Aiken

The formation of 1-and 2-aIkenes can be understood by the following mechanism. In the presence of formate anion, the 7r-allylpalladium complex 572 is converted into the 7r-allylpalladium formate 573. The most interesting feature is the attack of the hydride from formate to the more substituted side of the (T-allylic system by the cyclic mechanism shown by 574 to form the 1-alkene 575[367]. The decarboxylation and hydride transfer should be a concerted... 

Complex a is readily converted into a Fe-y-H agnostic complex b within an early picosecond timescale and then the 7i-allyl hydride complex c is generated by hydride abstraction. The energy level of the 2-alkene isomer d, which is calculated by DPT experiments, is similar to that of the 1-alkene complex b. In the next step, Fe (CO)3(t -l-alkene)(ri -2-alkene) f, which is generated via intramolecular isomerization of the coordinated 1-alkene to 2-alkene and the coordination of another 1-alkene, is a thermodynamically favored product rather than formation of a Fe(CO)3(ri -l-alkene)2 e. Subsequently, release of the 2-aIkene from f regenerates the active species b to complete the catalytic cycle. 

As shown in Scheme 8.2, increasing the temperatnre to 50°C resulted in the selective formation of (ii)-2-aIkenes. While the formation of 1-dodecene was observed within minntes, isomerisation to 2-dodecene is slow, accounting for the timescale of hours required for reaction. 

The tellurolate-promoted anfi -debromination by method G is extended to the preparation of conjugated dienes, starting from 1,2,3,4-tetrabromoalkanes and cycloalkanes, 1, 4-dibromo-2-aIkenes and aUylic dibromides. ... 

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