Environmentally friendly approach to α-acyloxy carboxamides: Via a chemoenzymatic cascade

Article abstract of DOI:10.1039/c6ra13078j

A new, green route for the synthesis of α-acyloxy carboxamides from an alcohol, a carboxylic acid and an isocyanide was developed. The reaction comprises the aerobic oxidation of an alcohol to the corresponding aldehyde, catalyzed by the Trametes versicolor laccase/TEMPO system, followed by a one pot Passerini reaction in an aqueous surfactant medium. The influence of different types of surfactants on the reaction efficiency was investigated. The best results were obtained by employing dioctadecyldimethylammonium bromide (DODAB), a known vesicle-forming cationic surfactant. Importantly, apart from the metalloenzyme used, the described procedure toward α-acyloxy carboxamides is metal-free and does not require hazardous organic solvents, what makes it environmentally friendly.

Full text of DOI:10.1039/c6ra13078j

View Article Online
View Journal
RSC Advances
This article can be cited before page numbers have been issued, to do this please use: D. Paprocki, D.
Koszelewski, A. Zadlo, P. Walde and R. J. Ostaszewski, RSC Adv., 2016, DOI: 10.1039/C6RA13078J.
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. This Accepted Manuscript will be replaced by the edited,
formatted and paginated article as soon as this is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the Ethical guidelines still
apply. In no event shall the Royal Society of Chemistry be held
responsible for any errors or omissions in this Accepted Manuscript
or any consequences arising from the use of any information it
contains.
www.rsc.org/advances

Please do not adjust margins
RSC Advances
Page 1 of 8
View Article Online
DOI: 10.1039/C6RA13078J
Journal Name
ARTICLE
Environmental Friendly Approach to α-Acyloxy carboxamides via
a Chemoenzymatic Cascade
Received 00th January 20xx,
Accepted 00th January 20xx
a
a
a
b
a
Daniel Paprocki, Dominik Koszelewski, Anna Żądło, Peter Walde and Ryszard Ostaszewski*
DOI: 10.1039/x0xx00000x
A new, green route for the synthesis of α-acyloxy carboxamides from an alcohol, a carboxylic acid and an isocyanide was
developed. The reaction comprises the aerobic oxidation of an alcohol to the corresponding aldehyde, catalyzed by the
Trametes versicolor laccase /TEMPO system, followed by a one pot Passerini reaction in an aqueous surfactant medium.
The influence of different types of surfactants on the reaction efficiency was investigated. The best results were obtained
by employing dioctadecyldimethylammonium bromide (DODAB), a known vesicle-forming cationic surfactant. Importantly,
apart from the metalloenzyme used, the described procedure toward α-acyloxy carboxamides is metal-free and does not
reqiure hazardous organic solvents, what makes it environmentally friedly.
www.rsc.org/
DODAB (dioctadecyldimethylammonium bromide), a vesicle-
forming surfactant, can have a beneficial effect on the P-3CR,
Introduction
1
6
leading to a substantial increase in reaction yield. Surfactant
aggregates like vesicles or micelles enable to overcome the
main disadvantage of water as a solvent, namely the low
solubility of organic compounds. In addition, the presence of
α-Acyloxy carboxamides and α-hydroxy carboxamides, are the
key building blocks for the synthesis of various natural
1
-4
5
6
7
products,
peptidomimetics and both enantiomers of α-amino acids.
synthetic γ-lactones, 2-furanones, peptides,
8
9
1
7
surfactant aggregates may even enhance reaction rates.
Various methods for the preparation of α-acyloxy
carboxamides have been reported in the literature. Standard
protocols usually require equimolar amounts of a coupling
agent like N,N'-dicyclohexylcarbodiimide (DCC) and a catalyst
Therefore, the combination of the P-3CR with aqueous
surfactant aggregates appears a valuable approach towards
the development of an ideal, environmentally friendly
1
8
1
0
synthesis. Furthermore, vesicle systems, may well be suited
for further combining the P-3CR with enzymatic
transformations.
like 4-(dimethylamino)pyridine (DMAP), which is corrosive
1
1
and very toxic. Furthermore, these reactions require organic
solvents like dichloromethane. Moreover, overall yields of
multistep syntheses are moderate.
Aldehydes (as carbonyl compounds) are typical starting
materials of the P-3CR, although they may be unstable during
storage, leading to the formation of the corresponding
A convenient way for obtaining α-acyloxy carboxamides is to
use a three component reaction between a carboxylic acid, a
carbonyl compound and an isocyanide, first described by
1
9
alcohols and other impurities. Moreover, the synthesis of
aldehydes through oxidation of alcohols or reduction of
carboxylic acids may be difficult since the reactions may not be
selective and they may result in overoxidations or
overreductions. One of the methods used to overcome this
drawback is generating aldehydes in situ, in the reaction
1
2
Passerini in 1921. This Passerini-three component reaction
P-3CR) is usually performed in aprotic organic solvents, e.g.
dichloromethane or toluene, which are toxic and
(
1
3
carcinogenic. To eliminate this inconvenience, the Passerini
reaction can also be conducted under solvent free
2
0
14
mixture, particularly as a first step of a reaction cascade
conditions. However, in this case at least one substrate has
to be in liquid state. Pirrung, Das Sarma and others have
shown that for certain substrates the P-3CR can be performed
(
reduction of waste, which is generated during the isolation
2
1
and purification of intermediates).
1
5
In this context it was reported in the literature about a P-3CR
efficiently also in water. Furthermore, we have recently
demonstrated that the application of aqueous suspensions of
with primary alcohols using o-iodoxybenzoic acid (IBX) as an
2
oxidant, which is a potentially shock-sensitive explosive
2
2
3
substance. Furthermore, there were reports on oxidations
with pure oxygen combined with the P-3CR, using the
2
4
2 2
CuCl /TEMPO/NaNO system or a MNST (magnetic core-shell
2
5
nanoparticles supported TEMPO)/TBN system, in both cases
with toluene as solvent.
