Hydroalumination of Ketenimines and Subsequent Reactions with Heterocumulenes: Synthesis of Unsaturated Amide Derivatives and 1,3-Diimines

Article abstract of DOI:10.1021/acs.joc.5b00466

The series of differently substituted ketenimines 1 was hydroluminated using di-iso-butyl aluminum hydride. For the sterically congested ketenimine 1a, preferred hydroalumination of the C=N-bond was proven by X-ray crystallography (compound 5a). In situ treatment of the hydroaluminated ketenimines 5 with various heterocumulenes like carbodiimides, isocycanates, isothiocyanates and ketenimines as electrophiles and subsequent hydrolytic workup resulted in novel enamine derived amide species in case of N-attack (sterically less hindered ketenimines) under formation of a new C-N-bond or in 1,3-diimines by C-C-bond-formation in case of bulky substituents at the ketenimine-nitrogen atom. Furthermore, domino reactions with more than 1 equiv of the electrophile or by subsequent addition of two different electrophiles are possible and lead to polyfunctional amide derivatives of the biuret type which are otherwise not easily accessible.

Full text of DOI:10.1021/acs.joc.5b00466

Article
pubs.acs.org/joc
Hydroalumination of Ketenimines and Subsequent Reactions with
Heterocumulenes: Synthesis of Unsaturated Amide Derivatives and
1,3-Diimines
Xing Jin,† Matthias Willeke,‡ Ralph Lucchesi,† Constantin-Gabriel Daniliuc,† Roland Frohlich,†
̈
Birgit Wibbeling,† Werner Uhl,‡ and Ernst-Ulrich Wurthwein*,†
̈
†Organisch Chemisches Institut der Universitat Munster, Corrensstrasse 40, D-48149 Munster, Germany,
̈
̈
̈
‡Institut fur Anorganische und Analytische Chemie der Universitat Munster, Corrensstrasse 30, D-48149 Munster, Germany
̈
̈
̈
̈
S
* Supporting Information
ABSTRACT: The series of differently substituted keteni-
mines 1 was hydroluminated using di-iso-butyl aluminum
hydride. For the sterically congested ketenimine 1a, preferred
hydroalumination of the CN-bond was proven by X-ray
crystallography (compound 5a). In situ treatment of the
hydroaluminated ketenimines 5 with various heterocumulenes
like carbodiimides, isocycanates, isothiocyanates and keteni-
mines as electrophiles and subsequent hydrolytic workup
resulted in novel enamine derived amide species in case of N-
attack (sterically less hindered ketenimines) under formation
of a new C−N-bond or in 1,3-diimines by C−C-bond-
formation in case of bulky substituents at the ketenimine-
nitrogen atom. Furthermore, domino reactions with more than 1 equiv of the electrophile or by subsequent addition of two
different electrophiles are possible and lead to polyfunctional amide derivatives of the biuret type which are otherwise not easily
accessible.
In 1919 Staudinger and Meyer12 published the first
INTRODUCTION
■
synthesis of ketenimines using the nitrogen analogue of the
later discovered Wittig-olefination by reacting isocyanates with
triphenylphosphorylides. Staudinger et al. also succeeded in a
related synthesis starting from ketenes and triphenylimino-
phosphoranes.13 Later, Wadsworth et al. reported on a similar
synthesis using dialkylphosphoramidates instead of tripheny-
liminophosphoranes.14 The synthesis of N-silylketenimines by
Watt15 and our group16 was achieved by treatment of
acetonitrile derivatives with lithium diisopropylamid (LDA)
and followed by N-silylation. In 1964 Stevens et al. published
a versatile synthesis of ketenimines by dehydation of amides
by phosphorus pentoxide in pyridine2,17 A synthesis under
milder conditions was described by Jochims et al. They used
imidoyl chlorides, which were prepared from secondary
amides, and subjected them to HCl-elimination reactions
using various bases (see Scheme 1).18
Ketenimines 1 belong to the class of heterocumulenes and
might be described as imine analogues of ketenes.1 Due to
their high reactivity they are frequently used as starting
materials for the synthesis of open-chain and heterocyclic
compounds2,3 and also of peptides (Scheme 1).4
Scheme 1
In heterocyclic chemistry ketenimines are not only used as
nucleophiles,5 but also for the addition of free radicals.6 They
are further employed for [2 + 2]-cycloaddition reactions7 or
for the synthesis of five- and six-membered ring systems.8
Dijkstra and Backer reported on Lewis-acid-catalyzed electro-
philic substitution reactions of arenes using ketenimines to
obtain aromatic imine derivatives.9 Ketenimines may be
transformed into metal organic species by deprotonation.
In this article, we report on the first hydroalumination
reactions of ketenimines. We were interested in the regio- and
chemoselectivity of such reactions and in the structural
properties of the metalated compounds of the aluminum
enamide type. Due to their nucleophilic character, the
organoaluminum intermediates should be applicable in
Schollkopf et al.10 reported the use of potassium-t-butoxide as
̈
base for the preparation of metalated ketenimines and
Wurthwein et al. observed the formation of 2-azabutadienes
̈
from ketenimines by deprotonation and subsequent reproto-
Received: March 2, 2015
nation reaction.11
© XXXX American Chemical Society
A
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Scheme 2. Synthesis of Ketenimines 1 from Amides 3 or Imidoyl Chlorides 4
organic synthesis by treatment with functional electrophiles.
We treated them with carbodiimides, isocyanates, isothiocya-
nates and a second equivalent of ketenimines. Even domino
reactions involving the successive use of two different
electrophiles are possible. After final aqueous workup, a
great variety of interesting and novel functionalized organic
molecules of the amide and 1,3-diimine type were isolated
and fully characterized. With this study, we continue our
investigations into the use of hydroalumination reactions of
CN-multiple bonds in organic synthesis on cyanamides19 and
hydrazones.20
Scheme 3. Hydroalumination of Ketenimine 1a Giving the
Aluminum Compound 5a (Left), ORTEP Diagram of 5a
with Ellipsoids Shown at the 30% Probability Level (Right)
RESULTS AND DISCUSSION
■
Synthesis of Ketenimines. To investigate ketenimines
with aromatic as well as aliphatic substitution patterns, two
different synthetic pathways were used for their preparation.
Thus, the C-diaromatic ketenimine derivates 1a−c were
generated following a literature procedure17 by elimination
of water from the corresponding secondary amides 3 using
P4O10 in excess of anhydrous pyridine or triethylamine
(Scheme 2, Route A). The C-dialiphatic ketenimines 1d−f
were readily obtained by chlorination of the corresponding
secondary amides 3 with phosphoryl chloride via established
procedures to give imidoyl chlorides 4, followed by their
dehydrochlorination using an excess of triethylamine18,21
(Scheme 2, Route B). These ketenimines reveal relatively
low thermal stability and must be stored under argon at low
temperatures (−20 °C).
Synthesis of the Monomeric Aluminum Enamide 5a
by Hydroalumination of Ketenimine 1a. Ketenimine 1a
(N-(diphenylvinylidene)-2,6-diisopropylaniline) was treated
with diisobutylaluminum hydride (DIBAL-H) in anhydrous
n-hexane to obtain the monomeric aluminum enamide 5a by
selective hydroalumination in 83% yield (Scheme 3).
The crystal structure determination (Scheme 3) of 5a
shows that the aluminum atom is bonded to the nitrogen
atom of the ketenimine moiety, which is also attached to the
2,6-diisopropylphenyl group, in spite of the steric shielding
exerted by this bulky N-substituent. Thus, hydroalumination
of the CN-bond of 1 seems to be highly preferred over
reduction of the CC-bond, even in sterically unfavorable
cases. The negative partial charge of the aluminum bound
hydrogen atom of DIBAL-H causes its addition to the central
carbon atom of the ketenimine. As the respective nitrogen
atom of ketenimine 1a bears a relatively high negative partial
charge (NBO-charges:22 N −0.458, C= 0.506, C −0.285
at M062x/6-311+G(d,p)+gd323−25), the attack of the electro-
philic aluminum atom to give 5a is electrostatically favored.
The resulting Al−N distance (1.859(2) Å) in 5a is in the
upper range usually observed for Al−N compounds,26
reflecting a relatively strong Al−N interaction between the
tricoordinated Al and N atoms. The CC bond length
(1.352(3) Å) is close to standard values.27 The NBO charges
(N −1.007, Al 2.010, β-C −0.196) indicate the strong
increase of nucleophilicity at the nitrogen atom upon
hydroalumination, which is well in line with Gutmann’s
charge-density variation rules.28 The presence of two adjacent
Lewis-acidic and -basic atoms in a single molecule is an
excellent prerequisite for their application in activation
processes.
For comparison, the NBO-charges for the corresponding on
nitrogen sterically less crowded N-propyl-substituted keteni-
mine 1b and its hydroalumination product 5b were also
calculated. For 1b, the NBO-charge at the nitrogen atom
(−0.451) is quite similar compared to the one of 1a; the β-
carbon atom (−0.256), bears a slightly less negative charge
B
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compared to 1a. The corresponding aluminum compound 5b
shows a smaller negative charge on nitrogen (−0.976) and a
less positive charge on aluminum (1.979) in comparison to
5a. According to the calculations, in 5b, the β-carbon atom
(−0.226) is significantly more nucleophilic compared to one
in 5a.
Reactions of the Active Al/N Compounds with
Heterocumulenes. (a). Reaction of Ketenimine 1b with
DIBAL-H and Di(cyclohexyl)-carbodiimide 6. In a first
reaction, we treated the ketenimine 1b with DIBAL-H in
anhydrous toluene at −78 °C and observed a complete
consumption of the starting materials after stirring at room
temperature for 2 h. The intermediate aluminum compound
5b was neither isolated nor characterized, but was directly
treated with di(cyclohexyl)-carbodiimide 6 at room temper-
ature (12 h). Compound 7 was formed quantitatively and
isolated in 42% yield after crystallization from the
concentrated reaction mixture. Quenching of 7 with aqueous
solution of NaOH (2 M) gave the unsaturated guanidine 8 in
55% yield (Scheme 4).
bond giving 5b and from the following insertion of the
carbodiimide 6 into the Al−N bond. Both nitrogen atoms of
the resulting guanidinate coordinate to the aluminum atom
forming a four-membered AlN2C heterocycle with a
delocalized π-electronic system across the N−C−N group
(C−N 1.333 Å; Al−N 1.936 Å (average)). Thus, the
formation of the new C−N single bond (1.403(1) Å)
between the former N-Al-enamine and the carbodiimide gives
rise to a unique unsaturated aluminum guanidinate complex
(R2Al)(RN)2C−N(R)-C(H)CR2. Insertion reactions of
carbodiimides into Al−N bonds of simple AlR2-(NR′2)
compounds to yield guanidinato complexes of aluminum
have been reported previously.29
Single crystals of 8 (Figure 1) were obtained by
crystallization from DMSO at room temperature and were
characterized by X-ray crystallography. They show an almost
planar R2N−C(NH)N−C chain (torsion angles −6.7(9)°
and 174.5(4)°). The length of the C4N6 bond is 1.292(3)
Å, the C4−N5(H) distance amounts to 1.355(3) Å. The
newly formed C4−N3 single bond (1.412(1) Å) is only
slightly longer compared to the corresponding C2−N4 bond
(1.403(1) Å) of the corresponding aluminum guanidinato
complex 7.
Scheme 4. Reaction of Ketenimine 1b with DIBAL-H and
Di(cyclohexyl)-carbodiimide 6
(b). Reaction of Ketenimines 1 with DIBAL-H and
Isocyanates 9. In accordance with the synthesis of compound
8, we treated the ketenimines 1a,b with DIBAL-H in
anhydrous n-hexane at −78 °C. The hydroalumination
products 5a,b were not isolated, but treated directly with 1
equiv of isocyanates 9a,b at −78 °C. After a stirring step at
room temperature, the urea derivates 10a,b, derived from 1a,
were isolated in moderate to excellent yields after hydrolytic
workup.
In case of compound 1b, after addition of 9a the aluminum
compound 11 was formed almost quantitatively and was
isolated in 85% yield after crystallization from the
concentrated reaction mixture. It gave the amide 12 in 88%
yield after quenching with aqueous NaOH-solution (2 M).
Single crystals of 12 for X-ray structure analysis (see
Supporting Information, Figure S39) were obtained from a
1:1 mixture of n-pentane and ethyl acetate (1:1) at room
The structure of aluminum compound 7 was elucidated by
X-ray crystallography (Figure 1). It results from the
hydroalumination of ketenimine 1b at the CN double
Figure 1. ORTEP diagram of 7 (left) and 8 (right) with ellipsoids shown at the 30% probability level.
C
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Scheme 5. Reactions of Ketenimine 1a,b with DIBAL-H and Isocyanates 9
temperature. In all cases, the crude products 10a,b and 12
were purified by column chromatography over silica gel
(Scheme 5).
attack of the isocyanate 9 at the more nucleophilic nitrogen
atom to give the n-acylated enamines 10a,b. The very bulky
N-substituent in 1b, however, directs the isocyanate to the β-
carbon atom of the ketenimine subunit. Consequently, in the
reaction course the aluminum compound 11 was formed,
leading after hydrolysis to the imino amide 12.
The X-ray structures of 10a and 10b indicate the formation
of C−N single bonds between the nitrogen atom of the
former ketenimine and the central carbon atom of the former
isocyanate 9 (10a, Figure 2; 10b, Supporting Information
Figure S37).
