Background:
Amide bond formation reactions are the most important transformations in
(bio)organic chemistry because of the widespread occurrence of amides in pharmaceuticals, natural products
and biologically active compounds. The Beckmann rearrangement is a well-known method used for the preparation
of secondary amides from ketoximes. But, most of the traditional protocols used for the Beckmann rearrangement
create enormous amount of wastes. Thus, the atom economical synthesis of amides has got high
priority among the chemists. However, under classical Beckmann conditions, aldoximes do not rearrange into
the corresponding primary amides. Indeed, reactions of aldoximes lead to nitriles. In recent years, it has been
demonstrated that the aldoxime rearrangements can be carried out efficiently and selectively with the help of
metal catalysts.
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Objective: This review focuses on the recent progress in the amides synthesis via ketoxime and aldoxime rearrangements.
Applications of the rearrangements in the synthesis of heterocycles and natural products are also
covered in this review.
Conclusion:
In the first part of the review, relevant pathways of oxime rearrangements are discussed and it is
shown that several catalytic systems have been developed for the atom-economical synthesis of N-substituted
amides from ketoximes. But similar reactions with aldoximes are, however, more challenging. The advances
reached in the aldoxime rearrangement are also covered in this review. It is revealed that a large variety of
homogeneous and heterogeneous metal catalysts have been developed to affect aldoxime rearrangements.
The Mechanochemical Beckmann Rearrangement: An Eco-efficient “Cut-and-Paste” Strategy to Design the “Good Old Amide Bond”
