Palladium-Based Hydroamination Catalysts Employing Sterically Demanding 3-Iminophosphines: Branched Kinetic Products by Prevention of Allylamine Isomerization

Article abstract of DOI:10.1021/acs.organomet.9b00025

A new allylpalladium triflate catalyst with a dimesitylphosphine moiety was synthesized, isolated, and characterized. The greatly increased steric bulk on the phosphine of this palladium catalyst inhibited product isomerization, which is often observed after hydroamination of terminal allenes with secondary amines. The considerably reduced rate of isomerization facilitated the isolation of many previously unknown branched allylamines, products that were inaccessible when using other, more active 3-iminophosphine palladium catalysts.

Full text of DOI:10.1021/acs.organomet.9b00025

Article
pubs.acs.org/Organometallics
Cite This: Organometallics XXXX, XXX, XXX−XXX
Palladium-Based Hydroamination Catalysts Employing Sterically
Demanding 3‑Iminophosphines: Branched Kinetic Products by
Prevention of Allylamine Isomerization
Rajendr S. Thakuri and Joseph A. R. Schmidt*
Department of Chemistry and Biochemistry, School of Green Chemistry and Engineering, College of Natural Sciences and
Mathematics, The University of Toledo, 2801 W. Bancroft Street, MS 602, Toledo, Ohio 43606-3390, United States
S
* Supporting Information
ABSTRACT: A new allylpalladium triflate catalyst with a dimesityl-
phosphine moiety was synthesized, isolated, and characterized. The
greatly increased steric bulk on the phosphine of this palladium catalyst
inhibited product isomerization, which is often observed after hydro-
amination of terminal allenes with secondary amines. The considerably
reduced rate of isomerization facilitated the isolation of many previously
unknown branched allylamines, products that were inaccessible when
using other, more active 3-iminophosphine palladium catalysts.
nisms available for the late transition metal, addition of
nitrogen to the central carbon atom is not observed.
Unsurprisingly, the more stable thermodynamic product is
usually produced, as seen with gold,6b,9 platinum,10 palla-
dium,11 copper,8a nickel,12 and other transition-metal cata-
lysts.6b Successful synthesis and isolation of the kinetic product
has been limited to very few catalysts, such as only those using
rhodium and palladium.4c,13 These branched products, bearing
a terminal vinyl group adjacent to a secondary or tertiary
carbon atom, are synthetically quite useful, and thus catalysts
capable of producing this isomer in isolable quantities remain
attractive goals in this field.
Given the usefulness of allylamines, our group has been
studying the hydroamination of allenes with primary and
secondary amines using 3-iminophosphine palladium com-
plexes over the past decade.4c,5f,6a,12,14 With respect to catalytic
hydroamination activity, we have studied the interrelationships
of the imine substituents, the ring size of the backbone, and the
phosphine substituents on these 3-iminophosphine ligands.14b
We previously reported that more electron-donating phos-
phines enhance the catalytic activity of their palladium
complexes.14b We also deduced that the electronics of the
imine substituent must be carefully optimized to maximize
catalytic activity.5f Furthermore, we showed that smaller
backbone ring sizes with decreased bite angles favor higher
catalytic activity by increasing the ring strain, an effect that
seems to be related to detaching the imine substituent from
palladium upon coordination of amines.14b,15 Throughout all
of our previous studies, relatively small phenyl and tert-butyl
groups were studied on the phosphine unit; so the effect of
sterically bulky phosphines has not been investigated. Herein,
we present the synthesis of sterically encumbered 3-
INTRODUCTION
■
Catalytic hydroamination is a green chemical method for the
production of new C−N bonds through the 100% atom-
economic addition of an amine to an alkene or alkyne. This
approach to creating C−N bonds can be used in the formation
of a variety of nitrogen-containing organic building blocks,1 but
a catalyst is necessary for hydroamination because of high
activation barriers and an unfavorable entropy term. Addition-
ally, [2 + 2] cycloaddition of an N−H bond and a C−C
unsaturated system is orbitally forbidden.2 So, a variety of
metals supported by a wide range of ligands have been used for
this reaction over the years.3 Hydroamination has been
successfully employed to regio- and enantioselectively yield
N-containing products as an economic means to synthesize
biologically active molecules or pharmaceuticals.3,4 With many
years of intense study, mechanistic analysis has enabled
chemists to decipher the critical steps in the relevant catalytic
cycles, leading to logical modulation of the ligands utilized in a
quest for the best catalytic process.5
One significant method to synthesize allylamines is through
the hydroamination of allenes with primary or secondary
amines.3,4c,6 Allylamines are useful building blocks in the
synthesis of heterocycles and complex bioactive molecules.7
Driven by this synthetic utility, there has been a substantial
interest in the hydroamination of allenes with various
transition-metal catalysts investigated to date.4c,8 The presence
of cumulated double bonds in an allene means that three
possible hydroamination regioisomeric products could be
produced, but only two regioisomers are expected to form
when using a late metal catalyst because of the operable
mechanisms. For a monosubstituted allene, a less stable kinetic
product is formed by addition of N to the substituted terminal
carbon of the 3-carbon cumulated system, whereas the
thermodynamic product is formed by addition of N to the
unsubstituted terminal carbon atom. Because of the mecha-
Received: January 17, 2019
© XXXX American Chemical Society
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a
Scheme 1. Synthesis of (3-Iminophosphine)palladium Triflate Complex
a
Legend: (i) 1.2 equiv mg, THF, 0 °C, 1 h and then RT. (ii) 0.45 equiv PCl3, THF, −78 °C and slow increase to RT. (iii) 1.5 equiv LiAlH4, Et2O,
0 °C and then RT. (iv) 1.1 equiv n-BuLi, Et2O, 0 °C and then RT. (v) Et2O, 0 °C for 1 h and then RT.