Aluminum compound 11 was also characterized by single-
crystal X-ray diffraction analysis (Figure 3, left). The six-
membered AlNC3O heterocycle in 11 represents the stable
intermediate formed by hydroalumination of ketenimine 1a
and subsequent addition of phenyl isocyanate 9a. The
formation of the C−C single bond is observed between the
active β-carbon atom of the former ketenimine 1a and the
central carbon atom of the former isocyanate 9a. The
aluminum atom is bonded to the oxygen atom (Al−O
Figure 2. ORTEP diagram of 10a with ellipsoids shown at the 30%
probability level.
It is quite evident that the outcome of these reactions
highly depends on the steric bulk of the N-substituent of the
ketenimine 1. Small substituents like the iPr-group allow the
Figure 3. ORTEP diagram of 11 (left) and 12 (right) with ellipsoids shown at the 30% probability level.
D
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1.771 (6) Å) and further coordinated by the nitrogen atom
via a dative Al−N bond with the expectedly long Al−N1
distance of 2.012 (0) Å.
In the X-ray structure of the hydrolysis product 12, the
intramolecular hydrogen bridge is the most interesting feature
with an N1−N5-distance of 2.729 Å, which is significantly
shorter than the sum of the nitrogen van der Waals radii
(2.92 Å,30) (Figure 3, right).
Similarly to the synthesis of compounds 10a,b, we treated
the aluminum intermediate 5b directly with 2 equiv of the
isocyanates 9 at −78 °C. After optimization of the reaction
conditions, the products of a domino-like reaction by
subsequent addition of 2 equiv of isocyanates 9 were formed,
leading in moderate isolated yields to the enamine-derived
biuret-type compounds 13a−c (Scheme 6).
Figure 5. ORTEP diagram of 16 with ellipsoids shown at the 30%
probability level.
Scheme 6. Reaction of Ketenimine 1b with DIBAL-H and 2
equiv of the Isocyanates 9
domino-like reactions were observed when 2 equiv of phenyl
isothiocyanate 14 were used.
In contrast, treatment of the bulky ketenimine 1a with
DIBAL-H and subsequent addition of 1 equiv of phenyl
isothiocyanate 14 gave the aluminum compound 16 after
stirring at −78 °C (2 h) and room temperature (1 h) in 53%
yield. Hydrolysis and column chromatography over silica gel
gave a few single crystals of the imino thioamide 17, which
could be characterized by X-ray crystallography (see
Supporting Information Figure S43). However, preparative
purification by column chromatography or recrystallization
failed. Here also a C−C bond between the former ketenimine
and the isothiocyanate was formed.
Single-crystal X-ray diffraction analyses confirm the
constitution of compounds 13a and 13b (Figure 4).
Single crystals of aluminum compound 16 were obtained by
recrystallization from an anhydrous n-hexane/toluene = 2:1-
mixture at −20 °C. The six-membered AlN2C3 ring in the
molecular center shows the activation of CN double bond
of the phenyl isothiocyanate 14 in a similar mode as observed
for 11 forming a coordination sphere of two nitrogen atoms
at aluminum (Al−N: 1.924, 1.995 Å) (Figure 5).
(d). Reaction of Ketenimines 1 with DIBAL-H and a
Second Equivalent of Another Ketenimine 1. The
compounds obtained by hydroalumination of ketenimines 1
should be able to react with a second equivalent of a
ketenimine as an electrophile to form highly interesting
oligomeric species. Therefore, we treated the ketenimine 1c
with DIBAL-H in anhydrous n-hexane at −78 °C. After
stirring for 1 h (−78 °C), ketenimine 1d was added directly
at the same temperature. Compound 18 was formed almost
quantitatively and isolated in 37% yield after crystallization
from the concentrated reaction mixture (Scheme 8). Attempts
to isolate the corresponding hydrolysis product by column
chromatography over silica gel or alumina B failed.
Figure 4. ORTEP diagram of 13a (left) and 13b (right) with
ellipsoids shown at the 30% probability level.
The structure of aluminum compound 18 was elucidated by
X-ray crystallography (Figure 6). In correspondence to the
structure of compound 16, the formation of a C−C single
bond indicates that the β-carbon atom of ketenimine 1c is
activated by hydroalumination and reacts with the CN
double bond of the second ketenimine 1d to form a chelating
N,N-ligand. It is interesting to note that the cyclohexyl
substituent at the nitrogen atom of 1c leads to preferred C−
C-bond formation, while the N-isopropyl substituent as in 1b
always gave C−N-bonding (see above).
Particularly noteworthy are the quite flexible biuret-sub-
structures in the solid state (dihedral angles along the
biuret-subunit: 13a, N1−C6−N7−C8, 4.84°; C6−N7−C8−
N9, 153.65°; 13b, N1−C6−N7−C8, 61.19°; C6−N7−C8−
N9, −170.61°). Thus, both compounds show significantly
different conformations of the backbone.
(c). Reaction of Ketenimine 1b with DIBAL-H and Phenyl
Isothiocyanate 14. Similarly to the synthesis of the aluminum
compound 11, the sterically less bulky ketenimine 1b gave the
vinyl thiourea derivative 15 as result of an electrophilic attack
of the phenyl isocyanate 14 at the nitrogen atom of the
former ketenimine after hydrolytic workup without isolating
the hydroalumination intermediate 5b (Scheme 7). No
In a similar way, the diimines 19a and 19b were obtained
by treating the ketenimine 1e or 1b with DIBAL-H and
afterward with a second equivalent of the ketenimine 1b or
1e. The crude products were subjected to column
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Scheme 7. Reaction of Ketenimine 1a,b with DIBAL-H and Phenyl Isothiocyanate 14
Scheme 8. Reaction of Ketenimine 1c with DIBAL-H and Subsequent Treatment with Ketenimine 1d
Figure 8. ORTEP diagram of 20a with ellipsoids shown at the 30%
probability level.
Figure 6. ORTEP diagram of 18 with ellipsoids shown at the 30%
probability level.
between the β-carbon atom of the first ketenimine and the α-
carbon atom of the second ketenimine. In case of 19b, the
C−C-bond formation starting from the N-i-Pr compound 1b
is surprising and presents an exception among the reactions of
this compound (see above). Possibly, the steric bulk of the
reagent 1e causes this different chemoselectivity. After
hydrolytic workup, compounds 19a and 19b were isolated
as multiply substituted diimines.
(e). Reactions of Ketenimines 1 with Carboxylic Chloride
2c. The aluminum intermediates 5b or 5f as nonisolated
intermediates from the hydroalumination of ketenimine 1b or
1f reacted also with 2 equiv of carboxylic chloride 2c in a one-
pot reaction. The reactions mixtures were quenched with an
aqueous solution of NaOH to yield the N-acyl enamides 20a
and 20b. The crude products were subjected to column
chromatography over silica gel and isolated in 22% and 61%
yield (Scheme 10).
Figure 7. ORTEP diagram of 19a with ellipsoids shown at the 30%
probability level.
chromatography over Al2O3 (B) after hydrolytic workup
(Scheme 9).
Single crystals of both compounds 19a and 19b were
obtained by recrystallization from a solvent mixture (n-
pentane/diethyl ether = 1:1) at room temperature (for 19a,
Figure 7; for 19b, see Supporting Information Figure S46).
Both structures indicate similar reactions as observed for the
synthesis of 18. Thus, a C−C single bond was formed
Single crystals of 20a were obtained from toluene at room
temperature (Figure 8). The structure shows the formation of
a C−N single bond between the nitrogen atom originally
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Scheme 9. Synthesis of Diimines 19a and 19b
31% and 45% yield. The constitutions of 21a, b were
confirmed by X-ray diffraction of single crystals, which were
obtained from a solution in DMSO at room temperature (for
21a, Figure 9; for 21b, see Supporting Information Figure
S49). Two new C−N single bonds were formed, the first one
between the nitrogen atom of the reduced ketenimine unit
and the central carbon atom of the isocyanate and the second
one after addition of acid chloride in the domino reaction
(Scheme 11). The chains of 21a and 21b show helical
conformations. These results underline the wide synthetic
utility of hydroaluminated ketenimines for a multistep
synthetic approach to multiply functionalized nitrogen
compounds, which otherwise are not easily accessible.
Scheme 10. Synthesis of the N-Acyl Enamides 20a and 20b
CONCLUSIONS
■
In this study, we have investigated the hydroalumination of
ketenimines and their unique reactivity toward various
heterocumulenic electrophiles. In one case (5a), we
determined the structure of the initial hydroalumination
product in the solid state by X-ray crystallography, indicating
that the hydroalumination of the CN-bond is preferred
over the reduction of the CC-bond, even in those cases, in
which the N-substituent is very bulky. These reactive
intermediates with coordinatively unsaturated aluminum and
nitrogen atoms showed an impressive reactivity in secondary
reactions with an activation of heterocumulenic electrophiles
such as carbodiimides, isocyanates, isothiocyanates and
ketenimines. In general, the regioselectivity of these secondary
reactions may be explained by the steric bulk of the N-
substituent of the ketenimines. Thus, both types of reactions
with electrophiles were found: Small N-substituents allow
insertion reactions into the aluminum−nitrogen bond leading
to various functionalized enamine and enamide derivatives,
Figure 9. ORTEP diagram of 21a with ellipsoids shown at the 30%
probability level.
bonded to aluminum in the intermediate 5b and the carbonyl
carbon atom of the carboxylic acid.
(f). One-Pot Reactions of Ketenimines 1 with Isocyanates
9 and Acid Chloride 2c. Finally, as a further example of a
domino reaction involving successively two different electro-
philes, the ketenimine 1b was first treated with DIBAL-H.
The addition of 1 equiv of isocyanate in a second step and
finally of 2 equiv of acid chloride 2c in a third step gave the
N-imido-substituted enamides 21a,b in a one-pot reaction
Scheme 11. One-Pot Synthesis of the N-Imido-enamides 21a,b
G
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1076 w, 1059 w, 1030 m, 988 w, 937 w, 880 m, 795 m, 737 s, 716
m, 696 s. HRMS (ESI+): calcd for C26H29NO + Na+, 394.2141;
found, 394.2140.
while bulky N-substituents lead to C−C-bond formation
giving products of the 1,3-diimine type. In several cases, the
constitution of the aluminum compounds before hydrolytic
workup could be determined by X-ray structure analysis,
showing coordination compounds with chelating N,N- or
N,O-ligands. Hydrolytic workup gave the corresponding
functionalized compounds in moderate to high yields. Even
the successive addition of two electrophiles of the same or of
different type was applied successfully and led to novel urea
derivatives including such of the biuret type. These results
verify convincingly the exceptional applicability of easily
available aluminum based nucleophiles for C−C and C−N
bond formation reactions and as efficient building blocks for
the generation of new functionalized unsaturated organic
nitrogen compounds. These reactions will clearly find wider
application in preparative chemistry and will stimulate further
experiments. Investigations into the synthesis of related or
even more complicated compounds are presently in progress.
N-Isopropyl-2,2-diphenylacetamide (3b). From diphenylacetic
acid and i-propylamine according to general procedure A. Yield:
20.0 g (79%, Lit. 70%31), colorless solid. Mp 159 °C (Lit.: 158−159
31
1
°C ). H NMR (300 MHz, CDCl3): δ = 7.50−7.27 (m, 10H, CH,
phenyl), 5.62 (d, JHH = 7.8 Hz, 1H, NH), 4.89 (s, 1H, CHPh2), 4.14
(dq, JHH = 7.9, 6.5 Hz, 1H, CH(CH3)2), 1.11 (d, JHH = 6.6 Hz, 6H,
CH3). 13C{1H} NMR (75 MHz, CDCl3): δ = 170.9 (CO), 139.7
(ipso-C), 128.8, 128.6, and 127.2 (CH, phenyl.), 59.1 (CHPh2), 41.7
(CH(CH3)2), 22.6 (CH3).
N-Cyclohexyl-2,2-diphenylacetamide (3c). From diphenylacetic
acid and cyclohexaneamine according to general procedure A. Yield:
22.1 g (75%, Lit. 50%32), colorless solid. Mp 150 °C (Lit.: 151−152
32
1
°C ). H NMR (300 MHz, CD2Cl2): δ = 7.43−7.19 (m, 10H, CH,
phenyl), 5.77 (d, JHH = 6.9 Hz, 1H, NH), 4.85 (s, 1H, CHPh2),
3.87−3.70 (m, 1H, CH(CH2)5), 1.90−1.84 (m, 2H, CH2), 1.69−1.56
(m, 3H, CH2), 1.25 (m, 2H, CH2), 1.25−1.01 (m, 3H, CH2).
13C{1H} NMR (75 MHz, CD2Cl2): δ = 170.8 (CO), 140.4 (ipso-
C), 129.3, 128.9, and 127.4 (CH, phenyl), 59.3 (CHPh2), 48.8 (CH,
cyclohexyl), 33.2, 25.9, and 25.2 (CH2 of cyclohexyl).
EXPERIMENTAL SECTION
■
N-(p-Tolyl)cyclohexanecarboxamide (3d). From p-toluidine (16.1
g, 150 mmol) and cyclohexanecarboxylic acid chloride 2a (20.4 mL,
150 mmol) according to general procedure B. Yield: 30.5 g (106
mmol, 94%, Lit. 96%33), colorless solid. Mp 154 °C (Lit.: 154−156
General. All air and/or moisture sensitive experiments were
performed under purified argon using standard Schlenk techniques.
n-Hexane and toluene were dried over sodium/benzophenone. A
solution of DIBAL-H in-n-hexane was applied as purchased. NMR
spectra were recorded at 298 K (1H, 300.13 MHz; 13C, 75.48 MHz),
(1H, 400.03; 13C, 100.59 MHz), (1H, 499.85 MHz; 13C, 125.67
MHz), (1H, 599.79 MHz; 13C, 150.83 MHz). Assignments of the
resonances were supported by 2D experiments and referenced
internally to residual solvent resonances (chemical shift data in δ).