Unfortunately, all the mentioned methods for the oxidation of
2
alcohols require hazardous reactants and toxic and expensive
0
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 1
Please do not adjust margins

Please do not adjust margins
RSC Advances
Page 2 of 8
View Article Online
DOI: 10.1039/C6RA13078J
ARTICLE
Journal Name
transition metals. Due to this fact, the products require
tedious and expensive purification procedures, what make
them unattractive for the pharmaceutical and cosmetic
Results and discussion
First, we examined the influence of the vesicle forming
surfactant dioctadecyldimethylammonium bromide (DODAB)
2
6
industries. Especially since in the pharmaceutical industry,
for which the pharmacopoeia limits of heavy metal
contaminations are below 5 ppm, most of the classical
chemical methods with metal catalysts are unacceptable.
In order to fulfil the requirements mentioned above, we report
about a new chemoenzymatic protocol based on a one-pot
oxidation-P-3CR procedure. The oxidation of a primary alcohol
to the corresponding aldehyde is conducted enzymatically by
on the aerobic oxidation of benzyl alcohol
benzaldehyde 2a catalyzed by laccase from Trametes
versicolor. We performed two experiments: (i) a mixture of 1a
0.1 M), TEMPO (20 mol%) and enzyme (4 mg/ml) in
(1a) to
(
)
(
phosphate buffer (pH=5.7, c=0.1 M) was stirred overnight at
room temperature in the presence of DODAB (0.02 mmol); and
(ii) the same mixture was stirred under the same conditions
but without DODAB. In both cases, after extraction followed by
TLC analysis, it was shown that only 2a was obtained. These
experiments demonstrated that the aerobic enzymatic
oxidation of 1a takes place in the presence of DODAB, what
enabled further studies on the combination of the enzymatic
transformation with the non-enzymatic P-3CR in the aqueous
DODAB vesicle system, according to the previously developed
2
oxygen from air (without usage of O , which can be potentially
explosive), with the enzyme laccase and the mediator TEMPO.
A schematic representation of this laccase/TEMPO system is
shown in Scheme 1. After the oxidation, a carboxylic acid and
an isocyanide are added, which initiate a P-3CR in the same
“
pot”, providing an α-acyloxy carboxamide. All reactions
proceed in an aqueous surfactant system, which excludes the
use of organic solvents like toluene, and reactants like NaNO2
and IBX, which are toxic, corrosive (IBX) and hazardous for the
1
6
procedure.
As components for a model Passerini reaction, benzaldehyde
2a), benzoic acid (3a) and p-methoxybenzyl isocyanide (4a
2
7
(
)
aquatic environment (NaNO2). Since, however, TEMPO and
the surfactant are not fully renewable and appear as waste,
16
were arbitrary selected. As shown before, if the reaction is
performed in phosphate buffer in the presence of 20 mol%
2
8
the environmental (E) factor is lower than in a surfactant-
free system. Therefore, we also investigated the reusability of
the catalytic system.
DODAB,
benzoate 5a is obtained with 92 % yield. With these results in
mind, we performed the reaction of 1a 3a and 4a in the
presence of laccase, TEMPO and DODAB in phosphate buffer
pH=5.7). Moreover, we investigated the influence of the
2-(4-methoxybenzylamino)-2-oxo-1-phenylethyl
,
(
enzyme, the mediator, and the reaction time on the reaction
yield. We also performed the reaction with 4-hydroxy-1H-
benzotriazole (HOBt) instead of TEMPO as a mediator and we
optimized the reaction time. The results are summarized in
Table 1.
H2O
O2
LaccaseOX
Laccase
TEMPO
TEMPOOX
O
OH
2
1
R1
R1
O
R1
H
N
COOH
NC
+
R2
R3
R2
R3
O
O
3
4
5
Scheme 1 Schematic representation of the laccase/TEMPO
oxidation-P3CR system. First of all, the laccase is oxidizing the
mediator (TEMPO) using aerobic oxygen as an oxidizing agent.
Afterwards, the oxidized TEMPO is oxidizing a primary alcohol
(
1
) to the corresponding aldehyde (
participates together with a carboxylic acid
isocyanide ( ) in the Passerini reaction to yield α-acyloxy
carboxamide ( ).
2
). Finally, the aldehyde
(
3) and an
4
5
2
| J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 3 of 8
PleaseRd So Cn oA t da vd aj un s ct ems argins
View Article Online
DOI: 10.1039/C6RA13078J
Journal Name
ARTICLE
Table 1 Aerobic oxidation of benzyl alcohol (1a) by the relatively narrow pH range. According to literature, laccase
Trametes versicolor laccase/TEMPO system combined with the from Trametes versicolor is active in the pH range from 3 to
a
30
6. We performed reactions of 1a, 3a and 4a in the presence
Passerini reaction.
of laccase, TEMPO and DODAB in phosphate buffers in the pH
range between 3 and 8. Appropriate buffers were prepared by
mixing 0.1 M solutions of orthophosphoric acid, sodium
dihydrogen phosphate and disodium hydrogen phosphate to
adjust the pH to the desired value. In the optimal range of pH,
between 5 and 6, additional experiments were performed. All
results are shown in Fig. 1.
