Unmodified Nano-Powder Magnetite or Iron(III) Oxide Catalyze the Easy and Fast Synthesis of 4-Substituted-4H-Pyrans
作者:Diego Ramón、Rafael Cano、Miguel Yus
DOI:10.1055/s-0030-1261162
日期:2011.9
Inexpensive and commercially available nano-power magnetite or iron(III) oxide can be used as catalyst in a new, straightforward, and fast protocol for the construction of 4-substituted-4H-pyrans. The reaction implies a tandem process, involving an aldol condensation, a Michael-type addition, and a dehydrating annulation.
A highly efficient and general method for the synthesis of polyfunctionalized 4H-pyrans is established through a one-pot multicomponent cyclocondensation of aromatic aldehydes with CH acids, malononitrile and ethyl acetoacetate using nano silica supported tin (II) chloride as a catalyst. In this method SnCl2/nano SiO2 was used as green and reusable catalyst. Excellent yields, short reaction times, simple workup, and inexpensiveness and commercially availability of the catalyst are the advantages of this method. (C) 2013 Javad Safaei-Ghomi. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
Improved synthesis of diethyl 2,6-dimethyl-4-aryl-4H-pyran-3,5-dicarboxylate under ultrasound irradiation
Diethyl 2,6-dimethyl-4-aryl-4H-pyran-3,5-dicarboxylates (1) have been synthesized by the reaction of aryl aldehyde and 1,3-diketone catalyzed by ZnCl2 under ultrasound irradiation. The effects of changes in the ultrasonic power, temperature, and reaction time are discussed. With the optimized reaction conditions, various aryl aldehydes were used to synthesize 4H-pyrans (1) under the influence of ultrasound irradiation. Compared with the conventional thermal methods, the remarkable advantages of this method are the simple experimental procedure, shorter reaction time and high yield of product. (C) 2009 Elsevier B.V. All rights reserved.