Mechanochemical Organic Synthesis

374 Pages·2016·17.913 MB·English

by  Davor Margetic, Vjekoslav Štrukil

Mechanochemical
Organic Synthesis
Davor Margetić
Vjekoslav Štrukil
Ruđer Bošković Institute
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Preface
Responsible management of natural resources and the diminution of environmental
impact of chemical industry in many ways rely on organic chemists, and develop-
ment of novel ecofriendly organic methods and processes is gaining in importance.
During 2010s mechanosynthesis by automated ball milling has become more widely
applied among researchers. Since the potential of the method for greener synthesis
has been recognized, more accounts appear and the number of research papers pub-
lished in scholarly journals is steadily increasing. Thus, there was a need to collect
the information scattered in the literature and organize an up-to-date overview.
In this book organic chemists could find the advantages and shortcomings of
the automated ball-milling technique and its applicability. In addition to benefits of
excluding solvents from reaction, by this way increasing the concentration and kinet-
ics, as well as better reproducibility than mortar and pestle manual grinding, excit-
ing opportunities lay before organic chemists to discover new products and reaction
pathways which differ from conventional synthesis, thus complementing the conven-
tional reaction conditions. Synthetic chemists will surely find it appealing to carry
out reactions in a new and unique way without solvent effects, and in most protocols
without special precaution against moisture. We strongly believe that this field of
chemistry will be further developed and find its application to variety of organic
transformations.
Application of environment friendly methods in organic synthesis is an ongoing
program in our research group focusing on application of extremely high pressures
and microwave-assisted synthesis, and this book is a part of our activity in the area
of mechanochemistry.
This book is intended for a broad audience, for the most part to practical organic
chemists working on development of new “greener” techniques for organic synthe-
sis, describing the advantages, possibilities, and downturns of the mechanosynthetic
method. Studies of reaction mechanisms in solid state have importance to physical
organic chemists, whereas industrial chemists interested in green technologies could
also find a wealth of information. Academic educators and advanced organic chem-
istry students will find relevant chapter devoted to undergraduate organic chemis-
try laboratory, which was initiated by our involvement in postgraduate-level course
entitled “Special techniques in organic synthesis.”
The first chapter gives a review on practical aspects of mechanochemical organic
synthesis, which is followed by an in-depth literature overview of examples divided
into chapters, according to the reaction types; however, in some cases additional
examples could be found in the other chapters, particularly for cycloadditions and
multicomponent or cascade reactions. These chapters are followed by chapters
devoted to applications of ball milling to fullerene and supramolecular chemistry.
Final chapter gives examples of ball-milling reactions which could be integrated in
undergraduate organic chemistry courses. Throughout the book, standard reaction
workup involving product extraction with solvent and purification is not specified,
xi
xii Preface
but rather examples given which differ from this standard procedure by complete
avoidance of the use of organic solvents. Wherever data were available, a comparison
with conventional synthesis is given. A great care has been taken to provide enough
experimental details, so that synthetic procedures can be applied on the new reac-
tions without the need to consult the original research papers.
Technical help of members of Laboratory for Physical Organic Chemistry is
acknowledged. Elsevier editorial staff is thanked for the opportunity to publish this
work and their continuous assistance during the project. We would like to thank
Mr. Milan Trenc for the book cover illustration. Croatian Science Foundation is
thanked for financial support (grant no. 9310). We are also very grateful to colleagues
who introduced mechanochemistry to us, Professor Koichi Komatsu (Kyoto, D.M.)
and Professor Tomislav Friščić (McGill, V.Š.). Great thanks go to our families, espe-
cially to our children Dominik, Karlo Ken, and Marina for their patience and under-
standing during the preparation of this manuscript.
