Development and application of a solution-phase automated synthesizer, 'ChemKonzert'

Article abstract of DOI:10.1248/cpb.58.87

In this paper we describe the development of a fully-automated solution-phase synthesizer, 'ChemKonzert' that can be used to prepare a wide variety of organic compounds. The automated synthesizer is ingeniously designed to perform most of the chemical reactions currently used by synthetic organic chemists and utilizes a centrifugal separator to efficiently achieve liquid-liquid extraction. The design of the hardware and software will be described in this paper, and several examples of organic reactions will also be presented as applications of the apparatus.

Full text of DOI:10.1248/cpb.58.87

January 2010
Chem. Pharm. Bull. 58(1) 87—93 (2010)
87
Development and Application of a Solution-Phase Automated Synthesizer,
‘ChemKonzert’
Kazuhiro MACHIDA, ,a Yoichiro HIROSE,a Shinichiro FUSE,b Tohru SUGAWARA,a and
*
b
Takashi TAKAHASHI
a Development Department, ChemGenesis Incorporated; 4–10–2 Nihonbashi-honcho, Chuo-ku, Tokyo 103–0023, Japan:
b
and Department of Applied Chemistry, Tokyo Institute of Technology; 2–12–1 Ookayama, Meguro-ku, Tokyo 152–8552,
Japan. Received October 20, 2009; accepted October 30, 2009; published online November 2, 2009
In this paper we describe the development of a fully-automated solution-phase synthesizer, ‘ChemKonzert’
that can be used to prepare a wide variety of organic compounds. The automated synthesizer is ingeniously de-
signed to perform most of the chemical reactions currently used by synthetic organic chemists and utilizes a cen-
trifugal separator to efficiently achieve liquid-liquid extraction. The design of the hardware and software will be
described in this paper, and several examples of organic reactions will also be presented as applications of the ap-
paratus.
Key words solution-phase synthesis; automated synthesizer; centrifugal separator; ChemKonzert; application example
Recently, one of the trends in synthetic organic chemistry in combinatorial chemistry. Furthermore, reaction methods
has been to use automated synthesizers for high speed syn- and conditions required for using a computer-controlled au-
thesis of libraries of compounds, in order to meet the require- tomated synthesizer can be left in each laboratory, and the re-
ments for bio-assay studies.1) Combinatorial and high actions can be repeatedly run by any operator to get the same
throughput parallel chemistry has become more popular, not compounds in the future.
only in pharmaceutical companies for developing drug can-
didates but also in chemical companies to develop catalysts they allow the facile exchange of data such as reaction condi-
and the like for making new materials.2)
tions, between research laboratories, especially regarding the
Secondly, automated synthesizers are beneficial because
Generally, chemists have to carry out many time-consum- lead optimization step. Medicinal chemists usually carry out
ing and routine tasks, such as optimizing reaction conditions, reactions manually using simple glassware, but for manufac-
synthesizing many derivatives, analyzing and purifying com- ture, process chemists use instruments such as calorimeters
pounds. Various types of automated synthesizers have be- to determine suitable reaction conditions for a large scale
come commercially available, but most of them are focused production. Thus, for process chemists, the data of reaction
on solid-phase chemistry. There are few reports on auto- conditions coming from the research laboratory will be noth-
mated synthesizers for solution-phase synthesis because the ing more than a starting reference, and they will have to
work-up process is much more diverse than that of solid- spend considerable time and effort into optimizing reaction
phase synthesis and not easy to adapt for automation.3,4) To conditions from the beginning. On the other hand, if medici-
achieve a truly versatile and efficient automated synthesizer nal chemists use an automated solution-phase synthesizer,
for organic synthesis, the ability to handle solution-phase the data exchange is very efficient, and the process is scaled-
chemistry is very important because most of the reactions up smoothly and reliably, eliminating differences that in-
that have been developed in organic chemistry are solution- evitably arise from human operators.
phase ones.
