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Terminal 1,2-dialkynylarenes undergo an unexpected cyclization hydroarylation reaction toward naphthalene derivatives in benzene as the solvent. The regioselectivity of the reaction can be controlled by careful catalyst tuning. Also, the preparation of a bench-stable cationic amine complex or simple heterogenization of the catalyst on neutral aluminum oxide, which enables efficient catalyst recycling, was possible. Intensive mechanistic investigations were undertaken, giving new insights into the so-far underestimated role of acetylides in gold chemistry. The gold plays a fascinating dual role serving to both catalyze the reaction and activate the substrate by Au−C-σ bond formation. Evidence of gem-diaurated compounds playing an important part for gold catalysis is also reported.

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A series of easily accessible arene-1,2diynes, bearing one aryl substituent on one of the alkynyl groups, is readily converted to dibenzopentalenes in good yields by gold(I) catalysts. The participation of gold acetylides could be proven by the direct conversion to the corresponding gem-diaurated dibenzopentalenes with a gold catalyst. From an experiment with a gold acetylide complex and stoichiometric amounts of the gold "catalyst" the corresponding gem-diaurated complex of a dibenzopentalene could be obtained and characterized by X-ray crystal structure analysis. Labelling studies with deuterated alkynes show the expected deuteration of the two remaining positions of the pentalene core. All this provides evidence for a dual activation mode of the reaction and gold(I) vinylidene complexes as intermediates of the catalytic cycle.In the highly active field of homogeneous gold-catalyzed reactions, [1] only recently, have diynes been employed as starting materials. The general reactivity pattern of the reactions is based on an initial attack of an intra-or intermoleculary offered nucleophile onto one of the triple bonds. The so-formed intermediate en-yne systems then undergo further transformations that lead to highly complex molecular structures. [2] We have just contributed a new hydroarylating aromatization of arene-diynes (Scheme 1). [3] This reaction is mechanistically highly interesting as it proves that the participation of gold acetylides can induce completely different selectivities in gold-catalyzed reactions. It also proves a double activation by the gold catalyst. By using basic additives or organo-gold compounds, the gold acetylide formation could be enforced and instead of the expected a-phenylnaphthalenes a-2, we observed the exclusive formation of isomeric b-phenylnaphthalene b-2. The results from that very complex mechanistic study indicate that so far only scarcely mentioned gold vinylidene species are involved in the reaction mechanism. [4] Here we report another exciting aspect of this completely new type of gold-catalyzed conversion. When we investigated arene-diynes possessing one terminal and one aryl-substituted alkyne, completely different products were obtained. No incorporation of the aro-Scheme 1. Selectivity switch in the hydroarylation-aromatization of 1.

Molecular sieves, such as nanoporous AlPO4-5, can host a wide variety of laser active dyes. We embedded pyridine 2 molecules as a representative of a commercially available dye which fits into the channel pores of the host matrix. Many efficient dye molecules, such as rhodamines, do not fit into the pores. But modifying the structure of the dyes to appear like the used templates allows to increase the amount of encapsulated dyes. The properties of resulting microlasers depend on size and shape of the microresonators, and we discuss a model for microscopic hexagonal ring resonators. In terms of pump needed to reach lasing threshold molecular sieve microlasers are comparable to VCSELs. For dyes which fit into the pores we observed a partial regeneration of photo-induced damage.

No abstract

Gold(I)-triflimide (AuNTf 2 )complexes of H-KITPHOS and o-MeO-KITPHOS have been prepared and shown to be efficient catalysts for a range of intramolecular cyclisations to afford phenols, acylindenes, alkylidene oxazoles, tetrahydropyrans and lactones, in the majority of cases these catalysts are superior to those previously reported.

Highly reactive gold vinylidene species are used for intermolecular C(sp(3))-H insertions into unactivated alkanes (see scheme). In addition, they can be regarded as synthons for alkylidene carbenes. Initiated by cyclopropanation of the vinylidene species/alkylidene carbenoide, cyclobutene derivatives are formed in a diastereoselective fashion by a ring-enlargement cascade in only one step.