No abstract

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).

An efficient and versatile synthesis of chiral tetralins has been developed using both inter- and intramolecular Friedel-Crafts alkylation as a key step. The readily available hydronaphthalene substrates were prepared via a highly enantioselective metal-catalyzed ring opening of meso-oxabicyclic alkenes followed by hydrogenation. A wide variety of complex tetracyclic compounds have been isolated with high levels of regio-, diastereo-, and enantioselectivity.

Two platinum(II)-catalyzed heterocyclization-migration reactions that provide five-membered heterocycle products are described. With 5 mol-% of PtCl 2 as a catalyst, 2-alkynyl-2-hydroxy carbonyl compounds 1 are converted into 3(2H)-furanones 2 at 80°C in moderate to excellent yields under very mild reaction conditions. The reaction is proposed to proceed through an oxonium ion intermediate B, which triggers a stereospecific 1,2-shift analogous to an α-ketol rearrangement. When exploited in a different manner, the 2-alkynyl-2-hydroxy carbonyl compounds 1 afford 3-pyrrolones 3 in 33-81 % yield. For this purpose, the starting compounds 1 are