Transition-metal-catalyzed asymmetric allylic substitutions are widely employed. Steric course and regioselectivity of these reactions vary considerably, depending on the metal ion, ligands, the nucleophile, and the leaving group. Today, Pd catalysts [1] are usually employed for 1,3-disubstituted allylic substrates, while Ir catalysts [2] serve well for a broad range of monosubstituted allylic substrates.The currently best Ir catalysts are prepared from [{Ir-(cod)Cl} 2 ] (cod = cycloocta-1,5-diene) and a chiral phosphoramidite by C À H activation with base (Scheme 1). Although enantioselectivity is high, this catalyst system suffers from several deficiencies: 1) It is sensitive towards oxygen.2) Long-term stability is low. 3) High selectivities are obtained only with solvents of low polarity, preferably THF. The catalyst system is stable against water and alcohols; however, enantioselectivity in these solvents is lower than in THF. 4) Regioselectivity can be as low as 3:1 (2/3), for example, with substrates 1 b-e.[3]We have now developed a modified catalyst derived from dibenzo[a,e]cyclooctatetraene (dbcot) and L2, which allows substitutions to be run without inert gas for the first time. In addition, regioselectivities with the new catalyst are considerably improved over those with presently used catalysts. Furthermore, we have observed that catalyst preparation by CÀH activation is reversible for complexes of L2 under the standard reaction conditions.The ligand cod can be removed from iridium or altered by a number of reactions. For improvement, dbcot appeared promising because its bonding to Ir is stronger than that of cod, its Ir complexes do not undergo intramolecular CÀH activation at the dbcot moiety, and it is a better electron acceptor than cod. [4] Preparations of dbcot [5] and [{Ir(dbcot)Cl} 2 ][4] were straightforward. The latter was subjected to C À H activation under argon by treatment with 1,5,7-triazabicyclo-[4.4.0]dec-5-ene (TBD) [6] or n-propylamine (Scheme 3). [7] Substitution reactions were investigated with ligands L1-L3 (Scheme 1); the best results were obtained with L2.

[reaction: see text] Enantioselective Ir-catalyzed intramolecular allylic aminations and etherifications are described. Up to 97% ee was achieved using catalysts prepared by in situ activation of mixtures of phosphorus amidites and [Ir(COD)Cl]2. Sequential aminations of bis-allylic carbonates, involving an inter- followed by an intramolecular reaction, gave trans-N-benzyl-2,5-divinylpyrrolidine and trans-N-benzyl-2,6-divinylpiperidine with > or = 99% ee. New phosphorus amidites as well as improved conditions for intermolecular aminations are reported.

Enantioselective iridium-catalysed intramolecular allylic aminations, using phosphinooxazolines or phosphorus amidites as ligands, provided ee values of >90%, at a catalyst loading of <0.5 mol-%, and displayed a marked preference for intra- over corresponding intermolecular reactions.

The synthesis of nicotine with enantiomeric excess of >99% ee was accomplished by asymmetric Ir-catalysed allylic amination followed by ring closing metathesis and racemization-free double bond reduction.

Carbocycles with > 90% ee were prepared via Ir-catalysed asymmetric allylic alkylation/ring closing metathesis sequences or enantioselective Ir-catalysed intramolecular allylic alkylations.