In this report we describe the development of a solution- Results and Discussion
phase automated synthesizer, ‘ChemKonzert®’, and its appli-
ChemKonzert is designed on a ‘unit concept’, which
cation in various organic syntheses to verify the performance means the instrument is divided by functions. For example,
of the apparatus. There are two main uses of solution-phase there is a solvent unit for holding reaction solvents and a
automated synthesizers. Firstly, they are useful for the prepa- reagent unit for reaction reagents. A schematic diagram of
ration of starting materials and building blocks for a lead the ‘unit concept’ is shown in Fig. 1. Other units are for, re-
generation. When chemists attempt to use combinatorial action, transfer, separation, drying, collection, washing and
chemistry for solid-phase synthesis, they often face the prob- waste, as shown in Fig. 2. In addition, each of the solvent,
lem of how to supply the large number of starting materials reagent and reaction units can easily be increased to 3 units.
and building blocks. For example, in the case of a 2-step syn- By applying this ‘unit concept’, we were able to construct the
thesis (target having molecular weight 300, target molecule system to be very user friendly and easily adaptable to cus-
volume 10 mg), at least 700 mg of the starting material will tomer requirements.
be needed for preparing 6 compounds (2ꢀ3), 12 g in the case
One of the most characteristic features in ChemKonzert is
of 100 compounds (10ꢀ10) and 120 g for 1000 compounds. that a centrifugal separator is installed in the synthesizer to
The most time-consuming steps in a combinatorial synthesis overcome problems due to emulsion formation in the extrac-
using solid-phase synthesis are for the preparation of the tion process, and the same centrifugal separator can also be
starting materials and building blocks. An automated synthe- used as an independent instrument. After using the centrifu-
sizer for solution-phase synthesis would thus make an effi- gal system to separate an emulsion into its component aque-
cient platform for high speed synthesis of library compounds ous and organic parts, these are divided by using the different
© 2010 Pharmaceutical Society of Japan
∗ To whom correspondence should be addressed. e-mail: kmachida@chemgenesis.com

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To handle the washing requirement, two solvent reservoirs
are equipped for washing all the glassware and Teflon tubes,
with both water and acetone. Subsequently, the lines are
dried using the vacuum pump (MZ-2C, Vacuumbrand,
GMBHꢁCO KG), which is also used for transferring the
solvents, reagents, and reaction mixtures.
The flow-lines and the insides of the solenoid valves
(MTV-02R-NM6G (DC-24V), MTV-2R-NM6G (DC-24V)
and MTV-3R-NM6G (DC-24V), Takasago Electric Inc.,
Japan) are all made of Teflon. The inside of the rotary valve
is made of PPS (polyphenylene sulfide) and Teflon. The reac-
tion flask, the separation funnel and the centrifuge flask are
made of PYREX® glass. In addition, the reaction unit flasks
can be easily connected to other glassware, such as distilla-
tion adaptors, through the use of ‘quickfit’ (15/25 or 25/42)
joints. The transferring of the reagents/solvents/reaction mix-
tures is carried out using a vacuum pump, which avoids the
risk of trouble, such as the bursting of tubes and leakage of
solvents/reagents that may occur if a syringe pump or nitro-
gen pressure is applied, or a tube becomes clogged. In addi-
tion, this system can be used for concentration under vacuum
and photosensors (EE-SPX613, OMRON Co., Japan) are in-
stalled to detect the flow of liquid in the Teflon tubes. For
safety, the system will be automatically shut down in the
event of an earthquake, and also an emergency button allows
the system to be immediately shut down. In the electrical
system, all temperature controllers (E5AN, OMRON Co.,
Japan) and solid state relays (G3NA-210B (DC-24V),
OMRON Co., Japan) that are used have been designed to be
spark-free.
Fig. 1. Schematic Diagram of the Units
Construction and Function of Units. Solvent Unit
The solvent unit has three commercially available solvent
bottles (500 ml or 1 l) and one measuring tube (MT, 20 ml) to
measure the solvent volume. For example, if the reaction re-
quires 40 ml of the solvent, the system will fill the set amount
(20 ml), deliver the solvent, and then the system will fill the
MT again and deliver to the reaction flask (totally 40 ml).