O
Ph
O
NC
Ph
O
HN
OH
COOH
+
+
Ph
Ph
OMe
4a
1
a
3a
5a
OMe
Entry
Mediator
TEMPO
-----
Time (h)
48
Yield (%)
b,c
<5
1
2
3
4
5
6
7
8
b
48
<5
27
d
TEMPO
TEMPO
HOBt
48
b,e
48
<5
b
48
<5
47
64
64
TEMPO
TEMPO
TEMPO
24
48
72
a
Reaction conditions: benzyl alcohol (1a, 0.5 mmol), benzoic
acid (3a, 0.5 mmol), p-methoxybenzyl isocyanide (4a, 0.5
mmol), mediator (0.1 mmol), laccase from Trametes versicolor
(20 mg), DODAB (0.1 mmol) were stirred at room temperature
in phosphate buffer (5 mL, pH=5.7).
b
Estimated by TLC, absence of spot of the product (5a), 1a still
Fig. 1 Effect of pH on the isolated yield of 5a of the model
laccase/TEMPO oxidation – P-3CR system. Reaction conditions:
benzyl alcohol (1a, 0.5 mmol), benzoic acid (3a, 0.5 mmol) and
p-methoxybenzyl isocyanide (4a, 0.5 mmol), TEMPO (0.1
mmol), laccase (20 mg), DODAB (0.1 mmol) in 5 mL of
phosphate buffer for 48 h at room temperature.
clearly present in the reaction mixture.
c
Reaction carried out without enzyme.
d
Reaction carried out without DODAB.
e
Reaction performed without benzoic acid (3a), with 1 mmol
of benzyl alcohol (1a).
The obtained results clearly prove, that the laccase/TEMPO
system is crucial for the oxidation of benzyl alcohol (1a) to
benzaldehyde (2a) (entries 1 and 2). If one of the two
components was absent, the reaction did not take place.
Comparison of entry 3 with entry 7 shows, that the presence
of DODAB significantly increased the yield of 5a from 27 % to
Although the optimal pH for the model laccase/TEMPO
oxidation – P-3CR system was found to be 5.2, in the range
from pH = 5 to 6 the yield of 5a varied only slightly. Decreasing
the pH value below 5, the yield of 5a dropped, probably due to
3
1
the acid catalyzed hydrolysis of the isocyanide. At pH>6, the
yield of 5a also dropped, which is probably due to a decrease
3
in laccase activity.
64 %. The observed improvement of the reaction yield may be
0
caused by the increase of the solubility of the reacting
molecules in the hydrophobic part of the vesicular aggregates
as well as by electrostatic attractions between the cationic
surface of the vesicles and the benzoic acid anions. Analysis of
the reaction conducted without 3a (entry 4) showed that
overoxidation of 1a to 3a did not occur. Furthermore, without
laccase there was no aerobic oxidation of 2a (entry 1), which
according to literature takes place, when pure water is used as
In a next step of our investigations, we focused on a variation
of the surfactant type. From our previous studies we already
know, that DODAB was the best among the surfactants and
other additives tested for performing the Passerini reaction in
1
6
aqueous systems. Afterwards, we checked whether DODAB is
also the most suitable surfactant for the enzymatic
transformation of 1a to 2a, preceding by the Passerini
reaction. To investigate this point, we performed reactions of
2
9
reaction medium. For the conditions of entry 5, i.e. for the
use of HOBt instead of TEMPO, no reaction took place, what
proves that TEMPO is an efficient and ideal mediator in this
type of biocatalytic oxidation reactions. Entries 6-8 show that
1
a
,
3a and 4a in the presence of laccase, TEMPO and different
additives (20 mol%). The formation of 5a was analyzed (Table
).
2
48 hours is an optimal time for this reaction, after 24 hours the
yield of 5a was 47 % and finally raised to 64 %. Further
reaction time prolongation did not impact the reaction yield.
Next, we focused on the optimizing of the buffer pH value. It is
well recognized that enzymes are stable and active in a
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

Please do not adjust margins
RSC Advances
Page 4 of 8
View Article Online
DOI: 10.1039/C6RA13078J
ARTICLE
Journal Name
Table
2 Effect of different additives on the model 20 mol%, the yield of 5a increased up to 67%. A further
a
laccase/TEMPO oxidation – P-3CR system.
elevation of the DODAB concentration from 20 to 50 mol%, did
not improve the yield further. Based on these data, DODAB
was used at a concentration of 20 mol % for all further
experiments as optimal concentration.
Entry
Additive (20 mol%)
----------
Yield (%)
1
2
3
4
21
16
6
Montmorillonite K 10 (10 mg)
Sodium dodecyl sulphate (SDS)
Sodium bis(2-ethylhexyl) sulfosuccinate
12
(AOT)
5
6
7
8
Cholesterol
Tween 80
22
23
47
23
Triton X-100
3-(N,N-Dimethylmyristylammonio)
propanesulfonate
9
Didodecyldimethylammonium bromide
Dioctadecyldimethylammonium bromide
34
67
10
(
DODAB)
a
Reaction conditions: benzyl alcohol (1a, 0.5 mmol), benzoic
acid (3a, 0.5 mmol) and p-methoxybenzyl isocyanide (4a, 0.5
mmol), TEMPO (0.1 mmol), laccase (20 mg), DODAB (0.1
mmol) in 5 mL of phosphate buffer (pH=5.2, c=0.1M) for 48 h
at room temperature.
Fig. 2 Effect of DODAB on the isolated yield of 5a for the model
laccase/TEMPO oxidation – P-3CR system. Reaction conditions:
benzyl alcohol (1a, 0.5 mmol), benzoic acid (3a, 0.5 mmol) and
p-methoxybenzyl isocyanide (4a, 0.5 mmol), TEMPO (0.1
mmol), laccase (20 mg), DODAB in 5 mL of phosphate buffer
For the reaction performed without any additive, 5a was
obtained with 21 % isolated yield. Addition of Montmorillonite
K 10 (entry 2) resulted in a decrease of the yield to 16%.
Entries 3 and 4 show, that the addition of anionic surfactants
(pH=5.2, c=0.1M) for 48 h at room temperature.
In order to try to improve the reaction yield to a level which is
close to the yield of the enzyme-free reaction carried out with
(
SDS or AOT) caused a significant decrease in reaction yield,
probably due to repulsive interactions between the benzoic
acid anions (deprotonated form of 3a) and the negatively
charged surface of the micellar or vesicular aggregates formed.
