Hydroxylamine substituted ethylenes

To synthesize isomeric 3-substituted isoxazoles (301) the reaction of ethylene acetals of )3-ketoaldehydes (300) (readily available from -chlorovinyl ketones (57IZV949)) with hydroxylamine was employed. Owing to the comparative stability of the dioxolane group, this reaction gave exclusively 3-substituted isoxazoles (301) (60ZOB954). The use of noncy-clic, alkyl S-ketoacetals in this reaction resulted in a mixture of 3- and 5-substituted isoxazoles (55AG395). 

Addition of lithium derivatives of acetylenides (Li—C=C-C02R) to chiral nitrones proceeds with high stereoselectivity, giving a-acetylene substituted hydroxylamines (410a,b) (656). This reaction has been successfully applied to the synthesis of y-hydroxyamino-a, 3-ethylene substituted acids (411a,b), formed in the reduction of (410) with Zn in the presence of acid (657, 658), and to chiral 5-substituted-3-pyrroline-2-ones (412a,b) (Scheme 2.184) (658). 

Types of compounds are arranged according to the following system hydrocarbons and basic heterocycles hydroxy compounds and their ethers mercapto compounds, sulfides, disulfides, sulfoxides and sulfones, sulfenic, sulfinic and sulfonic acids and their derivatives amines, hydroxylamines, hydrazines, hydrazo and azo compounds carbonyl compounds and their functional derivatives carboxylic acids and their functional derivatives and organometallics. In each chapter, halogen, nitroso, nitro, diazo and azido compounds follow the parent compounds as their substitution derivatives. More detail is indicated in the table of contents. In polyfunctional derivatives reduction of a particular function is mentioned in the place of the highest functionality. Reduction of acrylic acid, for example, is described in the chapter on acids rather than functionalized ethylene, and reduction of ethyl acetoacetate is discussed in the chapter on esters rather than in the chapter on ketones. 

The reaction of ketone derivatives (89) with chloromethyleneiminium salt (1) gives iminium salts (90) which yield, after hydrolysis, (3-chloroacrolein derivatives (91 Scheme 7).42 Numerous 3-chloroacrolein derivatives have been prepared by this method and yields are generally moderate to good. 3-Chloroacryl-onitrile derivatives (92) are also available in good yield from iminium salts (90 R2 = H) by treatment with hydroxylamine.43 Ketals (93) can be prepared from iminium salts (90) by treatment with the monosodium salt of ethylene glycol followed by hydrolysis under basic conditions (32-69%).44 If the group R1 in ketone (89) is aromatic and electron rich, then intramolecular electrophilic substitution of iminium salt... 

In the second method, the alkoxyamine-ftmctionalized backbone is prepared by a chemical modification of a preformed polymer. Abbasian and Entezami prepared alkoxyamine-functionalized poly(vinyl chloride) (PVC) in a three-step procedure. PVC was first arylated with toluene by Friedel-Crafts acylation followed by a bromination step using N-bromosuccinimide. The bromine atom was finally reacted via nucleophilic substitution by the TEMPO hydro-xylamine anion. PVC-g-PS was finally obtained after TEMPO-mediated polymerization of styrene. A TEMPO-functionalized isotactic poly(l-butene) macroinitiator was synthesized by Jo et al. who used a rhodium-catalyzed activation of the alkane C-H bonds and subsequent transformations of the boronate ester group into an hydroxyl pendant group. This reactive moiety was then used to attach a TEMPO-based alkoxyamine bearing another hydroxy function by an ether linkage. A method to prepare PE-g-PS from a poly(ethylene-co-m,p--methylstyrene) obtained by metallocene-catalyzed polymerization was also reported. The macroalkoxya-mine was synthesized after bromination with N-bromosuccinimide followed by a nucleophilic reaction with the TEMPO hydroxylamine anion. 

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