iminophosphine palladium complexes and the resulting impact
on product selectivity in their catalytic hydroamination of
allenes.
isomerization occurred, but unfortunately, many of the
substrates proved to have rapid enough isomerization reactions
that the amount of branched product never reached large
enough levels to warrant quenching and attempted isolation,
meaning that only the linear products were synthetically viable
in those cases. So, in the present investigation, we
hypothesized that by adding more steric bulk on the phosphine
fragment, we could enhance selectivity for the kinetic products
while simultaneously eliminating or reducing the relative rate
of isomerization of the kinetic products in the hydroamination
of monosubstituted allenes.
The desired sterically bulky ligand was synthesized similar to
our previously reported 3-iminophosphines, and its palladium
complex was produced in the usual fashion (Scheme 1).14b
Specifically, the Grignard reagent of mesityl bromide was
synthesized, and it was reacted with phosphorus trichloride to
make dimesitylchlorophosphine.16 After reduction with
LiAlH4,17 deprotonation with n-butyl lithium yielded lithium
dimesitylphosphide.17 Next, the ligand was assembled by the
reaction of dimesitylphosphide with the appropriate β-
chloroimine. The palladium precatalyst was then formed by
ligand coordination with allyl palladium chloride, followed by
salt metathesis with silver triflate.
Recrystallization of the final palladium complex from a
solution of tetrahydrofuran (THF) layered with pentane
resulted in X-ray quality crystals of the mesityl-substituted
catalyst, and its crystal structure was solved (Figure 1). As has
been the case with many of the related catalysts synthesized in
our group, the allyl group was disordered over two positions,
which we have previously termed the cis and trans isomers of
these complexes.15 In this case, refinement of the occupancy of
these allyl groups yielded a 56:44 ratio of the two isomers.
Despite the presence of the sterically bulky mesityl groups
bound to the phosphorus atom and flanking the metal center,
the ligand−metal bond lengths and the relevant bond angles
about the pseudo-square planar palladium center were near the
middle of the ranges found in related complexes and proved
unremarkable.6a,13a,14,15 As such, the unique reactivity
RESULTS AND DISCUSSION
■
3-Iminophosphine ligands have three permutable components:
the alicyclic ring, the imine substituent, and the phosphine
group. On the basis of our previous reports, we have observed
that the ligand containing a cyclobutenyl backbone, a tert-butyl
substituent on the imine, and ditert-butylphosphine provides
the palladium complex that is most effective in catalytic
hydroamination.4c,14b We also showed that the electron
donation provided by the imine group was critically important
for both the deprotonation of the amine substrate and the
hemilabile displacement of the imine from the active palladium
metal center.5f Hence, tuning of the electron donation of the
imine substituent is crucial for effective catalytic hydro-
amination.5f
Additionally, we reported the successful synthesis of kinetic
hydroamination products (addition of N- to the more
substituted terminal carbon of the allene) using a ditert-
butylphosphine-substituted catalyst for the hydroamination of
monosubstituted allenes with various secondary amines.4c
Unfortunately, a major drawback of this highly active system
was that the kinetic products isomerized quickly to produce
the thermodynamic products in the presence of the catalyst,
especially after the substrates were completely consumed.4c In
general, access to the branched kinetic hydroamination
products in this chemistry proves to be a question of relative
rates. The rate of hydroamination to yield the branched
products must be substantially larger than the rate of the
subsequent isomerization reaction converting these branched
products to the linear isomers. This is especially relevant as the
hydroamination reaction nears completion given the increasing
concentration of the product branched allylamine and the
decreasing concentrations of the initial substrates. In our
previous work,4c there were several substrates where we could
monitor and then quench the reaction before significant
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observed formation of the thermodynamic product exclusively
with pyrrolidine and piperidine, as has been the case with other
similarly slow catalysts we have investigated previously.5f,6a,12
Surprisingly, the reaction between cyclohexylallene and
morpholine using the mesitylphosphine catalyst, though
much slower than the tert-butylphosphine substituted ana-
logue, yielded a 47:53 ratio of the kinetic and thermodynamic
isomers after reaction completion at 14 h. This was the first
time we had observed a very slow catalysis (requiring many
hours to reach completion) that yielded anything other than
exclusively the linear (thermodynamic) isomers. Continued
observation of this reaction mixture revealed very slow
isomerization of the kinetic product into the thermodynamic
product in this sterically bulky system, taking nearly 3 days to
fully isomerize (Table 2). In our previous work,4c the kinetic
hydroamination products isomerized to the thermodynamic
