1,6-Addition Arylation of para-Quinone Methides: An Approach to Unsymmetrical Triarylmethanes
作者:Shang Gao、Xiuyan Xu、Zhenbo Yuan、Haipin Zhou、Hequan Yao、Aijun Lin
DOI:10.1002/ejoc.201600385
日期:2016.6
A 1,6-addition arylation reaction of para-quinone methides with α-isocyanoacetamides and electron-rich aromatic compounds under metal-free conditions has been developed. BF3·Et2O plays two roles in the reaction: catalyzing the cyclization of α-isocyanoacetamides to give oxazoles, and activating the para-quinone methides to achieve the 1,6-addition arylation process. The reaction shows good functional
Synthesis of spiro[2.5]octa-4,7-dien-6-one with consecutive quaternary centers <i>via</i> 1,6-conjugate addition induced dearomatization of <i>para</i>-quinone methides
作者:Kuo Gai、Xinxin Fang、Xuanyi Li、Jinyi Xu、Xiaoming Wu、Aijun Lin、Hequan Yao
DOI:10.1039/c5cc06287j
日期:——
An efficient one-pot approach for the synthesis of spiro[2.5]octa-4,7-dien-6-ones by employing para-quinone methides has been developed. The reaction proceeded smoothly in high yields under mild conditions without the use of...
We report herein a tandem reaction of para-quinonemethides with TMSCF2Br to construct bromofluoroalkenes in a Z-selective manner. While TMSCF2Br has been documented as the precursor of difluoro carbene, it exhibits another possibility in this transformation, a formal bromofluoro carbene surrogate. The alkenyl bromide unit of the products could directly engage in a variety of transformations.
Propofol Analogues. Synthesis, Relationships between Structure and Affinity at GABA<sub>A</sub> Receptor in Rat Brain, and Differential Electrophysiological Profile at Recombinant Human GABA<sub>A</sub> Receptors
A number of propofol (2,6-diisopropylphenol) congeners and derivatives were synthesized and their in vitro capability to affect GABA(A) receptors determined by the inhibition of the specific [S-35]-tert-butylbicyclophosphorothionate ([S-35]TBPS) binding to rat whole brain membranes. Introduction of halogen (Cl, Br, and I) and benzoyl substituents in the para position of the phenyl group resulted in ligands with higher potency at inhibiting [S-35]TBPS binding. A quantitative structure-affinity relationship (QSAR) study demonstrated that affinity is enhanced by increases in lipophilicity of the ligand whereas affinity is adversely affected by increases in size of the substituent para to the phenolic hydroxyl group. Consistent with the displacement of [S-35]TBPS and with the activation of GABA(A) receptors, we demonstrate that ligands displaying high affinity (i.e., 2-4, and 8) are able to increase GABA-stimulated chloride currents in oocytes expressing human GABA(A) receptors and to directly activate chloride currents in an electrophysiological assay. Among them, compound 4 showed a rather peculiar profile in the electrophysiological examination with cloned alpha(1) beta(2) gamma(2) GABA(A) receptors. Indeed, compared to propofol, it displayed a much greater efficacy at potentiating GABA-elicited chloride currents, but a much lower efficacy at producing a direct activation of the chloride channel in the absence of GABA. This behavior may give to compound 4 pharmacological properties that are more similar to anxiolytic and anticonvulsant drugs than to those of general anesthetics.