The MT can be easily changed to handle different volumes,
if necessary, appropriate for the desired reaction scale.
Reagent Unit The reagent unit has three reagent reser-
voirs and three wash solvent reservoirs. The entire reagent
that is set in the reagent bottle will be transferred to the reac-
Fig. 2. Photograph of ChemKonzert
electric conductivity of the two layers to detect the interface tion flask. This method is more useful than using an auto-
between them. The system of flow-line type instruments uses sampler because auto-samplers require some dead volume
many valves to connect each unit. Rotary valves (UV-9444P, and the entire reagent in the vials cannot be delivered. The
UV-9844P, UV-9144P and UV-9454S, Uniflows Co., Japan) reagent reservoirs can be easily replaced with new ones,
are adopted in this instrument for three reasons; firstly to re- which may be pre-filled in another place, such as a laboratory
duce the size of the system. By using rotary valves, the fume hood.
dimensions of the system can be kept relatively small
Reaction Unit This unit usually consists of two reaction
(1550(W)ꢀ540(D)ꢀ730(H)), while including 2 reaction vessels. The reaction unit has one commercially available re-
units, 2 solvent units, 2 reagent units and a work-up unit, as action flask (maximum 1 l) with an oil bath, one filtration
shown in Fig. 2. Secondly, the electrical circuit boards and flask and two thermometers to measure the inside and out-
the Teflon® flow-lines can be well separated to guard against side temperature of the reaction flask. Each reaction flask has
potential fire risks. Thirdly, easy maintenance of the system one reflux condenser, one mechanical stirrer, and five Teflon
for the user is based on all flow-lines of the system being tube flow-lines, which come from the reagent, solvent and
arranged for access from the front of the system.
washing units and are connected to the transfer unit. Also,
In ChemKonzert, each unit and all the glassware are con- one spout allows for the addition of solid reagents or the tak-
nected by Teflon tubes, which make up the “flow-line” sys- ing of small portions of the reaction mixture for monitoring
tem. This flow-line system is easy to keep under inert atmo- by TLC, if required. A filtration flask is set next to the reac-
sphere during experiments, but washing of the whole system tion flask, for collecting crystals or precipitates that may be
is necessary and it is very difficult to handle solid reagents. generated after or during the reaction. In addition to solid fil-

January 2010
89
trates, this system can also handle scavenger resins, which ment work before unattended full automation is attempted.
may be put into the filtration flask as part of the work-up of The power to the unit is switched on with one relay and the
the reaction mixture. Temperature control of the reaction speed can be set at 0—2000 rpm, either manually or from the
flask is performed locally with two thermostatic controllers, control computer. One further relay switch controls a sole-
one for measuring the inside of the reaction flask and another noid that pushes the cap down onto the mouth of the flask to
for measuring the outside.
form seal. After the emulsified sample is transferred to the
The dropping speed of solvents and reagents can be con- separating flask and the phases are separated, the sample is
trolled under inert atmosphere, by opening and closing the transferred out of the flask passing a flow-type conductivity
valve that is located between the reagent or solvent unit and sensor and a conductivity meter (WBM-100, DKK TOA Co.,
the reaction unit. In addition, solvents and reagents can be Japan), which can detect the boundary between the phases
dropped while keeping the desired temperature within ꢂ2 °C and then control a solenoid valve to direct the phases into
in the apparatus. A feature that is very useful for both tem- separate collection flasks.
perature controlled reactions, such as anion type reactions,
Drying Unit The drying unit is equipped with three dry-
and the quenching of reactions, which often benefits from ing tubes. Usually anhydrous sodium sulfate is used as a dry-
temperature control to prevent undesirable decomposition of ing reagent. For easy use, this system is compatible with
the products. After finishing the reaction, the reaction mix- commercially available disposable tubes (5010-19111, Varian
ture can be quenched in the flask by delivering the quenching Instruments, U.S.A.), and a variety of columns, such as silica
solution from the solvent unit. Then the mixture can be trans- gel for short column purification, may be used.
