265107-67-3Relevant academic research and scientific papers
Intramolecular Acetyl Transfer to Olefins by Catalytic C?C Bond Activation of Unstrained Ketones
Rong, Zi-Qiang,Lim, Hee Nam,Dong, Guangbin
supporting information, p. 475 - 479 (2018/02/21)
A rhodium-catalyzed intramolecular acetyl-group transfer has been achieved through a “cut and sew” process. The challenge arises from the existence of different competitive pathways. Preliminary success has been achieved with unstrained enones that contain a biaryl linker. The use of an electron-rich N-heterocycilc carbene (NHC) ligand is effective to inhibit undesired β-hydrogen elimination. Various 9,10-dihydrophenanthrene derivatives can be prepared with excellent functional-group compatibility. The 13C-labelling study suggests that the reaction begins with cleavage of the unstrained C?C bond, followed by migratory insertion and reductive elimination.
Monoligated Pd(0)-catalyzed intramolecular ortho- and para-arylation of phenols for the synthesis of aporphine alkaloids. Synthesis of (-)-lirinine
Hellal, Malik,Singh, Shambhavi,Cuny, Gregory D.
experimental part, p. 1674 - 1681 (2012/03/10)
An intramolecular palladium(0)-mediated ortho-arylation of phenols applied to the synthesis of various substituted aporphines is reported. Most significantly, the efficiency of the transformation was enhanced by the use of monoligated Pd(0) complexes. This methodology was extended to para-arylation of phenols and employed in the synthesis of the aporphine alkaloid (-)-lirinine.
Hydrogen-bonding catalysis and inhibition by simple solvents in the stereoselective kinetic epoxide-opening spirocyclization of glycal epoxides to form spiroketals
Wurst, Jacqueline M.,Liu, Guodong,Tan, Derek S.
, p. 7916 - 7925 (2011/07/08)
Mechanistic investigations of a MeOH-induced kinetic epoxide-opening spirocyclization of glycal epoxides have revealed dramatic, specific roles for simple solvents in hydrogen-bonding catalysis of this reaction to form spiroketal products stereoselectively with inversion of configuration at the anomeric carbon. A series of electronically tuned C1-aryl glycal epoxides was used to study the mechanism of this reaction based on differential reaction rates and inherent preferences for SN2 versus SN1 reaction manifolds. Hammett analysis of reaction kinetics with these substrates is consistent with an SN2 or SN2-like mechanism (ρ = -1.3 vs ρ = -5.1 for corresponding SN1 reactions of these substrates). Notably, the spirocyclization reaction is second-order dependent on MeOH, and the glycal ring oxygen is required for second-order MeOH catalysis. However, acetone cosolvent is a first-order inhibitor of the reaction. A transition state consistent with the experimental data is proposed in which one equivalent of MeOH activates the epoxide electrophile via a hydrogen bond while a second equivalent of MeOH chelates the side-chain nucleophile and glycal ring oxygen. A paradoxical previous observation that decreased MeOH concentration leads to increased competing intermolecular methyl glycoside formation is resolved by the finding that this side reaction is only first-order dependent on MeOH. This study highlights the unusual abilities of simple solvents to act as hydrogen-bonding catalysts and inhibitors in epoxide-opening reactions, providing both stereoselectivity and discrimination between competing reaction manifolds. This spirocyclization reaction provides efficient, stereocontrolled access to spiroketals that are key structural motifs in natural products.
