Kneading Ball‐Milling and Stoichiometric Melts for the Quantitative Derivatization of Carbonyl Compounds with Gas–Solid Recovery

Abstract

A ray of hope for the environment is sustainable and green synthesis without the production of (toxic) waste. Solvent-free stoichiometric melting or kneading ball-milling reactions of aldehydes or ketones with carbonyl reagents yields arylhydrazones and oximes in quantitative yield. The carbonyl compounds can be quantitatively recovered from the imino derivatives by using gaseous NO(2).An effective methodology of kneading with a ball mill under temperature control was used for the stoichiometric quantitative preparation of synthetically versatile oximes and 2,4-dinitrophenylhydrazones from low-melting aldehydes and ketones. Also, a large number of phenylhydrazones are obtained by safe stoichiometric quantitative melt reactions. Advantages of this technique are short reaction times, eco-friendliness, and ease of handling under solvent-free conditions, as no waste-producing purifying workup is necessary. The different reactivities of aldehydes and ketones allow for easy separation of mixtures containing aldehydes and ketones. Furthermore, a new effective, gas-solid deprotection methodology for oximes was developed, using nitrogen dioxide as the reagent under solvent-free conditions to recover the aldehydes or ketones. The corresponding aldehydes were obtained free of overoxidized acids in quantitative yields.

Sodium Tetraalkoxyborates: Intermediates for the Quantitative Reduction of Aldehydes and Ketones to Alcohols through Ball Milling with NaBH4

“…40-111°C), or polymer (1 entry), but NaBH 4 (2) did not readily dissolve in them. Therefore, three types of milling procedures with substrates in a 4:1 ratio were used (Scheme 1, Table 1): (1) proper solvent-free kneading ball milling, [9] (2) proper solid-state molecular [a] Melting points in parentheses are from refs. [13][14][15][16] [b] rac-Benzoin.…”

“…Furthermore, other recent reviews (covering different reaction types, but homogeneous liquids should not be milled) [10] did not particularly stress these technical points, which increase yields and decrease milling times. [8,9] We report herein the sustainable, rapid, and quantitative stoichiometric ball milling of 32 aldehydes and ketones with complete use of all four hydrogen atoms of the reducing agent for obtaining the alcohols. This method has the additional benefit of possessing the easiest thinkable synthesis of the versatile solid intermediate sodium tetraalkoxyborates that escape detection and isolation in the presence of water or moisture or excessive amounts of NaBH 4 .…”

“…[7] All of these techniques, however, were not waste free, and the yields were less than quantitative. Highly versatile and varied stoichiometric ball milling at controlled temperature and moderate milling impact [8,9] has not yet and stereoselective. Varied substituents are not attacked, including the bromine of α-bromo ketones.…”

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.…”

Organocatalytic clean synthesis of densely functionalized 4H-pyrans by bifunctional tetraethylammonium 2-(carbamoyl)benzoate using ball milling technique under mild conditions

“…Subsequently, some specific books and review papers have been published on the topic. Some typical examples include the carbon-carbon or carbon-heteroatom bond formation, oxidation by solid oxidants, asymmetric organocatalytic reactions, dehydrogenative coupling, and peptide or polymeric material synthesis (9,(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31). Furthermore, organocatalysis, namely the use of small organic molecules to catalyze organic transformations, is a relatively new and popular field within the domain of organic synthesis.…”