One-Pot Controlled Reduction of Conjugated Amides by Sequential Double Hydrosilylation Catalyzed by an Iridium(III) Metallacycle

Article abstract of DOI:10.1002/ejoc.202001061

A single and accessible cationic iridium^III metallacycle effectively catalyzes the one-pot sequential double hydrosilylation of challenging α,β-unsaturated secondary and tertiary amides to afford, in a controlled and straightforward way, the co

Full text of DOI:10.1002/ejoc.202001061

European Journal of Organic Chemistry
Accepted Article
Accepted Article
Title: One-pot controlled reduction of conjugated amides by sequential
double hydrosilylation catalyzed by an iridium(III) metallacycle
Authors: Yann Corre, Vincent Rysak, Márton Nagyházi, Dorottya
Kalocsai, Xavier Trivelli, Jean-Pierre Djukic, Francine
Agbossou-Niedercorn, and Christophe Michon
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To be cited as: Eur. J. Org. Chem. 10.1002/ejoc.202001061
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1/2020

European Journal of Organic Chemistry
10.1002/ejoc.202001061
FULL PAPER
One-pot controlled reduction of conjugated amides by sequential
double hydrosilylation catalyzed by an iridium(III) metallacycle
[a]
[a]
[a]
[a]
[b]
Yann Corre, Vincent Rysak, Márton Nagyházi, Dorottya Kalocsai, Xavier Trivelli, Jean-Pierre
[c]
[a]
[a,d]
Djukic, Francine Agbossou-Niedercorn,* and Christophe Michon*
[a]
Y. Corre, V. Rysak, M. Nagyházi, D. Kalocsai, Dr. F. Agbossou-Niedercorn, Dr. C. Michon
UCCS UMR 8181
Univ. Lille, CNRS, Centrale Lille, Univ. Artois, UMR 8181 - UCCS - Unité de Catalyse et Chimie du Solide
F-59000 Lille, France.
Homepage: http://uccs.univ-lille1.fr/index.php/annuaire/15-fiches-personnels/81-agbossou-niedercorn-francine
[
[
[
b]
c]
d]
Dr. X. Trivelli
IMEC – Institut Michel-Eugène Chevreul FR 2638
Univ. Lille, CNRS, INRA, Centrale Lille, Univ. Artois, FR 2638 – IMEC –Institut Michel-Eugène Chevreul
F-59000 Lille, France.
Dr. J.-P. Djukic
Institut de Chimie de Strasbourg, CNRS UMR 7177
Université de Strasbourg
4
rue Blaise Pascal F-67000 Strasbourg, France.
Dr. C. Michon (new address)
Ecole Européenne de Chimie, Polymères et Matériaux - LIMA UMR 7042
Université de Strasbourg, Université de Haute-Alsace, Ecole Européenne de Chimie, Polymères et Matériaux, CNRS, LIMA, UMR 7042
25 rue Becquerel, F-67087 Strasbourg, France.
Email: cmichon@unistra.fr
Homepage: http://lima.unistra.fr/applied-organometallic-chemistry/
Supporting information for this article is given via a link at the end of the document.
III
Abstract: A single and accessible cationic iridium metallacycle
catalyzes effectively the one-pot sequential double hydrosilylation of
challenging -unsaturated secondary and tertiary amides to afford
in a controlled and straightforward way the corresponding reduced
products, that is to say the related secondary and tertiary amides and
amines. The catalytic hydrosilylations of the conjugated amides
described herein proceeded in good yields and high
chemoselectivities. The critical silyl enolate, in other words silyl ketene
aminal intermediate, has been observed and characterized by using
control experiments, mass spectrometry and state of the art Nuclear
Magnetic Resonance analyses. The present achievements indicate a
promising potential of catalysts based on metallacycles for future
significant developments in one-pot multicatalytic synthesis and
therefore the production of highly functionalized and complex organic
molecules.
hydroboration-hydrosilylation have allowed powerful and
selective pot-economical conversions of bulk materials to highly
functionalized molecules.[6]
The selective reduction of carbon–carbon double bonds in
-unsaturated carbonyl compounds still remains challenging in
hydrogenation[ and hydrosilylation due to several competing
reactions: 1,2-addition, 1,4-additions, - or -additions to the
alkene, de-oxygenation or even polymerizations. Interestingly,
among the possible 1,4-addition products, metal- (or silyl-) enol
ethers or ketene acetals, are versatile nucleophiles in Mukaiyama
aldol, Michael reactions, allylic alkylations, asymmetric
protonations and haloketone or ketol formations.[9]
7]
[8]
Introduction
The quests for chemically effective syntheses of commodity
and complex chemicals with lower waste production, minimal
physical separation operations and catalyst’s recyclability are now
the major challenges in the domain of homogenous catalysis for
economic and environmental benefits. These challenges are
embodied nowadays into new strategies of research wherein
efficiency, selectivity as well as modularity and adaptivity of
[
1]
catalytic systems are the main goals. Sequential multimetallic
catalysis,[ cooperative and non-cooperative dual catalysis[3] as
well as tandem catalysis[4] are presently some of the developed
approaches towards one-pot multicatalytic synthesis.[1,5] Among
those, sequential double hydrofunctionalization of alkynes has
recently received a rising interest. Consecutive reactions like
2]
Scheme 1. Sequential hydrosilylation of enamides 3a-j into silyl ketene aminal
4a-j, amides 5a-j and amines 6a-j using iridacycle catalyst 1 or 2.
hydroamination-hydrogenation,
hydroboration-hydrogenation,
1
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European Journal of Organic Chemistry
10.1002/ejoc.202001061
FULL PAPER
Although there have been efforts made to achieve
chemoselective C-C hydrosilylation of -unsaturated ketones
and esters,[ there are, to the best of our knowledge, very few
examples of chemoselective hydrosilylation of -unsaturated
amides[ and no sequential hydrofunctionalization of enamides.
