Iridium Complex- Catalyzed Carbon-Carbon and Carbon-Heteroatom Bond Formation

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We have studied the following reactions.1)[Ir(cod)Cl]_2/DPPE-catalyzed allylic alkylation of 1,1-disubstituted-2,3-butadienyl acetates gives a product bearing a quaternary carbon center α to allene in high yield. The reaction is an efficient method for constructing a quaternary carbon center α to allene. The reaction proceeds via 1-methylene-3,3-disubstituted π-allyl iridium intermediate2)1,6-Enynes reacted with monoynes to give cyclohexadiene derivatives in the presence of a catalytic amount of [Ir(cod)Cl]_2/ligand. DPPE was most suitable for cycloaddition. Diastereoselective cycloaddition was also possible. In the absence of monoynes, 1,6-enynes cycloisomerized to (Z)-1-alkylidene-2-methylenecyclopentane derivatives. DPPF was most suitable for cycloisomerization. These results are the first examples of highly Z-selective cycloisomerization.3)[Ir(cod)Cl]_2/DPPE was found to be a new catalyst for the cycloaddition of α,ω-diynes with monoynes to give polysubstituted benzene derivatives … More in high yields. Internal monoynes as well as terminal monoynes could be used. The reaction tolerates a broad range of functional groups such as alcohol, amine, alkene, ether, halogen and nitrile. The reaction of 1,6-octadiyne derivatives with 1-alkynes gives ortho-products and meta-products. The regioselectivity could be controlled by the choice of ligand. The reaction using DPPE was meta-selective, with meta-selectivity of up to 82%. The reaction using DPPF was ortho-selective, with ortho-selectivity of up to 88%. We propose a mechanism to account for this regioselective cycloaddition. [Ir(cod)Cl]_2/DPPE also catalyzed the cycloaddition of α,ω-diynes with 2,5-dihydrofuran to give bicyclic cyclohexadiene derivatives. The reaction with 2,3-dihydrofuran and n-butyl vinyl ether gave benzene derivatives instead of cyclohexadiene derivatives. We also propose a mechanism to account for this novel aromatization that includes cleavage of the C-O bond.4)The stereochemistry of [Ir(cod)Cl]_2/P(OPh)_3-catalyzed allylic amination has been studied. The reaction of (R)-1-phenyl-2-propenyl carbonate with benzylamine gave (R)-allylic amine. The reaction was found to proceed with the retention of the stereochemistry. Less