1257982-97-0Relevant articles and documents
Solvent-dependent regio- and stereo-selective reactions of 3-formylchromones with 2-aminobenzothiazoles and transacetalization efficiency of the product 3-((benzo[: D] thiazol-2-ylimino)butyl)-4 H -chromen-4-one
Ahmed, Owais,Cherkadu, Vandana,Kalavagunta, Praveen Kumar,Shang, Jing
, p. 20573 - 20581 (2019)
Using 2-propanol as the solvent, 3-formylchromones and 2-aminobenzothiaoles formed corresponding imines, while 1° and 2°-alcohols formed the corresponding 2-alkoxy-3-enamines with selectivity for the Z-isomer. Changing the substrates with similar molecules such as 3-formylchromone with quinoline-, quinolone- and indole-3-carbaldehydes sometimes resulted in the formation of the corresponding imines, whereas replacing 2-aminobenzothiazole with amides resulted in the formation of acetals. Considering the effect of the solvent, replacing alcohols with the aprotic solvents THF and CH2Cl2 resulted in the formation of imines and enamines, which are the characteristic reactions of 2-propanol and other 1° and 2°-alcohols, respectively. 2-Alkoxy-3-enamines were found to undergo transacetalization with both short and long chain alcohols. The novelty of these reactions is that they did not require an external catalyst, all the reactions were performed at the same temperature, and purification was achieved by filtration. The transacetalization we performed herein is a new concept, which has not been reported to date. In contrast, other similar reactions, such as transalkoxylation, transalkylation, and transetherification, are performed on a commercial scale using expensive catalysts such as Otera's catalyst. The highly sensitive nature of 3-formylchromones towards variations in the substrates and solvents to form different products and the reason behind the selective formation of the Z-isomer of 2-alkoxy-3-enamines and its transacetalization efficiency need further studies to understand the reaction mechanism and possibly other factors such as solvent effects.
New synthesis of (Z)-and (E)-3-styryl-4-quinolones
Seixas, Raquel S. G. R.,Silva, Artur M. S.,Cavaleiro, José A. S.
experimental part, p. 2257 - 2262 (2010/11/04)
A novel and efficient route for the synthesis of (Z)-and (E)-3-styryl-4-quinolones is described. Wittig reaction of 4-(chloroquinoline- and quinolone)-3-carbaldehydes with benzylic ylides is the key transformation for this synthetic route. The (Z)-1-methyl-3-styryl-4-quinolone is obtained with high diastereoselectivity from the reaction of 1-methyl-4-quinolone-3- carbaldehyde; while (E)-3-styryl-4-quinolone is prepared through the Wittig reaction of 4-chloroquinoline-3-carbaldehyde followed by acid hydrolysis. Both synthetic routes are efficient regardless of the substituents on the benzylic ylides. Georg Thieme Verlag Stuttgart - New York.