13C NMR spectra were all proton decoupled. IR spectra were
recorded as Nujol mull between CsI plates or with an ATR sampling
system. Electron impact (EI) mass and electron spray ionization
(ESI) spectra were recorded. Elemental analyses were determined by
the microanalytic laboratory in our institute.
33
1
°C ). H NMR (300 MHz, CDCl3): δ (ppm) = 1.10−1.39 (m, 3H,
CH2), 1.42−2.00 (m, 7H, CH2), 2.14−2.41 (m, 4H, CH and CH3),
7.08 (d, JHH = 8.3 Hz, 2H, CHarom.), 7.42 (d, JHH = 8.4 Hz, 2H,
CHarom.), 7.67 (br s, 1H, NH). 13C NMR (75 MHz, CDCl3): δ
(ppm) = 20.8 (CH3), 25.7 (3C, CH2), 29.6 (2C, CH2), 46.4 (CH),
120.1, 129.4 (4C, CHarom.), 133.6, 135.7 (2C, i-Carom.), 174.7 (C
O).
N-(2,6-Diisopropylphenyl)-cyclohexanecarboxamide (3e). From
cyclohexanecarboxylic acid chloride 2a and 2,6-di-i-propylaniline
according to general procedure B. Yield: 33.9 g (118 mmol, 95%),
1
colorless solid. Mp 315 °C. H NMR (300 MHz, CDCl3): δ (ppm)
= 7.31−7.01 (m, 3H, CH, phenyl.), 6.60 (br. s, 1H, NH), 2.97 (hept,
JHH = 6.9 Hz, 2H, CH(CH3)2), 2.29 (tt, JHH = 18.3, 3.5 Hz, 1H,
CH(CH2)5), 2.06−1.87 (m, 2H, CH2), 1.86−1.40 (m, 6H, CH2 of
cyclohexyl), 1.40−0.78 (m, 14H, CH2, cyclohexyl, and CH3).
13C{1H} NMR (75 MHz, CDCl3): δ = 175.2 (CO), 146.2 (2C,
ipso-C−CH(CH3)2), 131.1 (ipso-C-NH), 123.3 and 128.2 (CH,
phenyl), 45.9 (CHCO), 29.9 (CH(CH3)2), 28.7, 25.8, and 25.7
(CH2, cyclohexyl), 23.6 (CH(CH3)2). IR (ATR, cm−1) = 3213 w,
ν(NH), 2963 m, 2924 s, 2855 m, 1645 s, ν(CO), 1558 m, 1539 s,
1522 s, 1472 s, 1447 s, 1381 m, 1362 w, 1339 m, 1258 m, 1217 s,
1180 w, 1136 w, 1101 w, 1061 m, 1045 m, 962 m, 937 (w), 897 w,
797 m, 766 m, 727 s. HRMS (ESI+): calcd for C19H29NO + H+,
288.2327; found, 288.2322.
Precursors. Synthesis of Amides. General Procedure A for 3a−
c: Thionyl chloride (2 equiv) was mixed with diphenylacetic acid (1
equiv) and refluxed until HCl gas evolution was no longer observed.
Then, excess thionyl chloride was removed using a water jet pump.
The resulting diphenylacetyl chloride 2a was added without isolation
to a solution of the corresponding acetamide (1 equiv) in sodium
hydroxide solution (1 M, 500−600 mL) under ice-cooling and then
stirred for 2 h at room temperature. The suspended solids were
collected and treated with dichloromethane. Then, the solution was
dried over sodium sulfate and the solvent was removed under
reduced pressure. The crude product was purified by crystallization
from ethanol. General Procedure B for 3d−f: Carboxylic acid
chloride (1 equiv) was added to a solution of the corresponding
alkylamine or allylamine (1 equiv) in pyridine (150 mL) under ice-
cooling, and then, the mixture stirred for 12 h at room temperature.
Pyridine was then evaporated in vacuo. The collected reaction
mixture was suspended in dichloromethane and washed with water
three times. Drying over sodium sulfate and evaporation of the
solvent gave the crude product, which was further purified by
crystallization from ethanol.
2-Ethyl-N-phenylbutanamide (3f). From 2-ethyl-butanoyl chlor-
ide 2b (57.0 g, 424 mmol) and aniline (38.8 mL, 425 mmol)
according to general procedure B. Yield: 53.3 g (279 mmol, 56%, Lit
40%34), white solid.
Synthesis of Imidoyl Chlorides 4. General Procedure C: 1.0
equiv of phosphorus pentachloride was added to a solution of the
corresponding amide 3 (1 equiv) in dry chloroform (120−180 mL)
under ice-cooling. The reaction mixture was vigorously stirred and
heated to reflux for 2 h. Then, chloroform and phosphoryl chloride
were evaporated in vacuo. The raw product was purified by fractional
vacuum distillation. The products were air and moisture sensitive and
had to be stored under argon at −20 °C.
N-(2,6-Diisopropylphenyl)-2,2-diphenylacetamide (3a). From
diphenylacetic acid and 2,6-diisobutylaniline according to general
1
procedure A. Yield: 29.3 g (79%), colorless solid. Mp 232 °C. H
NMR (300 MHz, CD2Cl2): δ = 7.50−7.27 (m, 11H, CH of phenyl),
7.20 (d, JHH = 6.9 Hz, 2H, CH of phenyl), 6.95 (br. s, 1H, NH),
5.17 (s, 1H, CHPh2), 2.97 (hept, JHH = 6.8 Hz, 2H, CH(CH3)2),
1.12 (d, JHH = 6.9 Hz, 12H, CH3). 13C{1H} NMR (75 MHz,
CD2Cl2): δ = 171.8 (CO), 146.8 (ipso-C−CH(CH3)2), 139.9
(ipso-C-CHPh2), 132.0 (ipso-C-NH), 129.5, 129.3, 128.9, 127.9, and
123.9 (CH, phenyl), 59.9 (CHPh2), 29.3 (CH(CH3)2), 23.8 (CH3).
IR (ATR, cm−1) = 3230 vw, ν (NH), 3030 w, 2968 m, 2924 w, 2868
w, 1647 s, ν(CO), 1558 w, 1539 w, 1522 s, 1493 m, 1466 m,
1456 m, 1383 w, 1362 m, 1337 w, 1256 w, 1217 m, 1173 m, 1107 w,
N-(p-Tolyl)cyclohexanecarbimidoyl Chloride (4a). From 3d and
phosphorus pentachloride according to the general procedure C.
1
Yield: 27.4 g (83%), yellow liquid. Bp 125 °C (1.4 × 10−2 mbar). H
NMR (300 MHz, CDCl3): δ = 7.20−7.12 (m, 2H, CH, phenyl),
6.85−6.77 (m, 2H, CH, phenyl), 2.69 (tt, JHH = 11.3, 3.4 Hz, 1H,
CH, cyclohexyl), 2.35(s, 3H, CH3), 2.20−2.09 (m, 2H, CH2,
cyclohexyl), 1.92−1.81 (m, 2H, CH2, cyclohexyl), 1.77−1.50 (m, 3H,
CH2, cyclohexyl), 1.46−1.20 (m, 3H, CH2, cyclohexyl). 13C{1H}
H
DOI: 10.1021/acs.joc.5b00466
J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
NMR (75 MHz, CDCl3): δ = 151.85 (CN), 144.3 and 134.7
(ipso-C, phenyl), 129.5, 120.4 (4C, CH, phenyl), 50.8 (CH,
cyclohexyl), 30.7 (CH2, cyclohexyl), 25.9 (CH2,cyclohexyl), 25.7
(CH2, cyclohexyl), 21.1 (CH3). IR (ATR, cm−1) = 3040 w, 2934 s,
2857 s, 1690 s, ν (CN), 1659 s, 1599 m, 1535 w, 1504 s, 1450 m,
1348 w, 1250 w, 1215 w, 1140 w, 1105 s, 1018 w, 966 s, 899 m, 841
s, 818 s, 764 m, 743 m, 714 m, 685 w, 646 m, 583 s. Elemental
analysis Calcd (%) for C14H18NCl (235.1): C, 71.32; H, 7.70; N,
5.94. Found: C, 71.22; H, 7.87; N 5.93.
CH3); 13C{1H} NMR (75 MHz, C6D6): δ = 183.7 (CCN),
136.0 (ipso-C, phenyl), 129.1, 127.9, and 126.1 (CH, phenyl), 76.2
(CCN), 55.0 (CH), 23.6 (2C, CH3). HRMS (ESI+): calcd for
C17H17N +Na+, 258.1253; found:, 258.1248.
N-(2,2-Diphenylvinylidene)cyclohexanamine (1c). From 3c and
phosphorus pentoxide according to the general procedure D. Yield:
32
1
4.80 g (34%, Lit. 50% ), yellow solid. Mp 58 °C). H NMR (300
MHz, C6D6): δ = 7.54−7.36 (m, 4H, CH, phenyl), 7.25−7.12 (m,
4H, CH, phenyl), 7.09−6.98 (m, 2H, CH, phenyl), 3.30 (tt, JHH
=
N-(2,6-Diisopropylphenyl)cyclohexanecarbimidoyl Chloride (4b).
From 3e and phosphorus pentachloride according to the general
procedure C. Yield: 27.0 g (76%), colorless liquid. Bp 185 °C (4 ×
10.1, 3.9 Hz, 1H, CH, cyclohexyl), 1.93−1.78 (m, 2H, CH2,
cyclohexyl), 1.64−1.21 (m, 5H, CH2, cyclohexyl), 1.10−0.84 (m, 3H,
CH2, cyclohexyl). 13C{1H} NMR (75 MHz, C6D6): δ = 183.6 (C
CN), 136.1 (ipso-C, phenyl), 127.9, 129.4, and 126.1 (CH,
phenyl), 75.6 (CCN), 61.8 (CH, cyclohexyl), 34.3(CH2,
cyclohexyl), 25.4 and 24.8 (CH2, cyclohexyl).
1
10−3 mbar). H NMR (400 MHz, C6D6): δ = 7.36−7.12 (m, 3H,
CH, phenyl). 3.23−2.97 (m, 2H, CH(CH3)2), 2.63 (tt, J = 11.1, 3.5
Hz, 1H, CH, cyclohexyl), 2.21 (pseudod, 2H, CH2, cyclohexyl),
1.82−1.51 (m, 5H, partially covered, CH2, cyclohexyl), 1.48−1.09
(m, 15H, partially covered, CH2, cyclohexyl and CH(CH3)2).
13C{1H} NMR (100 MHz, C6D6): δ = 150.6 (CN). 143.7 and
136.7 (ipso-C, phenyl), 125.1 (CH, phenyl), 123.4 (CH, phenyl),
51.0 (CH, cyclohexyl), 31.1 (CH2, cyclohexyl), 28.9 (CH(CH3)2),
26.0 and 25.8, (CH2, cyclohexyl), 23.4 and 23.1 (4C, CH(CH3)2). IR
(ATR, cm−1) = 3040 w, 2963 w, 2934 s, 2859 s, 1738 br. s, ν (C
N), 1726 s) 1715 s, 1553 w, 1468 m, 1450 m, 1366 s, 1229 w, 1217
s, 1211 s, 968 m, 826 w, 791 w, 756 w, 723 w, 596 w, 581 s.
Elemental analysis Calc (%) for C19H28NCl (305.2): C, 74.60; H,
9.23; N, 4.58. Found: C, 74.27; H, 9.44; N, 4.52.
N-(Cyclohexylidenemethylene)-4-methylaniline (1d). From 4a
according to the general procedure E. Yield: 9.50 g (54%), yellow
1
liquid. Bp 100 °C, 6.0 × 10−3 mbar. H NMR (300 MHz, C6D6): δ
= 7.40−7.27 (m, 2H, CH, phenyl), 7.01−6.96 (m, 2H, CH, phenyl),
2.12−1.96 (m, 7H, CH3 and CH2), 1.47−1.35 (m, 4H, CH2,
cyclohexyl), 1.31−1.23 (m, 4H, CH2, cyclohexyl). 13C{1H} NMR (75
MHz, C6D6): δ = 192.4 (CCN), 142.3 (ipso-C-CH3), 136.4
(ipso-C-N), 130.2 and 123.5 (CH, phenyl), 65.8 (CCN), 27.5,
27.1, and 26.3 (CH2), 21.0 (CH3). IR (ATR, cm−1) = 3048 w, 2976
m, 2928 w, 2920 w, 2880 w, 2012 s, ν (CCN), 1738 s, br.
(CC), 1504 w, 1443 w, 1366 s, 1356 s, 1319 w, 1229 s, 1217 s,
1206 s, 1092 w, 895 w, 820 w.
2-Ethyl-N-phenylbutanimidoyl Chloride (4c). From 3e and
phosphorus pentachloride according to the general procedure C.
