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Nitrones intermolecular reactions

Intermolecular Reactions Intermolecular 1,3-dipolar cycloaddition reactions of nitrones to olefins seem to be the most studied. They are widely used for the synthesis of different enantiomerically pure compounds, including biologically active ones. For example, two new glycosidase inhibitors have been obtained by the nitrone cycloaddition strategy (Fig. 2.32) (733). [Pg.314]

In intramolecular [3+ 2]-cycloaddition reactions, silyl nitronates also lead to substantially higher stereoselectivity than intermolecular reactions (see, e.g., Scheme 3.178) (193). [Pg.600]

Isoxazolidines from Intermolecular Nitrone Cycloaddition Reactions. 59... [Pg.1]

Further examples of the endocychc nitrone route to spirocychc adducts are the total syntheses of (—)-histrionicotoxin (230) by Holmes and of cyhndricines by Weinreb. Histrionicotoxin is one of many spiropiperidine alkaloids isolated from the poison-arrow frog Dendrobates histrionicus and has been the subject of many attempted total syntheses by a nitrone cycloaddition strategy that failed to provide the desired regioisomer, possibly through unfavorable steric interactions (265-268). Unlike these reports, Holmes and co-workers (101) found that the intermolecular reaction of nitrone (231), prepared by the 1,3-APT of the corresponding alkynyl-hydroxylamine carrying Oppolzer s chiral sultam auxiliary, afforded the styrene... [Pg.41]

The use of mediators to improve reactivity or selectivity in nitrone cycloaddition chemistry begins with the nitrone generation step. As is well known, the N-alkyla-tion of oximes provides one of the most direct and convenient synthetic routes to N-alkylated nitrones from readily available aldehydes and ketones. Electrophilic mediators have been employed to activate alkenes for N-alkylation, both in intramolecular and intermolecular reactions. They include activation of the internal alkene function by the action of (a) strong nonmetallic electrophiles such as phenyl-selenenyl sulfate (159), and (b) metallic catalysts such as Ag(I) (160) and Pd(II) ions... [Pg.795]


See other pages where Nitrones intermolecular reactions is mentioned: [Pg.56]    [Pg.48]    [Pg.364]    [Pg.48]    [Pg.845]    [Pg.58]    [Pg.691]    [Pg.82]   
See also in sourсe #XX -- [ Pg.59 , Pg.60 , Pg.61 , Pg.62 , Pg.63 , Pg.64 , Pg.65 , Pg.66 , Pg.67 ]

See also in sourсe #XX -- [ Pg.59 , Pg.60 , Pg.61 , Pg.62 , Pg.63 , Pg.64 , Pg.65 , Pg.66 , Pg.67 ]




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Alkenes intermolecular nitrone cycloaddition reactions

Dipolarophiles intermolecular nitrone cycloaddition reactions

Hydroxylamines, intermolecular nitrone cycloaddition reactions

Nitronates intermolecular

Nitrone reactions

Nitrones, reactions

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