Gold-Catalyzed Oxidative Aminocyclizations of Propargyl Alcohols and Propargyl Amines to Form Two Distinct Azacyclic Products: Carbene Formation versus a 3,3-Sigmatropic Shift of an Initial Intermediate

Gold-catalyzed oxidations of propargyl alcohols with nitrones by using a P(tBu)₂(o-biphenyl)Au⁺ catalyst, afforded bicyclic annulation products from the Mannich reactions of gold enolates. The same reactions of propargyl amines with nitrones by using the same gold catalyst gave distinct oxoarylation products. Our DFT calculations indicate that oxidation of propargyl alcohols with nitrones by using electron-rich gold catalysts lead only to gold carbenes, which can generate gold enolates or oxoarylation intermediates with enolate species having a barrier smaller than that of oxoarylation species.     

Chemical Composition of Essential Oil from Pilea microphylla and its Antimicrobial Activity

Chemistry of Natural Compounds -     

C−C Bond Formation of Benzyl Alcohols and Alkynes Using a Catalytic Amount of KOtBu: Unusual Regioselectivity through a Radical Mechanism

We report a C?C bond‐forming reaction between benzyl alcohols and alkynes in the presence of a catalytic amount of KO^tBu to form α‐alkylated ketones in which the C=O group is located on the side derived from the alcohol. The reaction proceeds under thermal conditions (125 °C) and produces no waste, making the reaction highly atom efficient, environmentally benign, and sustainable. Based on our mechanistic investigations, we propose that the reaction proceeds through radical pathways.     

Synthesis of 3′-fluoro-4′-amino-hexitol nucleosides with a pyrimidine nucleobase as building blocks for oligonucleotides

The synthesis of 3′-fluoro-4′-amino-hexitol nucleosides with a uracil and cytosine nucleobase was performed. The synthesis started from 1,5:2,3-dianhydro-4,6-benzylidene-allitol and afforded the target compounds in 15 steps. These protected hexitol nucleosides are valuable building blocks for the preparation of a new class of oligonucleotides.     

Isometries of absolute order unit spaces

Positivity - We prove that a unital, bijective linear map between absolute order unit spaces is an isometry if and only if it is absolute value preserving. We deduce that, on (unital) JB-algebras,...     

Garratt–Braverman cyclization on basic alumina: a green protocol with improved selectivity

A green protocol (compared to the existing methodology) for carrying out Garratt–Braverman cyclization has been developed. The method involves stirring a pre-absorbed bispropargyl sulfone/ether/sulfonamide over basic alumina. The reaction with sulfones was over within 10–15 min at room temperature whereas for the ether/sulfonamide the reaction took 6–8 h at 130 °C. The products, aryl naphthalene derivatives, are obtained by simple filtration through Celite, in excellent yields.     

Bistable characteristics of thick-walled axisymmetric domes

We apply a finite element analysis to examine the stability of spherical, thick-walled domes undergoing large deformation. We identify three energetic states, mono-stable, bi-stable, and pseudo-bi-stable that uniquely characterize the behavior of the dome during deformation. An empirical relation is developed using finite element simulations relating the stability of the dome to pertinent geometric parameters like height, length and thickness, which is verified experimentally. Using this relation, similar domes can be designed to have desired stability characteristics.     

Orthogonal Olefination with Organogermanes

Reported herein is a fully orthogonal olefination, which involves the site- and E-selective coupling of aryl germanes with alkenes, tolerating otherwise widely employed coupling handles such as aromatic (pseudo)halogens (C−I, C−Br, C−Cl, C−F, C−OTf, C−OSO₂F), silanes and boronic acid derivatives as well as alternative functionalities. This unprecedented [Ge]-based oxidative Heck coupling proceeds at room temperature with high speed (10 min to 2 hours) and operational simplicity owing to its base-free and air-tolerant features.