Moreover, the catalytic carbon-carbon and carbon-heteroatom
bond formation at the α-position of amides remains challenging.[11]
Because of the hydrogens of amides or esters being much less
acidic than those of aldehydes or ketones, amides are relunctant
to form enolates, i.e. silyl ketene aminals. Up to now, only few
catalytic methods have been able to form such a critical
intermediate and enable alkylation,[11b] 1,4-addition,[11c] Mannich-
type reaction[11d] and α‑amination.[11e] Following our ongoing
interest in metal catalyzed hydrosilylation reactions of C-C and C-
heteroatom unsaturated compounds,[12] we report herein the
application of an accessible iridiumIII metallacycle like 1 or 2 to
catalyze the first one-pot sequential double hydrosilylation of
secondary and tertiary -unsaturated amides 3a-j to afford in a
controlled and chemoselective way the related silyl ketene aminal
The chlorinated iridiumIII metallacycles 1 and 2 were respectively
based on 2-phenylpyridine and 1-phenylisoquinoline chelating
8]
2
ligands, both functionalized by a NMe - electron donating group.
As already demonstrated in our previous studies, such a feature
is critical in order to get a higher hydricity for the transient metal-
hydride species (i.e. a feature of strong hydride donor) and
10]
therefore a faster reduction of the organic unsaturation for a
highest catalytic activity.[
12h]
At first, the hydrosilylation of tertiary
conjugated amides 3a was performed using 0.05 mol% of catalyst
1 or 2 in combination with 0.1 mol% of Ph CBArF20 and 1
3
equivalent of TMDS (entries 1, 2). Whereas reduced amide 5a
was rapidly obtained in a high yield using pre-catalyst 1 at 25 °C,
no reaction was observed with pre-catalyst 2. Though the catalytic
reaction could proceed at 100 °C in 1,1’,2,2’-tetrachloroethane
(TCE), the lower reactivity of iridacycle 2 at 25 °C was rather
surprising in reference to its high performances in the
hydrosilylation of challenging bulky secondary and tertiary
amides.[12h] The scope of the hydrosilylation reaction was then
studied with aromatic and aliphatic tertiary conjugated amides
3b–f (Table 1). Under the optimized conditions described above,
the corresponding amides 5b–f were obtained generally in high to
quantitative yields (entries 3-7). By comparison to conjugated
amides 3a and 3d, substrate 3e issued from trans-2-methyl-2-
butenoic acid and dibenzylamine led to a moderate yield of 5e
4a-j, amides 5a-j and amines 6a-j (Scheme 1).
Results and Discussion
(
entry 6). This indicated possible limitations of the 1,4-addition
Our investigations on the double reduction of -unsaturated
reaction to trisubstituted substrates. Afterwards, the scope of the
hydrosilylation reaction was studied with aromatic and aliphatic
secondary conjugated amides 3g–j (Table 1, entries 8-11). Due
to the lower reactivity of secondary amides,[12h,13] higher loadings
amides started by studying the first step of the targeted sequential
reaction, i.e. the hydrosilylation of the conjugated CC double bond.
The use of iridiumIII catalyst precursors, additives and reaction
conditions was directly inspired by our previous study on
3
of catalyst 1 (0.5 mol%) and Ph CBArF20 (1 mol%) were required
in order to allow the reaction to proceed smoothly and get high
hydrosilylation reactions of secondary and tertiary amides using
chlorinated iridiumIII metallacycles 1 and 2 as pre-catalysts,
yields of amides 5g-j. With the exception of 3g which required a
trityltetra(pentafluorophenyl)borate
(Ph
3
CBArF20
)
as
the
15 hours reaction time, other conjugated amides 3h-j were
dechlorination agent, equivalent of inexpensive 1,1,3,3-
1
effectively reduced in few hours at 25 °C.
tetramethyldisiloxane (TMDS) as reducing agent and
dichloromethane as a solvent (Scheme 1, Table 1).[12h]
Table 1. Hydrosilylation of enamides 3a-j into amides 5a-j using catalyst 1 or 2.
Yield (%)[a]
(isolated
yield %)[
Enamide
pre-cat
(mol%)
Entry
R1
R2
R3
R4
t (h)
3
b]
1[c]
2
3a
3a
3b
3c
3d
3e
3f
Bn
Bn
Bn
Bn
Ph
Ph
H
H
1 (0.05)
0.5
14
5a 100 (90)
5a 0 (-)[c]
2
(0.05)
Ph
Ph
H
H
H
-(CH
)
2 2
-O-(CH
Me
2 2
) -
1 (0.05)
1 (0.05)
14
14
0.5
24
2
5b 100 (61)
3
Me
Bn
Bn
Me
H
5c 100 (77)
5d 98 (98)
5e 37 (31)
5f 98 (76)
4
Me
Me
H
Bn
Bn
Ph
1
1
(0.05)
(0.05)
5
6
Me
Ph
Ph
Ph
Ph
Ph
1 (0.05)
7
3g
3h
3i
H
n-Bu
Bn
1
1
(0.5)
(0.5)
15
6
5g 88[d] (84)
5h 100 (89)
5i 100 (90)
5j 100 (100)
8
9
H
H
H
H
Ph
1 (0.5)
0.5
4
1
0
1
1
3j
H
H
-CH -1-thiophene
2
1 (0.05)
[
a] yield (%) measured by GC; Ph
3
CBArF20: trityl tetra(pentafluorophenyl)borate; TMDS: 1,1,3,3-tetramethyldisiloxane.
[
b] isolated yield (%) after flash chromatography or recrystallisation. [c] 90 % yield of 5a at 100 °C in 1,1’,2,2’-tetrachloroethane (TCE).
[
d] along with 12% of the related secondary amine.
2
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European Journal of Organic Chemistry
10.1002/ejoc.202001061
FULL PAPER
the molecular structure of silyl ketene aminal 4a. The latter was
further confirmed by 13C and 1H- C HSQC NMR experiments
13
(
Figures S6 and S8). Among the observed 13C and 1H NMR
chemical shifts, the most significants were the non-aromatic olefin
carbon at 90.5 ppm and the related proton at 3.75 ppm, which
were typical of an enolate system like 4a (Scheme S4). A further
1
1
NMR analysis by NOESY H- H confirmed the molecular structure
of silyl ketene aminal 4a. The ethyl, benzyl and Ph-CH -CH spin
2
1
1
systems which were observed by H- H COSY were part of the
same molecule as confirmed by unambiguous NOEs (Scheme
S4). The two benzyl groups on the nitrogen and the three ethyl of
the silicon were all in fast exchange and led to single couplings.
