82865-29-0Relevant articles and documents
Reactivity of (Z)-4-Aryliden-5(4 H)-thiazolones: [2 + 2]-Photocycloaddition, Ring-Opening Reactions, and Influence of the Lewis Acid BF3
Sierra, Sonia,Dalmau, David,Higuera, Sheila,Cortés, Darío,Crespo, Olga,Jimenez, Ana I.,Pop, Alexandra,Silvestru, Cristian,Urriolabeitia, Esteban P.
, p. 12119 - 12140 (2021/09/07)
The irradiation of (Z)-2-phenyl-4-aryliden-5(4H)-thiazolones 2 with blue light (465 nm) in CH2Cl2 solution promotes [2 + 2]-photocycloaddition of the exocyclic C═C bonds and the formation of the dispirocyclobutanes 3. This reaction takes place with high stereoselectivity, given that the ?-isomer (1,3 head-to-tail syn coupling) is formed in more than 90% yield in most of the cases. However, irradiation of 5(4H)-thiazolones 2 with blue light (456 nm) in dry MeOH in the presence of BF3·OEt2 leads to the monospirocyclobutanes 4 with full stereoselectivity, also affording the ?-isomer. A ring-opening reaction of only one of the thiazolone rings appears to have taken place in 4 upon methanolysis, leading to the corresponding ester and thioamide groups. The treatment of free 4-aryliden-5(4H)-thiazolones 2 with a base in alcohol (NaOR/ROH) also produces a ring-opening reaction of the heterocycle by methanolysis, although, under these reaction conditions, further intramolecular S-attack at the exocyclic C(H)═C bond and cyclization is observed, forming the dihydrothiazoles 5 or 6 as mixtures of cis (RS/SR)- and trans (RR/SS)-isomers with high diastereomeric excess. trans-(RR/SS)-Dihydrothiazoles 6 can be isolated as pure diastereoisomers by column chromatography. Surprisingly, dihydrothiazoles 5 can also be obtained by the treatment of 4-aryliden-5(4H)-thiazolones 2 with BF3·OEt2 in methanol in the absence of a base.
Synthesis of symmetrical 2,2′,4,4′-tetrasubstituted [4,4′-bithiazole]-5,5′(4H,4′H)-diones and their reactions with some nucleophiles
Andersen, Kenneth K.,Bray, Diana D.,Kjaer, Anders,Lin, Yuhui,Shoja, Massud
, p. 1000 - 1015 (2007/10/03)
Symmetrical ,2′,4,4′-tetrasubstituted-[4,4′-bithiazole]-5,5′(4H, 4′H)-diones were obtained in high yields by oxidation of 5(4H)-thiazolones by KMnO4 in acetic acid. In some cases, the isomeric 2,4′- and 2,2′-bithiazolones were also formed. Results from two crossover reactions were consistent with a free radical mechanism. Four series of thiazolones were prepared, each based on a different substituent at the 2-position; i.e., phenyl, ethoxy, ethyl and ethylthio. The effects of substituents on the isomer distributions of the dehydrodimers indicated that electronic factors were less important than steric factors. X-Ray crystallography established the structure of the dehydrodimer (4R*,4′R*)-2,2′-diethoxy-4,4′-dibenzyl-[4,4′ -bithiazole]-5,5′(4H,4′H)-dione. One stereoisomer of 2,2′-diphenyl-4,4′-dimethyl-[4,4′-bithiazole]-5,5′(4H, 4′H)-dione and a mixture of the stereoisomers of 2,2′ -diphenyl-4,4′-dibenzyl-[4,4′-bithiazole]-5,5′(4H,4′H)- dione were treated with nucleophiles. The former gave imide derivatives of ,′-dehydrodimeric amino acids when the nucleophile was L-alanine ethyl ester or 1-butylamine. The structure of one of the reaction products, (4R*,5R*)-2,5-diphenyl-2-thiazoline-4-carboxylic acid piperidylamide, was established by X-ray crystallography. Treatment of stereoisomeric mixtures of 2,2′-diethoxy-4,4′-bithiazolones with HCl in benzene gave the corresponding racemic and meso bis-(N-carboxythioanhydride)s. A stereoisomeric mixture of the bis(N-carboxythioanhydride)s of leucine treated with glycine ethyl ester gave a bicyclic derivative of the ,′-dehydrodimeric amino acid. Acta Chemica Scandinavica 1997.
