Hydroxylamine nucleophilic cleavage with

Cl Cl 6 p r= /= MeNHOH OH r= Y nA/om 0 0 [26] Only one example of nucleophilic cleavage with hydrox-ylamine has been described. Recently, many different hydroxylamine-based linkers have been described based on attachement of hydrox-ylamine to trityl-, Wang-, Sasrin- or Rink-resin. [26] [33] [175-177]... 

Hydroxamic acids and hydrazides can also be prepared by nucleophilic cleavage of resin-bound esters, activated amides, or thiol esters [359] with hydroxylamine and... 

Strategies that lead to the formation of isoxazoles during cleavage from an insoluble support include the oxidative cleavage of /V-(4-alkoxybenzyl)isoxazolidincs with DDQ to yield isoxazolines (Entry 14, Table 15.16), the nucleophilic cleavage of 2-acyl enamines with hydroxylamine (Entry 15, Table 15.16), and the acidolysis of 2-cyano-phenols etherified with an oxime resin (Entry 17, Table 15.16). The required oxime ethers for the latter synthesis were prepared by reaction of the corresponding 2-fluorobenzonitriles with Kaiser oxime resin [203],... 

Most of the compounds under discussion are quite labile in acid, but with two important exceptions they are resistant to mild alkaline hydrolysis (0.1-1 N base, 25°C). One exception is the mixed anhydrides of phosphate and carboxylic acids, such as acetyl phosphate. They are very susceptible to alkaline cleavage or cleavage by nucleophiles such as hydroxylamine. The other relatively alkali-labile phosphate compounds are phosphodiesters, in which the phosphate is attached to one of two vicinal hydroxyl groups (as in RNA or derivatives of phosphatidic acid). In these instances, the neigh-... 

Hydroxylcmine and hydrazines. Tertiary enaminones react as typical 1,3-biselec-trophiles with hydroxylamine as a nucleophile to give high yields of 5-alkylisoxazoles after substitution and cyclization. The obtained isoxazoles are a source of fi-ketonitriles after cleavage of the isoxazole ring by EtONa (equation 192). 

Triazine (1) reacts with various nucleophiles under ring cleavage. Reactions with ammonia, hydroxylamines and amines follow a similar scheme.18 The initial step is a nucleophilic attack of the nitrogen nucleophile to an electron-deficient triazine carbon. The reaction is assumed to proceed via ring opening and further addition of the nucleophile as shown below. The result, in every case is the complete destruction of the triazine ring with formation of three moles of ammonia and three moles of formimidamide derivatives 2.18... 

In contrast to most other nucleophiles (e.g. amines, alkoxides), hydroxylamine and hydrazine derivatives may also react with acylphosphonates as with ketones, and lead to the formation of imines, although these reactions are often accompanied with C—P bond cleavage. The extent of this side-reaction depends on the reagents, reaction conditions and/or the groups linked to the phosphorus. 

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