ferred to the separation unit, drying unit or collection unit,
and through the transfer unit to complete the work-up of the to collect the desired fractions or final products.
reaction. Re-extraction of the separated aqueous layer and Washing Unit This unit is equipped with two solvent
Collection Unit This unit is equipped with three flasks
washing of the combined organic layer can also be per- bottles, one for water and another for organic solvent such as
formed in the reaction flask. For achieving efficient and ef- acetone or methanol. The unit is connected to the solvent
fective stirring, a modified magnetic-induced mechanical unit to allow washing of the MTs and also to the reagent unit
stirrer is used in each reaction vessel.
to enable washing of the reagent bottles, if required. After
Transfer Unit This unit is situated between the reaction washing the MTs or reagent bottles, the wash solvent is
unit and the separation unit, the drying unit and the collec- transferred into the reaction unit to wash the flow-lines and
tion unit. The Transfer unit allows the destination of the reac- reaction flasks. After washing all the tubes and glassware
tion mixture in the reaction flask to be varied between the using water and acetone, the system can perform drying of
separation unit, the drying unit, the collection unit or another all the tubes and glassware, using a vacuum pump and dry air
reaction unit.
or inert gas.
Separation Unit The unit is equipped with two separa-
Waste Unit This unit is equipped with a cold trap, vac-
tion flasks and a centrifuge instrument.5) After the reaction uum pump, two waste bottles, a recycling chiller and seven
mixture is quenched, the mixture is transferred into the cen- valves for the coolant. A waste solution, such as the solvent
trifuge through the transfer unit. A common difficulty en- that has been used for washing the system or waste layer
countered when using automated separation is that it may after an extraction process, is transferred into the waste bot-
take an excessively long time for the mixed phases to sepa- tles through a cold trap. The coolant continually flows inside
rate. Indeed, it may be found that some mixtures (e.g., aque- the cold trap from the time the instrument is turn on. If the
ous alkaline/CH2Cl2) form particularly stable emulsions that reaction unit requires cooling or reflux, the control system
do not separate even after several hours. In order to overcome will direct the flow of the coolant using the valves in this
this problem we devised an automated means to separate unit, to cool the oil bath or the reflux condenser.
emulsified extracts, using centrifugal force to rapidly sepa-
Computer Control System The control software,
rate and divide the individual phases.6) The centrifugal sepa- ‘KonzertMeister’, is well designed for easy operation by or-
rating unit offers the ability (1) to shorten the time, (2) to ganic chemists. The concept of the software is based on
avoid the need to add another reagent or solvent and (3) to using the familiar chemical terms that appear in experiments,
handle volumes of about 50 ml to 2 l.
as the names of commands, for example, ‘Extraction’, ‘Stir
The emulsified sample is transferred into a robust round Reaction Flask’, ‘Separation’ etc. For delivering solvents or
glass flask that is spun at high speed (maximum 2000 rpm). reagents, the commands use abbreviated forms such as
As the flask is rotated, the emulsified sample spins and the ‘RR1-RF1’, which means transfer the solvent/reagent in the
two phases separate under the centrifugal force that is cre- reagent bottle 1 (RR1) to the reaction flask 1 (RF1). The
ated. The bottom of the flask is connected to the central transcription system is very simple and easy and soon be-
motor and the top is held by a collar containing ball bearings. comes familiar to organic chemists. The commands, called
The flask can be easily removed for maintenance by un- ‘Steps’ in the software, are pre-prepared and available to eas-
screwing the top holder. In order to transfer solutions into the ily make into a sequence as an experimental protocol for a
flask when it is stationary, the top cap is pushed down onto reaction, simply by double clicking on the required ‘Steps’.
the mouth of the flask to form a seal. Three tubes are fixed to In addition, if the user wants to modify the step or make a
the cap, one extending to the bottom and the other two into new step, the software can be easily modified. A record of
the top of the flask. Using these tubes it is possible to apply temperature is sometimes important, so the software records
vacuum or pressure to accomplish the transfer of solutions. A both inside and outside temperatures for the reaction flasks,
window is fitted in the front panel of the unit to allow visual once every minute.
