A rapid, convenient, solventless green approach for the synthesis of oximes using grindstone chemistry

Abstract

BackgroundSynthesis of oximes is an important reaction in organic chemistry, because these versatile oximes are used for protection, purification, and characterization of carbonyl compounds. Nitriles, amides via Beckmann rearrangement, nitro compounds, nitrones, amines, and azaheterocycles can be synthesised from oximes. They also find applications for selective α-activation. In inorganic chemistry, oximes act as a versatile ligand.Several procedures for the preparation of oximes exist, but, most of them have not addressed the green chemistry issue. They are associated with generation of pollutants, requirement of high reaction temperature, low yields, lack of a generalized procedure, etc. Hence, there is a demand for developing an efficient, convenient, and non-polluting or less polluting alternative method for the preparation of oximes. In this context, bismuth compounds are very useful as they are cheap in general, commercially available, air stable crystalline solids, safe, and non-toxic, hence easy to handle.ResultsCarbonyl compounds (aliphatic, heterocyclic, and aromatic) were converted into the corresponding oximes in excellent yields by simply grinding the reactants at room temperature without using any solvent in the presence of Bi2O3. Most importantly, this method minimizes waste disposal problems, provides a simple yet efficient example of unconventional methodology and requires short time.ConclusionsWe have developed a novel, quick, environmentally safe, and clean synthesis of aldoximes and ketoximes under solvent-free grinding condition.

A versatile and green mechanochemical route for aldehyde–oxime conversions

“…Six of the aldehydes contained electron withdrawing substituents (1-6), one was decorated with electron donating substituent (7), nine aldehydes contained structurally active functional groups such as -COOH (8-9), -OH (10-13) and pyridyl group (14)(15)(16), three other aldehydes were multifunctionalized 65 (17)(18)(19)) and finally we also included an aliphatic aldehyde (20). The broad spectrum of aldehydes examined was meant to provide sufficient data to determine the limits and limitations (if any) of a solvent-free grinding for the conversion of aldehydes to oximes.…”

“…2 They are useful starting materials for various functional groups such as nitriles, 3 nitro compounds, 4 amines 5 and amides. 6,7 Furthermore, they can offer structure-directing capabilities in supramolecular chemistry by 15 virtue of being strong hydrogen-bond donors (as well as being self-complementary synthons). 8 Finally, upon deprotonation, they serve as efficient ligands in the field of coordination chemistry for complexation with various metals.…”

Practical Approach to Green Chemistry

“…The filtrate was concentrated, and water was added which separated the product from the solution. The precipitates were filtered and dried in vacuum to give the pure oxime 2 in 60-98% yield (Scheme 7) [28].…”

Mechanochemical and Conformational Study of N-heterocyclic Carbonyl-Oxime Transformations

“…Some advances have been made in the greener synthesis of aldoximes from carbonyl compounds, for example, by use of calcium oxide with elevated temperature and solvent free conditions, 17 microwave irradiated synthesis in presence of basic Al 2 O 3 and pestle & mortar synthesis with molecular sives, 18 grinding of some aliphatic and aromatic ketones and aldehydes with the addition of sodium hydroxide without solvent 19 and liquid assisted grinding, 20 grinding in conjunction with Bi 2 O 3 . 21 Up to now, only one study of solvent free mechanochemical transformation of N-heterocyclic aldehydes (pyridine-2-, 3-and 4-carbaldehydes) was conducted 20 but no investigations concerning the use of the N-heterocyclic carbonyl compound as a substrate and base at the same time has been reported so far.…”