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Hydrides organozincs

A variety of organozinc reagents can be utilized in this reaction as shown in Scheme 17.32 In the case of Et2Zn, however, the H-substituted a,/Uunsaturated carboxylic acid, such as Bn0CCH2CH2CH=CHC02H, was obtained as a major product as a result of / -hydride elimination of the ethylnickel intermediate followed by reductive elimination of the resultant hydride species (entry 3). [Pg.543]

The use of lithium aluminum hydride gives slightly lower yields and probably involves a displacement reaction by hydride ion. The zinc-copper couple technique probably involves formation of an organozinc intermediate. Sodium, magnesium, and aluminum metal may be used to replace the zinc-copper couple [59a, b]. These organometal intermediates react with aldehydes and... [Pg.17]

Dimethylzinc was the first organozinc compound to be studied by mass spectrometry (MS), as part of early MS studies performed by Aston aiming to examine natural abundances of Zn isotopes. Soon thereafter, Bainbridge showed that Aston s data were imprecise because the formation of hydride ions [ZnH]+ was overlooked, and therefore their contribution to the measured abundances of Zn isotopes was not taken into consideration. In the years that followed, numerous studies addressed the subject of Zn isotopic abundances In 2001, the data presented in Table 1 were accepted as the most accurate. It was by mass spectrometry that this best measurement from a single terrestrial source was obtained. [Pg.165]

A number of compounds having a direct zinc transition metal bond are known for long time, that is, zinc-bis(transition metal) such as Zn[Co(C04)]2 and transition metal zinc halides such as (CO)4Fe(ZnCl)2. However, organozinc-transition metal compounds RZn-TM are comparatively more recent. They can be prepared by hydrocarbon elimination between a diorganozinc derivative and a transition metal hydride (see Hydrides) (equation 35), but dialkyl- and diarylzinc compounds usually fail to react or react very slowly. Furthermore, when they do react they give unstable products that show a very strong tendency to disproportionate and cannot be isolated (equation 36). [Pg.5224]

Terminal and internal (Z)-l-alkenylboronates are prepared from (Z)-(l-halo-l-alkenyl)boronates [23]. which can be readily obtained by hydroboration of 1-halo-1-alkynes (Scheme 16.2). The internal Sv,2-like displacement of the halogen with hydrides [24] or organolithiums [25] takes place wath complete inversion of configuration at the sp carbon. On the other hand, the palladium-catalyzed alkylation of the C—X bond with organozinc reagents provides ( )-l-alkenylboronates [26] which are not available by conventional hydroboration of internal alkynes. [Pg.349]


See other pages where Hydrides organozincs is mentioned: [Pg.158]    [Pg.228]    [Pg.25]    [Pg.310]    [Pg.312]    [Pg.315]    [Pg.379]    [Pg.379]    [Pg.67]    [Pg.511]    [Pg.502]    [Pg.69]    [Pg.544]    [Pg.240]    [Pg.885]    [Pg.886]    [Pg.888]    [Pg.370]    [Pg.377]    [Pg.318]    [Pg.217]    [Pg.5346]    [Pg.469]    [Pg.469]    [Pg.258]    [Pg.804]    [Pg.132]    [Pg.448]    [Pg.323]    [Pg.92]    [Pg.5345]   
See also in sourсe #XX -- [ Pg.2 , Pg.5 , Pg.5 , Pg.7 ]




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