Development of Gold‐catalyzed [4+1] and [2+2+1]/[4+2] Annulations between Propiolate Derivatives and Isoxazoles

Two new gold‐catalyzed annulations of isoxazoles with propiolates have been developed. Most isoxazoles follow an initial O attack on the alkyne to afford a [4+1] annulation product. This process results in a remarkable alkyne cleavage of initial propiolates. Unsubstituted isoxazoles proceed through an N attack step to yield formal [2+2+1]/[4+2] annulation products. These two annulation products arise initially from two seven‐membered heterocyclic intermediates, which then lead to products.     

Jahn‐Teller‐Ordnung in pipzH2[Mn2F8], einem Fluoromanganat(III) mit neuer Schichtstruktur

Jahn‐Teller Ordering in pipzH₂[Mn₂F₈], a Fluoromanganate(III) with a New Layer Structure From a solution of (pipzH₂)[MnF₂(HPO₄)(H₂O)]·(H₂PO₄) in concentrated hydrofluoric acid the title compound could be crystallized and was characterized by X‐ray crystallography: monoclinic, space group P2₁/n, Z = 8, a = 13.275(1), 10.400(1), c = 14.928(1) Å, β = 112.337(8), R = 0.0265. The structure shows a new type of anionic layers [Mn₂F₈] built of dimers of edge‐sharing [MnF₆] octahedra linked via common vertices, alternating with layers of piperazinium(2+) cations. A dense network of hydrogen bonds N–H···F achieves a strong 3D interconnection. Strong elongation of the [MnF₆] octahedra is observed due to the Jahn‐Teller effect.The long axes show parallel (ferrodistortive) orientation within the dimers, but the ordering between the dimers is antiferrodistorive. A possible mechanism of formation is discussed on the basis of precursor structures.