Ru-catalyzed cycloisomerizations of aromatic homo- and bis-homopropargylic alcohols effectively afford benzofurans and isochromenes. These processes proved to be chemo- and regioselective (5-, and 6-endo cyclizations) derived from key Ru vinylidene intermediates. The presence of an amine/ammonium base-acid pair is crucial for the catalytic cycle.

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.

Ruthenium-catalyzed cycloisomerizations of aromatic homo-and bis-homopropargylic amines/amides efficiently afford indoles, dihydroisoquinolines and dihydroquinolines. These processes were regioselective (5-and 6-endo cyclizations) on using key Ru vinylidene intermediates. The presence of an amine/ammonium base-acid pair increased the rate of cyclization and facilitated the catalytic turnover.Keywords: alkynylamines; azaheterocycles; cyclo-A C H T U N G T R E N N U N G isomerization; ruthenium; vinylidenes Nitrogen heterocycles like indole, isoquinoline and quinoline are prominent structural units in a variety of biologically active natural products and in synthetic organic materials.[1] In recent years, a plethora of synthetic methods to obtain these benzoheterocycles has been developed [2] and transition metal-catalyzed intramolecular cyclizations of aromatic alkynylamines and derivatives are particularly successful.[3] Typically, in the case of internal alkynes, heterocyclization is initiated by p-activation of the alkyne by coordination with transition metals. This favors the formation of electrophilic species that immediately undergo nucleophilic attack. This strategy has been used to prepare efficiently many types of heterocycles including indoles, isoquinolines and quinolines (Scheme 1).In the case of terminal alkynes, the use of metal vinylidenes as electrophilic species represents an attracScheme 1. Metal-catalyzed synthesis of indoles, isoquinolines and quinolines.

Os im Katalysator, O im Heterocyclus: Regioselektive osmiumkatalysierte 7‐endo‐Heterocyclisierungen aromatischer Alkinole liefern Benzoxepine in guten Ausbeuten. Der vorgeschlagene Katalysezyklus umfasst die Bildung eines Osmium‐Vinyliden‐Komplexes über einen Alkinyl‐Hydrid‐Osmium(IV)‐Komplex aus der Ausgangsverbindung.

. -The presence of an amine/ammonium base-acid pair is crucial for the catalytic cycle. Only substrates bearing a terminal alkyne and an alcohol function in ortho-position can be used for the preparation of the target compounds. The cyclization of substrate (XIII) bearing benzylic and phenolic OH groups proceeds with complete regioselectivity. -(VARELA-FERNANDEZ, A.; GONZALEZ-RODRIGUEZ, C.; VARELA, J. A.; CASTEDO, L.; SAA*, C.; Org. Lett. 11 (2009) 22, 5350-5353; Dep. Quim. Org., Fac. Quim