The three phenyl groups were on free rotation. The NOE between
the olefin proton and those of the benzyl groups of the nitrogen (-
Scheme 2. Sequential hydrosilylation of enamides 3a into silyl ketene aminal
2
CH -) was hardly observed due to the close chemical shifts (3.75
4a and amide 5a.
and 3.91 ppm). There was no NOE observed between the olefin
proton (3.75 ppm) and the ortho- aromatic protons (7.15 ppm) of
We next focused on the characterization of the silyl ketene
aminal 4a (Schemes 1 and 2). At first, the hydrosilylation of
enamide 3a was studied using pre-catalyst 1, Ph CBArF20 and 1
equivalent of Et SiH in CH Cl at 25°C during 30 minutes
Scheme 2). In the prospect of performing second
hydrosilylation reaction, we had to exclude water due to the high
sensitivity of the catalytic system. Therefore, we found the silyl
enolate / silyl ketene aminal 4a resulting from a hydrosilylation
through a 1,4-addition was smoothly protonated by an equivalent
of phenol to afford amide 5a. Three different alcohols, i.e. Gaiacol,
isopropanol and phenol, were tested for the protodesilylation of
2
the Ph-CH -CH spin system, these protons being not close to
each other. Finally, the last NMR experiment by 29Si HSQC
2
3
highlighted the main correlation observed through the J(Si-H)
and J(Si-H) with a 29Si chemical shift of +21.0 ppm and could be
3
3
2
2
(
a
in agreement with a silicon atom bound to three carbons and one
oxygen, the 29Si chemical shift for HSiEt being of +0.2 ppm.[15]
3
Once the protodesilylation of silyl ketene aminal 4 had been
set in anhydrous conditions, we studied the scope of the
sequential double hydrosilylation reaction of aromatic and
aliphatic conjugated amides 3a-j into amines 6a-j (Table 2).
Similar to the hydrosilylation of the conjugated CC double bond,
the double hydrosilylation of the conjugated CC and CO double
bonds was performed using: 0.05 mol% of catalyst 1 or 2 and 0.1
4
a (Table S1). Phenol, the most acidic and the less coordinating
reagent, led to 5a in 97 % yield after 30 minutes of reaction. The
silyl ketene aminal 4a was first evidenced by a reaction with D
2
O
mol% of Ph
of catalyst 1 or 2 and 1 mol% of Ph
3
CBArF20 for tertiary amides 3a-f and, using 0.5 mol%
CBArF20 for secondary amides
and formation of deuterated amide 5k (Scheme 2). After
purification by flash chromatography, product 5k was
3
3g-j.[12h,13] All reactions were run according to a one-pot and 3
steps procedure. The first step accomplished the hydrosilylation
of the conjugated CC double bond using one equivalent of TMDS.
In order to accelerate these catalytic reactions, they were run at
100 °C in 1,1’,2,2’-tetrachloroethane (TCE) for 3 hours. After
cooling, the second step, i.e. the protodesilylation of silyl ketene
aminals 4a-j, proceeded by reaction with one equivalent of
recrystallized phenol dissolved in dry TCE at 25 °C for 1 hour.
Afterwards, the third step, i.e. the hydrosilylation of the amide CO
bonds, was performed based on our previous study on
hydrosilylation of secondary and tertiary amides.[12h] Two
additional equivalents of TMDS were added to the reaction
mixture which was subsequently heated to 100 °C for 15 hours.
At the exception of reagent 3a which was better reduced using
catalyst 1, the sequential double hydrosilylations of tertiary
conjugated amides 3b-f were conducted along with catalyst 2
(entries 1-12). The desired amines 6a-f were isolated in fair to
high yields. We noticed the reaction of substrates 3b,d,e bearing
donor substituents led to the expected amines 6b,d,e as major
products along with some amounts of amides 5b,d,e (entries 3-
4,7-10). Regarding the sequential double hydrosilylation of
secondary conjugated amides 3g-j, the corresponding amines
6h-j were obtained in good yields with minor amounts of amides
5h-j (entries 15-20). It was worth to note that substrate 3g bearing
a n-butyl substituent on the amide nitrogen led to almost equal
amounts of amide and amine products with catalyst 1 or 2 (entries
13,14). While catalyst 1 performed better with substrates 3h,j
bearing benzyl groups on the nitrogen (entries 15-16, 19-20),
1
13
characterized by H and C NMR (Figure S1 and Figure S2) as
well as by HRMS ESI (+) (Figure S3). It was worth to compare the
coupling of benzylic protons of deuterated amide 5k with those of
5a (see Figure S1). While a triplet was observed for 5a, a doublet
was observed for 5k due to the neighboring deuterium. Moreover,
the 13C NMR spectrum of 5k confirmed the presence of a
deuterium because a triplet resulting from the coupling of
deuterium (spin 1) and carbon nuclei C
Hz) was observed at 34.8 ppm (Scheme 2, Figure S2).
In another experiment, the hydrosilylation of enamide 3a was
performed under the same reaction conditions, i.e. in CD Cl
using pre-catalyst 1, Ph CBArF20 additive and 1 equivalent of
Et SiH at 25°C during 30 minutes (Schemes 2 and S2). The mass
a a
(spin ½) (J C -D = 19.4
2
2
3
3
spectrometry ESI-(+) analysis of a reaction mixture aliquot diluted
in dry acetonitrile showed evidence of the silyl ketene aminal 4a
and the related sodium ketene aminal 4b along with amide 5a and
several side products issued from a bimolecular 1,4-addition[14]
and a Diels-Alder [4+2]-cycloaddition (Figure S4, Scheme S3).
Furthermore, the crude solution of silyl enolate / silyl ketene
aminal 4a was transfered in a dry NMR Young tube under argon
in order to be studied. 1H and 1H- H COSY NMR analyses
confirmed the molecular structure of 4a (Figures S5 and S7). We
could identify the scalar couplings between some key spin
1
2
systems like: an ethyl, a benzyl and a Ph-CH -CH system
(
Scheme S4). The conventional correlations were observed
3
through the J(H,H) coupling constants (ethyl, CH
through the weak J(H,H) of the benzylic systems. This defined
2
-H) as well as
4
the chemical shifts of the ortho aromatic protons and supported
3
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European Journal of Organic Chemistry
10.1002/ejoc.202001061
FULL PAPER
Table 2. Sequencial hydrosilylation of enamides 3a-j into amides 5a-j and amines 6a-j using catalysts 1 or 2.
