18484-04-3Relevant articles and documents
Highly selective tetrahydropyranylation/dehydropyranylation of alcohols and phenols using porous phenolsulfonic acid-formaldehyde resin catalyst under solvent-free condition
Rajkumari, Kalyani,Laskar, Ikbal Bahar,Kumari, Anupama,Kalita, Bandita,Rokhum, Lalthazuala
, (2020/02/18)
An efficient protocol for solvent-free chemoselective tetrahydropyranylation/depyranylation of alcohols and phenols is reported herein using mesoporous Phenolsulfonic Acid Formaldehyde Resins as a heterogeneous acid catalyst. The catalyst successfully performed chemoselective protection and deprotection reactions of a wide range of substrates ranging from primary to secondary and tertiary alcohols and also phenols. The reactions were carried out at ambient temperature under solvent-free condition (SolFC) which resulted in high yields within a very short time. FT-IR, TEM, SEM, EDS and TG-DSC analysis techniques were employed to characterize the synthesized polymeric catalyst. The chemoselective nature of our method was confirmed using 13C DEPT-135 NMR studies. The polymer catalyst was found to be recoverable even after 10th catalytic cycle without much depreciation in its activity. The heterogeneity of the catalyst was verified by hot filtration method. Good yield, energy and cost- effective method, solvent-free protocol, mild reaction conditions, no inert atmosphere, metal-free heterogeneous polymer catalyst and excellent recoverability of the catalyst are notable milestones of the reported protocol.
Magnetic Fe3O4@silica sulfuric acid nanoparticles promoted regioselective protection/deprotection of alcohols with dihydropyran under solvent-free conditions
Rajkumari, Kalyani,Kalita, Juri,Das, Diparjun,Rokhum, Lalthazuala
, p. 56559 - 56565 (2017/12/27)
Protection (and deprotection) of hydroxyl groups via tetrahydropyranylation was carried out effectively using a catalytic amount of Fe3O4 supported silica sulphuric acid nanoparticles (Fe3O4@SiO2@SO3H) under solvent-free conditions. The synthesized nanocatalyst was characterized by XRD, TEM, FT-IR etc. A wide range of tetrahydropyranylated alcohol derivatives were synthesized using this heterogeneous magnetic nanocatalyst within 10-20 min with high yields. In addition, tetrahydropyranyl ethers could also be deprotected to the parent alcoholic compounds in the presence of MeOH using the same catalyst. After completion of the reactions, the catalyst was easily separated from the reaction medium using an external magnet, which ameliorated the overall synthetic process. The catalyst was recovered and reused for five successive reactions without any appreciable loss in its activity. Mild reactions conditions, operational simplicity, solvent free conditions, high selectivity, easy recyclability of the magnetic nanocatalyst, and high yields can be considered as the advantageous features of our procedure.
Polystyrene-supported GaCl3: A new, highly efficient and recyclable heterogeneous Lewis acid catalyst for tetrahydropyranylation of alcohols and phenols
Rahmatpour, Ali
, p. 66 - 71,6 (2012/12/11)
A new, simple and highly chemoselective method for tetrahydropyranylation of alcohols and phenols with 3,4-dihydro-2H-pyran (DHP) in the presence of polystyrene-supported gallium trichloride (PS/GaCl3) as a highly active and reusable heterogeneous Lewis acid catalyst at room temperature is presented.
