Discovery and Structure-Activity Relationships of 2,5-Dimethoxyphenylpiperidines as Selective Serotonin 5-HT2A Receptor Agonists

Classical psychedelics such as psilocybin, lysergic acid diethylamide (LSD), and N,N-dimethyltryptamine (DMT) are showing promising results in clinical trials for a range of psychiatric indications, including depression, anxiety, and substance abuse disorder. These compounds are characterized by broad pharmacological activity profiles, and while the acute mind-altering effects can be ascribed to their shared agonist activity at the serotonin 2A receptor (5-HT2AR), their apparent persistent therapeutic effects are yet to be decidedly linked to activity at this receptor. We report herein the discovery of 2,5-dimethoxyphenylpiperidines as a novel class of selective 5-HT2AR agonists and detail the structure-activity investigations leading to the identification of LPH-5 [analogue (S)-11] as a selective 5-HT2AR agonist with desirable drug-like properties.

Electrochemical Dearomatizing Methoxylation of Phenols and Naphthols: Synthetic and Computational Studies

The electrochemical oxidative dearomatizing methoxylation of phenols and naphthols was developed. It provides an alternative route for the preparation of methoxycyclohexadienones, important and versatile synthetic intermediates, that eliminates the need for stoichiometric high-energy chemical oxidants and generates hydrogen as a sole by-product. The reaction proceeds in a simple constant current mode, in an undivided cell, and it employs standardized instrumentation. A collection of methoxycyclohexadienones derived from various 2,4,6-tri-substituted phenols and 1-substituted-2-naphthols was obtained in moderate to excellent yields. These include a complex derivative of estrone, as well as methoxylated dearomatized 1,1'-bi-2-naphthols (BINOLs). The mechanism of the reaction was subject to profound investigations using density functional theory calculations. In particular, the reactivity of two key intermediates, phenoxyl radical and phenoxenium ion, was carefully examined. The obtained results shed light on the pathway leading to the desired product and rationalize experimentally observed selectivities regarding a side benzylic methoxylation and the preference for the functionalization at the para over the ortho position. They also uncover the structure-selectivity relationship, inversely correlating the steric bulk of the substrate with its propensity to undergo the side-reaction. Moreover, the loss of stereochemical information from enantiopure BINOL substrates during the reaction is rationalized by the computations.

Synthesis of meta-arylphenol derivatives via acid-promoted rearrangement of cyclohexadienones

A highly effective strategy for the synthesis of meta-arylphenol derivatives through the selective rearrangement of 4-alkyl-4-aryl-2,5-cyclohexadienones under metal-free conditions was developed, in which acid-promoted [1,2]-migration of the aryl group at C-4 occurred exclusively when the alkyl group at C-4 was a methyl group. Treatment of 4-methyl-4-aryl-2,5-cyclohexadienones with 37% HCl in Ac2O at room temperature provided polysubstituted meta-arylphenyl acetates in 75-94% yields. The application of this protocol in the synthesis of polycyclic aromatic compounds was also described.

Nanocrystalline rhenium-doped TiO2: an efficient catalyst in the one-pot conversion of carbohydrates into levulinic acid. The synergistic effect between Brønsted and Lewis acid sites

A new approach of inserting rhenium into a TiO2 structure generates Brønsted acid sites which are essential for conversion of carbohydrates into levulinic acid.

The Ligand Free Palladium(II)-Catalyzed Regioselective 1,2-Addition of Enol Silanes to Quinones to Access 4-Hydroxy-4-(2-oxo-2-arylethyl)cyclohexadien-1-ones and Synthetic Applications

In contrast to the conventional 1,4-addition process, regioselective 1,2-addition of silyl enol ethers to quinones can now be achieved via a palladium(II) enolate pathway that provides access to 4-hydroxy-4-(2-oxo-2-arylethyl)cyclohexa-2,5-dien-1-one derivatives. This quinone alkylation protocol proceeds under mild reaction conditions at ambient temperature under open air and does not require either an external ligand for the palladium or the use of a base. Additionally, the cyclohexadienone products have been exploited as synthetic precursors for the construction of fused heteroaryl systems.

Selective Cleavage of C-O Bonds in Lignin Catalyzed by Rhenium(VII) Oxide (Re2 O7 )

The selective cleavage of C-O bonds in typical model lignin β-O-4 compounds and deconstruction of a realistic lignin feedstock catalyzed by Re₂ O₇ is described. High yields of C-O cleavage products (up to 97.8 %) from model compounds and oils (76.3 %) from organosolv pinewood lignin were obtained under mild conditions. Evidence for the pathway of this catalytic process is also provided.

Regioselective Rearrangement of 4,4-Disubstituted 2-Hydroxycyclohexa-2,5-Dienones under Deoxyfluorination Conditions

The dienone-phenol rearrangement is a useful tool for the synthesis of highly substituted phenols. In our previous study of the rearrangement of 4,4-disubstituted 2-hydroxycyclohexa-2,5-dienone under deoxyfluorination conditions, bond migration proceeded with very poor regioselectivity. In this paper, an acid-mediated rearrangement of O-perfluoroalkylsulfonyl difluorides with regioselective migration toward the β'-carbon is reported. This method allowed the synthesis of a fluorinated analog of allocolchicinoids with improved total yield. Successful application to other substrates was also demonstrated.

Tandem allylic alcohol isomerization/oxo-Michael addition reaction promoted by Re2O7

Re₂O₇ enables a tandem allylic alcohol isomerization/oxa-Michael addition reaction of cyclohexadienone.