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Metal acetates allylic oxidation

In comparison with metal porphyrins, the corresponding metal phthalocyanines are much more stable against oxidative decomposition. Murahashi et al. reported that chlorinated Fe(II) phthalocyanine is particularly well suited for aerobic allylic oxidation employing acetic aldehyde as a cofactor (Scheme 3.27) [118]. Under these conditions, cyclohexene la is converted to a mixture of 2a and 3a in 70% overall yield and the epoxide 4a as byproduct (30%). Acetic aldehyde is proposed to autoxidize by... [Pg.98]

The cyclohexene 121, which was readily accessible from the Diels-Alder reaction of methyl hexa-3,5-dienoate and 3,4-methylenedioxy-(3-nitrostyrene (108), served as the starting point for another formal total synthesis of ( )-lycorine (1) (Scheme 11) (113). In the event dissolving metal reduction of 121 with zinc followed by reduction of the intermediate cyclic hydroxamic acid with lithium diethoxyaluminum hydride provided the secondary amine 122. Transformation of 122 to the tetracyclic lactam 123 was achieved by sequential treatment with ethyl chloroformate and Bischler-Napieralski cyclization of the resulting carbamate with phosphorus oxychloride. Since attempts to effect cleanly the direct allylic oxidation of 123 to provide an intermediate suitable for subsequent elaboration to ( )-lycorine (1) were unsuccessful, a stepwise protocol was devised. Namely, addition of phenylselenyl bromide to 123 in acetic acid followed by hydrolysis of the intermediate acetates gave a mixture of two hydroxy se-lenides. Oxidative elimination of phenylselenous acid from the minor product afforded the allylic alcohol 124, whereas the major hydroxy selenide was resistant to oxidation and elimination. When 124 was treated with a small amount of acetic anhydride and sulfuric acid in acetic acid, the main product was the rearranged acetate 67, which had been previously converted to ( )-lycorine (108). [Pg.279]

While allylic oxidation products may arise by elimination of a metal hydride from an intermediate adduct or metd-alkene complex, allylmercury species (34) are thought to be intermediates in the case of mercuty(II) acetate. A number of pathways have been suggested, for example involving radical and catbenium ion intermediates, and addition--elinimation and rearrangement processes. ... [Pg.92]

Overall, many transition metal complexes have been investigated. Among those not mentioned above which may carry out catalytic allylic oxidation to give enones under certain drcumstances are Co(PPh3)Cl/02, Mn(TPP)Cl/02, [Fe(PPh3)]20AJV, Ni(phthalocyanine)/02 and an unusual mercury(II) acetate example in which the enone is formed rather than the expected acetate. [Pg.108]

Other transition metal salts mediate in similar oxidations. For example, mercury(II) acetate, a milder reagent than LTA, effects a-acetoxylation through a comparable mechanism. However the corresponding yields for these processes are poor. 3,3-Dimethylcyclohexanone, for example, is oxidized to the a-acetoxy derivative in only 14% yield.The, 7-unsaturated ketone, isopugelone, exhibits no oxidation at the a- or a -positions, but affords a product derived from isomerization of the alkene and allylic oxidation. Not surprisingly therefore the reagent has found little synthetic application for this transformation. [Pg.154]

Among oxi tions producing allylic alcohols or their derivatives the modem variants of selenium dioxide oxidations are by far the most popular. Systems based on metal acetates, particularly palladium tri-fluoroacetate, can be very useful and are receiving increasing attention but the Kharasch-Sosnovsky reaction, once very common for allylic oxidation, is now rarely used. Sensitized photooxidation with singlet oxygen, a very well-known procedure, is still somewhat unpredictable and has periu K received less consideration than it deserves. [Pg.84]

CHLORURE PERRIQUE (French) (7705-08-0) Very hygroscopic contact with moisture in air forms ferric chloride hexahydrate. Aqueous solution is highly acidic, precipitating hydroxide and phosphate salts, and forming corrosive fumes. Violent reaction with strong bases, allyl chloride, bromine pentafluoride, ethylene oxide, oxygen difluoride. Shock- and friction-sensitive explosive is formed with potassium, sodium, potassium-sodium aUoy, and possibly with other active metals. Aqueous solution is incompatible with sulfuric acid, caustics, ammonia, aliphatic amines, alkanolamines, amides, organic anhydrides, isocyanates, vinyl acetate, alkylene oxides, epichlorohydrin. Attacks metals in the presence of moisture. [Pg.315]


See other pages where Metal acetates allylic oxidation is mentioned: [Pg.516]    [Pg.516]    [Pg.208]    [Pg.445]    [Pg.84]    [Pg.92]    [Pg.92]    [Pg.95]    [Pg.28]    [Pg.23]    [Pg.803]    [Pg.496]    [Pg.588]    [Pg.589]    [Pg.590]    [Pg.956]    [Pg.977]    [Pg.1007]    [Pg.34]    [Pg.155]    [Pg.340]    [Pg.730]    [Pg.1114]    [Pg.1232]    [Pg.13]    [Pg.376]    [Pg.84]   
See also in sourсe #XX -- [ Pg.92 ]

See also in sourсe #XX -- [ Pg.92 ]

See also in sourсe #XX -- [ Pg.7 , Pg.92 ]

See also in sourсe #XX -- [ Pg.7 , Pg.92 ]

See also in sourсe #XX -- [ Pg.92 ]




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1.1- allyl metals

2- allyl acetate allylation

Acetal allylation

Acetalization-oxidation

Acetals allylations

Acetals oxidation

Acetate oxidation

Acetic oxide

Allyl acetate

Allyl oxide

Allylic acetals

Allylic acetates

Allylic acetates acetate

Allylic metalation

Allylic oxidation

Allylic oxidation metallation

Metal acetates

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