products quite rapidly after reaction completion, yielding only
the linear products if the reaction was left unquenched for 1−2
h after hydroamination was complete. The slow isomerization
observed after nearly complete hydroamination with the
mesityl-substituted catalyst proved to be the case with many
substrate combinations, especially those with moderate
hydroamination reactivity (see the Supporting Information
file for detailed data). Because of the very slow isomerization
rates relative to the hydroamination rate, we set out to utilize
this catalyst system to isolate various branched products that
had proven untenable with our previously published highly
active catalysts.4c
Another substrate that we tested thoroughly in the past is
phenylallene, whose hydroamination with various secondary
amines and anilines met with only limited success using one of
our most active catalysts.4c For example, the reaction of
phenylallene with morpholine was so fast that both hydro-
amination and complete isomerization occurred within 10 min,
making it very challenging for us to isolate the kinetic product
in this reaction.4c The hydroamination of phenylallene with 1-
methylpiperazine, 1-(diphenylmethyl)piperazine, and various
substituted anilines also failed to yield the kinetic products.4c
In each of these cases, the isomerization rate was observed to
be very competitive with the hydroamination rate, and we were
unable to find a combination of catalyst loading and time point
Figure 1. Oak Ridge thermal ellipsoid plot diagram (50% thermal
ellipsoids) of the mesityl-substituted palladium complex. Hydrogen
atoms and disordered allyl carbon atoms have been omitted for
clarity. Selected bond lengths (in Å): Pd1−P1 = 2.3153(5), Pd1−N1
= 2.157(2), Pd1−C29 = 2.164(6), Pd1−C30 = 2.254(6). Bond angles
(in deg): P1−Pd1−N1 = 87.03(4), C29−Pd1−C30 = 65.7(3), N1−
Pd1−C29 = 114.5(2), N1−Pd1−C30 = 175.5(2), P1−Pd1−C29 =
158.3(2), P1−Pd1−C30 = 93.1(2).
displayed by this catalyst (as described below) must result
from the large area occupied by the mesityl groups near the
metal center rather than any significant changes in the ligand−
metal bond strengths. Thus, the main role of these mesityl
groups is likely in restricting access to palladium by substrates
within these catalytic reactions.
A few years ago, we showed that catalysts using tert-
butylphosphine substituents provided for the successful
synthesis and isolation of the kinetic (branched) products in
the hydroamination of cyclohexylallene with various secondary
amines, but we also observed that these kinetic products
quickly isomerized to their thermodynamically more stable
isomers when the reaction mixture was left unquenched after
reaction completion.4c As an initial screening of our new
mesityl-substituted catalyst, we tested the hydroamination of
cyclohexylallene with morpholine, pyrrolidine, and piperidine
(Table 1). Overall, the catalytic results using cyclohexylallene
were disappointing as catalysis was very slow (requiring 14−48
h to reach completion), taking substantially longer than our
previous report (reaching completion in 30−60 min for the
same substrates). Because of this long reaction time, we
a
Table 1. Hydroamination of Cyclohexylallene with Secondary Amines
entry
amine
time (h)
conversion (br:l)
1.1
1.2
1.3
morpholine
pyrrolidine
piperidine
14
48
46
95 (47:53)
95 (0:100)
95 (0:100)
a
br is branched allylamine (kinetic product) and l is linear allylamine (thermodynamic product).
C
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a
Table 2. Hydroamination Followed by Slow Isomerization of the Kinetic Product to the Thermodynamic Product
time (h)
conversion (%)
conversion (branched/linear)
1
2
4
6
18
26
42
59
72
88
95
95
95
95
95
95
95
95
50/50
50/50
48/52
47/53
47/53
47/53
47/53
43/57
40/60
34/66
27/73
15/85
8/92
8
11
14
20
24
30
36
48
60
72
0/100
a
Catalytic procedure: Reactions were carried out at 25 °C in NMR tubes prepared in a glovebox using benzene-d6 as the solvent (800 μL), catalyst
1
(0.025 mmol), secondary amine (0.50 mmol), and allene (0.50 mmol). Conversion was monitored by H NMR spectroscopy.
where quenching would allow a synthetically useful amount of
branched product to be isolated.4c Given the very slow
isomerization of the kinetic product to the thermodynamic
product observed using the mesityl catalyst above, we set out
to study the hydroamination of phenylallene with various
secondary amines and anilines in the hope that our new
sterically bulky catalyst would allow access to the elusive
kinetic products. Hydroamination of phenylallene with aniline
was very slow, taking several days and forming the
thermodynamic product only; however, we were pleased to
find that hydroamination of phenylallene with morpholine
produced almost entirely the kinetic product (the ratio of
kinetic to thermodynamic product was 92:8) and required only
30 min to reach completion (Table 3, entry 3.1). Moreover,
since the amount of isomerization product was minimal, the
kinetic product was readily isolated via column chromatog-
raphy. Similarly, we successfully isolated the kinetic products
from hydroamination of phenylallene with 2,6-dimethylmor-
pholine, 1-methylpiperazine, 1-(diphenylmethyl)piperazine,
indoline, and thiomorpholine (Table 3, entries 3.2−3.6).
