A combination of gold(I) complexes and amine bases catalyzes the 5-exo-dig cyclization of formyl alkynes. This direct alpha-functionalization of aldehydes with unactivated alkynes does not involve the use of preformed enol equivalents.

Au‐spicious! Under silver‐free conditions, simple 3‐silyloxy‐1,5‐enynes were converted into complex cyclopentenes by a gold(I)‐catalyzed sequence that likely proceeds through a carbocyclization followed by a pinacol rearrangement. For the final demetalation step, isopropyl alcohol and N‐iodosuccinimide are effectively utilized, and the resulting products are set up for a wealth of further reactions.

PtCl2‐catalyzed alkyne activation initiates a domino reaction, in which a heterocyclization is followed by a 1,2‐alkyl migration, for the construction of a variety of substituted 3(2H)‐furanones. This stereospecific reaction is proposed to proceed through an oxonium ion intermediate (see scheme).

Rugulactone is a dihydro-α-pyrone isolated from the plant Cryptocarya rugulosa in 2009. It has been reported to display IkB kinase (IKK) inhibitory activity, as well as antibiotic activity in several strains of pathogenic bacteria. However, its biological targets and mode of action in bacteria have not yet been explored. Here we present enantioselective syntheses of rugulactone and of some corresponding activity-based protein profiling (ABPP) probes. We found that the ABPP probes in this study are more potent than rugulactone against Staphyloccocus aureus NCTC 8325, S. aureus Mu50, Listeria welshimeri SLCC 5334 and Listeria monocytogenes EGD-e, and that molecules of this class probably exert their antibacterial effect through a combination of targets. These targets include covalent inhibition of 4-amino-5-hydroxymethyl-2-methylpyrimidine phosphate (HMPP) kinase (ThiD), which is an essential component of the thiamine biosynthesis pathway in bacteria. This represents the first example of a small-molecule inhibitor of ThiD.

[reaction: see text] The application of easily accessed propargyl vinyl ethers for the synthesis of monocyclic 2H-pyrans was achieved. Under the reaction conditions, highly substituted heterocycles were obtained in moderate to excellent yields. The one-pot sequence proceeds via a Ag(I)-catalyzed propargyl-Claisen rearrangement, followed by a base-catalyzed isomerization, and 6pi-oxaelectrocyclization, leading to the formation of stable 2H-pyrans.