Enamide
pre-cat
(%)
Yield
(%, isolated)[
Entry
R1
R2
R3
R4
a]
3
1[c]
2
3a
3a
3b
3b
3c
3c
3d
3d
3e
3e
3f
Bn
Bn
Bn
Bn
Ph
Ph
H
H
1 (0.05)
2 (0.05)
6a (93)
6a (72)
Ph
Ph
Ph
Ph
H
H
H
-(CH
-(CH
)
)
-O-(CH
-O-(CH
)
-
-
1 (0.05)
5
b (36) + 6b (10)
3
2
2
2
2
4
2
2
2
)
2
2
(0.05)
5b (16) + 6b (63)
6c (67)
H
Me
Me
Bn
Bn
Bn
Bn
Me
Me
H
Me
Me
Bn
Bn
Bn
Bn
Ph
Ph
1 (0.05)
5
H
2
1
(0.05)
(0.05)
6c (83)
6
Me
Me
Me
Me
H
5d (35) + 6d (31)
5d (17) + 6d (61)
5e (27) + 6e (46)
5e (21) + 6e (51)
6f (74)
7
H
2 (0.05)
8
Me
Me
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
1
2
(0.05)
(0.05)
9
10
11
12
13
14
15
16
17
18
19
1 (0.05)
3f
H
2
(0.05)
(0.5)
6f (91)
3g
3g
3h
3h
3i
H
n-Bu
n-Bu
Bn
1
5g (32) + 6g (21)
5g (26) + 6g (34)
5h (11) + 6h (68)
5h (28) + 6h (53)
5i (8) + 6i (64)
5i (9) + 6i (83)
H
H
2 (0.5)
H
H
1
2
(0.5)
(0.5)
H
H
Bn
H
H
Ph
1 (0.5)
(0.5)
3i
H
H
Ph
2
-
CH
thiophene
CH -1-
thiophene
2
-1-
3j
Ph
Ph
H
H
H
H
1 (0.5)
2 (0.5)
5j (5) + 6j (82)
5j (21) + 6j (43)
-
2
20
3j
[
a] isolated yield (%) after flash chromatography or recrystallisation; Ph
3
CBArF20: trityl tetra(pentafluorophenyl)borate;
TMDS: 1,1,3,3-tetramethyldisiloxane; TCE: 1,1’,2,2’-tetrachloroethane.
catalyst 2 was more effective with conjugated amide 3i substituted
by a phenyl (entries 17,18).
Regarding the reaction mechanism (Scheme 3), an ionic
hydrosilylation[16] pathway could be presumed. However, Djukic
et al. had already shown through a combination of organometallic
complexes 8a-b and silane reagent form adducts 9a-b which are
sources of hydrido-iridium intermediates 10a-b and silylium cation
R
3
Si+.[12h,18-20] The latter may activate the carbonyl group of amide
substrate 3a and generate silyloxy carbonium species A.
Reaction with the first equivalent of the iridium hydride complex
10 affords silyl ketene aminal 4 resulting from a 1,4-addition
addition as well as the cationic iridium complex 8. Afterwards, the
addition of one equivalent of phenol allows the protodesilylation
of the enolate 4 and affords amide 5a. Reaction with the second
equivalent of silylium cation and iridium hydride complex 10 leads
first to silyloxy carbonium species B which is then reduced into
silyl hemiacetal C. At this stage, elimination of a silyloxide
fragment may be helped by any electrophilic species present in
the medium to lead to the iminium intermediate D which we
evidenced by mass spectrometry in a previous study.[12h] The
latter can then react with the third equivalent of the iridium hydride
complex 10 and affords the amine product 6a along with the
cationic iridium catalytic species 8 (Scheme 3).
syntheses
and
DFT
calculations
a
cohesive
hydridoiridium(III)→silylium donor−acceptor complex could
exist.[
12h,17]
Hence, we assumed our reaction pathway may
differentiate from the others by the activation mode of the silane.
As already calculated before by us, the necessary dechlorination
of precatalyst 1 or 2 to yield putative electron deficient cationic
intermediate 8 results from a reaction with an in-situ-produced
form of a stabilised silylium cation generated by the reaction of
the tritylium cation with the silane reagent (Scheme 3).[12h,18] For
+
instance, the reaction of Et
triphenylmethane and cation [Et
3
SiH with Ph
3
C is expected to produce
+
3
Si-H-SiEt
3
]
according to
Heinekey,[18a] and our previous DFT-D computations.
[12h]
In the
framework of the mechanism depicted in Scheme 3, cationic
4
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European Journal of Organic Chemistry
10.1002/ejoc.202001061
FULL PAPER
3
Scheme 3. Reaction mechanism of the sequential hydrosilylation of enamide 3a into amide 5a and amine 6a catalyzed by iridium(III) complex 1 or 2 and Ph CBArF20,
trityl tetra(pentafluorophenyl)borate.
General procedure for the hydrosilylation of conjugated amides 3
into amides 5
Conclusion
In a Schlenk tube, conjugated amide reagent 3 (1.54 mmol, 1 eq.) and
III
iridium catalyst 1 (0.05 mol% / 0.0005 eq. / 0.34 mg for a tertiary enamide
We have shown accessible cationic iridiumIII metallacycles
or 0.1 mol% / 0.001 eq. / 0.68 mg for a secondary enamide) are introduced.
Ph
in a glovebox. Under nitrogen, 1 mL of CH
mL) are transferred by syringe and the reaction mixture is heated at 25 °C
under stirring for 0.5 to 24 h (the Schlenk tube being closed under N ).
3
CBArF20 salt (0.1 mol% / 1.42 mg or 1 mol% / 14.2 mg) is then added
catalyze effectively the one-pot sequential double hydrosilylation
of challenging -unsaturated secondary and tertiary amides to
afford in a controlled and selective way the corresponding
reduced products, that is to say the related secondary and tertiary
amides and amines. The catalytic hydrosilylation reactions
described herein proceeded with low catalyst loadings, in good
yields and high chemoselectivities. The critical silyl ketene aminal
intermediate has been observed and characterized by using
control experiments, mass spectrometry and state of the art
Nuclear Magnetic Resonance analyses. The present
achievements indicate a promising potential of catalysts based on
metallacycles for future significant developments in one-pot
multicatalytic synthesis and therefore the production of highly
functionalized and complex organic molecules.
2
Cl and TMDS (1 eq., 0.272
2
2
Afterwards, the solvent is evaporated under vacuum (using a Schlenk line)
to afford the desired amide 5 which was further purified by recrystallization
or flash chromatography using mixtures of petroleum ether and ethyl
acetate.
General procedure for the sequential hydrosilylation of conjugated
amides 3 into amines 6.
