′-tetramethylethylenediamine). This reactivity contrasted with that of tBu4ZnLi2·TMEDA, which was inefficient below one equivalent. DFT calculations allowed us to rationalize the formation of N...Li stabilized polypyridyl zincates in the reaction. The one-pot difunctionalization of dibromopyridines was also realized using the reagent stoichiometrically. The direct creation of C-Zn bonds in bromopyridines enabled us to perform efficient Negishi-type cross-couplings. Mild zincation! nBu4ZnLi2·TMEDA (in substoichiometric amounts) promoted efficient and chemoselective room-temperature bromine-metal exchange of a range of bromopyridines (see scheme). DFT calculations strongly supported the formation of a stabilized tripyridylzincate, which could be reacted with electrophiles or be directly involved in palladium-catalyzed cross-coupling reactions.
- Chau, Nguyet Trang Thanh,Meyer, Maxime,Komagawa, Shinsuke,Chevallier, Floris,Fort, Yves,Uchiyama, Masanobu,Mongin, Florence,Gros, Philippe C.
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experimental part
p. 12425 - 12433
(2011/01/05)
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- Shape-persistent cyclyne-type azamacrocycles: Synthesis, unusual light-emitting characteristics, and specific recognition of the Sb(V) ion
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Simple members of arene-azaarenecyclynes as a novel family of geometrically-controlled and shape-persistent azamacrocycles have been synthesized. Noteworthy is the specific recognition function for Sb(V). The synthesized azamacrocycles, in particular the
- Kobayashi, Shigeya,Yamaguchi, Yoshihiro,Wakamiya, Tateaki,Matsubara, Yoshio,Sugimoto, Kunihisa,Yoshida, Zen-Ichi
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p. 1469 - 1472
(2007/10/03)
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- Regiocontrolled deprotonative-zincation of bromopyridines using aminozincates
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Regiochemistry in the deprotonation of bromopyridines was found to be greatly influenced by the choice of metal amide base, and DA-zincate and TMP-zincate turned out to be excellent complementary practical agents for regioselective metalation of bromopyri
- Imahori,Uchiyama,Sakamoto,Kondo
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p. 2450 - 2451
(2007/10/03)
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- New syntheses of substituted pyridines via bromine-magnesium exchange
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Bromine-magnesium exchange using iPrMgCl in THF at room temperature on 2-, 3- and 4-bromopyridines allowed the synthesis of various functionalized pyridines. The methodology was successfully used for the synthesis of 4- azaxanthone. Moreover, single exchange reactions observed on 2,6-, 3,5-, 2,3- and 2,5-dibromopyridines, with complete regioselectivity in the case of 2,3- and 2,5-dibromopyridines, afforded substituted bromopyridines, which were then involved in a second exchange step to provide difunctionalized pyridines. (C) 2000 Elsevier Science Ltd.
- Trécourt, Fran?ois,Breton, Gilles,Bonnet, Véronique,Mongin, Florence,Marsais, Francis,Quéguiner, Guy
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p. 1349 - 1360
(2007/10/03)
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- Pyridylmagnesium chlorides from bromo and dibromopyridines by bromine- magnesium exchange: A convenient access to functionalized pyridines
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Various bromopyridines were converted to the corresponding pyridylmagnesium chlorides at room temperature by treatment with iPrMgCl. The resulting Grignard reagents were quenched by various electrophiles to afford functionalized pyridines. The bromine-magnesium exchange of some dibromopyridines was also studied.
- Trecourt, Francois,Breton, Gilles,Bonnet, Veronique,Mongin, Florence,Marsais, Francis,Queguiner, Guy
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p. 4339 - 4342
(2007/10/03)
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