Addition of cholesterol (entry 5) had a negligible effect,
similarly to the addition of the non-ionic surfactant Tween 80
1
2a, 3a and 4a (92 %), we performed a few experiments in
6
which the amount of benzyl alcohol (1a) as one of the starting
materials was changed. Usage of 2 equivalents of 1a resulted
in product 5a with 76 % yield, and with 5 equivalents the yield
of 5a was 79 %. For a reaction carried out with 2 equivalents of
(entry 6) or the zwitterionic surfactant 3-(N,N-
isocyanide
(3a) resulted in 5a with 88 % yield. These
dimethylmyristylammonio)propanesulfonate. In all these
cases, the reaction yields were almost the same as without
additive. In the presence of the non-ionic surfactant Triton X-
experiments indicate that very high yields cannot be achieved
with the laccase/TEMPO – P-3CR system due to the possible
accompanying hydrolysis of 3a. In order to overcome this
problem the reaction was conducted stepwise: first 24 hours
oxidation of 1a with laccase, TEMPO and surfactant, followed
by the Passerini reaction with 3a and 4a for another 24 hours,
resulting in product 5a with 86 % yield (Table 3, entry 1).
100, the reaction yield was significantly increased, probably
due to a positive effect of this neutral surfactant on the P-3CR,
associated with an increased solubility of the reactants in the
reaction medium. Addition of the two different cationic
surfactants with the long aliphatic side chains;
didodecyldimethylammonium bromide or DODAB (entries 9
and 10) enhanced the yield of 5a. The best result was obtained
From an environmental point of view, the reusability of the
catalytic system is a critical issue. Therefore, we investigated
in the presence of DODAB, which is known to form bilayers in whether the catalytic system based on the laccase/TEMPO
3
2
aqueous solutions, present as dispersed vesicles, the reaction oxidation and the DODAB vesicular suspension can be used
yield was increased from 21 % without any additive (entry 1) more than once. The model reaction was carried out according
to 67 % (entry 10). This indicates that DODAB is the most to the optimized procedure, benzyl alcohol (1a, 0.5 mmol),
suitable additive among the ones checked for the Passerini TEMPO (0.1 mmol), DODAB (0.1 mmol) in 5 mL of phosphate
reaction preceded by the laccase-catalyzed oxidation.
Next, the reaction was studied by varying the DODAB (4 mg/mL) for 24 h at room temperature, then benzoic acid
concentration, ranging from 5 to 50 mol%. For each condition,
3a, 0.5 mmol) and p-methoxybenzyl isocyanide (4a, 0.5 mmol)
the critical concentration for aggregate formation (cac) was were added and the reaction mixture was stirred for additional
buffer (pH=5.2, c=0.1M) were incubated with laccase
(
-5
33
reached (for H O, 25°C, cac(DODAB) = 4.28*10 M). The 24 h. During the progress of the reaction, solid product 5a
2
results are shown in Fig. 2. In the presence of 5 mol% DODAB formed and felt out in impure form from the reaction mixture.
the reaction yield remained comparable to the one without The product could be separated by filtration through a cotton
surfactant. Upon increasing the amount of DODAB from 5 to pad, followed by purification using column chromatography.
4
| J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 5 of 8
PleaseRd So Cn oA t da vd aj un s ct ems argins
View Article Online
DOI: 10.1039/C6RA13078J
Journal Name
ARTICLE
The filtrate containing DODAB, enzyme and TEMPO in Table 4 Effect of different alcohols (
a
phosphate buffer was employed for another run: 1a was oxidation – P-3CR system.
1) on the laccase/TEMPO
added first, then − after 24 h − 3a and 4a were added, and the
reaction was carried out for additional 24h. After filtration
through a cotton pad, the filtrate containing the surfactant,
laccase and TEMPO was used for the reaction one more time.
The results from these catalytic system reusability tests are
shown in Table 3 (entries 2 and 3). The laccase/TEMPO and
DODAB catalytic system could be reused one time with an
appreciable decrease in yield from 86 % (entry 1) to 67 %
(
entry 2). Afterwards, there was a large drop in yield to 19 %
entry 3). This decrease in reaction yield may be due to a
(
Entry
R
5
Yield (%)
deactivation of the enzyme with time and/or a significant loss
in laccase, TEMPO or DODAB during the filtration step.
1
2
3
4
5
6
7
8
9
C
6
H
5
5a
5b
5c
5d
5e
5f
86
78
72
65
68
62
0
p-NO
2
C
6
H
4
p-FC
p-ClC
p-MeC
p-OMeC
CH=CH
6
H
4
Table 3 Reusability of the catalysts for the laccase/TEMPO
a
oxidation – P-3CR system .
6 4
H
6 4
H
6 4
H
Entry
Recycle
Fresh catalysts
I recycle
Yield (%)
2
----
5g
5h
5i
1
2
3
86
67
19
C
11
H
23
11
b
30
CH(C H )C H
4 9
2
5
II recycle
1
0
CH=CHC H
6
81
5
a
Reaction conditions: 1a (0.5 mmol), TEMPO (initially 0.1
a
Reaction conditions: alcohol (1, 0.5 mmol), TEMPO (0.1
mmol), laccase (initially 20 mg), DODAB (initially 0.1 mmol) in 5
mL of phosphate buffer (pH=5.2, c=0.1M) were mixed for 24 h
at room temperature, then 3a (0.5 mmol) and 4a (0.5 mmol)
were added and the reaction mixture was stirred for additional
mmol), laccase (20 mg), DODAB (0.1 mmol) in 5 mL of
phosphate buffer (pH=5.2, c=0.1 M) were mixed for 24 h at
room temperature. Then benzoic acid (3a, 0.5 mmol) and p-
methoxybenzyl isocyanide (4a, 0.5 mmol) were added and the
reaction mixture was stirred for additional 24 h.
24 h.
b
1
Mixture of diastereoisomers, dr = 1:1, determined by H NMR.
