Dehydrative Beckmann rearrangement and the following cascade reactions
The Beckmann rearrangement has been predominantly studied for the synthesis of amide and lactam. By strategically using the in situ generated Appel's salt or Mitsunobu's zwitterionic adduct as the dehydrating agent, a series of Beckmann rearrangement and following cascade reactions have been developed herein. The protocol allows the conversion of various ketoximes into amide, thioamide, tetrazole and imide products in modular procedures. The generality and tolerance of functionalities of this method have been demonstrated.
Liu, Yinghui,Wei, Yongjiao,Xie, Lan-Gui
supporting information
(2021/11/16)
Copper-catalyzed synthesis of oxime ethers from iminoxy radical (C[dbnd]N–O[rad]) and maleimides via radical addition
An efficient Cu(II)-catalyzed radical addition of maleimides has been achieved. The identified copper catalyst enables the formation of oxime radicals (N–O[rad]) by cleaving the O–H bond in ketoximes, followed by the radical addition to N-substituted male
A mild system for synthesis of aldoximes and ketoximes in the presence of N-hydroxyphthalimide in aqueous system
An efficient method for synthesis of oximes from aldehydes or ketones with N-hydroxyphthalimide or N-hydroxysuccinimide in water has been described. It is the first time to utilize NHPI as an oximation reagent to synthesize aldoximes and ketoximes from the corresponding organic carbonyl compounds without other reagents. The reaction tolerates various functional groups and affords the corresponding oximes in 76%–98% yields. The by-product phthalic acid can be recycled from the system. In addition, this method has been successfully applied to the synthesis of the precursor of some pharmacologically active amide molecules.
Dichloroimidazolidinedione-Activated Beckmann Rearrangement of Ketoximes for Accessing Amides and Lactams
A novel protocol for the activation of the Beckmann rearrangement utilizing the readily available and economical geminal dichloroimidazolidinediones (DCIDs) on a substoichiometric scale (10 mol %) has been developed. A unique self-propagating mechanism for the substoichiometric dichloroimidazolidinedione-activated transformation was proposed and validated. The substrate scope of the developed protocol has been demonstrated by 23 examples with good to excellent yields (mostly 90-98%) in a short time (mostly 10-30 min), including a substrate for synthesizing the monomer of nylon-12 and a complicated steroidal substrate on a preparative scale. This research not only unveils for the first time the synthetic potential of substoichiometric amounts of dichloroimidazolidinediones in promoting chemical transformation but also offers yet another important illustration of the self-propagating cycle in the context of the Beckmann rearrangement activated by a structurally novel organic promoter.