Note that for each entry in Table 3, reactions were monitored
by nuclear magnetic resonance (NMR) spectroscopy, and the
data is reported at the time point at which 95% conversion of
the starting material was observed (with the corresponding
branched to linear ratios). In general, all of the reactions with
phenylallene proceeded at a moderate rate, reaching
completion within a few hours and producing primarily the
branched kinetic products. Similarly, kinetic products were
strongly favored in a series of three representative reactions to
test the hydroamination of p-fluorophenylallene (Table 3,
entries 4.1−4.3).
kinetic products in each of these reactions. Overall, hydro-
amination of n-hexylallene and n-butylallene was generally
complete within 2 to 3 h and usually gave >80% selectivity for
branched products. Furthermore, we also successfully carried
out hydroamination of 5-phenyl-1,2-pentadiene with morpho-
line, 2,6-dimethylmorpholine, and thiomorpholine to predom-
inantly yield their corresponding branched products (Table 3,
entries 7.1−7.3). Again, the reactions were complete within 1
to 3 h. All of these branched products were successfully
isolated by column chromatography.
To put the results displayed in Table 3 into proper context, a
comparison with our fastest and most effective hydroamination
catalyst to date is warranted. Table 4 shows the allene/amine
combinations that are present in both Table 3 and our
previous report.4c Because all entries with the mesityl catalyst
are reported at the time point in which 95% conversion was
achieved, it is clear that the rate of hydroamination with the
sterically hindered catalyst is generally slower than that
observed using the more active tert-butyl substituted ligand.
For example, in the hydroamination of phenylallene with
morpholine, it requires 30 min for the mesityl catalyst to reach
95% conversion (with a 92:8 branched to linear ratio), whereas
the same catalyst loading with the tert-butyl catalyst completes
not only the hydroamination step but also the isomerization in
just 10 min. For additional comparison data, see the
Supporting Information file. It also seems that the rate of
isomerization is much slower when employing the mesityl-
substituted species. If the mesityl catalyst effected isomer-
ization at the same rates as the tert-butyl catalyst, the branched
products would not be observed at all because they would be
isomerized almost as soon as they were produced, given that
hydroamination is so much slower with the mesityl catalyst.
Thus, the presence of the mesityl group in these catalysts
causes both the hydroamination and the subsequent isomer-
ization reactions to take place slower than in our previously
To expand the scope of this reaction, two aliphatic allenes
were also tested using the representative set of secondary
amines (Table 3, entries 5.1−5.3 and 6.1−6.2). Both n-
hexylallene and n-butylallene showed good selectivity for
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a
Table 3. Hydroamination of Allenes with Secondary Amines
a
Catalytic procedure: Reactions were carried out at 25 °C in NMR tubes prepared in a glovebox using benzene-d6 as the solvent (800 μL), catalyst
1
(0.025 mmol), secondary amine (0.50 mmol), and allene (0.50 mmol). Conversion was monitored by H NMR spectroscopy. Products were
subsequently isolated by column chromatography (see the Experimental Section for isolated yields).
a
Table 4. Comparison of Hydroamination Results Using Mesityl- and tert-Butyl-4c Substituted Ligands
t
allene
amine
conversion (br:l) (R* = Mes)
conversion (br:l) (R* = Bu)
phenylallene
morpholine
95 (92:8) (30 min)
95 (72:28) (1 min)
95 (5:95) (4 min)
95 (0:100) (10 min)
95 (0:100) (30 min)
95 (0:100) (3 h)
phenylallene
phenylallene
p-fluorophenylallene
N-methylpiperazine
N-(diphenylmethyl)piperazine
N-methylpiperazine
95 (74:26) (6.5 h)
95 (80:20) (2.5 h)
95 (91:9) (1 h)
95 (40:60) (1.5 h)
95 (0:100) (2 h)
a
Catalytic procedure: Reactions were carried out at 25 °C in NMR tubes prepared in a glovebox using benzene-d6 as the solvent (800 μL), catalyst
1
(0.025 mmol), secondary amine (0.50 mmol), and allene (0.50 mmol). Conversion was monitored by H NMR spectroscopy.
