A grinding-induced catalyst- and solvent-free synthesis of highly functionalized 1,4-dihydropyridines via a domino multicomponent reaction (original) (raw)
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Synthesis of 1,4-dihydropyridines via a four component one pot reaction starting from α,β-unsaturated aldehyde, β-keto ester, amine and alcohol, catalysed by SO 4 2− /Ce x Zr 1−x O 2 is explored. The method has several advantages such as reusability of catalyst, avoidance of a multistep procedure and readily available starting materials. The protocol gives high to moderate yields for structurally diverse amines, β-keto esters and α,β-unsaturated aldehydes. SO 4 2− /Ce x Zr 1−x O 2 (x = 0.02-0.15 mol%) catalysts were prepared and characterized by various analytical techniques such as XRD, FT-IR, TGA-DSC, SEM-EDAX and the total acidity.
Journal of Heterocyclic Chemistry, 2007
Small libraries of 3,5-unsubstituted 4-substituted-6-aryl-3,4-dihydropyridin-2(1H)-ones derivatives were synthesized from the condensation-products of aldehydes with Meldrum's acid, aromatic ketones and ammonium acetate using acetic acid as energy transferring-agent under microwave irradiation without catalyst. This method has the advantages of excellent yields (65 90%), short reaction time (5 10 min) and being environmentally friendly. It aimed to provide new series of potential biologically active compounds for biomedical screening.
Synthesis of natural products and related compounds
Dedicated to………. my parents "Science can only determine what is, but not what shall be, and beyond its realm, value judgments remain indispensable. Religion, on the other hand, is concerned only with evaluating human thought and actions; it is not qualified to speak of real facts and the relationships between them." Albert Einstein CONTENTS ABSTRACT a PREFACE c ACKNOWLEDGEMENT e Part I : Titanocene(III) mediated radical cyclizations of epoxides
Green Chemistry, 2010
Microwave irradiation was carried out with microwave oven Emrys Creator from Personal Chemistry, Uppsala, Sweden. Melting points were determined in open capillaries and were uncorrected. IR spectra were taken on a FT-IR-Tensor 27 spectrometer in KBr pellets and reported in cm-1. 1 H NMR spectra were measured on a Bruker DPX 400 MHz spectrometer in DMSO-d 6 with chemical shift (δ) given in ppm relative to TMS as internal standard. ESI-MS was determined by using the LCQ Advantage HPLC/MS instrument (Thermo Finnigan). HRMS (ESI) was determined by using microTOF-QⅡ HRMS/MS instrument(BRUKER).X-Ray crystallographic analysis was performed with a Siemens SMART CCD and a Siemens P4 diffractometer. General procedure for the synthesis of compounds 4 and 5 Preparation of compounds 4: In a 10-mL Emrys reaction vial, a Meldrum's acid (1, 1 mmol), aromatic aldehydes (2, 2 mmol), 3-methyl-1-phenylpyrazol-5-amine (3a) or 3-methyl-isoxazol-5-amine (3b) (1.0 mmol) and water (2.0 mL) were mixed and then capped. The mixture was heated for a given min at 100 o C under microwave irradiation (initial power 100 W and maximum power 200 W). Upon completion, monitored by TLC, the reaction mixture was cooled to room temperature and then poured into cold water. The solid product was collected by Büchner filtration and subsequently purified recrystallized from EtOH (95%) to give the pure products 4. Preparation of compounds 5: In a 10-mL Emrys reaction vial, a Meldrum's acid (1, 1 mmol), aromatic aldehydes (2, 1 mmol), 3-methyl-pyrazol-5-amine (3c) or 3-methyl-1-methyl-pyrazol-5-amine (3d) (1.0 mmol) and water (2.0 mL) were mixed and then capped. The mixture was heated for a given min at 100 o C under microwave irradiation. Upon completion, monitored by TLC, the reaction mixture was cooled to room temperature and then poured into cold water. The subsequent work-up produce was the same as in the above reactions.
Neat reaction microwave technology for the synthesis of N -substituted-1,4-dihydropyridines
Canadian Journal of Chemistry, 2004
Hantzsch synthesis of N-substituted-1,4-dihydropyridines (1,4-DHP) was carried out using an environmentally benign procedure. Neat reactants were subjected to microwave irradiation (MWI) to give the required products in excellent yield. Appreciable results were not obtained when conventional synthesis using neat reactants was carried out. The good yield and rate enhancement observed in the case of microwave irradiation is attributed to the uniform heating effect of microwaves.Key words: 1,4-dihydropyridines (1,4-DHP), microwave irradiation (MWI), neat reaction, solid support.