monitoring of the separation, which is useful during develop-
Fundamental Reaction Applications Some typical re-

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Vol. 58, No. 1
actions were carried out to demonstrate the performance of
the apparatus. The first application was the protection of an
amino functional group, as shown in Fig. 3,7) which demon-
strated the usefulness of the filter attached to the reaction
flask and the dropwise addition of reagents from the reagent
unit. As an example of the protection of only one amino
group of a compound containing two equivalent amino
groups, the di-amino compound, ethylenediamine, was pro-
tected with a single t-butoxycarbonyl (Boc) group. In this re-
action, the byproduct (di-Boc derivative) was crystallized
during the work-up process by the addition of water, which
then facilitated its separation and removal using the filter.
The next application shows the protection of a hydroxyl
group with a tetrahydropyranyl (THP) group, which demon-
strates the apparatus for starting material synthesis. Espe-
cially, the protection of only one functional group, a hydroxyl
group in this case, in a compound having two equivalent
functional groups is very useful for the synthesis of building
blocks in combinatorial chemistry. In this manner, useful
starting materials can be obtained in a straightforward and
reliable manner using the synthesizer. The protection reac-
tion of an alcohol is reported as a two phase reaction and the
yield drops down if the mixing is not enough.8) Thus, this re-
action demonstrates the stirring and work-up performance of
the instrument, as shown in Fig. 4.
Another protection reaction, that of an alcohol with a
t-butyldimethylsilyl (TBS) group using NaH, was carried
out to demonstrate the ability to keep an inert environment in
the system, as shown in Fig. 5.9) In addition, the handling of
NaH was shown, including the ability to wash the reagent
with dry hexane before use, in order to clean it.
Fig. 4. Flowchart for the Synthesis of 5-(Tetrahydropyran-2-yloxy)pentan-
1-ol
A C–C bond formation reaction was carried out as shown
in Fig. 6. Masamune reaction requires the activation of each
starting material before starting the reaction. Each starting
Fig. 3. Flowchart for the Synthesis of (2-Amino-ethyl)-carbamic Acid t- Fig. 5. Flowchart for the Synthesis of 5-(t-Butyldimethylsilanyloxy)pen-
Butyl Ester tan-1-ol

January 2010
91
Fig. 7. Flowchart for the Synthesis of (4-t-Butoxy-phenoxyl)-acetic Acid
Fig. 6. Flowchart for the Synthesis of 3-Oxo-3-phenylpropionic Acid
Ethyl Ester
material needed to be activated in different reaction flasks,
before being mixed to perform the Masamune reaction. With
this reaction, it was possible to demonstrate the usefulness of
the apparatus with two reaction flasks and show their simul-
taneous use.
A two step reaction was also carried out in this apparatus.
One of the important features of ChemKonzert is that it can
perform multi-step synthesis. The first step was to form an
O–C bond (O-alkylation reaction) under reflux conditions
and the next step was to perform a hydrolysis reaction using
a different solvent, as shown in Fig. 7. In addition, the heat-
ing and filtration ability of the instrument was demonstrated,
as the reaction required reflux and the main product was gen-
erated as a solid.
After several types of reactions under inert environment
had been successfully carried out in the instrument, we at-
tempted to demonstrate the use of moisture sensitive reagents
such as Grignard reagents, as shown in Fig. 8. The experi-
mental protocol included a quenching step during the work-
up process, where the reaction mixture was poured into an
aqueous layer. One reaction flask was used to perform the re-
action and the second flask was used for the work-up. The in-
strument does not have a purification unit but the instrument
has drying tubes to dry the organic layer, and these tubes can
also be exchanged for commercially available silica gel tubes
Fig. 8. Flowchart for the Synthesis of Acetophenone
for short column purification. Anhydrous sodium sulfate was Weinreb amidation, the organic layer was dried and purified
put into the first tube to dry the organic layer and silica gel through the tubes. Finally, the organic layer was concen-
was put into the second tube to purify the organic layer. After trated, in order to change the solvent to perform the Grignard

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Vol. 58, No. 1
flask from the reagent bottles. The reaction mixture was stirred at 30 °C for
2 h. After adding 100 ml of AcOEt to the reaction mixture, 5% aq. sodium
hydrogen sulfate (40 ml) was delivered from the reagent bottle to the solu-
tion with stirring, to quench the reaction. Then the mixture was transferred
to the centrifuge through the transfer unit and separated into two layers. The
reaction.