E
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reported tert-butyl analogues. Although this means that the
reactions are longer overall, these slower rates allow for much
more facile synthesis and isolation of the kinetic (branched)
products. This is evident in the straightforward isolation of the
branched product resulting from phenylallene and morpholine,
a reaction that almost fully isomerizes from branched to linear
products in the period between 1 and 4 min of reaction time
with the previously reported catalyst.4c The other three
comparative reactions show that the mesityl-substituted
catalyst allows access to other branched allylamines that were
difficult or impossible to isolate in our previous report.4c
On the basis of the kinetics experiments and a Hammett plot
analysis, we recently proposed a catalytic cycle explaining the
reactivity of (3-iminophosphine)palladium catalysts in the
hydroamination of monosubstituted allenes with secondary
amines (Scheme 2).5f In the first step, an amine substrate
the palladium center (via the principle of microscopic
reversibility), rotation of the allyl group to the opposite
orientation, and then reductive elimination to give the final
thermodynamic product. Thus, by using our bulky dimesityl-
phosphine substituent, it seems that this isomerization pathway
is almost completely inhibited.
CONCLUSIONS
■
A new 3-iminophosphine ligand with a sterically bulky
dimesitylphosphine group and its corresponding precatalyst
[3IPMesPd(allyl)]OTf were synthesized. The additional steric
bulk on the phosphine moiety of the ligand led to a
considerable decrease in the rate of isomerization of the
kinetic product to the thermodynamic product following
hydroamination of monosubstituted allenes with various
secondary amines. Although the overall catalysis was slower
than some of our previously published catalysts, the very slow
isomerization rates displayed by this new catalyst enabled the
successful isolation of branched, kinetic products in significant
amounts. Thus, despite its overall slower hydroamination
reaction rates, the new sterically bulky catalyst reported herein
provides a synthetically viable route for the production of
significant quantities of many branched allylamine hydro-
amination products. Additionally, several previously unattain-
able kinetic products were produced through the hydro-
amination of phenylallene and p-fluorophenylallene with
various secondary amines. Overall, this new mesityl catalyst
has allowed for the isolation of 13 new branched allylamine
products, several of which had previously proven impossible to
isolate using our related catalysts. Our laboratory continues to
pursue new catalysts with sufficient steric bulk to completely
shut down isomerization of the kinetic product to the
thermodynamic product while in turn still maintaining overall
acceptable hydroamination reaction rates.
Scheme 2. Catalytic Cycle5f Adapted to the Present
Sterically Bulky System
reacts with the 3-iminophosphine palladium precatalyst to
generate the active Pd(II) hydride complex, which enters the
catalytic cycle. After allene insertion, a substrate amine
coordinates with palladium by displacing the imine unit of
the ligand. Then, there is a proton transfer from the substrate
amine to the imine, followed by reductive elimination of the
kinetic product, regenerating the Pd(II) hydride catalyst.
Invoking this catalytic cycle, regiocontrol during hydro-
amination depends entirely on the orientation of the allene
during the insertion step. Of the two regioisomers, a forms the
kinetic product, whereas b gives the thermodynamic product
after reductive elimination (Figure 2). Thus, we believe that
the added sterics provided by the dimesitylphosphine group
restrict the orientation, which in turn inhibits the formation of
the thermodynamic product. Furthermore, in the cases where
isomerization occurs after reaction completion, we believe that
this is due to oxidative addition of the product allylamine to
EXPERIMENTAL SECTION
■
General Methods, Instrumentation, and Synthesis. All
reactions and manipulations were performed under an inert
atmosphere of nitrogen using a standard glovebox or Schlenk
techniques. Benzene, C6D6, was purchased from Cambridge Isotope
Laboratories, dried over sodium metal, freeze−pump−thawed three
times, vacuum transferred, stored over 4 Å molecular sieves in the
glovebox, and used for hydroamination reactions. Chloroform,
CDCl3, was purchased from Cambridge Isotope Laboratories and
was directly used for product characterization. Solvents were dried
and degassed before use. Pentane, diethyl ether, and THF were passed
through columns of activated alumina and 4 Å molecular sieves and
degassed with nitrogen. Methylene chloride was passed through two
columns of 4 Å molecular sieves and degassed with nitrogen. Styrene
was purchased from Acros Organics, and 1-hexene, 1-octene, and
bromoform were purchased from Sigma-Aldrich and used as received.
4-Fluorostyrene was purchased from Matrix Scientific and used as
received. (Allyl)-palladium(II) chloride dimer and silver triflate were
purchased from Strem and used without further purification.
Cyclohexylallene was purchased from Alfa Aesar and was used
without further purification. Amines were purchased from commercial
sources and dried over calcium hydride, freeze−pump−thawed three
times, vacuum-transferred, and stored over 4 Å molecular sieves in the
glovebox. Silica gel (porosity: 60 Å, particle size: 40−63 μm) was
1
purchased from Sorbent Technologies and used as received. H and
13C NMR data were obtained on a 600 MHz Bruker AVANCE III
1
spectrometer at 599.9 MHz for H NMR and 150.8 MHz for 13C
NMR. 31P NMR and 19F NMR data were obtained on a 400 MHz
Varian NMR spectrometer at 161.90 and 376.29 MHz, respectively.
