Carbon Tetrabromide/Triphenylphosphine‐Activated Beckmann Rearrangement of Ketoximes for Synthesis of Amides

Abstract

An efficient Beckmann rearrangement of ketoximes was developed using carbon tetrabromide/triphenylphosphine as an organocatalyst without addition of any acids or metals. The reaction showed good functional group tolerance and gave various amides in moderate to good yields.

Design, synthesis and cytotoxic evaluation of a library of oxadiazole-containing hybrids

“…A reasonable mechanism for the cyclization of the disubstituted hydrazides with CBr 4 and Ph 3 P, would involve an initial formation of salt A which undergoes nucleophilic attack by the carbonyl oxygen giving the intermediate B. Cyclization followed by release of adduct D 26 and aromatization gives the corresponding 1,3,4-oxadiazole ( Scheme 6 ).…”

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.…”

Beckmann Rearrangement of Ketoxime Catalyzed by N-methyl-imidazolium Hydrosulfate

“…Over the past years, amide derivatives have received much attention owing to their broad range of applications in many fields such as the pharmaceutical industry, chemical biology, the agrochemical industry, engineering plastics, and so on [ 1 , 2 , 3 , 4 , 5 , 6 ]. Various approaches have been developed for the synthesis of amide compounds including nucleophilic acyl substitution reactions with amines [ 7 ], Staudinger ligation [ 8 ], Schmidt reaction [ 9 ] and Beckmann rearrangement [ 10 ]. However, generations of large amounts of undesired by-products and corrosive phenomenon associated with common acid (H 2 SO 4 and SOCl 2 ) based on liquid phase protocols provide a challenging task for chemists to develop alternative methods [ 11 , 12 ].…”