III
In a Schlenk tube, enamide reagent 3 (1.54 mmol, 1 eq.) and iridium
catalyst 1 or 2 (0.05 mol% / 0.0005 eq. / 0.34 mg of 1 or 0.38 mg of 2 for
a tertiary enamide as well as 0.1 mol% / 0.001 eq. / 0.68 mg of 1 or 0.76
mg of 2 for a secondary enamide) are introduced. BArF salt (0.1 mol% /
1.42 mg or 1 mol% / 14.2 mg) is then added in a glovebox. Under nitrogen,
1
mL of TCE and TMDS (1 eq., 0.272 mL) are transferred by syringe and
the reaction is heated to 100 °C under stirring for 3 hours (the Schlenk tube
being closed under N ). After cooling to 25°C, a solution of recrystallized
2
phenol in TCE (1.54 mmol, 1 eq. in 1 mL TCE) was transferred by canula
to the reaction mixture and the resulting solution was allowed to react for
1
hour. Afterwards, TMDS (2 eq., 0.545 mL) was added and the reaction
Experimental Section
was heated to 100 °C for 15 hours. The solvent is then evaporated under
vacuum (using a Schlenk line) and the reaction mixture is hydrolysed using
dichloromethane (3 mL) and NaOH 1M (5 mL). The resulting solution is
stirred vigorously at 20°C during
dichloromethane and brine, the organic phase was dried with MgSO
evaporated to afford the desired amine 6 which was further purified by
flash chromatography using mixtures of petroleum ether and ethyl acetate
with 5% NEt
General procedure for the synthesis of amides[21]
In a Schlenk, a solution of trimethylphosphite (P(OMe)
in dichloromethane (CH Cl ) (20 mL) is cooled at 0°C under nitrogen gas.
After addition and solvation of iodine (I ) (1.52 g, 1.5 eq.), the carboxylic
acid reagent (1.5 eq.) was added followed by triethylamine (NEt ) (1.4 mL,
.5 eq.). After 10 minutes of stirring, the amine reagent (1 eq.) was added
3
) (0.7 mL, 1.5 eq.)
1
hour. After extraction with
and
2
2
4
2
3
2
3
.
to the reaction. The resulting mixture was first stirred at 0°C for 10 minutes
and then for 14 hours at room temperature. The reaction was then
hydrolyzed using a saturated aqueous solution of sodium bicarbonate
5a N,N-dibenzyl-3-phenylpropanamide CAS [180747-56-2][22]
Isolated as solid after recrystallisation using
a
a
(
NaHCO
phase was subsequently washed with HCl 1M, water and brine. After
drying over magnesium sulfate (MgSO ), solvents were evaporated and
3
) and extracted three times with dichloromethane. The organic
dichloromethane/cyclohexane solvent mixture (0.457 g, 90% yield).
1
3
H NMR (300 MHz, CDCl ): δ 2.73 (t, J = 7.6 Hz, 2H), 3.06 (t, J = 7.9 Hz,
2H), 4.38 (bs, 2H), 4.62 (bs, 2H), 7.07 (d, J = 6.5 Hz, 2HAr), 7.19 (m, 5HAr),
4
the residu was purified by flash chromatography over silica gel using a
mixture of petroleum ether and ethyl acetate. Evaporation of solvents led
to the desired amide as a solid or an oil.
7.29 (m, 8HAr).
13
C NMR (75 MHz, CDCl
3 2 2 2
): δ 31.8 (CH ), 35.2 (CH ), 48.5 (CH ), 50.0
(CH ), 126.3 (CH), 126.5 (2CH), 127.5 (CH), 127.7 (CH), 128.5 (2CH),
2
1
1
28.6 (2CH), 128.7 (2CH), 128.8 (2CH), 129.1 (2CH), 136.6 (C), 137.5 (C),
41.3 (C), 172.9 (CO).
5
This article is protected by copyright. All rights reserved.

European Journal of Organic Chemistry
10.1002/ejoc.202001061
FULL PAPER
5
b 1-morpholino-3-phenylpropan-1-one CAS [17077-46-2][22,23]
1H NMR (300 MHz, CDCl
3
): δ 2.49 (t, J = 7.2 Hz, 2H), 2.98 (t, J = 7.5 Hz,
Isolated as an oil by flash chromatography on silica gel using a (60/35/5)
petroleum ether / ethyl acetate / triethylamine solvent mixture (Rf = 0.4)
2H), 4.57 (d, J = 5.7 Hz, 2H), 5.72 (bs, 1H, NH), 6.88 (m, 1HAr), 6.92 (m,
1HAr), 7.20 (m, 4HAr), 7.27 (m, 2HAr).
13
(
0.206 g, 61% yield).
3 2 2 2
C NMR (75 MHz, CDCl ): δ 31.6 (CH ), 38.2 (CH ), 38.3 (CH ), 125.1
1
H NMR (300 MHz, CDCl
H), 3.35 (t, J = 6.0 Hz, 2H), 3.51 (t, J = 6.0 Hz, 2H), 3.62 (bs, 4H), 7.21
m, 3HAr), 7.30 (m, 2HAr).
3
): δ 2.61 (t, J = 6.0 Hz, 2H), 2.98 (t, J = 6.0 Hz,
(CH), 125.9 (CH), 126.3 (CH), 126.9 (CH), 128.4 (2CH), 128.6 (2CH),
140.8 (C), 141.0 (C), 171.7 (CO).
2
(
1
3
C NMR (75 MHz, CDCl
CH ), 66.6 (CH ), 67.0 (CH
41.2 (C), 171.0 (CO).
3
): δ 31.6 (CH
2
), 34.9 (CH
), 126.4 (CH), 128.6 (2CH), 128.7 (2CH),
2
), 42.1 (CH
2
), 46.1
5k N,N-dibenzyl-3-phenylpropanamide-2-d
(
2
2
2
Isolated as
a
white solid after recrystallisation using
a
1
dichloromethane/cyclohexane solvent mixture (0.499 g, 98% yield).
Melting point: 104°C.
H NMR (300 MHz, CDCl ): δ 2.73 (t, J = 7.6 Hz, 2H), 3.08 (d, J = 7.7 Hz,
3
c N,N-dimethyl-3-phenylpropanamide CAS [5830-31-9][22,23]
1
5
Isolated as a solid after flash chromatography on silica gel using a (1/1)
2H), 4.40 (s, 2H), 4.64 (s, 2H), 7.10 (d, J = 6.6 Hz, 2HAr), 7.22 (m, 5HAr),
mixture of petroleum ether and ethyl acetate (Rf = 0.3) (0.210 g, 77% yield).