1H NMR shifts are given relative to residual solvent resonances at 7.26
Figure 2. Possible orientations of the allyl group after insertion.
F
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1
ppm, and 13C NMR shifts are given relative to CDCl3 (77.36 ppm).
19F and 31P NMR data were externally referenced to 0.00 ppm with
CFCl3 and 5% solution of H3PO4 in D2O, respectively. High-
resolution mass spectrometry data were determined by either The
University of Illinois Mass Spectrometry Laboratory, Urbana, IL, USA
or The University of Toledo Mass Spectrometry Laboratory, Toledo,
OH, USA. All product spectra were taken using CDCl3 as the NMR
solvent. Elemental analyses were determined by Atlantic Microlab,
Inc., Norcross, GA, USA. Infrared samples were prepared on NaCl
plates as Nujol mulls and were obtained from a PerkinElmer
Spectrum 2 Fourier transform infrared spectrometer. Melting points
were determined in sealed capillary tubes under nitrogen using a
capillary melting point apparatus.
Pale yellow solid, 2.73 g (91.7%). mp 197 °C (dec). H NMR
(CDCl3): δ 7.88 (d, 4JP‑H = 4.0 Hz, 1H), 6.94 (d, 4JP‑H = 3.1 Hz, 2H),
6.90 (d, 4JP‑H = 3.3 Hz, 2H), 5.68−5.57 (m, 1H), 4.74−4.70 (m, 1H),
3.48 (dd, 3J = 13.2 Hz, 11.2 Hz, 1H), 3.37 (d, 3J = 7.9 Hz, 1H), 2.94
3
3
(m, 2H), 2.62 (d, J = 13.2 Hz, 1H), 2.54 (d, J = 7.9 Hz, 2H), 2.34
(s, 6H), 2.32 (s, 3H), 2.27 (s, 3H), 2.24 (s, 6H), 2.24−2.16 (m, 2H),
1.11 (s, 9H). 13C{1H} NMR (CDCl3): δ 161.6 (d, JP−C = 6.0 Hz),
3
153.8 (d, 1JP−C = 16.6 Hz), 142.2 (d, 2JP−C = 10.6 Hz), 141.9 (d, 2JP−C
2
1
= 10.6 Hz), 141.7 (d, JP−C = 7.5 Hz), 139.2 (d, JP−C = 31.6 Hz),
132.0 (d, JP−C = 9.0 Hz), 131.6 (d, JP−C = 7.5 Hz), 125.9, 125.6,
122.9 (d, JP−C = 42.2 Hz), 122.4 (q, JF−C = 316.7 Hz), 119.8 (d,
3
3
1
1
2JP‑C = 7.5 Hz), 76.2 (d, JP−C = 33.2 Hz), 64.1, 62.1 (d, JP−C = 6.0
Hz), 38.5, 37.8 (d, 2JP−C = 10.6 Hz), 30.0, 25.0 (d, 3JP−C = 10.6 Hz),
24.1 (d, 3JP−C = 9.0 Hz), 23.1 (d, 2JP−C = 6.0 Hz), 21.2, 21.1. 31P{1H}
NMR (CDCl3): δ −7.20. 19F{1H} NMR (CDCl3): δ −78.3. IR
(cm−1) 3027 (m), 2993 (m), 2834 (m), 1621 (s), 1585 (m), 1477
(s), 1360 (s), 1218 (s), 1022 (s), 680 (s). Anal. Calcd for
C32H43F3NO3PPdS·0.4 CH2Cl2: C, 51.88; H, 5.89; N, 1.87. Found:
C, 51.92; H, 6.16; N, 1.87.
2
3
Ligand and Catalyst Synthesis.
Allene Synthesis. All allenes were synthesized following the
previously reported procedure via ring opening of the corresponding
dibromocyclopropane.18,19 The synthetic allenes were freeze−pump−
thawed three times, vacuum-transferred, and stored over 4 Å
molecular sieves in the glovebox freezer. The allenes were confirmed
2-Dimesitylphosphinocyclopentene-1-(t-butyl)imine. 2-Chlorocy-
clopent-1-enecarbaldehyde and its corresponding β-chloroimine were
prepared at an ambient temperature, and the reactions were
performed under an inert atmosphere of nitrogen using standard
Schlenk techniques via previously published procedures.14a A solution
of freshly prepared chloroimine in dry ether was degassed and cooled
to 0 °C. Lithium dimesitylphosphide was prepared by adapting the
previously published procedure.16,17 Lithium dimesitylphosphide
(1.50 g; 1.1 equiv) was dissolved in diethyl ether and added to β-
chloroimine (0.92 g) through a cannula. The mixture was allowed to
warm to room temperature (RT) overnight. Then, the reaction
mixture was passed through a pad of celite to remove the LiCl
byproduct. The resulting solution was concentrated under reduced
pressure and was kept under nitrogen at −20 °C overnight to give the
3-IP ligand as yellow crystals. Subsequently, the supernatant liquid
was filtered, and the solid residue was placed under reduced pressure
to remove volatiles.
