Shigeo Yamanoi

MAO-Catalyzed Allylzirconation of 1-Alkynes

Abstract A regio- and stereocontrolled method for the allylmetallation of 1-alkynes is described. The allylzirconium species, generated by hydrozirconation of allenes, undergo regioselective addition to 1-alkynes in the presence of organoaluminum reagents among which methylaluminoxane (MAO) is particularly effective.

REACTION OF 1-IODOALKYNES WITH ALLYLZIRCONIUMS : GENERATION OF ALKYLIDENE CARBENOID VIA ALLYLZIRCONATION

Abstract Allylzirconium species, generated by hydrozirconation of allenes, react with 1-iodoalkynes in the presence of methylaluminoxane (MAO) to give the substitution products of the iodide by an allyl group. Labelling study for 2-(iodoethynyl)naphthalene suggested that the reaction involves allylzirconation of iodoalkynes to generate an alkylidene carbenoid that undergoes 1,2-rearrangement.

REGIOSELECTIVITY OF MAO-CATALYZED ALLYLMETALLATION OF CONJUGATED ENYNES WITH ALLYLZIRCONIUMS

Abstract Various conjugated enynes 1 were subjected to the MAO-catalyzed reaction with the allylzirconium, generated by hydrozirconation of allenes. In light of the regiochemisty, the CC bond formation occurs exclusively between the α carbon of the allylzirconium and the “yne” part of the conjugated enyne 1 . Steric demand of the α-substituent X in 1 is the decisive factor for determing the the reactive site for 1 .

Regioselective alkylzirconation of internal alkynes

Abstract Described herein is the carbometallation of unsymmetrically 1,2-disubstituted alkynes with alkylzirconocene complexes, which are generated by hydrozirconation of alkenes. High regioselectivity is achieved when the two substituents of the alkynes are sterically different enough, giving rise to the regio- and stereodefined trisubstituted alkenes.

Alkylzirconation of alkynes catalyzed by triphenylcarbenium tetrakis(pentafluorophenyl)borate

Abstract [(C 6 H 5 ) 3 C] + [B(C 6 F 5 ) 4 ] − effectively catalyzes the alkylmetallation of alkynes by using the alkylzirconium species, which is generated by the hydrozirconation of alkenes.