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Selenones vinyl

Selenones/ y-Hydroxy vinyl selenides (1) are labile and readily undergo dehydration on standing, but can be oxidized successfully to y-hydroxy vinyl selenones (2) by m-chloroperbenzoic acid in the presence of K2HP04 in CH3OH at 25°. [Pg.404]

These vinyl selenones are of interest because they undergo a 1,4-fragmentation at room temperature in the presence of bases to give an ethylenic ketone (equation I). If 1 he double bond is tetrasubstituted, the fragmentation results in an acetylenic ketone (equation II). [Pg.404]

A variety of a,jS-unsaturated esters and nitriles bearing a leaving group at the a-carbon" ", vinyl selenones" ", vinylsulfoxonium salts" and vinylsulfonium salts" "" have been found to react with doubly activated methylene compounds, such as... [Pg.341]

Rearrangement in the intermediates sometimes leads to unexpected products. In the reactions of the monoenolates of 1,3-diones with vinyl selenones, 2-acylcyclopropanecar-baldehydes have been obtained in good yields (equation 96) " ... [Pg.342]

Synthesis of a-Selenoalkyl Metals by Addition of Organometallics to Vinyl Selenides, Vinyl Selenoxides and Vinyl Selenones... [Pg.629]

Lithium enolates derived from methyl ketones and acetates successfully add to vinyl selenoxides - and to vinyl selenones to give cyclopropyl ketones and esters (Scheme 110). The a-lithioalkyl selenoxide or selenone intermediates presumably exchange to the lithium enolates which, after displacement of the seleno or selenoxy group, lead to the observed products. [Pg.670]

Additions of various nucleophiles to vinyl selenoxides - and vinyl selenones have been described. Thus potassium hydroxide and amines add to vinyl selenones and directly produce epoxides and aziridines, respectively, whereas 3-methoxyoxetanes have been obtained from 7-hydroxy-a-alkenyl selenones and st ium methoxide (Scheme 111). ... [Pg.670]

Treatment of vinyl selenones with active methylene compounds in a basic medium gave electrophilic cyclopropanes via a similar procedure (Table 30). [Pg.100]

Table 30. Synthesis of Electrophilic Cyclopropanes Using Vinyl Selenones... Table 30. Synthesis of Electrophilic Cyclopropanes Using Vinyl Selenones...
The chemistry of selenones (11) has not been studied as extensively as that of selenoxides. However, it has been demonstrated that selenones function as good leaving groups, comparable to tosylates or halides. For example, they are readily solvolyzed in methanol and produce rearranged products when jS-substituents with high migratory aptitudes are present (equations 7 and 8). Vinylic selenones also act as Michael acceptors, as in the first step of the process shown in equation (9). [Pg.4318]

Shimizu et al. prepared the cyclic ( )-vinyl ether (270) in moderate yield by an addition-fragmentation reaction of the diol (271) by treatment with sodium hydride in THF overnight. The conjugate addition of the alkoxide to the vinyl selenone generates (272), then (273), leading to bond rupture and the expulsion of phenylselenone to form (270) (Scheme 31) <84JOC1230>. [Pg.773]

In 2011, Marini and co-workers [49] described an organocascade for the synthesis of spirolactones from cyclic (3-ketoesters and a vinyl selenone by an enantioselective Michael addition followed by intramolecular nucleophilic substitution of the phenyl-selenoyl leaving group (Scheme 16.24). [Pg.569]

Michael addition of a-aryl-a-isocyanoacetates (352) to vinyl selenone (353), catalysed by the quinine derivative (351), has been reported to proceed readily at —40 °C, affording... [Pg.454]

In the same year, Marini and coworkers developed an interesting synthesis of spirolactones 85 based on an organocatalyzed Michael addition-cyclization reaction sequence (Scheme 10.29) [49]. tert-Butyl ketoesters 82 reacted with vinyl selenone... [Pg.295]

Michael addition/cyclization sequence. Angewandte Chemie International Edition, 50, 9382-9385. (b) Sternativo, S., Batistelli, B., Bagnoli, L., Santi, C., Testaferri, L., Marini, F. (2013). Synthesis of y-lactams via a domino Michael addition/cyclization reaction of vinyl selenone with substituted amides. Tetrahedron Letters, 54, 6755-6757. [Pg.306]

SCHEME 2 Formation of aziridine ring by aza-Michael-initiated ring-closure reaction between vinyl selenone and paimary amines. [Pg.165]

A recent study revealed that the rate of aza-Michael-initiated ring-closure reaction between vinyl selenone 8 and primary amines 9 forming aziridines 10 (Scheme 2) was accelerated significantly in water [25]. The reactions in case of many substrates were accomplished in 3-7h as against over 24h when carried out in toluene. An asymmetric aziridination under the reaction conditions in the presence of either catalyhc or stoichiometric amounts of (R)-BINOL gave excellent yields of aziridines, but very poor enantioselectivity (ee 18% and 10% in two reactions investigated) was observed. [Pg.165]

S. Sternativo, F. Marini, F.D. Verme, A. Calandriello, L. Testaferri, M. Tiecco, One pot s)fnthesis of aziridines from vinyl selenones and variously functionalized amines. Tetrahedron 66 (2010) 6851-6857. [Pg.181]

At the same time as the emergence of the vinyl sulfones as Michael acceptors in organocatalyzed conjugate additions, a new type of acceptor appeared in the form of vinyl selenones. [Pg.1037]

Scheme 34.36 Addition of a-cyanoesters to vinyl selenone 99 and postfiinctionalizations. Scheme 34.36 Addition of a-cyanoesters to vinyl selenone 99 and postfiinctionalizations.
Scheme 34.37 Synthesis of cyclopropanes by sequential addition to vinyl selenone and cyclization. Scheme 34.37 Synthesis of cyclopropanes by sequential addition to vinyl selenone and cyclization.
A highly efficient synthesis of spirolactone 110 was described by Marini et al. in 2011 [82] using the addition of cyclic 5-ketoester 111 to vinyl selenone 99 and subsequent cyclization of intermediate 112 in the presence of silica (Scheme 34.39) under mild conditions. This reaction exhibited a wide scope (selected examples are given in Scheme 34.39) but was limited to P-ketoesters with a cydopentanone core. Moreover this process could be extended to stereodivergent parallel kinetic resolution of a racemic mixture of chiral P-ketoesters with a high degree of enantioselectivity. [Pg.1039]

The authors suggested a transition state (Figure 34.3) to explain the observed stereoselectivity in which the tertiary amine included in the catalyst 113 would be responsible for formation of the enolate, while the hydroxyl group would play a role in guiding the vinyl selenone by H-bonding. [Pg.1039]

For the same sequence, vinyl sulfones and vinyl selenones have appeared as new partners in organocatalyzed asymmetric conjugate addition, giving access to valuable building blocks. [Pg.1040]


See other pages where Selenones vinyl is mentioned: [Pg.773]    [Pg.773]    [Pg.341]    [Pg.669]    [Pg.773]    [Pg.669]    [Pg.418]    [Pg.508]    [Pg.508]    [Pg.1013]    [Pg.1037]    [Pg.1037]    [Pg.1037]    [Pg.1038]    [Pg.1038]    [Pg.1039]    [Pg.1437]   
See also in sourсe #XX -- [ Pg.123 ]




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