1
by H and 13C NMR spectroscopies.
Catalytic Reactions and Isolation of Allylamines. All
hydroamination reactions were carried out inside a nitrogen-filled
glovebox in NMR tubes. [(3IP)Pd(allyl)]+OTf (0.025 mmol, 17.9
mg) was dissolved in deuterated benzene (800 μL), and the
secondary amine (0.50 mmol) was added. Finally, the allene (0.50
mmol) was added to the mixture. The ratio of each substrate to the
1
hydroamination product was monitored by H NMR spectroscopy.
After reaction completion was observed, the reaction mixture was
passed through a plug of silica. Solvents were removed under reduced
pressure, and the colorless liquid was isolated by column
chromatography using pentane/ethyl acetate (9/1 by volume) as an
eluent. Linear hydroamination products: (3-cyclohexyl-2-propenyl)-
morpholine (1.1 l),12 (3-cyclohexyl-2-propenyl)-1-pyrrolidine (1.2
l),12 (3-cyclohexyl-2-propenyl)-piperidine (1.3 l),12 (3-phenyl-2-
propenyl)-morpholine (3.1 l),12 (3-phenyl-2-propenyl)-1-methylpi-
perazine (3.3 l),12 (3-phenyl-2-propenyl)-N-diphenylmethylpipera-
zine (3.4 l),12 [3-(4-fluorophenyl)-2-propenyl]-1-methylpiperazine
(4.1 l),12 4-(non-2-en-1-yl)-morpholine (5.1 l),12 4-(non-2-en-1-yl)-
2,6-dimethylmorpholine (5.2 l),12 4-(non-2-en-1-yl)-thiomorpholine
(5.3 l),12 4-(hept-2-en-1-yl)-2,6-dimethylmorpholine (6.1 l),12 4-
(hept-2-en-1-yl)-thiomorpholine (6.2 l)12 and branched hydro-
amination products: (1-cyclohexyl-2-propenyl)-morpholine (1.1
br),4c (1-cyclohexyl-2-propenyl)-1-pyrrolidine (1.2 br),4c (1-cyclo-
hexyl-2-propenyl)-piperidine (1.3 br),4c (1-phenyl-2-propen-1-yl)-
morpholine (3.1 br),20 (1-phenyl-2-propen-1-yl)-1-methyl-piperazine
(3.3 br),21 (1-phenyl-2-propen-1-yl)-2,3-dihydroindoline (3.5 br),22
and (non-1-en-3-yl)morpholine (5.1 br),20 were reported previously.
Characterization of New Hydroamination Products.
Pale yellow solid, 1.81 g (87%). mp 105−106 °C. 1H NMR
(CDCl3): δ 8.51 (d, 4JP‑H = 4.0 Hz, 1H), 6.79 (d, 4JP‑H = 2.8 Hz, 4H),
2.79−2.71 (m, 2H), 2.59−2.48 (m, 2H), 2.24 (s, 6H), 2.20 (s, 12H),
1.89−1.77 (m, 2H), 1.07 (s, 9H). 13C{1H} NMR (CDCl3): δ 153.4
(d, 3JP‑C = 19.6 Hz), 150.5 (d, 1JP‑C = 21.1 Hz), 147.3 (d, 1JP‑C = 22.7
2
2
Hz), 142.6 (d, JP−C = 15.1 Hz), 138.0, 131.3 (d, JP−C = 16.6 Hz),
3
2
130.0 (d, JP−C = 3.0 Hz), 57.6, 40.2, 34.3 (d, JP−C = 6.0 Hz), 30.1,
3
3
23.1 (d, JP−C = 16.6 Hz), 22.9 (d, JP−C = 3.0 Hz), 21.2. 31P{1H}
NMR (CDCl3): δ −42.65. IR (cm−1): 3018 (m), 2963 (m), 1912
(m), 1614 (s), 1598 (m), 1572 (m), 1495 (s), 1363 (m), 1183 (m),
806 (s), 512 (s). HRMS m/z: [M + H]+ calcd for C28H39NP,
420.2820; found, 420.2816.
[(2-Dimesitylphosphinocyclopentene-1-(t-butyl)imine)Pd(allyl)]-
OTf. The 3-iminophosphine ligand (1.05 equiv, 1.82 g) was dissolved
in dichloromethane and added to allylpalladium chloride dimer (0.5
equiv, 0.76 g) in dichloromethane at an ambient temperature and
stirred overnight. The resulting solution was placed under vacuum to
remove the volatiles, and the residue was washed with pentane. The
solid residue was then dissolved in dichloromethane and added to a
slurry of silver triflate (0.65 equiv, 0.68 g) in dichloromethane and
then stirred overnight in the dark. The reaction mixture was allowed
to pass through a thick pad of celite, and the solvent was reduced
under vacuum. The dark yellow solid was washed with pentane and
dried under vacuum before transferring into the glovebox.
