.pi.-Facial Selectivity in Nucleophilic Additions to 4,4-Disubstituted Dienones: Experimental Support for Electrostatic Control

Oxidative De‐aromatization of para‐Alkyl Phenols into para‐Peroxyquinols and para‐Quinols Mediated by Oxone as a Source of Singlet Oxygen

“…Finally, the reaction of phenol 1 k , bearing a C 3 chain at the para position, with oxone in H 2 O (entry 11) gave rise to para ‐peroxyquinol 2 k (Method A) in 74 % yield, or para ‐quinol 3 k (Method B) in 50 % yield. It is also noteworthy that the reaction of phenol 1 k with hypervalent iodine reagents did not yield para ‐quinol 3 k but exclusively afforded, through intramolecular attack of the aliphatic OH on the para position of the phenolic OH, the corresponding oxa‐spiro cyclohexadienone,19 which was not detected in our case.…”

Torsional steering as friend and foe: development of a synthetic route to the briarane diterpenoid stereotetrad

“…Initially, we were inspired by a report by Taber, in which a formal conjugate addition of an allyl fragment could be accomplished in two steps by first performing a 1,2-addition of allylmagnesium bromide followed by an anionic oxy-cope rearrangement. 22 Thus, addition of allylmagnesium bromide into cyclohexadienone 6 gave tertiary alcohol 7 as a 1:1 mixture of diastereomers 23 (Scheme 5). Treating 7 with KH and 18-crown-6 in THF affected the desired anionic oxy-cope rearrangement, but this was accompanied by a significant amount of decomposition.…”

A Concise Synthetic Route to the Stereotetrad Core of the Briarane Diterpenoids

“…It is possible that the C11 methoxy group coordinates to the metal and delivers the acetylide to the same face of the dienone. But, the same sense of diastereoselectivity can be achieved in the absence of a coordinated delivery if one invokes the syn -oxygen phenomenon identified by Wipf 22 and Paquette. 23 This is a Cieplak-type effect, 24 in which the σ *-orbital of the developing C–C bond is stabilized by hyperconjugation with the anti C11–CH 3 bond.…”