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Cycloaddition /reactions nitrones

In the nitrone cycloaddition reactions catalyzed by the l ,J -DBFOX/Ph transition metal complexes also, the diastereo- and enantioselectivities were found to depend upon the presence of MS 4 A [71]. Thus, both the selectivities were much lowered in the iron(II) or nickel(II) complex-catalyzed reactions without MS 4 A,... [Pg.270]

The formation of enantiopure tricyclic compounds takes place by intramolecular 1,3-dipolar cycloadditions of acyclic nitrones to cyclic olefinic fragments (Scheme 2.214a,b) (706, 707a), or of cyclic nitrones to acyclic olefins (Scheme 2.214c) (116). Recently (707),b intramolecular nitrone cycloaddition reactions (according to Scheme 2.211a) have been applied in the synthesis of... [Pg.301]

Nitrone cycloaddition reactions with alkynes have been widely used for the synthesis of imidazolidine nitroxides (736) and (737), containing chelating enam-ino ketone groups (821). Different heterocyclic systems were obtained, such as 3-(2-oxygenated alkyl)piperazin-2-ones (738) (822), also compounds containing the isoxazolo[3,2-i]indole ring system (739) (823) and a new class of ene-hydroxylamino ketones- (l )-2-( 1-hydroxy-4,4,5,5-tetraalkylimidazolidin-2-ylidene)ethanones (740) (824) (Fig. 2.46). [Pg.374]

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

Cycloaddition to endocyclic unsaturation has been used by many researchers for the preparation of isoxazoUdinyl adducts with y-lactams derived from pyrogluta-minol and is discussed later in this chapter as a synthesis of unusual amino acids (Scheme 1.20, Section 1.6) (79,80). A related a,p-unsaturated lactam has been prepared by a nitrone cycloaddition route in the total synthesis of the fungal metabolite leptosphaerin (81). A report of lactam synthesis from acyclic starting materials is given in the work of Chiacchio et al. (82) who prepared isoxazolidine (47) via an intramolecular nitrone cycloaddition reaction (Scheme 1.11). [Pg.10]

The rare reports of quinolizidine formation by a nitrone cycloaddition strategy include the racemic total synthesis of lasubine II (58), one of a series of related alkaloid isolated from the leaves of Lagerstoemia subcostata Koehne (Scheme 1.14) (104). While these alkaloids were previously accessed by infennolecular nitrone cycloaddition reactions, this more recent report uses an intramolecular approach to form the desired piperidine ring. Thus, cycloaddition of nitrone 59 affords predominantly the desired bridged adduct 60 along with two related... [Pg.13]

Aggarwal et al. (198) reported nitrone cycloaddition reactions with the unusual disulfoxide dipolarophile fran5-2-methylene-l,3-dithiolane (168) (Scheme 1.37). The question of exo/endo selectivity of the cycloaddition reaction is avoided by the use of this C2-symmetric dipolarophile for which only two transition states are... [Pg.31]

In a related strategy, the dihydropiperidine skeleton of the macrocyclic alkaloid cannabisativine (208) (Fig. 1.6), isolated from the leaves and roots of the common cannabis plant, was prepared with regio- and stereoselectivity using an intramolecular allylsilane-nitrone cycloaddition reaction as a key step (260). [Pg.37]

A chelating enone employed in a Lewis acid catalyzed nitrone cycloaddition reaction should result in a rate enhancement. The first example of such catalysis... [Pg.795]


See other pages where Cycloaddition /reactions nitrones is mentioned: [Pg.248]    [Pg.248]    [Pg.249]    [Pg.249]    [Pg.274]    [Pg.3]    [Pg.3]    [Pg.34]    [Pg.59]    [Pg.67]    [Pg.68]    [Pg.804]    [Pg.1164]    [Pg.1165]    [Pg.13]    [Pg.13]    [Pg.44]    [Pg.69]    [Pg.77]    [Pg.78]   
See also in sourсe #XX -- [ Pg.364 ]

See also in sourсe #XX -- [ Pg.216 , Pg.217 , Pg.218 ]

See also in sourсe #XX -- [ Pg.364 ]

See also in sourсe #XX -- [ Pg.325 ]

See also in sourсe #XX -- [ Pg.305 ]




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1,3-dipolar cycloaddition reactions cyclic nitrones

1,3-dipolar cycloaddition reactions with nitrones

1.3 dipolar cycloaddition reaction of nitrones

1.3- Dipolar cycloaddition reactions nitrones

Alkenes intermolecular nitrone cycloaddition reactions

Alkynes-nitrones cycloaddition reaction

Cycloaddition asymmetric reaction with nitrones

Cycloaddition reactions alkyl nitronates

Cycloaddition reactions cyclic nitronate preparation

Dipolarophiles intermolecular nitrone cycloaddition reactions

Enantioselectivity nitrone cycloadditions, catalyzed reactions

Hetero Diels-Alder reaction nitrone cycloaddition

Hydroxylamines, intermolecular nitrone cycloaddition reactions

Intramolecular reaction nitrone cycloaddition

Isoxazolidines nitrone cycloaddition reactions

Ketones nitrone 1,3-dipolar cycloadditions, reaction

Nitronates cycloadditions

Nitrone cycloaddition Wittig reaction

Nitrone reactions

Nitrone reactions with cyclopropanes 3+2]dipolar cycloaddition

Nitrones 1,3-dipolar cycloaddition reactions, external

Nitrones cycloaddition

Nitrones reversible cycloaddition reactions

Nitrones, cycloaddition with Diels—Alder reaction

Nitrones, cycloadditions

Nitrones, reactions

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