A simplified green chemistry approach to the Biginelli reaction using ‘Grindstone Chemistry’

Multiphasic Heterogeneous Catalysis Mediated by Catalyst‐Philic Liquid Phases

“…The latter occurs likely either in the third 'wet' phase, or at the phase boundary between the aqueous and the 'wet' TBAB phases. 63 A third reddish interfacial layer of an ammonium salt (tetran-butylammonium tribromide: TBABr 3 ) was also observed when to a suspension of TBAHSO 4 , NaBr, and aqueous NaOCl, was added benzene or CCl 4 . This system could be used to brominate or oxidize a range of substrates, and the interfacial third layer could be used repeatedly, demonstrating the recyclability of the catalytic system.…”

“…Just mixing two solids can often lead efficiently and cleanly to a product, however there are limitations mainly due to the choice of reagents and to mass and heat transport. 4,5 It should be pointed out that many biphasic systems have found their way in the chemical industry, starting from PTC and continuousflow (CF) processes. The reasons are that efficiency can be increased (rates, selectivity, energy requirements, process intensification), making them more economic, and often more environmentally compatible, in short more sustainable.…”

“…cyclohexane), water, and an ionic liquid was assembled by Earle, Seddon et al, and applied for the Heck coupling reaction. 72 The new feature was represented by the presence of an ionic liquid [cation: 1-butyl-3-methylimidazolium (bmim), 1-pentyl-3-methylimidazolium (pmim), N-hexylpridinium (C 6 py)] as the 'third phase', coupled with anions such as halide, BF 4 , and PF 6 . These liquid salts are virtually insoluble in water and alkanes, but readily dissolve transition metal catalysts.…”

Reações multicomponentes de biginelli e de mannich nas aulas de química orgânica experimental: uma abordagem didática de conceitos da química verde

“…[25][26][27][28][29][30] De modo a contornar estes obstáculos, as metodologias a serem trabalhadas em aulas experimentais devem empregar condições brandas, tempos de reação curtos (não superiores a 4 h) e reagentes comerciais a um custo acessível, preferencialmente sem o envolvimento de solventes orgânicos em quantidades excessivas. Diversas condições reacionais descritas na literatura para a síntese das di-hidropirimidin-2-onas multissubstituídas 6a-c (Esquema 3) a partir de acetoacetato de etila (3), aldeídos aromáticos 4 e ureia (5) possuem estas características e podem ser previamente apresentadas pelo professor, [31][32][33][34][35][36][37][38][39] 4 .K 2 SO 4 ) ou ainda condições na ausência de qualquer aditivo. 39 As reações foram conduzidas, preferencialmente, na ausência de solvente e sob aquecimento durante um período de 1-3 h, dependendo da condição reproduzida (ver Parte Experimental).…”

Vulnerability of substituted aromatic hydroxy aldehydes to undergo Biginelli reaction in water

“…Other systems such as tetrahydrofuran (THF)/ HCl, acetic acid (22), acetic acid/HCl (22), dioxin/HCl (22), tartaric acid/methanol (23), and acetonitrile with a substantial amount of iodine have been also employed (24). Several solvent-free methods have been recently reported using different Lewis acids such as LiBr (25), ZnCl 2 (26), benzyltriethylammonium chloride (18,19), chlorosulfonic acid (27) and many other methods including microwave irradiations (28).…”