Silica-supported Phosphorus Chloride: An Efficient and Recyclable Catalyst for Beckmann Rearrangement of Ketoximes and Dehydration of Aldoximes Under Microwave Irradiation

Abstract

Silica-supported phosphorus chloride has been proved to be an efficient and recyclable catalyst for Beckmann rearrangement of a variety of ketoximes and dehydration of various aldoximes in anhydrous THF under microwave irradiation. This protocol has advantages of high conversion, high selectivity, short reaction time, no environmental pollution, and simple work-up procedure.

Au/Ag-Cocatalyzed Aldoximes to Amides Rearrangement under Solvent- and Acid-Free Conditions

“…Interestingly, water scavengers such as molecular sieves or MgSO 4 did not inhibit amide formation by stopping the reaction at the nitrile stage, suggesting a concerted mechanism (i.e., by interaction of water with the gold catalyst). The essential role of the silver salt, which serves as both activator of the [(NHC)AuCl] complex and as a catalyst for the oxime dehydration, also raises the interest in the development of well-defined silver catalysts for oxime dehydration and rearrangement …”

Comprehensive updates on Beckmann Rearrangement

“…Li et al [104] demonstrated phosphorous dichloride supported by silica, catalyzed Beckmann rearrangement when exposed to 195 W of microwave radiation. This protocol has advantages of high conversion, high selectivity, short reaction time, no environmental pollution, and simple work-up procedure.…”

“…Li et al [104] . demonstrated phosphorous dichloride supported by silica, catalyzed Beckmann rearrangement when exposed to 195 W of microwave radiation.…”

β‐Cyclodextrin: A Green and Efficient Supramolecular Catalyst for Organic Transformations

“…Conventional Beckmann rearrangement usually requires relatively high temperature, large amount of strongly acidic and dehydrating media such as concentrated H 2 SO 4 (forms ammonium sulfate as byproduct), polyphosphoric acid, P 2 O 5 ‐methanesulfonic acid, that leads to the large waste products (formation of inorganic salts caused by neutralization) and not applicative to sensitive substrate. Some other reported methods for Beckmann rearrangement includes use of cyanouric chloride along with ZnCl 2 , mercury(II) chloride, silica‐supported phosphorus chloride, Bromodimethylsulfonium bromide along with imidazolium‐based ionic liquid [bmim]PF 6 , triflic anhydride, CBr 4 /PPh 3 , ammonium persulfate‐DMSO, Mukiyama reagent, etc. However, some of these processes require hazardous high cost solvents like DCM, DMF, acetonitrile, toluene, etc.…”