After the optimization of the reaction conditions for benzyl
alcohol (C -CH OH, 1a), experiments with other alcohols (R-
CH OH, ) were also carried out. Alcohol was mixed with
6
H
5
2
For the reactions carried out with derivatives of benzyl alcohol
entries 2-6), the resulting yields varied between 62 and 86 %,
2
1
1
(
laccase, TEMPO and DODAB in phosphate buffer at room
temperature, after 24 h 3a and 4a were added, and the
isolated yields were determined after additional 24 h. The
results are summarized in Table 4.
with the highest one obtaining for benzyl alcohol (1a). These
results indicate that there is only a slight influence of the type
of substituent in the benzene ring on the reaction yield. In case
of allyl alcohol (entry 7), no reaction occurred. This could be
due to the highly reactive and polymerizable acrolein, which is
the product of the oxidation reaction. This is probably the
reason why – to the best of our knowledge - acrolein has never
been used successfully as a substrate in P-3CR. Reactions
carried out with alkyl alcohols, dodecanol (entry 8) and 2-
ethylhexanol (entry 9) resulted in products 5g and 5h with
1
1 % and 30 % yields respectively, what corresponds to
literature data for aliphatic alcohols oxidized by the
3
4
laccase/TEMPO system.
The reaction with the more
demanding cinnamyl alcohol (entry 10) provided product 5i
with 81 % yield.
Conclusions
We have developed a new, environmentally friendly protocol
which provides α-acyloxy carboxamides with high yields. This
protocol comprises the enzymatic aerobic oxidation of an
alcohol, followed by a multicomponent Passerini reaction in an
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 5
Please do not adjust margins

Please do not adjust margins
RSC Advances
Page 6 of 8
View Article Online
DOI: 10.1039/C6RA13078J
ARTICLE
Journal Name
aqueous surfactant medium. The elaborated protocol excludes hexane/AcOEt as eluent. NMR spectra are given in Supporting
employment of explosive pure oxygen, flammable and toxic Information.
organic solvents, and transition metals, what makes it 2-(4-Methoxybenzylamino)-2-oxo-1-phenylethyl benzoate 5a
1
attractive for the pharmaceutical industry. Moreover, the White powder; mp 141-142 °C; H NMR (400 MHz; CDCl
.
3
)
presented protocol reveals a very low E value. Further studies δ 3.77 (3H, s, CH O), 4.04-4.45 (2H, m, CH N), 6.36 (1H, s, CH),
H
3
2
towards an application of the procedure for other 6.42 (1H, br s, NH), 6.81-6.84 (2H, m, Ph), 7.13-7.15 (2H, m,
multicomponent reactions, which require aldehydes as a Ph), 7.36-7.46 (5H, m, Ph), 7.53-7.60 (3H, m, Ph), 8.05-8.08
3
substrate, are in progress in our laboratory.
5
13
(2H, m, Ph); C NMR (100 MHz; CDCl
3
) δ
14.15, 127.38, 128.60, 128.82, 128.95, 129.03, 129.23,
29.84, 130.13, 133.62, 135.55, 159.11, 165.02, 168.28; HRMS
C
42.91, 55.28, 76.01,
1
1
+
Acknowledgements
calcd. for C23
4
H21NO Na [M+Na] : 398.1368, found: 398.1366.
2
-(4-Methoxybenzylamino)-1-(4-nitrophenyl)-2-oxoethyl
We gratefully acknowledge the financial support of the NCN
project Harmonia No 2014/14/M/ST5/00030, and the COST
action CM1304 for providing a stimulating environment which
led to this collaborative research.
1
benzoate 5b. White powder; mp 127-128 °C; H NMR (400
MHz; CDCl ) δ 3.78 (3H, s, CH O), 4.42-4.45 (2H, m, CH N),
.44 (1H, s, CH), 6.61 (1H, br s, NH), 6.82-6.86 (2H, m, Ph),
.13-7.16 (2H, m, Ph), 7.46-7.50 (2H, m, Ph), 7.61-7.65 (1H, m,
3
H
3
2
6
7
Ph), 7.72- 7.75 (2H, m, Ph), 8.05-8.10 (2H, m, Ph), 8.21-8.25
1
3
Experimental
(2H, m, Ph); C NMR (100 MHz; CDCl
114.25, 123.89, 128.05, 128.45, 128.52, 128.83, 129.00,
29.36, 129.83, 134.13, 148.19, 159.27, 164.61, 167.05; HRMS
3 C
) δ 43.10, 55.29, 74.79,
1
13
H NMR and C NMR spectra were recorded with Varian 200
1
MHz and Bruker 400 MHz spectrometers, with TMS used as an
internal standard or the signal of residual chloroform. High
resolution mass spectrometry (HR:MS) spectra were recorded
on an Mariner (PerSeptiveBiosystems) and Synapt G2:SHD
apparatus. Melting points were determined with a model SMP-
+
calcd. for C23
20 2 6
H N O Na [M+Na] : 443.1219, found: 443.1218.
2
-(4-Methoxybenzylamino)-1-(4-fluorophenyl)-2-oxoethyl
1
benzoate 5c. White powder; mp 130-131 °C; H NMR (400
MHz; CDCl ) δ 3.78 (3H, s, CH O), 4.41-4.49 (2H, m, CH N),
.34 (1H, s, CH), 6.48 (1H, br s, NH), 6.83-6.86 (2H, m, Ph),
.05-7.10 (2H, m, Ph), 7.15-7.17 (2H, m, Ph), 7.44-7.48 (2H, m,
3
H
3
2
6
7
20 device (Büchi, Flawil, Swizerland). Laccase from Trametes
versicolor, powder, light brown, ≥0.5 U/mg was purchased
from Sigma Aldrich, product number 38429, lot number #
BCBQ2928V. The following products were also from Sigma
Aldrich: Dioctadecaldimethylammonium bromide (DODAB),
Ph), 7.48- 7.55 (2H, m, Ph), 7.55-7.64 (1H, m, Ph), 8.02-8.07
1
3
(
2H, m, Ph); C NMR (100 MHz; CDCl
3
) δ
14.16, 115.67, 115.89, 128.63, 128.96, 129.28, 129.36,
29.70, 129.79, 131.49, 131.52, 133.72, 159.16, 164.30,
C
42.93, 55.26, 75.24,
1
1
1
4
2
purity ≥98.0
% (AT), product number 40165; dioctyl
+
64.91, 168.07; HRMS calcd. for C23
16.1274, found: 416.1276.
