Hydroxamic acids Weinreb amides

Aldehydes and ketones have also been prepared by nucleophilic cleavage of resin-bound O-alkyl hydroxamic acids (Weinreb amides [744]) with lithium aluminum hydride [745] or Grignard reagents (Entries 1 and 2, Table 3.41). Similarly, support-bound thiol esters can be cleaved with Grignard reagents to yield ketones [272], or with reducing agents to yield aldehydes (Entry 3, Table 3.41). Polystyrene-bound sele-nol esters (RCO-Se-Pol) react with alkynyl cuprates to yield alkynyl ketones [746]. 

In 2001, De Luca and GiacomeUi " reported a new simple and high-yielding one-flask synthesis of Weinreb amides from carboxylic acids and A-protected amino acids that uses different 1,3,5-triazine derivatives (such as 236) as the coupling agents (Scheme 104). The method allows the preparation of Weinreb amides 237 and hydroxamates as O-benzyl and 0-silyl hydroxamates that can be easily transformed into hydroxamic acids. 

Deoxo-Fluor reagent is a versatile reagent for acyl fluoride generation and subsequent one-flask amide coupling. Georg and coworkers have explored the utility of this reagent for the one-flask conversion of acids to hydroxamic acids and Weinreb amides (Scheme 105) ". ... 

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