Yield: 49.5 g (85%, Lit 93%34), colorless liquid. Bp 66−68 °C (0.4
mbar, Lit: 60 °C, 0.3 mbar34). 1H NMR (300 MHz, C6D6): δ =
7.41−7.37 (m, 2H, CH of phenyl), 7.24−7.08 (m, 3H, CH of
phenyl), 2.81−2.70 (m, 1H, CH), 1.99−1.87 (m, 2H, CH2), 1.70−
N-(Cyclohexylidenemethylene)-2,6-diisopropylaniline (1e). From
4b according to the general procedure E. Yield: 9.00 g (67%),
1
colorless liquid. Bp 111 °C, 4.0 × 10−3 mbar. H NMR (400 MHz,
CD2Cl2): δ = 7.26−7.04 (m, 3H, CH, phenyl), 2.89−2.69 (m, 3H,
CH(CH3)2), 2.42−2.16 (m, 2H, CH2, cyclohexyl), 1.96−1.59 (m,
5H, partially covered, CH2, cyclohexyl), 1.51−1.03 (m, 15H, partially
covered, CH2, cyclohexyl and CH(CH3)2). 13C{1H} NMR (100
MHz, CD2Cl2): δ = 176.3 (CCN), 143.6 (ipso-C-N), 137.3 (2C,
ipso-C(i-Pr)2), 125.2 and 123.6 (CH, phenyl), 75.6 (CCN), 31.4
(CH2, cyclohexyl), 28.9 (CH(CH3)2), 26.5 and 26.3 (CH2,
cyclohexyl), 23.4 (CH3). IR (ATR, cm−1) = 3010 w, 2959 m,
2930 w, 2859 w, 2033 s, ν(CCN), 1738 s. br, ν(CN), 1728 s,
1462 w, 1441 w, 1371 m, 1229 m, 1223 m, 1211 m, 972 w, 895 w,
758 w, 652 w.
3
1.58 (m, 2H, CH2), 1.15 (t, JHH = 7.4 Hz, 6H, CH3).
Synthesis of Ketenimines. General Procedure D for 1a−c: 5.4
equiv of phosphorus pentoxide with sea sand (75 g) were added to a
solution of the corresponding carboxylic amide VV (1 equiv) in dry
triethylamine or pyridine and were diluted with 200 mL of dry
triethylamine or pyridine. The reaction mixture was vigorously stirred
and heated to reflux for 7 h. Then, the suspended solids were filtered
off and freed from the solvent in vacuo. This raw product was
purified by crystallization from n-heptane. General Procedure E for
1d−f: Dry triethylamine (8.4 equiv) was added to a solution of the
corresponding imidoyl chloride V (1 equiv) in dry toluene. Then,
the mixture was heated to reflux for 20 h. The suspended solids were
filtered off. Evaporation of the solvent gave the raw product, which
was purified by fractional vacuum distillation. The products were air
and moisture sensitive and had to be stored under argon at −20 °C.
N-(2,2-Diphenylvinylidene)-2,6-diisopropylaniline (1a). From 3a
and phosphorus pentoxide according to the general procedure D.
N-(2-Ethylbut-1-en-1-ylidene)aniline (1f). From 4c according to
the general procedure E. Yield: 9.50 g (54.8 mmol, 60%, Lit 55%34),
colorless liquid. Bp 64 °C, 8.0 × 10−3 mbar (lit.: 60−64 °C, 0.04
34
1
mbar ). H NMR (300 MHz, C6D6): δ = 7.43−7.34 (m, 3H, CH,
phenyl), 7.15−7.05 (m, 2H, CH, phenyl), 7.02−6.92 (m, 1H, CH,
3
3
phenyl), 1.86 (q, JHH = 7.4 Hz, 4H, CH2), 0.97 (t, JHH = 7.4 Hz,
6H, CH3). 13C{1H} NMR (75 MHz, C6D6): δ = 195.0 (CCN),
144.9 (ipso-C), 129.6, 126.8, and 123.4 (CH, phenyl), 72.8 (CC
N), 22.6 (CH2), 12.9 (CH3).
35
1
Yield: 11.6 g (66%, lit. 82% ), yellow solid. Mp 92 °C. H NMR
(600 MHz, C6D6): δ = 7.34 (dd, JHH = 8.4, 1.1 Hz, 4H, CH,
phenyl). 7.12−7.08 (m, 4H, CH, phenyl), 7.04−7.02 (m, 3H, CH,
phenyl), 6.97 (pseudo-s, 2H, CH, phenyl), 3.39 (hept, JHH = 6.9 Hz,
2H, CH(CH3)2), 1.07 (d, JHH = 6.9 Hz, 12H, CH(CH3)2). 13C{1H}
NMR (150 MHz, C6D6): δ = 184.3 (CCN); 141.3 (ipso-C(i-
Pr.)), 136.9 (ipso-C-N), 135.5 (ipso-C−N-CC, phenyl), 129.2,
128.4, 127.0, and 126.3 (CH, phenyl), 124.0 (CH−C(i-Pr)), 72.7
(CCN), 29.0 (2C, CH(CH3)2), 23.7 (4C, CH(CH3)2). IR
(ATR, cm−1) = 3028 w, 2963 m, 2928 w, 2862 w, 2010 s, ν (C
CN), 1593 m, 1493 m, 1456 m, 1433 m, 1383 w, 1360 w, 1325 w,
1256 w, 1167 m, 1121 w, 1107 w, 1063 w, 1030 w, 934 m, 926 m,
797 m, 754 s, 692 w, 662 w, 644 w. Elemental analysis Calcd (%) for
C26H27N (353.2): C, 88.34; H, 7.70; N, 3.96. Found: C, 88.08; H,
7.54; N, 3.94.
(2,6-Diisopropylphenyl)(2,2-diphenylvinyl)amino)di(iso-butyl)-
aluminum 5a. Ketenimine 1a (410 mg, 1.16 mmol, 1.0 equiv) was
dissolved in 20 mL of n-hexane and treated with DIBAL-H (1.16
mL, 1 M in n-hexane, 1.16 mmol, 1.0 equiv) at −78 °C with stirring.
Stirring was continued for 2 h at −78 °C; then, the mixture was
slowly warmed to room temperature over 2 h. Red crystals (360 mg,
726 mmol, 63%, moisture sensitive) were obtained upon
1
concentration of the reaction mixture at −20 °C. Mp 151 °C. H
NMR (400 MHz, C6D6): δ = 7.32−7.06 (m, 11H, CH, phenyl),
7.04−6.78 (m, 2H, CH, phenyl), 6.75 (s, 1H, CHC), 3.69 (hept,
JHH = 6.8 Hz, 2H, CHMe2), 1.69 (dp, JHH = 13.4, 6.8 Hz, 2H, Al-
CH2CH), 1.39 (d, JHH = 6.9 Hz, 6H, CHMe2), 1.26 (d, JHH = 6.7
Hz, 6H, CHMe2), 0.92 (d, JHH = 6.5 Hz, 12H, Al-CH2−CHMe2),
0.10 (d, JHH= 7.1 Hz, 4H, Al−CH2). 13C{1H} NMR (100 MHz,
C6D6): 146.6 (CHN), 146.5 and 144.7 (ipso-C(i-Pr), 144.2 (ipso-
C-N), 130.9, 129.6, 129.0, 128.7, 124.9, and 126.3 (CH, phenyl),
110.8 (CPh2), 29.5 (CHMe2), 28.2 (Al-CH2−CHMe2), 25.8 (Al-
CH2−CH), 25.7 (CHMe2), 23.6 (Al-CH2), 23.5 (CHMe2). IR (CsI-
plates, nujol, cm−1): 3418 w, 3167 w, 3146 w, 3061 s, 3055 s, 2953−
2851 vs, (nujol), 2679 s, 2641 m, 2606 m, 2548 w, 2498 w, 2336 w,
N-(2,2-Diphenylvinylidene)propan-2-amine (1b). From 3b and
phosphorus pentoxide according to the general procedure D. Yield:
10.5 g (89%, Lit. 54%36), yellow solid. Mp 45 °C (Lit.: 45−46 °C36).
1H NMR (300 MHz, C6D6): δ = 7.58−7.43 (m, 4H, CH, phenyl),
7.29−7.20 (m, 4H, CH, phenyl), 7.17−7.06 (m, 2H, CH, phenyl),
3.36 (dt, JHH = 12.9, 6.5 Hz, 1H, CH), 1.16 (d, JHH = 6.5 Hz, 6H,
I
DOI: 10.1021/acs.joc.5b00466
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The Journal of Organic Chemistry
Article
2313 w, 1958 w, 1937 m, 1877 w, 1811 w, 1587 s, 1557 s, ν(CC),
1454−1435 vs, (nujol), 1362 s, 1304 w, 1254 m, 1231 w, 1177 w,
1157 m, 1126 w, 1111 w, 1072 m, 1057 w, 1032 w, 1015 w, 972 w,
953 w, 918 w, 887 m, 802 s, 779 m, 754 s, 721 s, 698 m, 638 w, 592
w, 556 w, 505 m, 436 s, 401 s, ν(AlC), ν(AlN). MS (EI, 20 eV, 25
°C): m/z (%) = 495 (32) [M]+, 438 (34) [M − i-Bu]+, 382 (16)
[M − (i-Bu)2 + H]+, 355 (80) [M − Al(i-Bu)2 + H]+, 188 (100) [M
− Al(i-Bu)2 − CPh2]+, 146 (76), 130 (8), 128 (2), 77 (2), 56 (3),
43 (5).
(CH, phenyl), 127.2 (0.6C, CCH), 126.6, 126.5, 126.2, and 125.9
(CH, phenyl), 55.9 (N-CH, cyclohexyl), 53.0 (0.4C, NCH(CH3)2),
52.7 (NH-CH, cyclohexyl), 51.7 (0.6C, NCH(CH3)2), 58.1 and 50.1
(partially covered, N−CH−CH2), 35.0 (N−CH-CH2), 34.9, 32.9,
26.7, and 25.9 (N−CH-CH2−CH2), 25.7 and 25.2, (N−CH-CH2−
CH2−CH2), 21.7 (NCHMe2), 21.3 (NCHMe2), *(Resonances of the
main isomer are assigned (ration 6:4)). IR (ATR, cm−1) = 3412 w,
ν(NH), 3128 w, 3012 w, 2922 s, 2845 m, 1626 s, ν(CN), 1587 m,
1570 w, 1493 w, 1462 w, 1443 m, 1400 m, 1364 m, 1327 w, 1308 m,
1238 s, 1180 m, 1150 m, 1128 m, 1117 w, 1067 m, 1028 w, 880 s,
866 s, 845 w, 758 s, 694 s, 640 w, 606 w. HRMS (ESI+): calcd for
C30H41N3 + H+, 444.3373; found, 444.3375. Elemental analysis Calcd
(%) for C30H41N3 (443.6): C, 81.21; H, 9.31; N, 9.47. Found: C,
80.84; H, 9.41; N, 9.34.
Reactions of Active Al/N Compounds with heterocumu-
lenes. Reactions with Carbodiimides 6. N,N′-Dicyclohexyl-3-(2,2-
diphenylvinyl)-3-isopropylguanidino-di(iso-butyl)-aluminum 7. Ke-
tenimine 1b (454 mg, 1.93 mmol) was dissolved in 20 mL of dry
toluene and treated with DIBAL-H (1.93 mL, 1.16 mmol, 1 M in n-
hexane, 1.0 equiv) at −78 °C with stirring. Stirring was continued for
2 h at −78 °C. Then, the reaction mixture was slowly warmed to
room temperature over 2 h, and dicyclohexylcarbodiimide 6 (398
mg, 1.93 mmol) in 20 mL of toluene was added followed by stirring
overnight. Colorless crystals 7 (475 mg, 0.84 mmol, 42%) were
obtained upon concentration of the reaction mixture at −20 °C. Mp
Reactions of Active Al/N Compounds 5 with Isocyanates 9
and Isothiocyanates 14. General Procedure F for the Synthesis
of 10a−d. A solution of DIBAL-H (1 M in n-hexane, 1 equiv) was
added to a cooled (−78 °C) solution of the ketenimine 1 (1 equiv)
in dry n-hexane (20 mL). After 2 h stirring at −78 °C, the solution
was allowed to warm to room temperature and stirred for 2 h. The
dry isocyanate 9 (1 or 2 equiv) or isothiocyanate 14 was added at
−78 °C and stirring was continued for 2 h. The solution was
warmed to room temperature and quenched with NaOH-solution (2
M). The organic layer was washed twice with NaOH-solution (2 M)
and brine and dried over magnesium sulfate. The solvent was
removed under reduced pressure. The crude product was purified by
column chromatography and/or recrystallization for X-ray analysis.
1-(2,2-Diphenylvinyl)-1-isopropyl-3-phenylurea 10a. From kete-
nimine 1b (591 mg, 2.52 mmol) and phenyl isocyanate 9a (605 mg,
5.08 mmol, 2.0 equiv) according to the general procedure F. The
reaction mixture was quenched with NaOH-solution (2 M).