4
H20NO FNa [M+Na] :
sulfosuccinate sodium salt (AOT = sodium bis (2-ethylhexyl)
sulfosuccinate, purity 98 %), product number 323586; sodium
dodecyl sulfate (SDS), purity ≥99.0 % (GC), product number
L6026; cholesterol, purity ≥99.0 %, product number C3045;
Triton X-100, product number T9284; and 3-(N,N-
dimethylmyristylammonio)propanesulfonate, purity ≥99.0 %,
product number T7763. Dilauryldimethylammonium bromide
-(4-Methoxybenzylamino)-1-(4-chlorophenyl)-2-oxoethyl
1
benzoate 5d. White powder; mp 149-150 °C; H NMR (400
MHz; CDCl ) δ 3.79 (3H, s, CH O), 4.41-4.45 (2H, m, CH N),
.32 (1H, s, CH), 6.47 (1H, br s, NH), 6.83-6.85 (2H, m, Ph),
.15-7.16 (2H, m, Ph), 7.35-7.37 (2H, m, Ph), 7.44-7.51 (4H, m,
3
H
3
2
6
7
1
3
Ph), 7.56- 7.62 (1H, m, Ph), 8.01-8.07 (2H, m, Ph); C NMR
100 MHz; CDCl ) δ 42.96, 55.27, 75.22, 114.18, 128.66,
28.72, 128.97, 128.99, 129.65, 129.80, 133.78, 134.11,
35.03, 159.18, 164.85, 167.83; HRMS calcd. for
(
= didodecyldimethylammonium bromide, purity >98.0 %), was
(
3
C
purchased from TCI, product number D1974. Tween 80, was
purchased from Schuchardt München (now Merck). p-
Methoxybenzyl isocyanide (4a) was synthetized from p-
mehoxybenzyl amine in a two-step synthesis (see Supporting
Information). The remaining starting materials were purchased
from Sigma Aldrich or TCI.
1
1
C
2
+
23
H20NO
4
ClNa [M+Na] : 432.0979, found: 432.0980.
-(4-methoxybenzylamino)-2-oxo-1-p-tolylethyl benzoate 5e
.
1
White powder; mp 133-134 °C; H NMR (400 MHz; CDCl
3
) δ
O), 4.36-4.49 (2H, m,
2
N), 6.33 (1H, s, CH), 6.40 (1H, br s, NH), 6.82-6.85 (2H, m,
H
2
3 3
.36 (3H, s, PhCH ), 3.78 (3H, s, CH
General procedure for the synthesis of compounds 5a-i.
A
CH
mixture of the corresponding alcohol (0.5 mmol), laccase from
Ph), 7.15-7.19 (4H, m, Ph), 7.42-7.46 (4H, m, Ph), 7.56-7.59
3
Trametes versicolor (20 mg), TEMPO (0.1 mmol) and DODAB
1
(
3
1H, m, Ph), 8.04-8.07 (2H, m, Ph); C NMR (100 MHz; CDCl )
(0.1 mmol) was stirred in phosphate buffer (5 mL, pH=5,2
δ
1
1
C
21.19, 42.87, 55.26, 75.92, 114.11, 127.38, 128.53, 128.94,
29.31, 129.49, 129.81, 129.87, 132.63, 133.52, 138.96,
59.108, 165.05, 168.38; HRMS calcd. for C24 Na
c=0,1M) at room temperature. After 24 h, benzoic acid (0.5
mmol) and p-methoxybenzyl isocyanide (0.5 mmol) were
added and the reaction mixture was stirred for additional 24 h.
Afterwards, the reaction mixture was extracted with
dichloromethane (3×20 mL). The combined organic layers
H23NO
4
+
[M+Na] : 412.1525, found: 412.1520.
2
-(4-Methoxybenzylamino)-1-(4-methoxyphenyl)-2-oxoethyl
1
benzoate 5f. White powder; mp 151-152 °C; H NMR (400
MHz; CDCl ) δ 3.79 (3H, s, CH O), 3.81 (3H, s, CH O), 4.39-4.50
N), 6.32 (1H, s, CH), 6.40 (1H, br s, NH), 6.83-6.85
4
were dried with MgSO and residuals of solvent were removed
3
H
3
3
by distillation under reduced pressure. The crude products
were purified by column chromatography on silica gel using
(
(
2H, m, CH
2
2H, m, Ph), 6.90-6.93 (2H, m, Ph), 7.16-7.17 (2H, m, Ph), 7.42-
6
| J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 7 of 8
PleaseRd So Cn oA t da vd aj un s ct ems argins
View Article Online
DOI: 10.1039/C6RA13078J
Journal Name
ARTICLE
7
.49 (4H, m, Ph), 7.56- 7.61 (1H, m, Ph), 8.05-8.08 (2H, m, Ph);
7
8
W. Szymański, R. Ostaszewski, Tetrahedron, 2008, 64, 3197.
W. Szymański, M. Zwolińska, R. Ostaszewski, Tetrahedron,
1
3
3 C
C NMR (100 MHz; CDCl ) δ 42.90, 55.27, 55.30, 75.70,
2
007, 63, 7647.
W. Szymański, R. Ostaszewski, Tetrahedron: Asymmetry,
006, 17, 2667.
114.14, 114.25, 127.72, 128.54, 128.96, 128.98, 129.34,
9
1
29.80, 129.88, 133.52, 159.10, 160.17, 165.08, 168.48; HRMS
+
Na [M+Na] : 428.1474, found: 428.1474.
2
calcd. for C24
H23NO
5
10 P. Saravanan, A. Bisai, S. Baktharaman, M. Chandrasekhar,
V.K. Singh, Tetrahedron, 2002, 58, 4693; Y. Jia, X. Dong, P.