Conclusion
We have designed and constructed ChemKonzert and the
accompanying control software for automated solution-phase separated aqueous layer was extracted with AcOEt twice (40 mlꢀ2). The
combined organic layers were washed with water (20 ml), and then collected
into the collection flask through the drying tubes filled with anhydrous
sodium sulfate. Finally, the organic layer was concentrated in vacuo using a
synthesis. This synthesizer is designed for flexible set up,
based on a unit concept, easy maintenance, and user friendly
software. The operating software for the system has been de-
signed to be intuitive for organic chemists, to allow operation
of the automated synthesizer using protocols that are familiar
and based on traditional synthesis techniques.
It is very important to carry out several types of actual re-
action to demonstrate the performance of the instrument, and
the following have been shown; (1) two phase reaction to
demonstrate mixing ability, (2) temperature controlled reac-
tion at reflux and 0 °C, (3) handling of air and moisture sen-
sitive reagents, (4) handling precipitates after reaction is
completed, (5) a continuous two step reaction. The results of
each reaction have shown that the synthesizer is useful and
reliable for organic chemists. In addition, the work-up
process was performed automatically and the centrifugal sep-
arator system worked well for all of the reactions. Thus the
automated synthesis system was shown to be capable of
rotary evaporator to give 1.68 g of 5-(tetrahydro-pyran-2-yloxy) pentan-1-ol
(isolated yield, 89%; cf. yield in literature,8) 92%).
Synthesis of 5-(t-Butyldimethylsilanyloxy)pentan-1-ol The reaction
was carried out as follows, and as shown in Fig. 5. Before starting the reac-
tion, the instrument was slightly modified by adding a Teflon filter and a
Teflon tube that reached to the bottom of the reaction flask (RF1) and con-
nected to the transfer unit. NaH (0.84 g) solid was placed in the reaction
flask on the filter and then the reaction flask was kept under inert atmo-
sphere. Dry hexane (20 ml) was delivering from the solvent bottle to the re-
action flask. After mixing, hexane was removed from the reaction flask to
the waste bottle through the filter. Tetrahydrofuran (THF) (40 ml) and the
starting material, pentane-1,5-diol (2.02 ml) in 20 ml of THF were delivered
from a solvent bottle and a reagent bottle, respectively, to the reaction flask.
The reaction mixture was stirred at 25 °C for 1 h, and then t-butyldimethylsi-
lyl chloride (TBSCl; 2.91 g) was manually added to the reaction flask
through the spout. The reaction mixture was diluted with Et2O (120 ml), and
then quenched by 10% aq. K2CO3 (140 ml). After separating the two layers,
the aqueous layer was extracted with Et2O four times (100 mlꢀ3). The com-
bined organic layers were washed with 10% aq. NaCl (100 ml), collected
preparing various types of organic compounds. The instru- into the collection flask through the drying tubes filled with anhydrous
sodium sulfate. The organic layer was concentrated in vacuo to give 3.85 g
ment can perform all the typical solution-phase reactions
used in the pharmaceutical and chemical industries that do
not require the use of high pressures or automated handling
of 5-(t-butyldimethyl-silanyloxy) pentan-1-ol (isolated yield, 92%; cf. yield
in literature,9) 87%).
Synthesis of 3-Oxo-3-phenylpropionic Acid Ethyl Ester The reaction
of solids.
