2963-12-4Relevant articles and documents
Ureas from Lossen Rearrangements of Hydroxamic Acids Induced by p-Toluenesulfonyl Chloride or 2-Chloro-1-methylpyridinium Iodide in the Presence of Amines: A Correction
Pihuleac, Justin,Bauer, Ludwig
, p. 61 - 64 (1989)
Hydroxamic acids reacted with amines in the presence of either p-toluenesulfonyl chloride or 2-chloro-1-methylpyridinium iodide to produce compounds whose structures are different from those which had been reported.These reactive halides converted hydroxamic acids first to Lossen-type of intermediates, which rearranged spontaneously in basic media to isocyanates which reacted further.In the absence of primary or secondary amines in the medium, the intermediate isocyanates acylated the starting hydroxamic acids to form O-carbamyl hydroxamic acids.However, when the reaction mixtures contained either primary or secondary amines, addition to the intermediate isocyanates provided ureas.Furthermore, it was found that amines caused the O-carbamyl hydroxamic acids to undergo facile Lossen degradations to furnish ureas.
Lossen rearrangements under heck reaction conditions
AbdelHafez, El-Shimaa M.N.,Aly, Omar M.,Abuo-Rahma, Gamal El-Din A.A.,King, S. Bruce
supporting information, p. 3456 - 3464 (2015/02/05)
The classical Lossen rearrangement converts activated hydroxamic acids to isocyanates that form numerous products upon their reaction with nucleophiles. We report a simple and highly efficient method of using Heck reaction conditions to initiate Lossen rearrangements of hydroxamic acids. In addition, Lossen rearrangements occur in the presence of palladium(II) acetate or triethylamine, components of the Heck reaction, alone. A potential mechanism is provided to explain this reactivity and these results show that Heck reactions and Lossen rearrangements occur under the same conditions and may provide new methods for facile initiation of Lossen rearrangements.
