No abstract

Chiral nonracemic alkynyl(alkoxy)carbene complexes of tungsten(0) undergo the [3 + 2] cyclization toward alpha-methylindoles and 1,6-dimethyl-1,2,3,4-tetrahydropyridine to provide 2,3-indoline-fused cyclopentenone and 2,3-piperidine-fused cyclopentenone skeletons, respectively, with very high enantiomeric purities (96-99% ee).

Fis(c)hing for cyclization! The sequential treatment of an acetylide with a Fischer carbene complex and an alkene/diene yields alkynylcyclopropanes with a wide substitution range. The intramolecular process provides 1‐alkynylbicyclo[3.1.0]cyclohexanes by starting from 1,6‐enynes. A non‐heteroatom‐stabilized metal alkynylcarbene is responsible for the selective transfer of the propargylene unit.

An allylic gold(I) cation, proposed as key intermediate in the gold-promoted rearrangement of 1,5-enynes bearing a fixed conformation, has been detected and characterized by NMR spectroscopy. Moreover, its participation in the overall transformation was confirmed. Computational studies indicate that the gold-catalyzed transformation occurs through an uncommon rearrangement. Additionally, this study led us to isolate and characterize a stable homoantiaromatic carbocation.

An allylic gold(I) cation, proposed as key intermediate in the gold‐promoted rearrangement of 1,5‐enynes bearing a fixed conformation, has been detected and characterized by NMR spectroscopy. Moreover, its participation in the overall transformation was confirmed. Computational studies indicate that the gold‐catalyzed transformation occurs through an uncommon rearrangement. Additionally, this study led us to isolate and characterize a stable homoantiaromatic carbocation.