During the last 100 years, an enormous number of solu-
was carried out according to the flowchart shown in Fig. 6. Potassium ethyl
malonate (4.08 g) was put into the reaction flask (RF1) and benzoic acid
(2.44 g) was put into the reaction flask (RF2) by manual operation. Triethy-
lamine (6.65 ml) in 20 ml of THF was delivered from the reagent bottle to
RF1, and then magnesium chloride (3.43 g) was put into RF1 by manual op-
eration through the spout of the reaction flask. The mixture was stirred at
25 °C for 2 h. Meanwhile, 1,1ꢃ-carbonyl-bis-1H-imidazole (CDI; 3.90 g) in
60 ml of THF was delivered from the reagent bottle to RF2, and the mixture
was stirred 25 °C for 2 h. The solution in RF1 was transferred to RF2 to
carry out the Masamune reaction. The reaction mixture was stirred at 25 °C
for 12 h, diluted with AcOEt (200 ml), quenched by addition of 2 M HCl
(100 ml), and then separated into organic and aqueous layers. The separated
aqueous layer was extracted with AcOEt twice (100 mlꢀ2). The combined
organic layers were washed with 5% aq. NaHCO3 solution (100 ml) and
water (60 ml), and then transferred to the collection flask through the drying
tubes filled with anhydrous sodium sulfate. The organic layer was concen-
tion-phase reactions have been developed by many organic
chemists, throughout the world. With an automated solution-
phase synthesizer such as ChemKonzert, it is now possible
for all scientists, not only specialist organic chemists, to ex-
ploit the vast wealth of knowledge and produce useful or-
ganic compounds. In fact, efficient preparations of key inter-
mediates for syntheses of TAXOL® and the 9-membered
masked enediyne have recently been achieved by using
ChemKonzert.10,11) It is indicated that the automated synthe-
sizer can be utilized in broad area of organic syntheses.
Experimental
Materials and reagents were purchased as follows: solvents were of spe- trated in vacuo to give 3.67 g of 3-oxo-phenyl-propionic acid ethyl ester12)
cial or first grade from Tokyo Kasei Kogyo Co., Ltd., Wako Pure Chemical (isolated yield, 96%).
Industries Ltd., and Aldrich Chemicals Ltd. Short column chromatography
was performed on Silica Gel 60 N, purchased from Kanto Chemical Co.
Synthesis of (4-t-Butoxy-phenoxy)-acetic Acid The reaction was done
as shown in Fig. 7. The starting material, 4-butoxy-phenol (2.02 g) was put
Synthesis of (2-Amino-ethyl)-carbamic Acid t-Butyl Ester The reac- into the reaction flask (RF1) by manual operation, and then ethyl bromoac-
tion was carried out as shown in Fig. 3. Starting material, ethylenediamine etate (1.34 ml) and K2CO3 (5.09 g) were also put into the same reaction flask
(5.25 g) in 32 ml of dioxane was delivering from the reagent bottle to the re- by manual operation. Acetone (50 ml) was delivered from the solvent bottle
action flask (RF1). Di-t-butyl dicarbonate, (Boc2O; 2.27 ml) in 31 ml of
to RF1. The reaction mixture was stirred at 58 °C for 12 h, and then concen-
dioxane was dropped from the reagent bottle to the reaction flask over 2.5 h trated in vacuo in RF1. The residue was diluted with Et2O (60 ml) and
at 0 °C. After delivering the reagent, the reaction mixture was stirred at quenched by addition of 10% aq. NaCl (60 ml). The separated aqueous layer
25 °C for 12 h. The reaction mixture was concentrated in vacuo in the reac- was extracted with Et2O three times (40 mlꢀ3). The combined organic lay-
tion flask. Then byproduct (di-Boc derivative, 55.5 mg, 2%) was filtered off ers were transferred to RF2 through the drying tubes filled with anhydrous
using the filtration unit, after 10% aq. NaCl (40 ml) was added from the sol-
sodium sulfate. The organic layer in RF2 was then concentrated in vacuo in
vent bottle to the reaction flask. The remaining reaction mixture was trans- order to change the reaction solvent from Et2O to methanol (60 ml). Aque-
ferred to the centrifuge through the transfer unit and the separated aqueous
layer was extracted with CH2Cl2 five times (40 mlꢀ5). The combined or-
ganic layers were collected into the collection flask through the drying tubes
filled with anhydrous sodium sulfate. The organic layer was concentrated in
vacuo to give 1.49 g of (2-amino-ethyl)-carbamic acid t-butyl ester (isolated
yield, 93%; cf. yield in literature,7) 90%).
ous 2 M NaOH solution (40 ml) was added dropwise from a reagent bottle to
RF2 and the mixture was stirred at 25 °C for 1 h. The solid was filtered using
the filtration unit to give 2.36 g of (4-butoxyphenoxy)acetic acid13) (isolated
yield, 87%).
