Palladium-catalysed borylsilylation and borylstannylative dimerization of 1,2-dienes

(E)‐ and (Z)‐β‐Borylallylsilanes by Alkyne Silaboration Followed by Regio‐ and Stereoselective Double‐Bond Migration

“…[5] These particular b-borylallylsilanes are best synthesized by the catalytic silaboration of terminal allenes, in which the internal C = C bond undergoes an addition reaction in a highly regioselective manner (Scheme 1, left). [6][7][8] This system was extended to asymmetric silaboration giving b-borylallylsilanes with high diastereoand enantioselectivities and these compounds were successfully utilized for asymmetric cyclization reactions. [9] Terminalselective silaboration of terminal allenes using a platinum catalyst has also been developed.…”

Hydroboration, Diboration, Silylboration, and Stannylboration

“…The diboration and silylboration of 1,2-dienes (allenes) affords another series of allylboron compounds (Scheme 1-36) [141][142][143]. The addition of diboron 82 has a strong tendency to occur at the internal double bond, but steric hindrance in both the allenes and the phosphine ligands forces the addition towards the terminal double bond.…”

“…The reaction selectively yields (E)-107b for 1,2-heptadiene (R 1 =C 4 H 9 , R 2 =H) by way of addition from the less-hindered side of the terminal double bond. The palladium-catalyzed silylboration [142,143] of allenes exhibits a much stronger tendency to occur at the internal double bond. However, it is interesting that addition to 1,1-dimethylallene reveals completely opposite selectivity between the palladium(0) and platinum(0) catalysts.…”

Silylboranes as New Tools in Organic Synthesis

“…Palladium-catalyzed silaboration of allenes was reported in 1999 independently by our group and Tanaka's group, which used Pd(acac) 2 /2,6-Me 2 C 6 H 3 NC (Pd/L = 1/4) 26 and Pd 2 (dba) 3 /etpo (Pd/L = 1/2) 27 as catalyst. The silaboration of allene proceeded with introduction of the boryl group to the central carbon atom of the allene to give ¢-borylallylsilanes (Table 6).…”