A Palladium-Catalyzed Novel Allylstannylation of Norbornene

Palladium-catalyzed novel addition–elimination reaction of alkenyltin reagents to norbornene

“…Subsequent norbornene insertion step appears to conform to carbopalladation, instead of stannylpalladation, to generate the key-intermediate A, stereoselectively. In the case of allylstannylation, reductive elimination took place from A to give the carbostannylation product, probably because the intermediate that corresponds to complex A is so labile owing to inefficient coordination by p-bond of the allylic moiety and b-hydride-elimination is not accessible [1,3]. The above mentioned product ratio of the arylstannylation would indicate that its p-system plays an important role in making the insertion of the second norbornene [2 Á/4].…”

“…The reaction of the former reagent afforded a mixture of the product with one norbornene moiety (1) and that with two norbornene moieties (2), while that of the latter gave the adduct with one norbornene, exclusively. The product ratio between 1 and 2 showed a certain level of dependence on electronic character of the aromatic substituent.…”

Palladium−Iminophosphine-Catalyzed Alkynylstannylation of Alkynes

“…We now report that a palladium−iminophosphine complex catalyzes the addition of alkynylstannanes to alkynes, leading to the regio- and stereoselective formation of conjugated (stannyl)enynes. − In particular, a bulky ligand is found to improve both yields and regioselectivities. The characteristic features of the alkynylstannylation compared with other carbometalation reactions are as follows: (1) Alkynyl moieties are introduced into alkynes in a manner that can hardly be achieved with an organometallic reagent having a polar C−M bond.…”