Rate acceleration of the intramolecular ene reactions of 1,6- and 1,7-enynes by electron-withdrawing substituents

Enantioselective cyclization of enamide-ynes and application to the synthesis of the kopsifoline core

“…While the thermal Alder ene reaction of 1,6-enynes has been known for some time, 1 transition metal-catalyzed processes are substantially younger. Beginning with the seminal work of Trost, 2 a wide variety of catalyst systems have been employed across a truly impressive range of substrates.…”

On the intramolecular pyrone Diels–Alder approach to basiliolide B

“…Scheme 2 illustrates the synthesis of IMPDA substrate 13. Corey-Fuchs homologation of citronellal (6), 20 Sonogashira coupling with iodide 5, chemoselective epoxidation, hydration to the diol, cleavage with periodic acid, and Wittig olefination provided enyne 12 (15% yield from 11). Iodocyclization provided iodopyrone 13 along with the iodobutenolide product of 5-exo cyclization in a 2.5:1 ratio.…”

Asymmetric, Protecting‐Group‐Free Total Synthesis of (−)‐Englerin A

“…[5] After the gem-dibromide 8 was obtained, elimination with tBuOK in the presence of [18]crown-6 was carried out and afforded a terminal alkyne, [6] which was subjected to oxidation [7] mediated by TBHP/SeO 2 and produced allylic alcohol 9 a and a,b-unsaturated aldehyde 9 b. As 9 a could be oxidized into 9 b with IBX in almost quantitative yield, [8] we were able to obtain the desired 9 b from 8 in 71 % overall yield.…”