Practical Diastereoselective Synthesis and Scale-up Study of (+)-2-((1R,2R,3R,5S)-2-Amino-6,6-dimethylbicyclo[3.1.1]hept-3-yl)ethanol: A Key Intermediate of the Novel Prostaglandin D2 Receptor Antagonist S-5751

Selective [2σ + 2σ] Cycloaddition Enabled by Boronyl Radical Catalysis: Synthesis of Highly Substituted Bicyclo[3.1.1]heptanes

In contrast to the traditional and widely-used cycloaddition reactions involving at least a π bond component, a [2σ + 2σ] radical cycloaddition between bicyclo[1.1.0]butanes (BCBs) and cyclopropyl ketones has been developed to provide a modular, concise, and atom-economical synthetic route to substituted bicyclo[3.1.1]heptane (BCH) derivatives that are 3D bioisosteres of benzenes and core skeleton of a number of terpene natural products. The reaction was catalyzed by a combination of simple tetraalkoxydiboron(4) compound B2pin2 and 3-pentyl isonicotinate. The broad substrate scope has been demonstrated by synthesizing a series of new highly functionalized BCHs with up to six substituents on the core with up to 99% isolated yield. Computational mechanistic investigations supported a pyridine-assisted boronyl radical catalytic cycle.

Reduction of liquid terminated-carboxyl fluoroelastomers using NaBH4/SmCl3

Using a simple one-pot method, the reduction of liquid terminated-carboxyl fluoroelastomers (LTCFs) by sodium borohydride and samarium chloride (NaBH₄/SmCl₃) was successfully realized and liquid terminated-hydroxyl fluoroelastomers (LTHFs) were obtained. The structure and functional group content of LTCFs and LTHFs were analyzed by FTIR, ¹H-NMR, ¹⁹F-NMR and chemical titration. The results showed that –C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C– and carboxyl groups of LTCFs were reduced efficiently, the reduction rate reached 92% under optimum reaction conditions. Compared with other frequently-used metal chlorides, SmCl₃ with a high coordination number could increase the reduction activity of NaBH₄ more effectively and the reduction mechanism was explored.

A facile method using NaBH₄/SmCl₃ allows for reduction of liquid terminated-carboxyl fluoroelastomers (LTCFs) in excellent yields and provides an attractive potential scheme for the reduction of other carboxyl organic compounds.

One-pot synthesis and antimicrobial evaluation of novel 3-cyanopyridine derivatives of (-)-β-pinene

A series of novel 3-cyanopyridine derivatives of (-)-β-pinene were designed and synthesized by one-pot four-component domino reactions. The targeted compounds were evaluated for their antimicrobial activity against four bacteria (Klebsiella pneumoniae, Enterobacter aerogenes, Staphylococcus aureus, Staphylococcus epidermidis) and a fungus (Candida albicans). The results showed that most of the minimal inhibitory concentrations (MICs) of these 3-cyanopyridine derivatives against the tested strains was in the range of 15.6-125 mg/L. Among these 3-cyanopyridine derivatives, the MICs of compound 5h against S. epidermidis and C. albicans were 15.6 mg/L, which revealed that compound 5h featured double fluoro substituents at meta- and para-position was the most active compound. In addition, the preliminary structure-activity relationship analysis indicated that the change of substituents on the pyridine ring and benzene ring of 3-cyanopyridine derivatives was an important factor for inducing antimicrobial activity. This research would promote the development of heterocyclic derivatives of β-pinene with antimicrobial activity.

An alternative solvent-free synthesis of nopinone under ball-milling conditions: Investigation of reaction parameters

A new method for the oxidative cleavage of β-pinene (1) yielding nopinone (2) with potassium permanganate as oxidant under solvent-free conditions was established. The reaction was performed in a conventional ball mill with use of a grinding auxiliary. The auxiliary has the ability to sorb liquid reactants such as 1 on its surface to make liquid(s) accessible for mechanical impact. Different reaction parameters and technical variables were assessed concerning their influence on yield and selectivity of 2. Different chemical parameters such as oxidants, grinding auxiliaries, and quantities were investigated. Also tuning parameters including milling time, rotation frequency, and number of milling balls were explored.