Zhou, X. Liu, L. Pan, H. Xin, Y.Z. Zhu, Y. Wang, Eur. J. Med.
Chem., 2012, 55, 176; D. Koszelewski, M. Cwiklak, R.
Ostaszewski, Tetrahedron: Asymmetry, 2012, 23, 1256.
1-(4-Methoxybenzylamino)-1-oxotridecan-2-yl benzoate 5g
.
1
White powder; mp 90-91 °C; H NMR (400 MHz; CDCl
3H, t, J 7.2 Hz, CH CH ), 1.19-1.36 (16H, br m, 8×CH
), 1.97-2.03 (2H, m, CH CH), 3.78 (3H, s,
O), 4.35-4.48 (2H, m, CH N), 5.44-5.47 (1H, m, CH), 6.30
3
) δ
H
0.87
(
3
2
2
), 1.36-
1.48 (2H, m, CH
2
CH
2
2
1
1 Sigma-Aldrich Product Directory, product number 29224,
D80002.
CH
3
2
(
1H, br s, NH), 6.83-6.86 (2H, m, Ph), 7.16-7.18 (2H, m, Ph), 12 M. Passerini, Gazz. Chim. Ital., 1921, 51, 126; M. Passerini,
Gazz. Chim. Ital., 1922, 52, 432.
7
.44-7.48 (2H, m, Ph), 7.74-7.61 (1H, m, Ph), 8.03-8.05 (2H, m,
1
3
13 W. Qu, Z. Zha, K. Ploessl, B.P. Lieberman, L. Zhu, D.R. Wise,
C.B. Thompson, H.F. Kung, J. Am. Chem. Soc., 2011, 133
122; A. Zajdlik, Z. Wang, J.L. Hickey, A. Aman, A.D.
Ph); C NMR (100 MHz; CDCl
3
) δ
9.30, 29.38, 29.49, 29.58, 31.88, 32.01, 42.67, 55.26, 74.68,
14.12, 128.60, 128.91, 129.73, 129.99, 133.54, 159.08,
C
14.07, 22.65, 24.95, 29.24,
,
2
1
1
4
3
5
1
Schimmer, A.K. Yudin, Angew. Chem. Int. Ed., 2013, 52, 8411;
D. Koszelewski, A. Redzej, R. Ostaszewski, J. Mol. Catal. B-
Enzym., 2007, 47, 51; S. Wang, M. Wang, D. Wang, J. Zhu,
Angew. Chem. Int. Ed., 2007, 47, 388.
+
65.41, 169.80; HRMS calcd. for C28
76.2777, found: 476.2781.
4
H39NO Na [M+Na] :
-ethyl-1-(4-methoxybenzylamino)-1-oxoheptan-2-yl benzoate
1
4 D. Koszelewski, W. Szymanski, J. Krysiak, R. Ostaszewski,
Synthetic Commun., 2008, 38, 1120.
1
h
– mixture of diasteromers. Colorless oil; H NMR (400 MHz;
) δ 0.87-0.89 (3H, m, CH CH
CH ), 1.16-1.43 (8H, br m, 4×CH
CH(CH ), 3.78 (3H, s, CH O), 4.31-4.39 (1H, m, CHHN), 4.41-
.50 (2H, m, CHHN), 5.56-5.62 (1H, m, CH), 6.23-6.29 (1H, m,
NH), 6.81-6.84 (2H, m, Ph), 7.16-7.18 (2H, m, Ph), 7.44-7.49
CDCl
CH
3
H
3
2
), 0.95-0.99 (3H, m, 15 M.C. Pirrung, K. Das Sarma, J. Am. Chem. Soc., 2003, 126
,
2
), 2.07-2.15 (1H, m,
444; E. Vessally, A. Ramazani, E. Yaaghubi, Monatsh. Chem.,
011, 142, 1143; J. Taran, A. Ramazani, S.W. Joo, K.
Slepokura, T. Lis, Helv. Chim. Acta, 2014, 97, 1088.
3
2
2
2
)
2
3
4
1
6 D. Paprocki, D. Koszelewski, P. Walde, R. Ostaszewski, RSC
Adv., 2015, 5, 102828.
1
3
(
2H, m, Ph), 7.58-7.60 (1H, m, Ph), 8.03-8.05 (2H, m, Ph);
NMR (100 MHz; CDCl ) δ 11.69, 11.71, 13.91, 13.98, 22.50,
2.74, 22.94, 23.13, 29.22, 29.28, 29.52, 42.06, 42.41, 42.68,
C
17 T. Dwars, E. Paetzold, G. Oehme, Angew. Chem. Int. Ed.,
2005, 44, 7174.
3
C
1
8 P. Walde, Curr. Opin. Colloid. Interface Sci., 1996, 1, 638; P.
2
4
1
1
Walde, S. Ichikawa, Biomol. Eng., 2001, 18, 143; P. Walde, K.
Cosentino, H. Engel, P. Stano, ChemBioChem, 2010, 11, 848.
9 W.L.F. Armarego, C.L.L. Chai, Purification of Laboratory
Chemicals, Elsevier, Amsterdam, 2009, 6th ed., ch. 2, pp 71.
2.70, 55.25, 75.80, 76.07, 114.07, 128.64, 128.93, 128.96,
29.34, 129.75, 130.01, 133.56, 133.75, 159.03, 165.39,
+
Na [M+Na] : 420.2151,
1
69.64; HRMS calcd. for C24
H31NO
4
found: 420.2149.
E)-1-(4-methoxybenzylamino)-1-oxo-4-phenylbut-3-en-2-yl
20 R.J.K. Taylor, M. Reid, J. Foot, S.A. Raw, Acc. Chem. Res.,
005, 38, 851; K. Ekoue-Kovi, C. Wolf, Chem.-Eur. J., 2008,
2
(
1
14, 6302; M. Davi, H. Lebel, Org. Lett., 2009, 11, 41; B.E.