7.31 (m, 8HAr).
C NMR (75 MHz, CDCl
1
13
H NMR (300 MHz, CDCl
3
): δ 2.61 (t, J = 7.5 Hz, 2H), 2.93 (s, 3H, Me),
3 2
): δ 31.6 (CH ), 34.8 (t, J = 19.4 Hz ,CDH), 48.4
2
.95 (s, 3H, Me), 2.99 (t, J = 7.2 Hz, 2H), 7.25 (m, 5HAr).
(CH
2
), 49.9 (CH ), 126.2 (CH), 126.4 (2CH), 127.5 (CH), 127.7 (CH), 128.4
2
13
C NMR (75 MHz, CDCl
3 2 2
): δ 31.5 (CH ), 35.4 (CH ), 35.5 (CH
2
), 37.3
(2CH), 128.5 (2CH), 128.6 (2CH), 128.7 (2CH), 129.0 (2CH), 136.6 (C),
137.5 (C), 141.3 (C), 172.8 (CO). HRMS (ESI+) m/z calculated for
(CH ), 126.2 (CH), 128.5 (2CH), 128.6 (2CH), 141.6 (C), 172.3 (CO).
2
23
C H25NO [MH+]: 331.19307, measured 331.19098.
5
d N,N-dibenzylisobutyramide CAS [6284-09-9][24]
Isolated as
a
solid after recrystallisation using
a
mixture of
6a N,N-dibenzyl-3-phenylpropan-1-amine CAS [27376-59-6][30]
Isolated as an oil by chromatography on silica gel using a (85/10/5) mixture
of petroleum ether, ethyl acetate and triethylamine (Rf = 0.8) (0.452 g, 93%
dichloromethane and cyclohexane (0.404 g, 98% yield).
1
H NMR (300 MHz, CDCl
3 3
): δ 1.19 (d, J = 9.0 Hz, 6H, 2CH ), 2.84 (pent, J
=
6.0 Hz, 1H), 4.47 (bs, 1H), 4.59 (bs, 1H), 7.18 (m, 4HAr), 7.32 (m, 6HAr).
yield).
13
1
C NMR (75 MHz, CDCl
CH ), 126.4 (2CH), 127.4 (CH), 127.7 (CH), 128.3 (2CH), 128.7 (2CH),
29.1 (2CH), 137.0 (C), 137.9 (C), 177.8 (CO).
3 3 3 2
): δ 19.9 (CH ), 30.6 (CH ), 48.2 (CH ), 49.8
H NMR (CDCl
3
, 300 MHz): δ 1.85 (quin, J = 7.4 Hz, 2H, CH
), 2.61 (t, J = 9.0 Hz, 2H, CH ), 3.60 (s, 4H, 2CH
(m, 2HAr), 7.17 (t*, J = 7.7 Hz, 1HAr), 7.25 (t*, J = 7.5 Hz, 4HAr), 7.33 (t*, J
7.5 Hz, 4HAr), 7.40 (d*, J = 6.6 Hz, 4HAr).
2
), 2.51 (t, J =
(
1
2
6.9 Hz, 2H, CH
2
2
2
), 7.10
=
e N,N-dibenzyl-2-methylbutanamide CAS [138943-74-5][25]
13
C NMR (CDCl
5
3 2 2 2
, 75 MHz): δ 29.2 (CH ), 33.7 (CH ), 53.1 (CH ), 58.5
Isolated as an oil after flash chromatography over silica gel using a (7/3)
(2CH ), 125.7 (2CH), 126.9 (CH), 128.3 (4CH), 128.4 (2CH), 128.5 (2CH),
2
mixture of petroleum ether and ethyl acetate (Rf = 0.2) (0.134 g, 31% yield).
H NMR (300 MHz, CDCl ): δ 1.51 (d, J = 6.6 Hz, 3H), 1.58 (s, 3H), 2.80
3
129.0 (4CH), 140.0 (C), 142.7 (2C).
1
(s, 2H), 3.39 (bs, 4H), 5.35 (m, 1H), 7.13 (m, 2H), 7.21 (t, J = 8.1 Hz, 4HAr),
6b 4-(3-phenylpropyl)morpholine CAS [25262-57-1][31]
7
.29 (d, J = 8.7 Hz, 4HAr).
C NMR (75 MHz, CDCl ): δ 13.4 (CH ), 14.7 (CH ), 32.8 (CH), 58.0
3 3 3
Isolated as an oil by chromatography on silica gel using a (60/35/5) mixture
of petroleum ether, ethyl acetate and triethylamine (Rf = 0.4) (0.199 g, 63%
1
3
(
1
2CH
2
), 62.9 (CH
2
), 122.0 (CH), 126.8 (2CH), 128.2 (2CH), 128.3 (2CH),
yield).
1
28.9 (2CH), 129.0 (CH), 134.4 (C), 140.3 (C), 178.0 (CO).
3
H NMR (300 MHz, CDCl ): δ 7.14 (m, 5HAr), 3.62 (t, J = 4.7 Hz, 4H), 2.56
(
t, J = 7.7 Hz, 2H), 2.34 (t, J = 4.7 Hz, 4H), 2.27 (t, J = 7.5 Hz, 2H), 1.75
5
f N-methyl-N,3-diphenylpropanamide CAS [18859-20-6][26]
(m, 2H).
1
3C NMR (75 MHz CDCl
Isolated as a solid after chromatography on silica gel using a (6/4) mixture
3
): δ 142.1 (C), 128.5 (2CH), 128.4 (CH), 125.9
), 53.8 (2CH ), 33.7 (CH ), 28.3 (CH ).
of petroleum ether and ethyl acetate (Rf = 0.7) (0.280 g, 76% yield).
(2CH), 67.1 (2CH
2
), 58.4 (CH
2
2
2
2
1
H NMR (300 MHz, CDCl
3
): δ 2.37 (t, J = 7.7 Hz, 2H), 2.92 (t, J = 7.8 Hz,
2
H), 3.25 (s, 3H), 7.04 (m, 4H), 7.18 (m, 3H), 7.28 (m, 3H).
