87830-83-9Relevant academic research and scientific papers
NEW PERSPECTIVES IN THIAZOLE CHEMISTRY
Dondoni, Alessandro
, p. 1 - 38 (2007/10/02)
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.
Additions and Cycloadditions of Ketenes to 1,3-Thiazole and Its Alkyl Derivatives
Medici, Alessandro,Fantin, Giancarlo,Fogagnolo, Marco,Pedrini, Paola,Dondoni, Alessandro,Andreetti, Giovanni Dario
, p. 590 - 596 (2007/10/02)
1,3-Thiazole and its 4-methyl and 5-methyl derivatives react with tert-butylcyanoketene (TBCK) and dichloroketene (DCK), affording Michael-type addition products at C2, viz., 2-acylthiazoles, and 2:1 cycloadducts (with TBCK only) which proved by X-ray analysis to be bicyclic systems constituted by a thiazoline and a piperidine-1,3-dione ring condensed across the C-N bond. 2-Ethyl- and 2-isopropyl-1,3-thiazole undergo acylation by DCK at the Cα of the alkyl chain.The latter thiazole gives also a 2:1 cycloadduct, which X-ray analysis showed to be a bicyclic system constituted by a thiazoline and an oxazinone ring condensed across the C-N bond.A mechanism is envisaged involving the quaternization of the thiazole nitrogen by the ketene to give an N-thiazolium enolate system which owing to proton exchange between the C2 of the ring or the Cα of the 2-alkyl chain and its enolate portion is in equilibrium with an N-acylthiazolium ylide or zwitterion, respectively.Subsequent reactions of these active intermediates with the ketene lead to the final products.
