Alkenylaluminum reagents

It was claimed that the Z-form of the allylic acetate 430 was retained in homoallylic ketone 431 obtained by reaction with the potassium enolate of 3-vinylcyclopentanone (429), after treatment with triethylborane[282]. Usually this is not possible. The reaction of a (Z)-allylic chloride with an alkenylaluminum reagent to give 1,4-dienes proceeds with retention of the stereochemistry to a considerable extent when it is carried out at -70 C[283]. 

Addition reactions. The mixed alane generated in situ from Me3Al and isobutyl-aluminoxane adds to 1-aIkynes to afford 2-methyl-1-alkenylaluminum reagents. This process has been applied to a synthesis of coenzyme Qio- ... 

The hydroalumination of alkynes using DIBAL-H (diisobutylaluminumhydride) is a general method for preparing various alkenylaluminum reagents [26]. Recently, it has been shown that this hydroalumination can be catalyzed with 3% Ni(dppe)Cl2 in THF at 22°C within 2 h. This hydroalumination tolerates some functional groups. Thus, the... 

The synthesis of 9-alkenyl-9-BBN via hydroboration of terminal alkynes with 9-BBN suffered from the formation of 1,1-diborylalkanes via dihydroboration along with desired monohydroboration products. Alternatively, selective monohydroboration of terminal alkynes with dicyclohexylborane was followed by transmetallation with 9-MeO-9-BBN (Equation (193)).710 Treatment of the hydroboration intermediates with DIBAL-H in the presence of a borane-trapping reagent such as 1-hexene gave 1-alkenylaluminum compounds with complete retention of the (E)-stereochemistry (Equation (194)).711... 

Aluminum Reagents. Alkenylaluminum compounds can also be used as reagents for alkenylation in reactions promoted by palladium. Formation of a 2-alkenylpyridine 216 is shown (Scheme 82).[i °i... 

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