Subsequent column chromatography (TBME/cyclohexane, 1:1)
gave the pure product (873 mg, 2.45 mmol, 96%) as colorless
solid (mp 139 °C). Colorless crystals were obtained by
recrystallization from toluene. 1H NMR (400 MHz, CD2Cl2): δ
(ppm) = 7.41−7.22 (m, 10H, CH, phenyl), 7.21−7.06 (m, 4H, CH,
phenyl), 6.98−6.92 (m, 1H, CH, phenyl), 6.84 (br s, 1H, NH), 6.51
(s, 1H, CCH), 4.61 (hept, JHH = 6.9 Hz, 1H, NCH(CH3)2), 1.24
(d, JHH = 6.9 Hz, 6H, NCH(CH3)2). 13C{1H} NMR (100 MHz,
CD2Cl2): δ =153.0 (CO), 141.4 (CCH), 141.3, 139.4 and
138.5(ipso-C), 129.9, 129.1, 129.0, 128.8, 128.8, 128.7, and 128.6
(CH, phenyl), 123.6 (CCH), 123.2 and 120.0 (CH, phenyl), 48.7
(NCH(CH3)2), 20.8 (2C, NCH(CH3)2). IR (ATR, cm−1) = 3420 s,
ν(NH), 3057 w, 3030 w, 2968 w, 2934 w, 1682 s, ν(CO), 1614
m, 1593 m, 1520 s, ν(CC), 1497 m, 1439 s, 1396 w, 1312 s, 1231
s, 1179 w, 1155 w, 1126 m, 1076 w, 1036 w, 1001 w, 903 s, 868 w,
858 w, 773 s, 750 s, 718 s, 700 s, 692 s, 644 w, 629 w, 611 m.
HRMS (ESI+): calcd for C24H24N2O + H+, 357.1961; found,
357.1965. Elemental analysis Calcd (%) for C24H24N2O (356.4): C,
80.87; H, 6.79; N, 7.86. Found: C, 80.74; H, 6.91; N, 7.91.
1
162 °C. H NMR (400 MHz, C6D6): δ = 7.49−7.09 (m, 10H, CH,
phenyl), 6.67 (s, 1H, CHC), 3.73 (hept, JHH = 6.6 Hz, 1H,
NCH(CH3)2), 2.96−3.21 (m, 2H, N−CH, cyclohexyl), 2.25 (dp, JHH
= 13.3, 6.7 Hz, 2H, Al-CH2CH), 1.57−1.89 (m, 10H, N−CH−CH2),
N−CH-CH2−CH2), 1.38 (d, JHH = 6.5 Hz, 12H, Al-CH2−CHMe2),
1.22−1.52 (m, 8H, N−CH-CH2−CH2 and N−CH-CH2−CH2−
CH2), 1.04−1.20 (m, 2H, N−CH-CH2−CH2−CH2), 1.15 (d, JHH
=
6.7 Hz, 6H, NCH(CH3)2), 0.10−0.53 (m, 4H, Al−CH2). 13C{1H}
NMR (100 MHz, C6D6): δ = 164.8 (N-C-N), 142.3 (CCH), 139.5
and 133.2 (ipso-C), 130.5, 129.1, 128.6, 127.4, and 127.3 (CH of
phenyl), 124.1 (CCH), 54.4 (N-CH, cyclohexyl), 52.1
(NCH(CH3)2), 36.5 (N−CH-CH2), 29.1 (Al-CH2−CHMe2), 27.2
(Al-CH2−CH), 26.5 (N−CH-CH2−CH2), 26.1 (N−CH-CH2−
CH2−CH2), 23.9 (Al-CH2), 20.6 (NCHMe2). IR (CsI-plates, nujol,
cm-1): 3076 w, 3048 w, 3019 w, 2922 vs, 2853 vs, (nujol), 2668 w,
2594 w, 1622 s, ν(CN), 1612 m, 1595 s, 1456 vs, (nujol), 1375 s
(nujol), 1362s, 1344 w, 1312 s, 1260 s, 1248 s, 1209 s, 1173 m, 1146
m, 1125 m, 1084 s, 1072 s, 1053 s, 1028 m, 995 m, 935 w, 881 m,
866 m, 843 m, 791 m, 773 m, 760 s, 721 w, 696 s, 687 s, 664 m, 635
m, 606 w, 575 w, 505 m, 478 w, 442 w, 401 s, ν(AlC), ν(AlN). MS
(EI, 20 eV, 25 °C): m/z (%) = 528 (6), 527 (37), 526 (100) [M −
i-Bu]+, 471 (3) [M − i-Bu − Buten]+, 470 (9), 427, 346 (4), 290
(11), 237 (32), 222 (6), 125 (1). Elemental analysis Calcd (%) for
C38H58AlN3 (583.8): C, 78.17; H, 10.01; N, 7.20. Found: C, 78.08;
H, 9.91; N, 7.32.
2,3-Dicyclohexyl-1-(2,2-diphenylvinyl)-1-(iso-propyl)guanidine 8.
Ketenimine 1b (560 mg, 2.38 mmol, 1 equiv) was dissolved in 20
mL of dry n-hexane and treated with DIBAL-H (2.40 mL, 2.40
mmol, 1 M in n-hexane, 1 equiv) at −78 °C with stirring. Stirring
was continued for 4 h at −78 °C. Then, the reaction mixture was
slowly warmed to room temperature over 4 h. Dicyclohexylcarbo-
diimide 3 (491 mg, 2.38 mmol, 1 equiv) was added at room
temperature and stirring was continued for at least 12 h. The
reaction was quenched with NaOH-solution (2 M), and the organic
layer was washed twice with alkaline solution and brine and dried
over magnesium sulfate. The solvent was removed under reduced
pressure; then the crude product was purified by recrystallization
from DMSO (573 mg, 1.29 mmol, 55%) as colorless crystals (mp
3-Cyclohexyl-1-(2,2-diphenylvinyl)-1-isopropylurea 10b. From
ketenimine 1b (373 mg, 1.59 mmol) and cyclohexyl isocyanate 9b
(198 mg, 1.59 mmol, 1 equiv) according to the general procedure F.
The crude reaction mixture was quenched with NaOH-solution (2
M). Subsequent column chromatography on Al2O3 (B, (V))
(cyclohexane/ethyl acetate, 12:1) gave the pure product (415 mg,
1.14 mmol, 72%) as colorless solid. Mp 99 °C. Colorless crystals
1
were obtained by recrystallization from DMSO. H NMR (600 MHz,
1
154 °C). H NMR (600 MHz, d8-toluene,): δ = 7.35−7.00 (m, 10H,
CD2Cl2): δ (ppm) = 7.24−7.38 (m, 10H, CH, phenyl), 6.33 (s, 1H,
CCH), 4.75 (d, JHH = 7.8 Hz, 1H, NH), 4.55 (hept, JHH = 6.9 Hz,
1H, NCH(CH3)2), 3.31−3.39 (m, 1H, NCH(CH2)5), 1.55−1.49 (m,
5H, CH2, cyclohexyl), 1.29−1.18 (m, 2H, CH2, cyclohexyl), 1.14 (d,
JHH = 6.9 Hz, 6H, NCH(CH3)2), 1.09−0.98 (m, 1H, CH2 of
cyclohexyl), 0.80−0.71 (m, 2H, CH2, cyclohexyl). 13C{1H} NMR
(150 MHz, CD2Cl2): δ = 154.7 (NH-CO), 141.9 (CCH),
140.5, 139.1(ipso-C), 130.1, 129.0, 128.9, 128.7, 128.5, and 128.3
(CH, phenyl), 124.6 (CCH), 49.7 (NCH(CH2)5), 48.2 (NCH-
(CH3)2), 33.9, 26.2, and 25.6 (CH2, cyclohexyl), 20.7 (CH(CH3)2).
IR (ATR, cm−1) = 3248 w, ν(NH), 3024 w, 2976 w, 2936 w, 2918
w, 2853 w, 1651 m, 1628 s, ν(CO), 1528 s, ν(CC), 1495 m,
CH, phenyl), 6.97 (s, 1H, NH), 6.42 (s, 0.4H, CHC), 6.37 (s,
0.6H, CHC), 4.24 (hept, JHH = 6.9 Hz, 0.6H, NCH(CH3)2), 3.41
(dp, JHH = 13.7, 6.8 Hz, 0.4H, NCH(CH3)2), 3.32−3.09 (m, 2H,
partially covered, N−CH−CH2 and N−CH, cyclohexyl), 2.86−2.74
(m, 1H, N−CH, cyclohexyl), 1.87−1.26 (m, partially covered, 12H,
N−CH-CH2−CH2 and N−CH−CH2), 1.34−0.62 (m, 13H, partially
covered, N−CH-CH2−CH2−CH2 and N−CH-CH2−CH2, NCH-
(CH3)2).* 13C{1H} NMR (160 MHz, d8-toluene): δ = 149.6 (N-C
N), 146.9 (CCH), 144.5 (ipso-C-CCH(0.4C)), 143.4 (ipso-C-
CCH), 140.7 and 141.0 (ipso-C-CCH(0.6C)), 129.6 (0.4C, C
CH), 130.5 and 131.3 (CH, phenyl), 128.5, 128.4, 128.3, and 128.2
J
DOI: 10.1021/acs.joc.5b00466
J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
1445 m, 1398 m, 1315 m, 1277 s, 1256 s, 1233 s, 1184 m, 1144 w,
1132 w, 1125 w, 1074 m, 868 m, 764 m, 696 s, 637 m. HRMS
(ESI+): calcd for C24H30N2O + Na+, 385.2250; found:, 385.2250.
Elemental analysis Calcd (%) for C24H30N2O (362.5): C, 79.52; H,
8.34; N, 7.73. Found: C, 79.14; H, 8.22; N, 7.76.
isocyanate 9a (256 mg, 2.15 mmol, 2.0 equiv) according to the
general procedure F. The crude reaction mixture was quenched with
NaOH-solution (2 M). Subsequent column chromatography (n-
pentane/ethyl acetate, 10:1) gave the pure product (261 mg, 0.55
mmol, 50%) as colorless solid. Mp 158 °C. Colorless crystals were
1
(3-((2,6-Diisopropylphenyl)imino)-2,2-diphenyl-1-(phenylimino)-
propoxy)-di(iso-butyl)aluminum 11. Ketenimine 1a (537 mg, 1.52
mmol) was treated dropwise with di(iso-butylaluminum hydride
(1.52 mL, 1.52 mmol, 1 M in n-hexane, 1.0 equiv) in 20 mL of dry
n-hexane at −78 °C with stirring. After 2 h stirring at −78 °C, the
mixture was slowly warmed to room temperature and stirred for
additional 2 h. Then, the reaction mixture was cooled to −78 °C,
and phenyl isocyanate 9a (198 mg, 1.67 mmol, 1.1 equiv) was added.
Stirring was continued for 1 h and then at room temperature for 2 h.
Colorless crystals (810 mg, 1.32 mmol, 87%) were obtained upon
obtained by recrystallization from ethyl acetate. H NMR (400 MHz,
CD2Cl2): δ (ppm) = 8.39 (s, 1H, NH), 7.49−6.99 (m, 18H, CH,
phenyl), 6.78−6.71 (m, 2H, CH, phenyl), 5.50 (s, 1H, CCH),
4.50 (sept, JHH = 6.8 Hz, 1H, CH(CH3)2), 1.34 (d, JHH = 6.8 Hz,
6H, CH(CH3)2). 13C{1H} NMR (100 MHz, CD2Cl2): δ = 158.6 (N-
CO), 152.0 (NH-CO), 141.0 (CCH), 139.6 138.9, 138.8, and
138.2 (ipso-C), 129.9, 129.8, 129.3, 129.1, 128.8, 128.7, 128.6, 128.5,
128.3, 127.5, and 123.6 (CH, phenyl), 122.0 (CCH), 120.3 (CH,
phenyl), 51.4 (CH(CH3)2), 20.5 (2C, CH(CH3)2). IR (ATR, cm−1)
= 3269 w, 3239 w, ν(NH), 3061 w, 3034 w, 2991 w, 2968 w, 1702 s,
ν(CO), 1651 m, 1590 s, ν(CO), 1549 s, ν(CC), 1490 m,
1436 m, 1300 m, 1271 m, 1229 s, 1178 m, 1118 w, 1089 m, 1028 w,
895 m, 757 s, 723 m, 693 s, 658 w, 626 w, 584 m. HRMS (ESI+):
calcd for C31H29N3O2 + Na+, 498.2152; found, 498.2157. Elemental
analysis Calcd (%) for C31H29N3O2 (475.5): C, 78.29; H, 6.15; N,
8.84. Found: C, 78.09; H, 6.25; N, 8.78.
1-Cyclohexyl-1-(cyclohexylcarbamoyl)-3-(2,2-diphenylvinyl)-3-
isopropylurea 13b. From ketenimine 1b (508 mg, 2.01 mmol) and
cyclohexyl isocyanate 9b (502 mg, 4.01 mmol, 2.0 equiv) according
to the general procedure F. The crude reaction mixture was
quenched with NaOH-solution (2 M). Subsequent column
chromatography (n-pentane/ethyl acetate, 5:1) gave the pure product
(412 mg, 0.84 mmol, 42%), as colorless solid. Mp 136 °C. Colorless
crystals were obtained by recrystallization from ethyl acetate. 1H
NMR (400 MHz, CD2Cl2): δ (ppm) = 7.38−7.18 (m, 10H, CH,
phenyl), 6.29 (s, 1H, CCH), 5.05 (d, JHH = 7.7 Hz, 1H, NH),
4.29 (sept, JHH = 6.9 Hz, 1 H, NCH(CH3)2), 3.54−3.34 (m, 2H,
NCH(CH2)5), 1.84−1.54 (m, 10H, CH2, cyclohexyl), 1.37−0.87 (m,
16H, CH(CH3)2, CH2, cyclohexyl). 13C{1H} NMR (100 MHz,
CD2Cl2): δ = 158.5 (N(i-Pr)CO), 155.3 (NH-CO), 142.2 (C
CH), 139.2 and 137.3 (ipso-C), 130.2, 129.0, 128.7, 128.6, 128.5,
128.3 and 128.1(CH, phenyl), 124.2 (CCH), 60.2 (NCH(CH2)5),
51.3 (NCH(CH3)2), 50.0 (NCH(CH2)5), 33.6, 31.3, 27.3, 26.2, 26.1,
and 25.5 (CH2, cyclohexyl), 20.7 (2C, CH(CH3)2). IR (ATR, cm−1)
= 3315 m, ν(NH), 3061 w, 3034 w, 2974 w, 2935 m, 2851 m, 1628
s, ν(CO), 1528 s, ν(CC), 1496 m, 1444 m, 1398 m, 1315 m,
1250 m, 1235 m, 1186 m, 1074 m, 869 m, 765 m, 752 m, 696 s, 639
w, 607 m. HRMS (ESI+): calcd for C31H41N3O2 + Na+, 510.3091;
found, 510.3097. Elemental analysis Calcd (%) for C31H41N3O2
(487.7): C, 76.35; H, 8.47; N, 8.62. Found: C, 76.23; H, 8.47; N,
8.63.
1-(2,2-Diphenylvinyl)-1-isopropyl-3-(p-tolyl)-3-(p-
tolylcarbamoyl)urea 13c. From ketenimine 1b (295 mg, 1.17
mmol) and p-tolyl isocyanate 9c (310 mg, 2.33 mmol, 2.0 equiv)
according to general procedure F. The crude reaction mixture was
quenched with NaOH-solution (2 M). Subsequent column
chromatography (n-pentane/ethyl acetate, 15:1) gave the pure
product (282 mg, 0.56 mmol, 48%) as colorless solid. Mp 170 °C.
Colorless crystals were obtained by recrystallization from ethyl
acetate. 1H NMR (300 MHz, CD2Cl2): δ (ppm) = 8.25 (s, 1H,
NH), 7.32−7.19 (m, 10H, CH, phenyl), 7.11−7.04 (m, 4H, CH,
phenyl), 7.02−6.97 (m, 2H, CH, phenyl), 6.77−6.74 (m, 2H, CH,
phenyl), 5.51 (s, 1H, CCH), 4.48 (sept., JHH = 6.9 Hz, 1H,
CH(CH3)2), 2.44 (s, 3H, ipso-C(CH3)), 2.30 (s, 3H, ipso-C(CH3)),
1.31 (d, JHH = 6.9 Hz, 6H, CH(CH3)2). 13C{1H} NMR (75 MHz,
CD2Cl2): δ = 158.6 (N(i-Pr.)CO), 152.2 (NH-CO), 141.0
(CCH), 138.6, 138.2, 137.4, 137.0, 136.2, and 133.2 (ipso-C),
129.8, 129.5, 129.4, 129.0, 128.7, 128.6, 128.5, 128.3, and 128.2 (CH,
phenyl), 122.3 (CCH), 120.3 (CH, phenyl), 51.3 (CH(CH3)2),
21.4 (ipso-CMe), 21.0 (ipso-C(CH3), 20.5 (CH(CH3)2). IR (ATR,
cm−1) = 3293 s br, ν(NH), 3059 w, 3030 w, 2967 w, 2942 w, 1707
s, ν(CO), 1644 m, ν(CO), 1590 s, 1540 s, ν(CC), 1510 s,
1434 m, 1407 m, 1311 m, 1299 m, 1273 m, 1231 m, 1180 m, 1170
m, 1116 m, 1082 m, 1027 w, 889 m, 821 m, 771 m, 762 s, 740 m,
697 s, 666 m, 598 w. HRMS (ESI+): calcd. for C33H33N3O2 + H+,
1
concentration of the reaction mixture at −20 °C. Mp 144 °C. H
NMR (400 MHz, C6D6): δ = 8.21 (s, 1H, CHN), 7.47−7.38 (m,
5H, CH, phenyl), 7.26−7.19 (m, 2H, CH, phenyl), 7.18−6.99 (m,
8H, CH, phenyl), 6.96−6.88 (m, 3H, CH, phenyl), 2.84 (dh, JHH
=
13.3, 6.6 Hz, 2H, CH(CH3)2), 1.92 (dp, JHH = 13.4, 6.7 Hz, 2H, Al-
CH2−CH), 1.28−1.16 (m, 6H, CH(CH3)2), 1.05 (d, JHH = 6.5 Hz,
6H, Al-CH2−CH−CH3), 0.98 (d, JHH = 6.5 Hz, 6H, Al-CH2−CH−
CH3), 0.90−0.76 (m, 6H, CH(CH3)2), −0.01 (qd, JHH = 14.0, 7.3
Hz, 4H, Al−CH2). 13C{1H} NMR (100 MHz, C6D6): δ = 185.6
(ipso-C-NCH), 159.6 (ipso-C-NC-O), 149.2 (ipso-C-NC−O),
142.0 (ipso-C), 141.8 (ipso-C(i-Pr.)2), 141.6 (ipso-C-NCH), 130.3,
129.0, 128.8, 128.4, 128.2, 124.9, 123.8, and 123.1 (CH, phenyl),
66.5 (CPh2), 28.5 (CH(CH3)2), 28.4 (Al-CH2−CHMe2), 26.5
(CH(CH3)2), 26.4 (Al-CH2−CH), 23.6 (CH(CH3)2), 21.6 (Al-
CH2). IR (CsI-plates, nujol, cm−1): 3993 m, 3850 m, 3645 w, 2953−
2849 vs, (nujol), 2720 m, 2704 m, 2666 w, 2644 m, 2602 m, 1948
m, 1892 m, 1867 m, 1800 m, 1645 m, ν(CN), 1611 m, 1516 s,
1447 s, 1435 s, 1354 s, 1339 w, 1304 w, 1292 w, 1273 w, 1153 m,
1057 w, 1003 w, 968 m, 926 m, 907 m, 837 m, 806 m, 772−723 s,
(nujol), 694 s, 679 m, 652 w, 637 w, 608 w, 559 m, 542 w, 517 m,
451 w, 428 w, 401 w, ν(AlC), ν(AlN). MS (EI, 20 eV, 25 °C): m/z
(%) = 557 (12) [M − i-Bu]+, 439 (15), 438 (47), 356 (22), 355
(80) [M − i-Bu2Al − PhCNO + H]+, 271 (8), 269 (12) [PhCN-
Ph2]+, 189 (15) [M − i-Bu2Al − PhCNO-Ph2 + H]+, 188 (100) [M
− i-Bu2Al − PhCNO-Ph2]+, 172 (10), 168 (11), 167 (12), 165 (15),
146 (71), 131 (9), 130 (15), 119 (35) [PhNCO]+, 91 (9), 43 (22),
42 (10). Elemental analysis Calcd (%) for C41H51AlN2O (614.8): C,
80.09; H, 8.36; N, 4.56. Found: C, 79.66; H, 8.39; N, 4.46.
3-((2,6-Diisopropylphenyl)imino)-N,2,2-triphenylpropanamide
12. From ketenimine 1a (382 mg, 1.08 mmol) and phenyl
isocyanate 9a (143 mg, 1.2 mmol) according to the general
procedure F. The crude reaction mixture was quenched with NaOH-
solution (2 M). Subsequent column chromatography (n-pentane/
ethyl acetate, 100:1) gave the pure product (451 mg, 0.95 mmol,
88%), as colorless solid (mp 168 °C). Colorless crystals were
obtained by recrystallization from a mixture of solvents (n-pentane/
1
ethyl acetate, 1:1). H NMR (400 MHz, CD2Cl2): δ (ppm) = 11.87
(s, 1H, NH), 8.11 (s, 1H, CHN), 7.66 (dd, JHH = 8.6, 1.1 Hz, 2H,
CH, phenyl.), 7.48−7.37 (m, 10H, CH, phenyl.), 7.37−7.32 (m, 2H,
CH, phenyl.), 7.18−7.08 (m, 4H, CH, phenyl), 2.75 (hept, JHH = 6.8
Hz, 2H, CH(CH3)2), 1.08 (d, JHH = 6.9 Hz, 12H, CH(CH3)2).
13C{1H} NMR (100 MHz, CD2Cl2): δ =169.4 (CO), 169.1
(CHN), 146.5 (ipso-C-NCH), 140.8 (ipso-C-NH), 139.0 (ipso-
C), 138.9 (ipso-C−CH(CH3)2, 130.1, 129.2, 128.5, 125.9, 124.8,
123.8, and 120.6 (CH, phenyl), 66.3 (C-CO), 28.4 (CH(CH3)2),
23.9 (CH(CH3)2). IR (ATR, cm−1) = 3309 w, ν(NH), 3069 w, 3030
w, 2965 m, 2926 w, 2868 w, 1684 s, ν(CO), 1647 m, ν(CN),
1599 m, 1558 s, 1543 w, 1489 s, 1443 s, 1312 s, 1260 s, 1217 w,
1177 w, 1121 w, 1103 m, 1043 w, 1032 w, 1005 w, 962 w, 912 m,
885 m, 835 w, 806 s, 777 m, 752 s, 692 s, 673 w, 660 w. HRMS
(ESI+): calcd for C33H34N2O + H+, 475.2744,; found, 475.2732.
Elemental analysis Calcd (%) for C33H34N2O (474.6): C, 83.51; H,
7.22; N, 5.90. Found: C, 83.12; H, 7.26; N, 5.78.
1-(2,2-Diphenylvinyl)-1-isopropyl-3-phenyl-3-(phenylcarbamoyl)-
urea 13a. From ketenimine 1b (272 mg, 1.07 mmol) and phenyl
K
DOI: 10.1021/acs.joc.5b00466
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The Journal of Organic Chemistry
Article
504.2646; found, 504.2640. Elemental analysis Calcd (%) for
C33H33N3O2(503.6): C, 78.70; H, 6.60; N, 8.34. Found: C, 78.42;
H, 6.78; N, 8.08.
dry n-hexane (20 mL). After 2 h stirring at −78 °C, the solution was
allowed to warm to room temperature and was stirred for 12 h. The
second ketenimine 1e or 1b (1 equiv) was added at −78 °C and
stirring was continued for 2 h. The solution was warmed to room
temperature and quenched with saturated Na2CO3-solution. The
organic layer was washed twice with saturated Na2CO3-solution and
brine and dried over magnesium sulfate. The solvent was removed
under reduced pressure. Then, the crude product was purified by
column chromatography and/or recrystallization for X-ray analysis.
((1-Cyclohexylidene-3-(cyclohexylimino)-2,2-diphenylpropyl)(p-
tolyl)amino)-di(iso-butyl)aluminum 18. From ketenimine 1c (270
mg, 0.98 mmol) and N-(cyclohexylidenemethylene)-4-methylaniline
1d (195 mg, 0.98 mmol) in 20 mL of n-hexane at −78 °C after
stirring for 2 h and then at room temperature for 12 h according to
the general procedure G, but without aqueous workup. Yellow solid
(225 mg, 0.36 mmol, 37%) was obtained upon concentration of the
reaction mixture. Mp 157 °C. Yellow sensitive crystals were obtained
by recrystallization from cyclopentane at −20 °C. 1H NMR (500
MHz, C6D6, 343 K): δ = 7.59−7.50 (m, 5H, partially covered, CH,
phenyl and CHN), 7.23−7.18 (m, 4H, CH, phenyl), 7.13−7.08
(m, 2H, CH, phenyl), 6.81−6.77 (m, 2H, CH, phenyl), 6.28−6.24
(m, 2H, CH, phenyl), 3.66−3.73 (m, 1H, N−CH, cyclohexyl), 2.33−
2.18 (m, 4H, partially covered, Al-CH2−CHMe2 and CH2,
cyclohexyl), 1.89−1.80 (m, 4H, CH2, cyclohexyl), 2.10 (s, 3H,
ipso-C−CH3), 1.46−1.19 (m, 21H, partially covered, Al-CH2−
CHMe2 and CH2, cyclohexyl), 0.77−0.65 (m, 2H, CH2, cyclohexyl),
1.06−0.99 (m, 2H, CH2, cyclohexyl), 0.62−0.49 (m, 5H, partially
covered, Al−CH2 and CH2,cyclohexyl). 13C{1H} NMR (125 MHz,
C6D6, 343 K): δ = 175.2 (CHN), 153.4 (ipso-C−N-Al), 140.7
(Al−N-CCc‑hex), 140.1 (ipso-C), 130.0 (ipso-C-CH3), 129.8, 129.4,
128.3 (CH, phenyl), 125.3 (Al−N−CCc‑hex.), 119.3 (CH, phenyl),
67.2 (spiro-C), 62.1 (Al−N-CH, cyclohexyl), 34.1, 33.2, and 32.0
(CH2, cyclohexyl), 29.2 (Al-CH2−CHMe2), 28.8 (CH2, cyclohexyl),
27.1 (2C, Al-CH2−CH), 26.8, 26.6, 25.9, 25.5, 25.2 (CH2,
cyclohexyl), 20.5 (ipso-C-CH3). IR (CsI-plates, nujol, cm-1): 3451
w, 2949−2848 vs, (nujol), 2754 w, 2719 w, 2657 w, 2609 w, 2333 w,
1651 s, ν(CN), 1577 s, ν(CC), 1454 s, (nujol), 1446 s, 1373 s,
1276 w, 1157 w, 1087 w, 1033 s, 1026 s, 891 w, 813 w, 719 s, 516 s,
460 s, 401 s, ν(AlC), ν(AlN). MS (EI, 30 eV, 25 °C): m/z (%) =
477 (20), 476 (54) [M − (i-Bu)2Al + H]+, 400 (7), 399 (23), 393
(14), 367 (18), 365 (24), 338 (6), 309 (8), 283 (35), 277 (59)
[Ph2C + CNC6H12 + H]+, 260 (33), 234 (21), 217 (53), 216
(100) [(Me)PhN + CNC6H12 + H]+, 200 (48), 193 (40), 167
(25), 165 (15), 110 (18), 107 (62), 91 (15), 83 (7).
1-(2,2-Diphenylvinyl)-1-isopropyl-3-phenylthiourea 15. From
ketenimine 1b (275 mg, 1.09 mmol) and phenyl isothiocyanate 14
(294 mg, 2.18 mmol, 2.0 equiv) according to general procedure F.
The crude reaction mixture was quenched with NaOH-solution (2
M). Subsequent column chromatography (n-pentane/ethyl acetate,
15:1) gave the pure product (264 mg, 0.71 mmol, 65%) as yellow
1
solid. Mp 109 °C. H NMR (300 MHz, CD2Cl2): δ (ppm) = 7.61
(s, 1H, NH), 7.44−7.06 (m, 13H, CH, phenyl), 6.91−6.81 (m, 2H,
CH, phenyl), 6.41 (s, 1 H, CCH), 5.70 (hept, JHH = 6.8 Hz, 1H,
NCH(CH3)2), 1.29 (d, JHH = 6.8 Hz, 6H, CH(CH3)2). 13C{1H}
NMR (75 MHz, CD2Cl2): δ = 180.6 (CS). 143.0(CCH), 140.7,
139.7 and 137.9, (ipso-C), 129.5, 129.0, 128.9, 128.8, 128.7, 128.6,
126.2, and 126.1 (CH, phenyl), 122.1 (CCH), 53.4 (NCH-
(CH3)2), 20.3 (CH(CH3)2). IR (ATR, cm−1) = 3193 w, ν(NH),
3176 w, ν(NH), 3106 w, 3055 w, 3023 w, 2969 w, 1591 m, 1528 m,
ν(CC), 1496 m, 1449 m, 1418 s, 1357 m, 1317 m, 1253 s, δ(C
S), 1179 m, 1157 m, 1119 m, 1079 w, 1044 m, 1026 m, 854 m, 759
s, 733 m, 690 s, 642 m, 616 w, 582 m. HRMS (ESI+): calcd. for
C24H24N2S + H+, 373.1733; found, 373.1732. Elemental analysis
Calcd (%) for C24H24N2S (372.53): C, 77.38; H, 6.49; N, 7.52.
Found: C, 77.24; H, 6.59; N, 7.47.
(3-((2,6-Diisopropylphenyl)imino)-N,2,2-triphenylpropanethioa-
mido)-di(iso-butyl)aluminum 16. From ketenimine 1a (1.06 g, 2.99
mmol) and phenyl isothiocyanate 14 (441 mg, 3.26 mmol, 1.1
equiv) in 25 mL of n-hexane at −78 °C with stirring for 2 h and
then at room temperature for 2 h according to the general procedure
F. Red crystals (648 mg, 1.59 mmol, 53%) were obtained upon
concentration of the reaction mixture and by recrystallization from n-
1
hexane and toluene at −20 °C. Mp 170 °C. H NMR (400 MHz,
C6D6): δ = 8.99 (s, 1H, CHN), 7.67−7.62 (m, 4H, CH, phenyl),
7.61−7.51 (m, 4H, CH, phenyl), 7.44−7.22 (m, 9H, CH, phenyl),
7.14 (pseudos, 1H, CH, phenyl), 3.14 (hept, JHH = 6.6 Hz, 2H,
CHMe2), 1.85−1.69 (m, 2H, Al-CH2CH), 1.49 (d, JHH = 6.7 Hz,
6H,CH(Me)2), 1.20 (d, JHH = 6.8 Hz, 6H, CHMe2), 1.06 (d, JHH
=
6.4 Hz, 6H, Al-CH2−CHMe2), 0.96 (d, JHH = 6.6 Hz, 6H, Al-CH2−
CHMe2), 0.02 (dd, JHH = 14.1, 8.5 Hz, 2H, Al−CH2), −0.30 (dd,
JHH = 14.1, 5.7 Hz, 2H, Al−CH2). 13C{1H} NMR (100 MHz, C6D6):
δ = 206.4 (SC), 190.7 (CHN), 148.8 (ipso-C-N(SC)), 145.2
(ipso-C.), 142.2 (ipso-C-NCH), 141.7 (ipso-C-CHMe2), 130.6,
129.4, 129.0, 128.6, 128.1, 128.0, 126.3, and 125.0 (CH, phenyl),
72.7 (Ph2C), 29.0 (Al-CH2−CHMe2), 28.5 (CHMe2), 27.7 (Al-
CH2−CHMe2), 26.6 (CHMe2), 26.0 (Al-CH2−CH), 23.4 (CHMe2),
22.2 (Al-CH2). IR (CsI-plates, nujol, cm−1): 3630 m, 3616 m, 2951−
2852 vs, (nujol), 2723 s, 2669 m, 2603 m, 2341 m, 1951 w, 1888 w,
1805 w, 1616 m, ν(CN), 1595 m, 1462 s, (nujol), 1377 s, 1344
m, 1307 w, 1155 w, 1041 s, δ(CS), 1026 s, 931 w, 912 w, 858 m,
804 w, 779 m, 748 m, 723 s, (nujol), 623 w, 551 m,528 m, 505 w,
453 s, 447 s, 422 w, 401s, ν(AlC), ν(AlN). MS (EI, 20 eV, 150 °C):
m/z (%) = 573 (13) [M − i-Bu]+, 495 (22), 382 (17), 355 (99) [M
− i-Bu2Al − PhCNS + H]+, 269 (4), 188 (100) [M − i-Bu2Al −
PhCNS − CPh2]+, 167 (13) [Ph2C]+, 146 (65), 135 (63)
[PhCNS]+, 91 (3), 77 (9), 56 (5). Elemental analysis Calcd (%)
for C41H51AlN2S (630.90): C, 78.05; H, 8.15; N, 4.44. Found: C,
77.99; H, 8.15; N, 4.38.
3-((2,6-Diisopropylphenyl)imino)-N,2,2-triphenylthiopropana-
mide 17. From ketenimine 1a (580 mg, 1.64 mmol) and phenyl
thioisocyanate 14 (330 mg, 2.43 mmol) according to the general
procedure F. The crude reaction mixture was quenched with NaOH-
solution (2 M). Subsequent column chromatography (n-pentane/
ethyl acetate, 100:1) did not lead to pure product, but inseparable
mixtures of compounds were obtained. A few single crystals suitable
for X-ray were obtained by recrystallization from a mixture of
solvents (n-pentane/ethyl acetate, 1:1).
2,6-Diisopropyl-N-((1-((E)-1-(isopropylimino)-2,2-diphenylethyl)-
cyclohexyl)-methylene)aniline (19a). From ketenimine 1e (1.48 g,
5.52 mmol) and ketenimine 1b (1.30 g, 5.52 mmol), according to
the general procedure G. Subsequent column chromatography on
alumina B. act. I (cyclohexane/TBME, 200:1) gave the pure product
(1.14 g, 2.25 mmol, 41%) as colorless solid. Colorless crystals were
obtained by recrystallization from n-pentane/diethyl ether (1:1). Mp
1
149 °C. H NMR (400 MHz, C6D6): δ (ppm) = 7.71 (s, 1H, CH
N), 7.36−7.27 (m, 3H, CH, phenyl), 7.27−7.21 (m, 3H, CH,
phenyl), 7.19−7.08 (m, 6H, CH, phenyl), 7.04 (dd, 1H, JHH = 8.5,
6.7 Hz, CH, phenyl), 3.74 (hept, 1H, JHH = 5.9 Hz, NCH(CH3)2),
5.64 (s, 1H, CHPh2), 3.20 (hept, 2H, JHH = 5.9 Hz, CH(CH3)2),
2.10−1.93 (m, 4H, C(CH2)2(CH2)2CH2), 1.73−1.51 (m, 5H,
partially covered, C(CH2)4CHH and C(CH2)2(CH2)2CH2), 1.36−
1.24 (m, 1H, partially covered, C(CH2)4CHH), 1.15 (d, JHH = 6, 9
Hz, 12H, CH(CH3)2), 0.69 (d, JHH = 5.9 Hz, 6H, NCH(CH3)2).
13C{1H} NMR (100 MHz, C6D6): δ = 171.7 (CHN), 168.8 (C
NCH(CH3)2), 149.9 (ipso-C-N), 141.6 (ipso-C-CH.), 138.2 (ipso-C−
CH(CH3)2), 129.9, 128.9, 127.0, 124.1, and 123.2 (CH, phenyl),
55.8 (C(CH2)5), 53.8 (CHPh2), 52.2 (NCH(CH3)2), 32.4 (partially
covered, C(CH2)2(CH2)2CH2 and C(CH2)2(CH2)2CH2), 27.9 (CH-
(CH3)2), 26.2 (partially covered, C(CH2)4CH2 and C-
(CH2)2(CH2)2CH2), 23.7 (CH(CH3)2), 23.1 (NCH(CH3)2), 23.0
(C(CH2)2). IR (ATR, cm−1) = 3089 w, 3040 w, 2967 s, 2936 s, 2864
m, 2860 m, 1636 s, ν(CN), 1601 m, 1539 w, 1495 m, 1452 s,
1439 s, 1379 m, 1362 m, 1339 m, 1321 m, 1256 w, 1179 m, 1150 m,
Reactions of Active Al/N Compounds 5 with Ketenimines
1. General Procedure G for the Synthesis of Diimines 19. A
solution of DIBAL-H (1 M in n-hexane, 1 equiv) was added to a
cooled (−78 °C) solution of the ketenimine 1b or 1e (1 equiv) in
L
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Article
1117 m, 1096 w, 1042 m, 991 m, 968 m, 935 m, 932 m, 880 m, 849
s, 843 s, 729 m, 698 s. HRMS (ESI+): calcd for C36H46N2 + H+,
507.3734; found, 507.3725. Elemental analysis Calcd (%) for
C36H46N2 (506.76): C, 85.32; H, 9.15; N, 5.53. Found: C, 85.26;
H, 9.14; N, 5.39.
(355.47): C, 84.47; H, 7.09; N, 3.94. Found: C, 84.21; H, 7.09; N,
4.04.
N-(2-Ethylbut-1-en-1-yl)-4-methyl-N-phenylbenzamide (20b).
From ketenimine 1f (1.22 g, 7.05 mmol) and 4-methylbenzoyl
chloride 2c (2.20 g, 15.2 mmol) after quenching with NaOH-
solution (2 M) according to the general procedure H. Subsequent
column chromatography (n-pentane/ethyl acetate, 100:1) gave the
pure product (460 mg, 1.57 mmol, 22%) as colorless liquid.1H NMR
(300 MHz, CD2Cl2): δ (ppm) = 7.49−7.39 (m, 2H, CH, phenyl).
7.38−7.09 (m, 7H, CH, phenyl), 6.09 (s, 1H, CHC), 2.37 (s, 3H,
CH3), 2.01 (dqd, JHH = 39.3, 7.6, 1.2 Hz, 4H, CH2CH3), 0.95 (t, JHH
= 7.5 Hz, 3H, CH2CH3), 0.76 (t, JHH = 7.6 Hz, 3H, CH2CH3);
13C{1H} NMR (75 MHz, CD2Cl2): δ = 170.9 (CO), 143.7 (ipso-
N-(1-Cyclohexyl-3-(isopropylimino)-2,2-diphenylpropylidene)-
2,6-diisopropyl-aniline (19b). From ketenimine 1b (972 mg, 4.13
mmol) and ketenimine 1e (1.11 g, 5.52 mmol) according to the
general procedure G. Subsequent column chromatography on
alumina B. act. I (cyclohexane/TBME, 10:1) gave the pure product
(550 mg, 1.08 mmol, 26%) as colorless solid. Mp 166 °C. Colorless
crystals were obtained by recrystallization from n-pentane/diethyl
1
ether (1:1). H NMR (400 MHz, CD2Cl2): δ (ppm) = 8.17 (s, 1H,
CHN), 7.52−7.46 (m, 4H, CH of phenyl), 7.42−7.25 (m, 6H,
CH, phenyl), 7.11−6.98 (m, 2H, CH, phenyl), 6.93 (dd, JHH = 8.3,
6.8 Hz, 1H, CH, phenyl), 3.25 (m, 1H, NCH(CH3)2), 2.90 (hept,
JHH = 6.7 Hz, 2H, CH(CH3)2), 2.34 (tt, JHH = 11.7, 2.3 Hz, 1H,
CH(CH2)5), 1.37−0.98 (m, 23H, NCH(CH3)2, CH(CH3)2, partially
covered, CH(CH2)2(CHH)2CH2 and CH(CH2)2CH2), 0.97−0.53
(m, 5H, partially covered, CH(CH2)4CH2, CH(CH2)2(CHH)2CH2)
and CH(CH2)2(CHH)2CH2). 13C{1H} NMR (100 MHz, CD2Cl2): δ
= 173.6 (CN), 163.7 (CHN), 146.5 (ipso-C-N), 140.5 (ipso-C),
134.9 (ipso-C−CH(CH3)2), 131.6, 128.2, 127.5, 122.8, and 122.3
(CH, phenyl), 71.0 (CPh2), 61.9 (NCH(CH3)2), 48.9 (CH(CH2)5),
30.9 (CH(CH2CH2)2CH2), 29.0 (CH(CH3)2), 27.2 (CH-
(CH2CH2)2CH2), 26.4 (CH(CH2CH2)2CH2), 24.2 (CH(CH3)2),
23.9 (NCH(CH3)2), 20.4 (CH(CH3)2). IR (ATR, cm−1) = 3059 w,
2962 s, 2929 s, 2864 m, 2852 m, 1670 s, ν(CN), 1653 s, ν(C
N), 1591 w, 1491 m, 1448 s, 1431 s, 1379 m, 1361 m, 1323 m, 1257
w, 1242 w, 1188 w, 1143 m, 1112 w, 1080 w, 1033 m, 974 m, 895
m, 840 w, 813 m, 756 s, 740 s, 704 vs. HRMS (ESI+): calcd for
C36H46N2 + H+, 507.3734; found, 507.3734. Elemental analysis Calcd
(%) for C36H46N2 (506.76): C, 85.32; H, 9.15; N, 5.53. Found: C,
85.18; H, 9.30; N, 5.43.
C-CH3), 142.9 (ipso-C), 141.1 (ipso-C-CO), 134.3 (CCH),
129.4, 129.1, 128.8, 126.5, and 126.1 (CH, phenyl), 124.5 (CCH),
26.4 (CH2CH3), 22.5 (CH2CH3), 21.7 (CH3), 12.6 (CH2CH3), 11.3
(CH2CH3), IR (ATR, cm−1) = 3012 w, 2967 w, 2945 w, 2878 w,
1649 s ν(CO), 1611 w, 1595 w, 1493 m, 1474 w, 1339 s, 1302 s,
1182 m, 1069 w, 876 w, 831 w, 633 s, 600 s. HRMS (ESI+): calcd
for C20H23NO + H+, 294.1852; found, 294.1848.
One-Pot Reactions of Hydroaluminated Ketenimines 1 with
Isocyanates 9 and Acid Chloride 2c. N-((2,2-Diphenylvinyl)-
(isopropyl)carbamoyl)-4-methyl-N-phenylbenzamide (21a). In
analogy to general procedure F, ketenimine 1b (514 mg, 2.18
mmol) was reacted with di(iso-butyl) aluminum hydride (2.18 mL,
2.18 mmol, 1 M in n-hexane, 1.0 equiv) in 20 mL of n-hexane at
−78 °C. Phenyl isocyanate 9a (258 mg, 2.18 mmol, 1 equiv) was
added at −78 °C and the mixture was stirred at this temperature for
1 h and then at room temperature for 24 h. Then, 4-methylbenzoyl
chloride 2c (0.77 g, 4.36 mmol) was added at room temperature.
The reaction mixture was quenched with saturated Na2CO3-solution.
Subsequent column chromatography (n-pentane/ethyl acetate, 20:1)
gave the pure product (464 mg, 0.98 mmol, 45%) as colorless solid.
Mp 150 °C. Colorless crystals were obtained by recrystallization
1
from DMSO. H NMR (400 MHz, CDCl3): δ (ppm) = 7.61−7.24
Reactions of Active Al/N Compounds with Acid Chlorides.
General Procedure H for the Synthesis of Enamides (N-Alkenyl-
amines) 20a and 20b. A solution of DIBAL-H (1 M in n-hexane, 1
equiv) was added to a cooled (−78 °C) solution of the ketenimine 1
(1 equiv) in dry n-hexane (5 mL per mmol). After 2 h stirring at
−78 °C, the reaction mixture was slowly warmed to room
temperature and then stirred for 2 h at room temperature. The
electrophiles (2.0 equiv) were added under ice-cooling or −78 °C
and stirring was continued for 4 h. The reaction was then quenched
with alkaline solution (NaOH). The organic layer was washed twice
with alkaline solution and brine and dried over magnesium sulfate.
The solvent was removed under reduced pressure, and then the
crude product was purified by column chromatography and/or
recrystallization for X-ray analysis.
(m, 12H, CH, phenyl), 7.20−7.00 (m, 5H, CH, phenyl), 6.45−6.35
(m, 2H, CH, phenyl), 6.34 (s, 1 H, CHC), 4.66 (hept, JHH = 6.6
Hz, 1H, NCH(CH3)2), 2.40 (s, 3H, CH3), 1.48 (d, JHH = 6.6 Hz,
6H, NCH(CH3)2). 13C{1H} NMR (100 MHz, CDCl3): δ = 171.2
(p-tolyl-CO), 156.3 (N2CO), 142.3 (ipso-C-CH3), 141.2 (CH
C), 140.6, 138.0, and 131.6 (ipso-C), 130.3, 129.8, 128.9, 128.8,
128.7, 128.5, 128.2, 128.1, 127.7, 127.4, and 126.6 (CH, phenyl),
124.5 (CHC), 51.7 (CH(CH3)2), 21.6 (CH3), 19.9 (CH3). IR
(ATR, cm−1) = 3024 w, 2984 w, 2874 w, 1668 s, ν(CO), 1626 m,
1605 m, 1574 w, 1549 w, 1495 m, 1445 m, 1408 m, 1319 m, 1265 s,
1207 s, 1180 s, 1150 m, 1125 w, 1074 w, 1034 w. HRMS (ESI+):
calcd for C32H30N2O2 + Na+, 497.2199; found, 497.2194. Elemental
analysis Calcd (%) for C32H30N2O2 (474.59): C, 80.98; H, 6.37; N,
5.90. Found: C, 80.79; H, 6.35; N, 5.97.
N-(2,2-Diphenylvinyl)-N-isopropyl-4-methylbenzamide (20a).
From ketenimine 1b (1.44 g, 6.11 mmol) and 4-methylbenzoyl
chloride 2c (1.89 g, 12.2 mmol) after quenching with NaOH-
solution (2 M) according to the general procedure H. Subsequent
column chromatography (n-pentane/DCM, 8:2) gave the pure
product (1.33 g, 3.76 mmol, 61%) as yellow solid. Mp 163 °C.
N-Cyclohexyl-N-((2,2-diphenylvinyl)(isopropyl)carbamoyl)-4-
methylbenzamide (21b). In analogy to general procedure F,
ketenimine 1b (502 mg, 2.13 mmol) was treated with di(iso-butyl)
aluminum hydride (2.13 mL, 2.13 mmol, 1 M in n-hexane, 1.0 equiv)
in 25 mL of n-hexane at −78 °C. Cyclohexyl isocyanate 9b (265 mg,
2.13 mmol, 1 equiv) was added with stirring at −78 °C for 1 h and
then at room temperature for 24 h. Then, 4-methylbenzoyl chloride
2c (329 mg, 2.13 mmol, 1 equiv) was added at room temperature.
The reaction mixture was quenched with saturated Na2CO3-solution.
Subsequent column chromatography (n-pentane/ethyl acetate, 50:1)
gave the pure product (318 mg, 0.66 mmol, 31%) as colorless solid.
Mp 148 °C. Colorless crystals were obtained by recrystallization
1
Yellow crystals were obtained by recrystallization from toluene. H
NMR (300 MHz, CD2Cl2): δ (ppm) = 7.36−7.06 (m, 8H, CH,
phenyl), 6.94 (pseudos, 4H, CH, phenyl), 6.68 (d, JHH = 6.4 Hz, 2H,
CH, phenyl), 6.49 (s, 1H, CCH), 4.77 (dq, JHH = 27.2, 13.4, 7.0
3
Hz, 1H, NCH(CH3)2), 2.27 (s, 3H, CH3), 1.40 (d, JHH = 6.8 Hz,
6H, NCH(CH3)2). 13C{1H} NMR (75 MHz, CD2Cl2): δ = 170.3
(CO), 142.2 (CCH), 140.3 (ipso-C-CH3), 138.7 (ipso-C), 134.4
(ipso-C-CO), 130.1, 128.7, 128.6, 128.5, 128.3, 128.1, and 127.6
(CH, phenyl), 124.4 (CCH), 48.7 (NCH(CH3)2), 21.6 (CH3),
20.9 (NCH(CH3)2). IR (ATR, cm−1) = 3049 w, 3018 w, 2984 w,
2968 w, 2916 w, 1614 s ν(CO), 1574 w, 1495 m, 1443 m, 1414 s,
1337 s, 1310 s, 1277 m, 1240 s, 1182 s, 1128 m, 1123 m, 1078 m,
1032 w, 1020 w, 964 w, 878 s, 827 m, 775 s, 745 s, 696 s, 640 s, 600
m, 581 m. HRMS (ESI+): calcd for C25H25NO + Na+, 378.1828;
found, 378.1834. Elemental analysis Calcd (%) for C25H25NO
1
from DMSO. H NMR (400 MHz, CD2Cl2): δ (ppm): = 7.57 (d,
JHH = 8.1 Hz, 2H CH, phenyl), 7.31−7.15 (m, 8H, CH, phenyl),
7.09 (m, 2H, CH, phenyl), 6.48 (d, JHH = 6.7 Hz, 2H, CH, phenyl),
6.15 (s, 1H, CCH), 4.13 (dt, JHH = 3.3, 11.8 Hz, 1H,
NCH(CH2)5), 3.57 (sept, JHH = 6.8, 13.2 Hz, 1H, NCH(CH3)2),
2.46 (s, 3H, p-tolyl−CH3), 1.12−1.80 (m, 10H, CH2 of cyclohexyl),
1.02 (d, JHH = 6.8 Hz, 6H, CH(CH3)2). 13C{1H} NMR (100 MHz,
CDCl3): δ = 170.1 (p-tolyl-CO), 156.6 (N2CO), 142.8 (ipso-C-
CH3), 142.5 (CCH), 138.4 and 135.0 (ipso-C), 130.2, 129.6,
M
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129.0, 128.7, 128.5, 128.3, and 128.1 (CH, phenyl), 125.8 (CCH),
58.1 (NCH(CH2)5), 53.5 (NCH(CH3)2), 31.0, 26.8, and 26.1 (CH2,
cyclohexyl), 21.8 (p-tolyl-CH3), 19.4 (CH(CH3)2). IR (ATR, cm−1)
= 3063 w, 3036 w, 3008 w, 2932 w, 2849 w, 1689 m, ν(CO),
1638 s, ν(CO), 1611 m, 1498 w, 1444 m, 1410 m, 1334 m, 1275
m, 1234 s, 1184 w, 1128 w, 1092 w, 1005 w, 881 m, 867 m, 834 m,
740 s, 723 m, 696 m, 646 w, 610 m. HRMS (ESI+): calcd for
C32H36N2O2 + H+, 481.2850; found, 481.2852. Elemental analysis
Calcd (%) for C32H36N2O2 (480.64): C, 79.96; H, 7.55; N, 5.83.
Found: C, 79.79; H, 7.58; N, 5.71.
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(19) Hellmann, J.; Rhotert, I.; Westenberg, H.; Frohlich, R.;
̈
Wibbeling, B.; Uhl, W.; Wurthwein, E.-U. Eur. J. Org. Chem. 2013,
ASSOCIATED CONTENT
* Supporting Information
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3356−3368.
S
(20) Hengesbach, F.; Jin, X.; Hepp, A.; Wibbeling, B.; Wurthwein,
̈
Experimental details (NMR-spectra and detailed X-ray data)
and quantum chemical DFT results. The Supporting
Information is available free of charge on the ACS
Publications website at DOI: 10.1021/acs.joc.5b00466.
E.-U.; Uhl, W. Chem.−Eur. J. 2013, 13901−13909.
(21) Schulte, N.; Moller, M. H.; Rodewald, U.; Wurthwein, E.-U.
̈
̈
Chem. Ber. 1994, 127, 1287−1293.
(22) Reed, A. E.; Weinstock, R. B.; Weinhold, F. J. Chem. Phys.
1985, 83, 735−746.
AUTHOR INFORMATION
Corresponding Author
*E-mail: wurthwe@uni-muenster.de. Fax: +49-251-8339772.
(23) Gaussian 09, Revision D.01; Frisch, M. J.; Trucks, G. W.;
Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.;
Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.; Nakatsuji,
H.; Caricato, M.; Li, X.; Hratchian, H. P.; Izmaylov, A. F.; Bloino, J.;
Zheng, G.; Sonnenberg, J. L.; Hada, M.; Ehara, M.; Toyota, K.;
Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao,
O.; Nakai, H.; Vreven, T.; Montgomery, J. A., Jr.; Peralta, J. E.;
Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin, K. N.;
Staroverov, V. N.; Kobayashi, R.; Normand, J.; Raghavachari, K.;
Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega,
N.; Millam, M. J.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.;
Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.;
Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Martin, R. L.;
Morokuma, K.; Zakrzewski, V. G.; Voth, G. A.; Salvador, P.;
■
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
Financial support from the Deutsche Forschungsgemeinschaft
(SFB 858) is gratefully acknowledged.
■
DEDICATION
■
Dedicated to Prof. Dr. Christian Reichardt at the occasion of
his 80th birthday.
̈
Dannenberg, J. J.; Dapprich, S.; Daniels, A. D.; Farkas, O.; Foresman,
J. B.; Ortiz, J. V.; Cioslowski, J.; Fox, D. J.; Gaussian, Inc.:
Wallingford, CT, 2009.
(24) Zhao, Y.; Truhlar, D. G. Theor. Chem. Acc. 2008, 120, 215−
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DOI: 10.1021/acs.joc.5b00466
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