- Addition of silyl enol ethers to imidazoles and thiazoles in the presence of alkyl chloroformate
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Various kinds of silyl enol ethers and ketene silyl acetals react with imidazole, thiazole and their benzo-derivatives in the presence of an alkyl chloroformate to give 2-substituted imidazolines and thiazolines in good yields.
- Itoh, Takashi,Miyazaki, Michiko,Hasegawa, Hiroshi,Nagata, Kazuhiro,Ohsawa, Akio
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- Addition reaction of imidazoles and thiazoles with silyl enol ethers in the presence of alkyl chloroformate
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Silyl enol ethers and ketene silyl acetals reacted with imidazole, thiazole, and their benzo derivatives in the presence of an alkyl chloroformate to give 2-substituted imidazolines and thiazolines in good yields via the intermediacy of unstable N-acylated quaternary salts of azoles. In addition, it was found that silyl enol ethers formed in situ were also useful for the reaction to afford the adducts only by simple sequential addition of five commercially available reagents. (C) 2000 Elsevier Science Ltd.
- Itoh, Takashi,Miyazaki, Michiko,Nagata, Kazuhiro,Ohsawa, Akio
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p. 4383 - 4395
(2007/10/03)
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- One pot reaction of unstable N-acyl quaternary salt of thiazoles or imidazoles with silyl enol ethers formed in situ
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Ketone, trimethylsilyl triflate, triethylamine, thiazole or imidazole, and alkyl chloroformate were sequentially added to methylene chloride to form 2-substituted N-alkoxycarbonylated thiazoline or imidazoline derivatives in good yields.
- Itoh, Takashi,Miyazaki, Michiko,Nagata, Kazuhiro,Matsuya, Yu?ji,Ohsawa, Akio
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p. 667 - 671
(2007/10/03)
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- NEW PERSPECTIVES IN THIAZOLE CHEMISTRY
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Carbon-carbon bond forming reactions at C-2 of the thiazole ring have been carried using two strategies, one involving the addition of organometallic reagents (lithium carbanions of esters, Grignard salts, silyl enol ethers, silyl ketene acetals, silylazoles) to N-acylthiazolium salts; the other involving the addition of carbon electrophiles (ketenes, acyl chlorides, anhydrides, aldehydes) to N-acylthiazolium ylides generated in situ.The reactions have been applied to 1,3-thiazole and 2-trimethylsilyl-1,3-thiazole, the latter being more reactive than the former toward electrophiles.This methodology constitutes a new entry to a variety of functionalized thiazoles and thiazolines which are potential building blocks for the synthesis of natural compounds and analogues of biologically active molecules (penems, arylpropionic acids).Some ring transformations of thiazoles induced by carbon-sulfur bond cleavage are also described.The fundamental role played by the sulfur atom of the thiazole ring in the observed reactions is pointed out and briefly discussed.
- Dondoni, Alessandro
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- REGIOSELECTIVE CARBON-CARBON BOND FORMATION AT C2 OF 1,3-THIAZOLE BY REACTION OF N-ETHOXYCARBONYLTHIAZOLIUM CHLORIDE WITH C-NUCLEOPHILES
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N-Ethoxycarbonylthiazolium chloride generated in situ from 1,3-thiazole and ethyl chloroformate, treated with lithium carbanions of esters, Grignard reagents, silyl enol ethers and esters, undergo nucleophilic addition at C2 affording the corresponding 2-substituted N-ethoxycarbonylthiazolines.
- Dondoni, Alessandro,Dall'Occo, Tiziano,Fantin, Giancarlo,Fogagnolo, Marco,Medici, Alessandro
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p. 3633 - 3636
(2007/10/02)
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