Hydromagnesiation of Alkenes

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

There is another choice of catalyst in hydromagnesiation of alkenes with Grignard... 

The hydromagnesiation of acetylenes, catalysed by titano- and zirconocenes is well known. A regioselective reaction occurs only if one of the substituents on the triple bond is silicon or an aryl group. Studies on its mechanism were reported by Sato.2 7 Cai has applied this reaction for the synthesis of a number of polysubstituted alkenes (Scheme p).28-28 -2 ... 

Furanes.3 Hydromagnesiation of 3-trimethylsilyl-2-propyne-l-ol (1) (11, 163) followed by reaction with an aldehyde or ketone provides E-3-trimethylsilyl-2-alkene-l,4-diols (2). These are converted into 3-trimethylsilyl-2,5-dihydrofuranes (3) on dehydration... 

When alkyncs are subjected to this hydromagnesiation in place of alkenes, (c/.v-l,2-disubstituted vinyl)magnesium reagents can be prepared in a highly stereoselective manner [21. 

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-... 

Optically active fiirfiiryl alcohols and hydroxy butenolides of the following type were prepared from /nms-l-trimethylsilyl-i-alken-l-ynes by successive asymmetric dihydroxylation and hydromagnesi-ation reactions <93TL 4975>. 

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