Synthesis of Acetophenone The first reaction was carried out as shown
in Fig. 8. Using the reaction flask 1 (RF1), benzoic acid (1.22 g) and CH2Cl2
Synthesis of 5-(Tetrahydro-pyran-2-yloxy)pentan-1-ol This reaction (60 ml) were delivered from the reagent and solvent bottles to RF1. 1-Hy-
was carried out as shown in Fig. 4. The reaction was started after adding the droxybenzotriazole (HOBt; 2.03 g) and 1-ethyl-3-(3-dimethylaminopropyl)-
starting material, pentane-1,5-diol (1.04 g) to the reaction flask (RF1) manu-
ally, and the reagents, 3,4-dihydro-2H-pyran (DHP; 3 ml) in 57 ml of toluene Diisopropylethylamine (DIEA; 2.55 ml) and N,O-dimethylhydroxylamine
and 5 M aq. sodium hydrogen sulfate (2 ml) were delivered to the reaction
(NHMe(OMe); 1.47 g) were delivered to RF1 by manual operation at 0 °C.
carbodiimide (WSCD; 3.15 g) were added to RF1 by manual operation. N,N-

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The reaction mixture was stirred at 25 °C for 15 h, and concentrated in vacuo
in RF1. The residue was diluted with Et2O (200 ml) and quenched by addi-
tion of 10% aq. NaHCO3 (40 ml). The mixture was separated into two layers
and the separated aqueous layer was extracted with Et2O twice (40 mlꢀ2).
The combined organic layers were delivered to the reaction flask 2 (RF2)
after washing with 10% aq. NaCl (40 ml), drying and purifying through
tubes packed with silica gel. After transferring the organic layer to RF2, the
RF1 was washed with water and acetone delivered from the washing unit.
After drying RF1 flask under reduced pressure, Et2O (100 ml) and 1 M HCl
(60 ml) were delivered from the solvent bottles to RF1 and the mixture was
stirred at 0 °C. Dry THF (80 ml) was delivered to RF2 and cooled to 0 °C
after the organic layer in RF2 was concentrated. After stirring at 0 °C,
methyl magnesium bromide (5.6 ml) in 20 ml of THF (0.1 M) solution was
added dropwise into RF2 at 0 °C. The reaction mixture was then stirred at
0 °C for 40 min, before being quenched by transferring the reaction mixture
from RF2 to RF1. The separated aqueous layer was extracted with Et2O
2) Schiedel M. S., Briehn C. A., Bauerle P., Angew. Chem. Int. Ed., 40,
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4) Jordan S., Moshiri B., Durand R., J. Assoc. Lab. Autom., 7, 74—77
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5) Sugawara T., Kato S., Japanese Patent, No. 3770698 (2006).
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twice (40 mlꢀ2). The combined organic layers were washed with 10% aq. 10) Doi T., Fuse S., Miyamoto S., Nakai K., Sasuga D., Takahashi T.,
NaCl (40 ml), and then collected into the collection flask through another
drying tube filled with anhydrous sodium sulfate and then concentrated in
vacuo using a rotary evaporator to give 0.72 g of acetophenone14) (isolated
yield, 60%).
Chem. Asian J., 1, 370—383 (2006).
11) Tanaka Y., Fuse S., Tanaka H., Doi T., Takahashi T., Org. Process Res.
Dev., accepted for publication.
12) Liang Y. Z., Narayanasamy J., Schinazi R. F., Chu C. K., Bioorg. Med.
Chem., 14, 2178—2189 (2006).
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