6c N,N-dimethyl-3-phenylpropan-1-amine CAS [1199-99-1][32]
Isolated as an oil by chromatography on silica gel using a (85/10/5) mixture
of petroleum ether, ethyl acetate and triethylamine (Rf = 0.5) (0.168 g, 67%
1
3
C NMR (75 MHz, CDCl
3 2 2
): δ 31.9 (CH ), 36.1 (CH ), 37.4 (CH
3
), 126.1
(2CH), 127.4 (CH), 127.8 (CH), 128.4 (2CH), 128.5 (2CH), 129.8 (2CH),
141.4 (C), 144.1 (C), 172.3 (CO).
yield).
1
3
H NMR (300 MHz, CDCl ): δ 7.20 (m, 3HAr), 7.12 (m, 2HAr), 2.57 (t, J =
7.8 Hz, 2H), 2.24 (t, J = 7.5 Hz, 2H), 2.17 (s, 6H),1.73 (tt, J = 7.8-7.4 Hz,
5
g N-butyl-3-phenylpropanamide CAS [10264-11-6][27]
Isolated as an oil after chromatography on silica gel using a (8/2) mixture
2H).
1
3C NMR (75 MHz, CDCl
of petroleum ether and ethyl acetate (Rf = 0.2) (0.266 g, 84% yield).
3
): δ 139.4 (C), 128.9 (2CH), 128.5 (2CH), 126.8
), 43.1 (2CH ), 32.7 (CH ), 25.7 (CH ).
1
H NMR (300 MHz, CDCl
3
): δ 0.88 (t, J = 6.0 Hz, 3H), 1.25 (m, 2H), 1.40
(CH), 57.5 (CH
2
3
2
2
(
m, 2H), 2.45 (t, J = 7.5 Hz, 2H), 2.96 (t, J = 7.8 Hz, 2H), 3.20 (q, J = 6.0
Hz, 2H), 5.36 (bs, 1H), 7.20 (m, 3HAr), 7.27 (m, 2HAr).
6d N,N-dibenzyl-2-methylpropan-1-amine CAS [121238-79-7][32]
Isolated as a solid by chromatography on silica gel using a (90/5/5) mixture
of petroleum ether, ethyl acetate and triethylamine (Rf = 0.8) (0.238 g, 61%
1
3
C NMR (75 MHz, CDCl
CH ), 38.7 (CH ), 39.3 (CH
41.1 (C), 172.4 (CO).
3 3 2 2
): δ 13.8 (CH ), 20.1 (CH ), 31.8 (CH ), 31.9
(
1
2
2
2
), 126.3 (CH), 128.5 (2CH), 128.6 (2CH),
yield).
1
3
H NMR (300 MHz, CDCl ): δ 7.20 (m, 10HAr), 3.43 (s, 4H), 2.08 (t, J = 7.3
5
h N-benzyl-3-phenylpropanamide CAS [10264-10-5][28]
Hz, 2H), 1.77 (m, 1H), 0.78 (d, J = 6.6 Hz, 6H).
13
Isolated as a solid after recrystallization using a dichloromethane /
C NMR (75 MHz, CDCl
3
): δ 140.2 (C), 129.0 (4CH), 128.2 (4CH), 126.8
cyclohexane mixture (0.328 g, 89% yield).
(2CH), 60.7 (CH ), 59.0 (2CH
2
2
), 32.8 (CH), 17.8 (2CH ).
3
1
H NMR (300 MHz, CDCl
3
): δ 2.52 (t, J = 7.9 Hz, 2H), 3.00 (t, J = 7.9 Hz,
2
5
H), 4.39 (d, J = 5.7 Hz, 2H), 5.48 (bs, 1H, NH), 7.21 (m, 5HAr), 7.27 (m,
6e N,N-dibenzyl-2-methylbutan-1-amine CAS [1620971-05-2][33]
Isolated as an oil by chromatography on silica gel using a (99/1) mixture
H
Ar).
1
3
C NMR (75 MHz, CDCl
3 2
): δ 31.8 (CH ), 38.5 (CH
2 2
), 43.6 (CH ), 126.3
of petroleum ether and ethyl acetate (Rf = 0.8) (0.210 g, 51% yield).
1
(CH), 127.5 (CH), 127.8 (2CH), 128.5 (2CH), 128.6 (2CH), 128.7 (2CH),
3
H NMR (300 MHz, CDCl ): δ 7.20 (m, 10HAr), 3.42 (q, J = 14.9 Hz, 4H),
1
38.3 (C), 140.9 (C), 172.1 (CO).
2.16 (m, 1H), 2.06 (m, 1H), 1.56 (m, 1H), 1.41 (m, 1H), 0.93 (m, 1H), 0.75
m, 6H).
(
i N,3-diphenylpropanamide CAS [3271-81-6][28]
13
C NMR (75 MHz, CDCl
(2CH), 60.8 (CH ), 59.0 (2CH
(CH ).
): δ 140.2 (2C), 130.0 (4CH), 128.2 (4CH), 126.8
5
3
Isolated
as
a
solid
after
recristallisation
using
a
2
2
), 32.8 (CH), 27.6 (CH ), 17.8 (CH ), 11.4
2
3
dichloromethane/cyclohexane mixture (0.312 g, 90% yield).
3
1
H NMR (300 MHz, CDCl
3
): δ 2.65 (t, J = 7.6 Hz, 2H), 3.05 (t, J = 7.6 Hz,
2
H), 7.14 (m, NH+1HAr), 7.29 (m, 7HAr), 7.43 (d, J = 7.9 Hz, 2HAr).
6f N-methyl-N-(3-phenylpropyl)aniline CAS [29514-68-9][34]
Isolated as an oil by chromatography on silica gel using a (85/10/5) mixture
of petroleum ether, ethyl acetate and triethylamine (Rf = 0.9) (0.316 g, 91%
1
3
C NMR (75 MHz, CDCl
3
): δ 31.7 (CH
2
2
), 39.6 (CH ), 120.1 (CH), 124.4
(CH), 126.5 (2CH), 128.5 (2CH), 128.8 (2CH), 129.1 (2CH), 137.9 (C),
140.8 (C), 170.5 (CO).
yield).
1
3
H NMR (300 MHz, CDCl ): δ 7.13 (m, 7HAr), 6.58 (m, 3HAr), 3.23 (t, J =
5
j
3-phenyl-N-(thiophen-2-ylmethyl)propanamide CAS [546097-42-
7.5 Hz, 2H), 2.80 (s, 3H), 2.55 (t, J = 7.7 Hz, 2H), 1.80 (tt, J = 7.7-7.5 Hz,
2H).
