Ball Milling Towards Green Synthesis
Applications, Projects, Challenges
By Brindaban Ranu, Achim Stolle
The Royal Society of Chemistry
Copyright © 2015 The Royal Society of Chemistry
All rights reserved.
ISBN: 978-1-84973-945-0
Contents
Chapter 1 Carbon-Heteroatom Bond Forming Reactions and Heterocycle Synthesis under Ball Milling Brindaban C. Ranu, Tanmay Chatterjee and Nirmalya Mukherjee, 1,
Chapter 2 Carbon-Carbon Bond Forming by Ball Milling Katharina Jacob, Robert Schmidt and Achim Stolle, 34,
Chapter 3 Oxidation and Reduction by Solid Oxidants and Reducing Agents using Ball-Milling Giancarlo Cravotto and Emanuela Calcio Gaudino, 58,
Chapter 4 Asymmetric Organocatalytic Reactions under Ball Milling Elizabeth Machuca and Eusebio Juaristi, 81,
Chapter 5 Cross Dehydrogenative Coupling Reactions by Ball Milling Jingbo Yu, Zhijiang Jiang and Weike Su, 96,
Chapter 6 Amino Acids and Peptides in Ball Milling Thomas-Xavier Métro, Evelina Colacino, Jean Martinez and Frédéric Lamaty, 114,
Chapter 7 Ball-milling Mechanochemical Synthesis of Coordination Bonds: Discrete Units, Polymers and Porous Materials Tomislav Friscic, 151,
Chapter 8 A Chromatography-free Method for the Isolation of Products from Mechanochemical Reactions James Mack, 190,
Chapter 9 Ball-milling Promoted Chemical Bonding between Cellulose and Plastics Takahiro Hirotsu, Takashi Endo and Myco Umemura, 203,
Chapter 10 Technical Implications of Organic Syntheses in Ball Mills Achim Stolle, 241,
Subject Index, 277,
CHAPTER 1
Carbon–Heteroatom Bond Forming Reactions and Heterocycle Synthesis under Ball Milling
BRINDABAN C. RANU, TANMAY CHATTERJEE AND NIRMALYA MUKHERJEE
1.1 Introduction
Chemical transformations involving mechanochemical (grinding) reactions using a mortar and pestle were initiated long ago during the early stage of evolution of chemistry. But due to variable and relatively low grinding strength and speed, limited chemical reactions were successfully carried out by grinding. To overcome this limitation, a mixer/shaker mill or a planetary mill has been developed and these devices provide much higher energy and are more reliable than hand grinding. Mixing in such a mill is generally referred to as "milling". Mechanical grinding in these mills is aided by the milling balls and hence it is called ball milling. Mechanochemistry using ball milling has received intense attention in organic synthesis in recent decades and is now a fast growing branch. Mechanochemical reactions in a ball mill depend on several parameters like milling frequency, milling time, size and number of milling balls, and the material of milling balls and beakers. The first two have been found to be the most important parameters. Basically two types of ball mills have been frequently used to perform organic transformations, i.e. mixer mill (MM) and planetary mill (PM) (for further details the reader is referred to Chapter 10).
The present chapter covers reactions involving carbon–heteroatom (C–N, C–O, C–S, C–Cl, C–Br, etc.) bond formation and synthesis of heterocycles under ball milling.
1.2 Carbon–Heteroatom Bond Forming Reactions under Ball Milling
1.2.1 C–N Bond Forming Reactions
Kaupp and co-workers have reported the quantitative formation of imines by ball milling a stoichiometric mixture of aldehyde and amine in less than 30 min (Scheme 1.1).
All the reactions were carried out below 0 °C except for the condensations of 4-nitroaniline with 4-hydroxybenzaldehyde and 4-nitrobenzaldehyde, which were performed at 60 and 80 °C, respectively.
The same group also investigated the solid-state reactions of hydrazine –hydroquinone (1 : 1 complex) and of hydrazine hydrochloride with solid aldehyde, ketone, carboxylic acid, thiohydantoin and 4-nitrophenyl isothiocyanate and found that only the hydrazine hydroquinone complex provides quantitative addition, condensation, ring opening and ring closure (Schemes 1.2 and 1.3).
Naimi-Jamal, Kaupp and co-workers employed "kneading ball-milling" for the stoichiometric quantitative preparation of synthetically versatile 2,4-dinitrophenylhydrazones from low-melting aldehydes and ketones. Owing to the potential explosive nature of dry 2,4-dinitrophenylhydrazine, 50 wt% deionized water was added to wet the crystals. Water was used as an auxiliary to minimize the risk of explosive destruction. The stoichiometric reaction of 2,4-dinitrophenylhydrazine with aldehydes or ketones occurred rapidly in the kneading ball mill at 25–70 °C for 10–20 min, giving the desired hydrazones in 58–100% yields (Scheme 1.4). When these reactions are performed in solution, strong acid catalysts are required. However, they occur much faster in the kneading ball mill in the absence of catalyst.
Similarly, aldehydes and ketones were stoichiometrically ball-milled with hydroxylamine hydrochloride at 25–140 1C for 10–120 min to provide the hydrated oxime salts in sticky form, which were then treated with a base to obtain the oximes in 75–100% yields (Scheme 1.5). NaCl in water and CO2 from carbonate were found to be the only wastes produced. Aldehydes were found to be more reactive than ketones towards hydroxylamine. The difference in reactivity of aldehydes and ketones can be utilized as a versatile method for selective protection of an aldehyde by oximation in the presence of a ketone.
Benzoylhydrazones were also obtained, by ball-milling benzhydrazide and solid aldehydes in a molar ratio of 1 : 1 for 1 h at 25–30 °C. However, the reaction of benzhydrazide with isatin required 3 h of ball milling for completion (Scheme 1.6).
Liquid assisted grinding (LAG) has been applied for the synthesis of imine from 5-aminosalicylic acid and vanillin or 2-hydroxy-1- naphthaldehyde in a ball mill for 5–30 min in the presence of a small amount of EtOH or EtOH-NEt3 (Scheme 1.7).
Wang and Gao have reported direct oxidative amidation of aldehydes with anilines under ball milling (Scheme 1.8). Oxone was used as an effective oxidant for the transformation of aldehydes into amides. Other oxidants like K2S2O8 and I2 failed to initiate the oxidative amidation.
MgSO4 was found to be the best dehydrating agent for removing the water formed in the reaction. In addition, when the oxidative amidation reaction was performed in organic solvents such as acetonitrile or toluene, under identical reaction conditions, the yield of the corresponding product was comparatively lower than the reaction under solvent-free condition in a ball mill. Anilines bearing electron-donating and electron-withdrawing groups underwent facile reaction with aldehydes bearing electron-withdrawing groups only. Reactions with aldehydes containing electron-donating groups were unsuccessful, indicating the importance of the electronic character of aldehydes. Aliphatic anilines were also inert under the reaction conditions. The replacement of an aldehyde by the corresponding carboxylic acid did not afford the amides, thereby discarding the possibility of oxidation of aldehyde to carboxylic acid by Oxone followed by reaction with aniline to give amide.
A tentative mechanism for the amidation reaction of aldehydes with anilines based on the above results was proposed (Scheme 1.9). This direct oxidative amidation reaction may proceed via two pathways. In pathway A, the interaction of an aldehyde and aniline...
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