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Arynes LUMOs

In spite of their high total energy, arynes in general are selective towards different nucleophiles thus benzyne selectively captures the anion of acetonitrile in the presence of an excess of the dimethylamide ion used to generate both it and the benzyne. Nucleophilicity towards benzyne, determined by competition experiments, is in the order RLi RS- > R2N RO and I- > Br > Cl, which is an order of softness. The low energy of the LUMO of benzyne, coupled with its being uncharged, makes it a soft electrophile. [Pg.145]

Arynes. Nucleophiles readily attack the reactive intermediate 2,3-pyridyne (104) entirely at C-2.93 A calculation 94 shows that the coefficient in the LUMO of the pyridyne... [Pg.73]

Theoretical calculations suggest that the strained bent alkyne form of benzyne is lower in energy than the diradical alternative (Figure 7.4). The calculations suggest that the Jt-overlap in the strained it bond is weaker and that the it component of the bond (i.e., the LUMO) is at lower energy than normal for a triple bond, hence arynes behave as powerful electrophiles. [Pg.236]

Despite the long history of arynes and their potential as a powerful enophile in the ene reaction (because of their low-lying LUMOs), reports on the ene reaction of arynes remain rare, especially with alkynes. Recently, an ene reaction of arynes with alkynes has been reported by Cheng and coworkers, which readily affords arylallenes (Equation 12.49) [106]. [Pg.446]

The strained nature of the aryne triple bond results in an easily accessible LUMO and so, arynes are excellent electrophiles that react with different anionic or neutral nucleophilic species. This low-lying LUMO also makes arynes prone to participate in a variety of pericyclic reactions. In addition, arynes are also able to undergo interesting transition metal-catalyzed processes. The increased availability of functionalized aryne precursors as well as the possibility of generating arynes under reagent-free conditions is allowing the development of new aryne-mediated synthetic strategies and the discovery of new reactivity patterns, which will expand the repertoire of chemistry that is actually possible with arynes. [Pg.332]


See other pages where Arynes LUMOs is mentioned: [Pg.484]    [Pg.512]    [Pg.143]    [Pg.74]    [Pg.194]    [Pg.181]    [Pg.227]    [Pg.237]    [Pg.301]    [Pg.302]   
See also in sourсe #XX -- [ Pg.227 ]




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