Davor Margetić
Vjekoslav Štrukil
Ruđer Bošković Institute
Zagreb, December 2015
List of Abbreviations
API Active pharmaceutical ingredients
ATR-IR spectroscopy Attenuated total reflectance infrared spectroscopy
Bn Benzyl
Boc tert-Butyloxycarbonyl
BQ Benzoquinone
BTC 1,3,5-Benzenetricarboxylate
n-Bu n-Butyl
CAN Cerium ammonium nitrate
CDC Cross-dehydrogenative coupling
CDI Carbonyl diimidazole
CPD Cyclopentadiene
CP-MAS Cross-polarization magic angle spinning
DABCO 1,4-Diazabicyclo[2.2.2]octane
DBU 1,8-Diazabicyclo[5.4.0]undec-7-ene
DCB 1,3-Dichlorobenzene
DCC N,N′-Dicyclohexylcarbodiimide
DDQ 2,3-Dichloro-5,6-dicyano-p-benzoquinone
DIC N,N′-Diisopropylcarbodiimide
DIEA Diisopropylethylamine
DKR Dynamic kinetic resolution
DMAD Dimethylacetylene dicarboxylate
DMAP 4-(Dimethylamino)pyridine
DMF N,N-Dimethylformamide
DMSO Dimethylsulfoxide
DMT 4,4′-Dimethoxytrityl
DSC N,N′-Disuccinimidyl carbonate
EDC·HCl N-Ethyl-N′-(3-dimethylaminopropyl)carbodiimide hydrochloride
EDTA Ethylenediaminetetraacetic acid
Et Ethyl
EtOAc Ethyl acetate
Fmoc 9-Fluorenylmethyloxycarbonyl
FRP Functional resin particles
Gn Graphene
GO Graphene oxide
n-Hex n-Hexyl
HMDS Hexamethyldisilazane
HPLC High-performance liquid chromatography
HRMS High-resolution mass spectrometry
HSVM High-speed vibration mill
IBA 2-Iodosobenzoic acid
IBX 2-Iodoxybenzoic acid
ICP-MS Inductively coupled plasma mass spectrometry
ILAG Ion- and liquid-assisted grinding
INA Isonicotinic acid
xiii
xiv List of Abbreviations
IR spectrocopy Infrared spectroscopy
KIE Kinetic isotope effect
LAG Liquid-assisted grinding
MA Maleic anhydride
MALDI Matrix-assisted laser desorption/ionization
MAPP Maleated poly(propylene)
MAS Magic angle spinning
mCPBA m-Chloroperbenzoic acid
Me Methyl
MeCN Acetonitrile
MI Maleic imide
MOF Metal organic framework
MSDS Material safety data sheet
MW Microwave
MWCNT Multiwalled carbon nanotube
NBS N-Bromosuccinimide
NCS N-Chlorosuccinimide
NHS ester N-Hydroxysuccinimidyl ester
NIS N-Iodosuccinimide
NMR Nuclear magnetic resonance
PCBs Polychlorinated biphenyls
PCP Pentachlorophenol
PEG Polyethylene glycol
Ph Phenyl
PM Planetary ball mill
PMMA Poly(methyl)methacrylate
POLAG Polymer-assisted grinding
iPr Isopropyl
PTC Phase transfer catalyst
PTFE Polytetrafluoroethylene
PXRD analysis Powder X-ray diffraction analysis
RCM Ring closing metathesis
rpm Rounds per minute
SDG Solvent-drop grinding
SEM Scanning electron microscopy
ssNMR spectrocopy Solid-state nuclear magnetic resonance spectroscopy
SWNH Single walled nanohorn
SWNT Single walled nanotube
TBAB Tetrabutylammonium bromide
TBAI Tetrabutylammonium iodide
TBDMS t-Butyldimethylsilyl
TBDPS t-Butyldiphenylsilyl
TLC Thin layer chromatography
TMS Trimethylsilyl
TOF Turnover frequencies
Tr Triphenylmethyl (trityl)
TsOH p-Toluenesulfonic acid
UNCA Urethane-protected α-amino acid N-carboxyanhydride
Z Benzyloxycarbonyl
CHAPTER
1
Practical Considerations
in Mechanochemical
Organic Synthesis
CHAPTER OUTLINE
1.1 A Historical Perspective .........................................................................................1
1.2 M odern Laboratory Instrumentation for Mechanosynthesis .....................................12
1.2.1 Planetary Ball Mills ..........................................................................13
1.2.2 Mixer (Shaker) Ball Mills ..................................................................14
1.2.3 Custom-Made Ball Mills ...................................................................15
1.2.4 Milling Parameters ...........................................................................16
1.3 C ontamination From Wear in Organic Mechanosynthesis .......................................18
1.4 A nalysis and Monitoring of Mechanochemical Reactions ......................................22
1.4.1 Analytical Methods in Organic Solid-State Chemistry ...........................22
1.4.2 Monitoring of Mechanochemical Reactions .........................................35
1.4.2.1 Ex Situ Monitoring .......................................................................37
1.4.2.2 In Situ Monitoring .......................................................................42
References ................................................................................................................50
1.1 A HISTORICAL PERSPECTIVE
From the beginnings of mankind, mechanical treatment and processing of grains
and seeds emerged as the first engineering technology in food preparation [1].
Later on, treating raw materials like minerals and ores in the same way, allowed
the production of finely powdered paints and medicines. Prototypical mortars dif-
fering in material, shape, size, and decorations, found at many archaeological sites
throughout the world, testify to early developments of tools that were intended to
make use of mechanical force exerted by a hand. In those primitive grindstones,
a stone ball was devised as a substitute to what later would become a pestle. Fol-
lowing the advancement of technology, simple grindstones eventually evolved into
a variety of stylized mortars. Beautiful pieces named molcajete made of basalt
stone, typical for pre-Hispanic Mesoamerican cultures, represent one such addi-
tion. Dating back to several thousand years, the Aztec and Maya people exten-
sively used them for crushing and grinding spices and for preparation of salsas
and guacamole. Even today, molcajete is a must-have kitchen utensil in traditional
Mexican cuisine. Another example is a metate or mealing stone, traditionally used
Mechanochemical Organic Synthesis. http://dx.doi.org/10.1016/B978-0-12-802184-2.00001-7 1
Copyright © 2016 Elsevier Inc. All rights reserved.
2 CHAPTER 1 Practical Considerations
by Mesoamerican cultures to grind lime-treated maize and to prepare food. How-
ever, mealing stones are not tied with Mexico only since variations are found all
over the world (Fig. 1.1).
