Evaluation of cyclopentyl methyl ether (CPME) as a solvent for radical reactions

Application of Biobased Solvents in Asymmetric Catalysis

The necessity of more sustainable conditions that follow the twelve principles of Green Chemistry have pushed researchers to the development of novel reagents, catalysts and solvents for greener asymmetric methodologies. Solvents are in general a fundamental part for developing organic processes, as well as for the separation and purification of the reaction products. By this reason, in the last years, the application of the so-called green solvents has emerged as a useful alternative to the classical organic solvents. These solvents must present some properties, such as a low vapor pressure and toxicity, high boiling point and biodegradability, and must be obtained from renewable sources. In the present revision, the recent application of these biobased solvents in the synthesis of optically active compounds employing different catalytic methodologies, including biocatalysis, organocatalysis and metal catalysis, will be analyzed to provide a novel tool for carrying out more ecofriendly organic processes.

Catalyst-free Synthesis of Aminomethylphenol Derivatives in Cyclopentyl Methyl Ether via Petasis Borono-Mannich Reaction

OBJECTIVE

Aminomethylphenol molecules have wider applications in pharmaceuticals, agrochemicals, plant protection and promising functional materials. The development of an efficient and practical method to prepare this class of compound is highly desirable from both environmental and economical points of view.

MATERIALS AND METHODS

In order to establish an effective synthetic method for preparing aminomethylphenol derivatives, the Petasis borono-Mannich reaction of salicylaldehyde, phenylboronic acid and 1,2,3,4- tetrahydroisoquinoline was selected as a model reaction. A variety of reaction conditions are investigated, including solvent and temperature. The generality and limitation of the established method were also evaluated.

RESULTS AND DISCUSSION

It was found that model reaction can be carried out in cyclopentyl methyl ether at 80 oC under catalyst-free conditions. This protocol, with broad substrate applicability, the reaction of various arylboronic acid, secondary amine and salicylaldehyde proceeded smoothly under optimal reaction conditions to afford various aminomethylphenol derivatives in high yields. A practical, scalable, and high-yielding synthesis of aminomethylphenol derivatives was successfully accomplished.

CONCLUSION

A catalyst-free practical method for the synthesis of minomethylphenol derivatives based on Petasis borono-Mannich (PBM) reaction of various arylboronic acid, secondary amine and salicylaldehyde in cyclopentyl methyl ether has been developed. The salient features of this protocol are avoidance of any additive/catalyst and toxic organic solvents, use of cyclopentyl methyl ether as the reaction medium, clean reaction profiles, easy operation, and high to excellent yield.

Generation of alkoxysulfonyl radicals from chlorosulfates and their intramolecular capture with alkynes to obtain sultones

An unprecedented radical-mediated reaction of alkyne-containing chlorosulfates to synthesize sultones has been established. The reaction leads to the formation and subsequent capture of alkoxysulfonyl radicals, which are species known for a long time but not studied for synthetic purposes.

Pyridine tetrafluoro-λ6-sulfanyl chlorides: spontaneous addition to alkynes and alkenes in the presence or absence of photo-irradiation

A radical addition reaction of Py-SF₄Cl to alkynes and alkenes provide pyridine-SF₄-alkenes and pyridine-SF₄-alkanes under blue LED light irradiation or absence of light irradiation in CPME or without solvent.

4-Methyltetrahydropyran (4-MeTHP): Application as an Organic Reaction Solvent

4-Methyltetrahydropyran (4-MeTHP) is a hydrophobic cyclic ether with potential for industrial applications. We herein report, for the first time, a comprehensive study on the performance of 4-MeTHP as an organic reaction solvent. Its broad application to organic reactions includes radical, Grignard, Wittig, organometallic, halogen-metal exchange, reduction, oxidation, epoxidation, amidation, esterification, metathesis, and other miscellaneous organic reactions. This breadth suggests 4-MeTHP can serve as a substitute for conventional ethers and harmful halogenated solvents. However, 4-MeTHP was found incompatible with strong Lewis acids, and the C-O bond was readily cleaved by treatment with BBr3 . Moreover, the radical-based degradation pathways of 4-MeTHP, THP and 2-MeTHF were elucidated on the basis of GC-MS analyses. The data reported herein is anticipated to be useful for a broad range of synthetic chemists, especially industrial process chemists, when selecting the reaction solvent with green chemistry perspectives.

Cyclopentyl Methyl Ether: An Elective Ecofriendly Ethereal Solvent in Classical and Modern Organic Chemistry

Solvents represent one of the major contributions to the environmental impact of fine-chemical synthesis. As a result, the use of environmentally friendly solvents in widely employed reactions is a challenge of vast real interest in contemporary organic chemistry. Within this Review, a great variety of examples showing how cyclopentyl methyl ether has been established as particularly useful for this purpose are reported. Indeed, its low toxicity, high boiling point, low melting point, hydrophobicity, chemical stability towards a wide range of conditions, exceptional stability towards the abstraction of hydrogen atoms, relatively low latent heat of vaporization, and the ease with which it can be recovered and recycled enable its successful employment as a solvent in a wide range of synthetic applications, including organometallic chemistry, catalysis, biphasic reactions, oxidations, and radical reactions.

Evaluation of green solvents: Oil extraction from oleaginous yeast Lipomyces starkeyi using cyclopentyl methyl ether (CPME)

Cyclopentyl methyl ether (CPME) was evaluated for extracting oil or triacylglycerol (TAG) from wet cells of the oleaginous yeast Lipomyces starkeyi. CPME is a greener alternative to chloroform as a potential solvent for oil recovery. A monophasic system of CPME and biphasic system of CPME:water (1:0.7) performed poorly having the lowest TAG extraction efficiency and TAG selectivity compared to other monophasic systems of hexane and chloroform and the biphasic Bligh and Dyer method (chloroform:methanol:water). Biphasic systems of CPME:water:alcohol (methanol/ethanol/1-propanol) were tested and methanol achieved the best oil extraction efficiency compared to ethanol and 1-propanol. Different biphasic systems of CPME:methanol:water were tested, the best TAG extraction efficiency and TAG selectivity achieved was 9.9 mg/mL and 64.6%, respectively, using a starting ratio of 1:1.7:0.6 and a final ratio of 1:1:0.8 (CPME:methanol:water). Similar results were achieved for the Bligh and Dyer method (TAG extraction efficiency of 10.2 mg/mL and TAG selectivity of 66.0%) indicating that the biphasic CPME system was comparable. The fatty acid profile remained constant across all the solvent systems tested indicating that choice of solvent was not specific for any certain fatty acid. This study was able to demonstrate that CPME could be used as an alternative solvent for the extraction of oil from the wet biomass of oleaginous yeast. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:1096-1103, 2017.

Cyclic ether synthesis from diols using trimethyl phosphate

Cyclic ethers are simply synthesized from diols by using trimethyl phosphate at room temperature.