Maki, K.A. Scheidt, Org. Lett., 2009, 11, 1651; J.R. Donald,
benzoate 5i. White powder; mp 126-127 °C; H NMR (400
MHz; CDCl ) δ 3.78 (3H, s, CH O), 4.44-4.47 (2H, m, CH N),
.05 (1H, dd, J 1.2 Hz J 6.8 Hz, CHCH=CH), 6.43 (1H, br s, NH),
3
H
3
2
M.G. Edwards, R.J.K. Taylor, Tetrahedron Lett., 2007, 48
5201.
,
6
6
.66 (1H, dd, J 6.8 Hz J 16 Hz, CHCH=CH), 6.83 (1H, dd, J 1.2 Hz 21 K.C. Nicolaou, D.J. Endmonds, P.G. Bulger, Angew. Chem. Int.
Ed., 2006, 45, 7134; S.F. Mayer, W. Kroutil, K. Faber, Chem.
Soc. Rev., 2001, 30, 332.
J 16 Hz, CHPh), 6.84-6.88 (2H, m, Ph), 7.20-7.22 (2H, m, Ph),
7
.27-7.34 (4H, m, Ph), 7.40-7.42 (2H, m, Ph), 7.45- 7.49 (2H, m,
2
2 T. Ngouansavanh, J. Zhu, Angew. Chem., Int. Ed., 2006, 45,
1
3
Ph), 7.59-7.63 (1H, m, Ph), 8.08-8.11 (2H, m, Ph); C NMR (100
MHz; CDCl ) δ
28.43, 128.60, 128.62, 129.02, 129.22, 129.77, 129.83,
33.65, 134.87, 135.66, 159.16, 165.19, 168.04; HRMS calcd.
3
495.
42.93, 55.28, 74.86, 114.17, 122.49, 126.87, 23 J.B. Plumb, D. Harper, J. Chem. Eng. News, 1990, 68, 3; A.P.
Thottumkara, M.S. Bowsher, T.K. Vinod, Org. Lett., 2005,
933.
24 J. Brioche, G. Masson, J. Zhu, Org. Lett., 2010, 12, 1432.
3
C
1
1
7,
2
+
4
for C25H23NO Na [M+Na] : 424.1525, found: 424.1519.
2
2
5 B. Karimi, E. Farhangi, Adv. Synth. Catal., 2013, 355, 508.
6 F. Gallou, N.A. Isley, A. Ganic, U. Onken, M. Parmentier,
Green Chem., 2016, 18, 14.
2
7 Sigma-Aldrich Product Directory, product number 661384,
237213.
8 R.A. Sheldon, Green Chem., 2007, 9, 1273.
9 N. Shapiro, A. Vigalok, Angew. Chem., 2008, 120, 2891.
0 M.J. Han, H.T. Choi, H.G. Song, J. Microbiol, 2005, 43, 555.
1 A.M.S Mayer, E. Aviles, A.D. Rodriguez, Bioorg. Med. Chem.,
Notes and references
2
2
3
3
1
W. Jiang, J. Wanner, R.J. Lee, P.Y. Bounaud, D.L. Boger, J. Am.
Chem. Soc., 2002, 124, 5288.
2
P.G. Jagtap, E. Baloglu, G.J. Southan, J.G. Mabley, H. Li. J.
Zhou, J. van Duzer, A.L. Salzman, C. Szabo, J. Med. Chem.,
2
Chem., 2002, 12, 105.
2 T. Kunitake, Y. Okahata, K. Tamaki, F. Kumamaru, M.
Takayanagi, Chem. Lett., 1977, 6, 387; E. Feitosa, P. C. A.
Barreleiro, G. Olofsson, Chem. Phys. Lipids, 2000, 105, 201; R.
O. Brito, E. F. Marques, Chem. Phys. Lipids, 2005, 137, 18; P.
Walde, H. Umakoshi, P. Stano, F. Mavelli, Chem. Commun.,
012, 20, 279; S. Kotha, M. Behera, R.V. Kumar, Bioorg. Med.
2
005, 48, 5100.
3
4
5
6
T.D. Owens, G.L. Araldi, R.F. Nutt, J.E. Semple, Tetrahedron
Lett., 2001, 42, 6271.
M. Sieńczyk, D. Podgórski, A. Błażejewska, J. Kulbacka, J.
Saczko, J. Oleksyszyn, Bioorgan. Med. Chem., 2011, 19, 1277.
M. Passerini, Gazz. Chim. Ital., 1923, 53, 331; M. Bos, E.
Riguet, J. Org. Chem., 2014, 79, 10881.
3
2
014, 50, 10177.
R. Bossio, Synthesis, 1993, 783, 1.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 7
Please do not adjust margins

Please do not adjust margins
RSC Advances
Page 8 of 8
View Article Online
DOI: 10.1039/C6RA13078J
ARTICLE
Journal Name
3
3 S. F. Clancy, P. H. Steiger, D. A. Tanner, M. Thies, H. H.
Paradies, J. Phys. Chem., 1994, 98, 11143; M. Thies, S. F.
Clancy, H. H. Paradies, J. Phys. Chem., 1996, 100, 9881.
4 M. Fabbrini, C. Galli, P. Gentili, D. Macchitella, Tetrahedron
Lett., 2001, 42, 7551.
5 I. Ugi, R. Meyr, U. Fetzer, Angew. Chem., 1959, 71, 386; I.
Ugi, C. Steinbrückner, Angew. Chem., 1960. 72, 267; P.
Biginelli, Chem. Ber., 1891, 24, 1317; K. Gewald, E. Schinke,
H. Böttcher, Chem. Ber., 1966, 99, 94; A. Hantzch, Chem.
Ber., 1881, 14, 1637; A. Strecker, Liebigs Ann., 1854, 91, 349;
A. Strecker, Liebigs Ann., 1850, 75, 27; C. Mannich, W.
Krösche, Arch. Pharm., 1912, 250, 647.
3
3
8
| J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins