Keywords: Iridium / Allyl complexes / NMR spectroscopy / Allylic substitution / Asymmetric catalysis Ir-catalysed allylic alkylations of enantiomerically enriched monosubstituted allylic acetates proceed with up to 87% retention of configuration using P(OPh) 3 as ligand. High regioand enantioselectivity of up to 86% ee in asymmetric allylic alkylations of achiral or racemic substrates is achieved with monodentate phosphorus amidites as ligands. Lithium N-tos-

The wizard of Os: Regioselective osmium‐catalyzed 7‐endo heterocyclization of aromatic alkynols affords benzoxepines in good yields. The proposed catalytic cycle involves the key formation of osmium–vinylidene complexes via an alkynyl‐hydride–osmium(IV) complex from the starting alkynol.

Reaction of OsH2(κ 2-OCOCH3){κ 1-OC(O)CH3}(PiPr3)2 (1) with 1/2HBF4·OEt2 leads to the dimer [{OsH2(κ 2-OCOCH3)(PiPr3)2}2(μ-OCOCH3)]BF4 (2), while the reaction with HBF4·OH2 gives the aquo-derivative [OsH2(κ 2-OCOCH3)(H2O)(PiPr3)2]BF4 (3). The structure of 2 in the solid state has been determined by an X-ray diffraction study. The structure consists of two OsH2(κ 2-OCOCH3)(PiPr3)2 units connected through an acetate bridge. Complex 3 reacts with phenylacetylene and 1,1-diphenyl-2-propyn-1-ol to give the metallacyclopropene complexes (4) and (7), respectively. The structure of 4 in the solid state has been determined by an X-ray diffraction study. The geometry around the metal center can best be described as a pentagonal bipyramid with the two phosphorus atoms of the phosphines occupying apical positions. The equatorial plane is defined by the hydride, the acetate ligand, and the two carbon atoms of the metallacyclopropene. Reaction of 3 with tert-butylacetylene or trimethylsilylacetylene affords the carbyne complexes [OsH(κ 2-OCOCH3)(⋮CCH2R)(PiPr3)2]BF4 [R = CMe3 (8), H (9)], respectively. Deprotonation of 8 and 9 with KOH gives the vinylidene derivatives OsH(κ 2-OCOCH3)(CCHR)(PiPr3)2 [R = CMe3 (10), H (11)]. The carbyne analogue of 8 and 9 bearing a phenyl group, [OsH(κ 2-OCOCH3)(⋮CCH2Ph)(PiPr3)2]BF4 (5), can be obtained upon protonation of OsH(κ 2-OCOCH3)(CCHPh)(PiPr3)2 (6) with HBF4·OEt2. In agreement with the experimental results, DFT (B3PW91) calculations show that the cyclopropene product is thermodynamically preferred for phenylacetylene, while the carbyne isomer is preferred for tert-butylacetylene.

Monodentate phosphorus amidites derived from 2,2Ј-binaphthol and a variety of chiral amines were employed as ligands in Ir I -catalysed allylic alkylations of unsymmetrically substituted allylic acetates. The enantio-and regioselectivities of these reactions were investigated. Phosphorus amidites of bulky secondary chiral amines induced enantioselectivities of up to 94% ee in reactions of linear substrates. Phosphorus