(A) (B) (C)
FIGURE 1.1
(A) A primitive grindstone, (B) Molcajete, a traditional Mexican tool for crushing and
grinding spices, (C) Diego Rivera’s La Molendera (The Woman Grinder, 1924) showing
traditional use of metate in making tortillas.
In his booklet De Lapidibus (On Stones), Theophrastus of Eresus described what
is believed to be the first surviving testimony on relationship between grinding, as
a means to introduce a mechanical force, and a chemical change as a consequence
thereof [2]. It was a reduction of native cinnabar to the liquid mercury metal in the
presence of vinegar, carried out in a copper mortar with a copper pestle:
HgS(s) + Cu(s) → Hg(l) + CuS(s)
In this, according to today’s standards, mechanochemical reaction, vinegar was
used to eliminate side-reactions that often take place during milling in air. Interestingly,
it would take another 2000 years for scientists to rediscover the effects of added liquid
on the course of mechanochemically promoted reactions in what has come to be known
as solvent-drop grinding (SDG), kneading, or liquid-assisted grinding (LAG) [3].
By entering the middle ages, much of the knowledge collected during the ancient
times was lost or forgotten. However, mortar and pestle continued to be the primary tool
for mechanical treatment of substances, and an alchemist laboratory could not be imag-
ined without this grinding equipment, as nicely illustrated in Jan Van der Straet’s painting
The Alchemist’s Studio (Fig. 1.2). While the medieval awakened interest in unraveling
the mysteries of nature and new revolutionary ideas of renaissance have greatly con-
tributed to the development of all fields of science, a systematic approach in studying
mechanochemical reactions was left out until the second half of the 19th century.
Although Michael Faraday performed reduction of silver chloride with zinc,
copper, tin, and iron by manual grinding demonstrating that chemical changes
induced by means of mechanical agitation was a common knowledge [4], it was
only with Walthère Spring and Matthew Carey Lea stepping up on the stage when
mechanochemical phenomena started to be investigated in a systematic fashion
[5]. While Spring, led by an aspiration to grasp the formation of minerals inside
the earth’s crust, focused his research on the effect of high pressure on phase
1.1 A Historical Perspective 3
FIGURE 1.2
Jan Van der Straet’s “The Alchemist’s Studio” (1571).
transformations and chemical reactions, M. C. Lea explored the behavior of silver,
gold, mercury, and platinum halides (Cl, Br, and I) under the conditions of static
pressure and shearing forces during manual agitation. He found that the potential
of large static pressure to bring about a chemical reaction is much less pronounced
compared to weak shearing forces exerted on the system as a result of manual
grinding. Notably, the most important and cited result of Lea’s research on mecha-
nochemistry, which earned him the title of “father of mechanochemistry,” is the
observation that mechanical grinding leads to effects different from those induced
by heat in thermochemical reactions. The two examples that illustrate this were
mechanochemical decomposition of silver and mercury chlorides to silver, liquid
mercury, and chlorine gas, as opposed to melting (AgCl) and sublimation (HgCl )
2
without decomposition upon exposure to heat:
2AgCl(s) → 2Ag(s) + Cl2(g)
HgCl2(s) → Hg(l) + Cl2(g)
As far as the mechanochemical synthesis involving organic molecules goes, the
earliest documented example dates back in 1893 in a paper published by Ling and
4 CHAPTER 1 Practical Considerations
Baker [6]. In their contribution, an equimolar mixture of metadichloroquinol 1 and
metadichloroquinone 2 was ground in a mortar to yield tetrachloroquinhydrone
co-crystal 3 (Scheme 1.1A). It took nearly 100 years for chemists to again engage in
mechanochemically promoted organic reactions. The work published by Paul in the
early 1980s dealt with syntheses of quinhydrone charge–transfer complexes in the
solid state by means of grinding with a mortar and pestle [7]. Specifically, mecha-
nochemical co-crystallization of benzoquinone 4 with several hydroquinones, for
example, naphthalene-1,4-diol 5 and 2-methylhydroquinone 7 resulted in charge–
transfer molecular complexes 6 and 8 (Scheme 1.1B and C) that are difficult to
synthesize in solution due to redox self-isomerization.
SCHEME 1.1
Solid-state synthesis of charge–transfer complexes.
Toda et al. succeeded in preparing several co-crystals of different compounds that
normally undergo redox isomerization, but did not display charge-transfer interaction
by agitation in a mechanical test tube shaker [8]. During the late 1980s, Etter’s group
embarked on a research project aimed at understanding hydrogen bonding preferences
and the viability of solution evaporation and solid-state grinding as synthetic methods
to prepare co-crystals [9]. Their research has shown that solvent-free (or neat grind-
ing) approach for promoting co-crystallization is a simple and rapid alternative to
solution-based methods that enables preparation of a wide range of hydrogen-bonded
co-crystals. The work by Etter, and also Caira, published in 1995 marked the begin-
ning of an extensive application of manual neat grinding and ball milling as preparative
methods for the synthesis of co-crystals of active pharmaceutical ingredients (API), and
offered new opportunities for the solid-state chemistry in pharmaceutical science [10].