[29]
1]
Isolated as an oil after recrystallization using a dichloromethane /
cyclohexane mixture (0.378 g, 100% yield).
6
This article is protected by copyright. All rights reserved.

European Journal of Organic Chemistry
10.1002/ejoc.202001061
FULL PAPER
13C NMR (75 MHz, CDCl
2CH), 128.4 (2CH), 126.0 (2CH), 116.2 (CH), 112.4 (CH), 52.4 (CH
): δ 149.4 (C), 141.9 (C), 129.3 (2CH), 128.5
),
6j 3-phenyl-N-(thiophen-2-ylmethyl)propan-1-amine CAS [1038212-
86-0][
3
37]
(
2
3
8.4 (CH
3
), 33.5 (CH
2
), 28.3 (CH
2
).
Isolated as an oil by chromatography on silica gel using a (75/20/5) mixture
of petroleum ether, ethyl acetate and triethylamine (Rf = 0.6) (0.292 g, 82%
6
g N-(3-phenylpropyl)butan-1-amine CAS [92111-13-2][35]
yield).
1
Isolated as an oil by chromatography on silica gel using a (55/40/5) mixture
of petroleum ether, ethyl acetate and triethylamine (Rf = 0.8) (0.1 g, 34%
H NMR (300 MHz, CDCl
), 2.60 (m, 4H), 1.76 (m, 2H), 1.77 (bs, NH).
C NMR (75 MHz, CDCl ): δ 144.2 (C), 142.2 (C), 128.5 (2CH), 128.4
(2CH), 126.7 (CH), 125.9 (CH), 125.0 (CH), 124.4 (CH), 48.7 (CH ), 48.4
(CH ), 33.7 (CH ), 31.7 (CH ).
3
): δ 7.14 (m, 6HAr), 6.84 (m, 2HAr), 3.90 (d, J =
1.0 Hz, 2H, CH
2
13
yield).
3
1
H NMR (300 MHz, CDCl
3
): δ 9.43 (bs, NH)
,
7.10 (m, 5HAr), 2.81 (m, 4H),
2
2
2
.60 (t, J = 7.2 Hz, 2H), 2.16 (m, 2H), 1.75 (m, 2H), 1.26 (q, J = 7.3 Hz,
H), 0.80 (t, J = 7.3 Hz, 3H).
2
2
2
1
3
C NMR (75 MHz, CDCl
CH), 47.7 (CH ), 47.2 (CH
CH ), 13.4 (CH ).
3
): δ 139.8 (C), 128.6 (2CH), 128.4 (2CH), 126.4
(
(
2
2
), 32.8 (CH ), 27.7 (CH ), 27.2 (CH ), 20.0
2
2
2
2
3
Acknowledgements
6
h N-benzyl-3-phenylpropan-1-amine CAS [32861-51-1][23]
Isolated as a solid by chromatography on silica gel using a (80/15/5)
mixture of petroleum ether, ethyl acetate and triethylamine (Rf = 0.3)
The University of Lille is acknowledged for a PhD fellowship (V.
R.). The Région Hauts-de-France and the University of Lille are
acknowledged for a PhD fellowship (Y. C.). The University of
Budapest, ENSCL and E.U. are thanked for Erasmus fellowships
(
0.236 g, 68% yield).
1
H NMR (300 MHz, CDCl
.63 (m, 4H, CH ), 3.73 (s, 2H, CH
m, 4HAr).
3
): δ 1.30 (bs, 1H), 1.79 (hept, J = 9.0 Hz, 1H),
2
2
2
), 7.14 (m, 3HAr), 7.22 (m, 3HAr), 7.33
(
(
M.N. and D.K.). The CNRS, the Chevreul Institute (FR 2638), the
1
3C NMR (75 MHz, CDCl
CH ), 125.9 (CH), 127.0 (CH), 128.2 (2CH), 128.4 (2CH), 128.5 (4CH),
40.7 (C), 142.3 (C).
3 2 2 2
): δ 31.9 (CH ), 33.8 (CH ), 49.1 (CH ), 54.1
Ministère de l'Enseignement Supérieur et de la Recherche, the
Région Hauts-de-France and the FEDER are acknowledged for
supporting and funding partially this work. Mr. Joseph Willy Danh
(
1
2
6
i N-(3-phenylpropyl)aniline CAS [1738-99-4][36]
(
ENSCL) is thanked for his help with some experimental works.
Dr. M. Kouach, Mrs N. Duhal, Mrs C. Lenglart and Ms A. Descat
Univ. Lille, CUMA / PSM-GRITA) are thanked for HRMS
Isolated as a solid by chromatography on silica gel using a (80/15/5)
mixture of petroleum ether, ethyl acetate and triethylamine (Rf = 0.5)
(
0.270 g, 83% yield).
(
1
H NMR (300 MHz, CDCl
3
): δ 7.15 (m, 7HAr), 6.66 (t, J = 7.4 Hz, 1HAr),
.58 (d, J = 8.7 Hz, 2HAr), 3.08 (t, J = 7.1 Hz, 2H), 2.65 (t, J = 7.6 Hz, 2H),
.90 (dt, J = 7.6-7.1 Hz, 2H).
analyses. Mrs C. Delabre (UCCS) is thanked for GC and GC-MS
analyses.
6
1
1
3
C NMR (75 MHz, CDCl
2CH), 128.5 (2CH), 126.1 (CH), 117.3 (CH), 112.9 (2CH), 43.5 (CH
3.5 (CH ), 31.2 (CH ).
3
): δ 148.5 (C), 141.8 (C), 129.3 (2CH), 128.6
(
3
2
),
Keywords: sequential catalysis • hydrosilylation • conjugated
amide • iridium • one-pot
2
2
7
This article is protected by copyright. All rights reserved.

European Journal of Organic Chemistry
10.1002/ejoc.202001061
FULL PAPER
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European Journal of Organic Chemistry
10.1002/ejoc.202001061
FULL PAPER
Silyl Ketene Aminals
III
A single cationic iridium metallacycle catalyzes effectively the one-pot sequential double hydrosilylation of challenging -
unsaturated secondary and tertiary amides to afford in a controlled and selective way the corresponding amides and amines. The
critical silyl ketene aminal intermediate has been characterized by using control experiments, mass spectrometry and state of the art
Nuclear Magnetic Resonance analyses.
1
0
This article is protected by copyright. All rights reserved.