The gold(I)‐catalysed cyclization of N‐tosyl‐protected 5‐benzyl‐6‐((trimethylsilyl)ethynyl)‐1,2,3,4‐tetrahydropyridines, prepared by the Sonogashira coupling of lactam‐derived enol triflates, provides tetrahydrobenzo[g]quinolines whose skeleton represents a recurrent motif in natural compounds. The Au(I)‐catalysed reaction is carried out with (C6F5)3PAuCl/AgNTf2 as the catalyst system and proceeds via a 6‐exo‐dig cyclization to form an exocyclic double bond, which eventually isomerises to the aromatic tetrahydrobenzo[g]quinoline. The mode of cyclization is discussed and supported by DFT calculations.
The Front Cover shows a chemist picking a fruit from a tree with his golden glove. The fruit represents tetrahydrobenzo[g]quinolines, and the chemist is going to add it to other fruits he has already collected from the δ‐valerolactam tree. Indeed, the gold‐catalysed synthesis of tetrahydrobenzo[g]quinolines enlarges the palette of molecular scaffolds accessible in few steps from the same simple lactam precursor. The authors acknowledge Federico Sini for graphical support. More information can be found in the Full Paper by C. Prandi et al.
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