- Sulphated zirconia as an eco-friendly catalyst in acylal preparation under solvent-free conditions, acylal deprotection assisted by microwaves, and the synthesis of anhydro-dimers of o-hydroxybenzaldehydes
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A solvent-free approach is described for the regioselective synthesis of acylals (1,1-diacetates) in shorter reaction times and higher yields, compared to conventional methodology using solvents. In the protection reaction of the o-hydroxybenzaldehyde the formation of acetyl compounds and anhydro-dimers was observed. The deprotection reaction involves microwave (MW) exposure of diluted reactants in the presence of solid sulphated zirconia (SZ) catalyst that can be easily recovered and reused. The sulphated zirconia was recycled several times without any loss of activity.
- Palacios-Grijalva, Laura Nadxieli,Cruz-Gonzalez, Deysi Y.,Lomas-Romero, Leticia,Gonzalez-Zamora, Eduardo,Ulibarri, Gerardo,Negron-Silva, Guillermo E.
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experimental part
p. 4065 - 4078
(2010/03/01)
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- Formation of Furan Derivatives from Phenacyl Bromides and Sodium Telluride; Attempted Extension to Coumarin Synthesis
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The enolates, generated from phenacyl bromides by sodium telluride, yield 2,4-diarylfurans in addition to the expected dehalogenation products.No 1,4-dicarbonyl compounds could be isolated even in the presence of excess oxidizing agent, copper(II) chloride.Condensation of 2-(methoxymethoxy)arenecarbaldehydes with ethyl bromoacetate in the presence of sodium telluride gave the expected α,β-unsaturated esters which resisted cyclization to yield the desired coumarin derivatives.Attempted intramolecular Reformatsky-type reaction of 2-(bromoacetoxy)benzaldehyde gave only 6,12-epoxy-6H,12H-dibenzo-dioxocin as the major product.
- Padmanabhan, Seetharamaiyer,Ogawa, Takuji,Suzuki, Hitomi
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p. 2114 - 2116
(2007/10/02)
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