Achieving Control over the Branched/Linear Selectivity in Palladium-Catalyzed Allylic Amination
摘要:
Palladium-catalyzed reaction of unsymmetrical allylic electrophiles with amines gives rise to regioisomeric allylic amines. We have found that linear products result from the thermodynamically controlled isomerization of the initially formed branched products. The isomerization is promoted by protic acid and active palladium catalyst. The use of base shuts down the isomerization pathway and allows for the preparation and isolation of branched allylic amines. Solvent plays a key role in achieving high kinetic regioselectivity and in controlling the rate of isomerization. The isomerization can be combined with ring-closing metathesis to afford the synthesis of exocyclic allylic amines from their endocyclic precursors.
Chasing the Proton Culprit from Palladium-Catalyzed Allylic Amination
作者:Igor Dubovyk、Iain D. G. Watson、Andrei K. Yudin
DOI:10.1021/ja076659n
日期:2007.11.1
We have found that the addition of base has a significant effect on palladium-catalyzed allylic amination. The long-standing problem of controlling the branched-to-linear ratio has been solved. In the presence of DBU and inexpensive, readily available ligands, palladium-catalyzed allylation proceeds under kinetic control, leading to high branched selectivity. Given the widespread utility of palladium-catalyzed allylic amination, we expect that these findings will be relevant in many areas ranging from asymmetric catalysis to target-oriented synthesis.
Achieving Control over the Branched/Linear Selectivity in Palladium-Catalyzed Allylic Amination
作者:Igor Dubovyk、Iain D. G. Watson、Andrei K. Yudin
DOI:10.1021/jo3025253
日期:2013.2.15
Palladium-catalyzed reaction of unsymmetrical allylic electrophiles with amines gives rise to regioisomeric allylic amines. We have found that linear products result from the thermodynamically controlled isomerization of the initially formed branched products. The isomerization is promoted by protic acid and active palladium catalyst. The use of base shuts down the isomerization pathway and allows for the preparation and isolation of branched allylic amines. Solvent plays a key role in achieving high kinetic regioselectivity and in controlling the rate of isomerization. The isomerization can be combined with ring-closing metathesis to afford the synthesis of exocyclic allylic amines from their endocyclic precursors.