Reaction Scope Allylsilane-Terminated Enantioselective Cyclizations

2 Reaction Scope Allylsilane-Terminated Enantioselective Cyclizations 

3 Reaction Scope Cascade (or Domino) Asymmetric Intramoiecuiar Mizoroki-Heck Reactions 

For the enantioselective formation of tertiary stereocentres, endocyclic alkenes or acyclic alkenes with -hydride-elimination-directing groups, such as allylsilanes, are often employed. In the case of endocyclic alkenes, the migratory insertion intermediate lacks a syn j8-hydrogen at the newly formed stereocentre and, therefore, cannot undergo termination. For instance, conjugated diene substrates such as 97 lead to a 7r-allylpalladium 

Enantioselective intramolecular cascade Mizoroki-Heck reactions have been shown to proceed with moderate to good selectivity via the cationic manifold. There are surprisingly few enantioselective examples, given the wide array of transformations known for cr-alkylpalladium intermediates in racemic or diastereoselective reactions. All of the nongroup-selective, enantioselective, cascade, intramolecular Mizoroki-Heck reactions reported to date involve formation of one quaternary centre. A substantial advance would be to expand the range of transformations available for the a-alkylpalladium species and 

(a) De Meijere, A. and Meyer, RE. (1994) Fine feathers make fine birds the Heck reaction in modem garb. Angew. Chem., Int. Ed. Engl., 33, 2379-411 (b) Link, J.T. (2002) The intramolecular Heck reaction, in Organic Reactions, Vol. 60 (ed. L.E. Overman), John Wiley Sons, Inc., Hoboken, NJ. 

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