Hydromagnesiation 1 - -1 -alkyne

Hydromagnesiation of 1-propynylic alcohols. The hydromagnesiation of alkynes (10,130) has been extended to propynylic alcohols (equation I), which provides a new route to terpenoids.1... 

Dicyclopentadienyltitanium dichloride is possibly superior to titanium tetrachloride as a catalyst. Nickel(ll) compounds are also active, but with these catalysts concurrent addition of the organomagnesium compounds to carbon-carbon multiple bonds (see Section 4.1) causes complications. Examples of hydromagnesiation by Grignard reagents are listed in Table 3.8. As will be seen from entries in Table 3.8, the stereochemistry of addition to alkynes is syn. The regiochemistry is also usually predictable in the relevant examples in Table 3.8, one regioisomer is obtained mainly or exclusively. In other cases, however, mixtures are formed [54]. 

HydromagnesiatUm vinylsilanes. The hydromagnesiation (10, 130-131) of 1-trimethylsilyl-1 -alkynes with isobutylmagnesium bromide followed by alkylation affords (Z)-l,2-dialkylvinylsilanes in high yield. 

ON THE MECHANISM OF Cp2TiCl2-CATALYZED HYDROMAGNESIATION OF ALKYNES WITH GRIGNARI)... 

Hydromagnesiation of Alkenes and Alkynes Eiimie Salo and Hirokazu Vrahe... 

On the Mechanism of CpsTiCli-catalyzed Hydromagnesiation of Alkynes with Grignard Reagents... 

Grignard Reagents New Developments Table 3.6. Hydromagnesiation of (irimethylsilyl)alkynes with Grignard reagents... 

Hydrotitanation of 1-silyl- and I-stannyl-1-alkynes leads to P-silyl (or p-stannyOalkenyltitanates, thus showing opposite regioselectivity to other related processes (hydroboration, hydroalumination, hydromagnesiation, hydrotitanation, hydrozincation, hydrozirconation).Well-defined alkenes are obtained on further reaction of the alkenylti-tanates, for example, with allylic carbonates an 8 2 displacement occurs to afford 1,4-di-... 

Generation of Optically Active a-Trimethylsilyl-butenolides. Sato and coworkers published a highly efficient method to prepare enantiomericahy pure a,/8-unsaturated butenolides from enantioenriched 4-TMS-3-but)m-2-ol through a Ti-catalyzed hydromagnesiation reaction of the alkyne, car-boxylation using CO2, and a subsequent lactonization (eq 3). This approach was later employed elegantly by Negishi in the synthesis of epolactaene. ... 

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