(1-Phenyl-2-propenyl)-2,6-dimethylmorpholine (3.2 br). Colorless
1
liquid, 84.1 mg (72.7%). H NMR (CDCl3): δ 7.38−7.32 (m, 4H),
7.30−7.25 (m, 1H), 5.93 (ddd, 3J = 17.1, 10.0, 8.8 Hz, 1H), 5.25 (dd,
2
3
2
3J = 17.1 Hz, J = 1.5 Hz, 1H), 5.13 (dd, J = 10.0 Hz, J = 1.5 Hz,
1H), 3.75 (dqd, 3J = 10.3, 6.2, 1.9 Hz, 1H), 3.65 (dqd, 3J = 10.3, 6.2,
1.9 Hz, 1H), 3.62 (d, 3J = 8.8 Hz, 1H), 2.99 (dd, 2J = 11.4 Hz, 3J = 1.9
Hz, 1H), 2.53 (dd, 2J = 11.4 Hz, 3J = 1.9 Hz, 1H), 1.75 (dd, 2J = 11.4
G
DOI: 10.1021/acs.organomet.9b00025
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Hz, 3J = 10.3 Hz, 1H), 1.60 (dd, 2J = 11.4 Hz, 3J = 10.3 Hz, 1H), 1.20
1087 (s), 999 (s), 659 (m), 537 (s). HRMS m/z: [M + H]+ calcd for
C14H20FN2, 235.1611; found, 235.1597.
(d, J = 6.2 Hz, 3H), 1.08 (d, J = 6.2 Hz, 3H). 13C{1H} NMR
(CDCl3): δ 142.0, 140.1, 128.9, 128.3, 127.6, 116.9, 75.5, 72.13,
72.09, 58.01, 57.98, 19.6, 19.5. IR (cm−1): 3117 (m), 3083 (m), 2952
(m), 2804 (m), 1639 (br), 1415 (m), 1015 (s), 758 (s), 619 (s).
HRMS m/z: calcd for C15H22NO, 232.1701 [M + H]+; found,
232.1690.
3
3
[1-(4-Fluorophenyl)-2-propenyl]-2,6-dimethylmorpholine (4.2
1
br). Colorless liquid, 88.1 mg (70.4%). H NMR (CDCl3): δ 7.34−
7.32 (m, 2H), 7.03−6.99 (m, 2H), 5.86 (ddd, 3J = 17.1, 10.1, 8.9 Hz,
1H), 5.21 (dd, 3J = 17.1 Hz, 2J = 1.5 Hz, 1H), 5.11 (dd, 3J = 10.1 Hz,
2J = 1.5 Hz, 1H), 3.70 (dqd, 3J = 10.0, 6.3, 2.2 Hz, 1H), 3.61 (dqd, 3J
= 10.0, 6.3, 2.2 Hz, 1H), 3.58 (d, 3J = 8.9 Hz, 1H), 2.93 (dd, 2J = 11.3
3
2
3
Hz, J = 2.2 Hz, 1H), 2.46 (dd, J = 11.3 Hz, J = 2.2 Hz, 1H), 1.71
(dd, 2J = 11.3 Hz, 3J = 10.0 Hz, 1H), 1.56 (dd, 2J = 11.3 Hz, 3J = 10.0
Hz, 1H), 1.16 (d, 3J = 6.3 Hz, 3H), 1.06 (d, 3J = 6.3 Hz, 3H).
13C{1H} NMR (CDCl3): δ 163.1 (d, 1JC−F = 245.8 Hz), 139.9, 137.8
(1-Phenyl-2-propenyl)-N-diphenylmethylpiperazine (3.4 br).
White solid, 124.2 mg (67.4%). 1H NMR (CDCl3): δ 7.51−7.39
3
(m, 5H), 7.39−7.23 (m, 8H), 7.23−7.14 (m, 2H), 5.91 (ddd, J =
(d, 4JC−F = 3.0 Hz), 129.7 (d, 3JC−F = 9.1 Hz), 117.0, 115.8 (d, 2JC−F
=
17.1, 10.1, 8.8 Hz, 1H), 5.25 (dd, 3J = 17.1 Hz, 2J = 1.6 Hz, 1H), 5.12
(dd, 3J = 10.1 Hz, 2J = 1.6 Hz, 1H), 4.27 (s, 1H), 3.71 (d, 3J = 8.8 Hz,
1H), 2.54−2.36 (br, 8H). 13C{1H} NMR (CDCl3): δ 143.12, 143.06,
142.1, 140.3, 128.78, 128.73, 128.69, 128.30, 128.27, 128.26, 127.4,
127.17, 127.15, 116.7, 76.5, 75.5, 52.3, 51.9. IR (cm−1): 3063 (m),
3033 (m), 2956 (m), 2807 (m), 1662 (m), 1643 (m), 1603 (m),
1489 (m), 1451 (m), 1131 (s), 995 (s), 704 (s). HRMS m/z: [M +
H]+ calcd for C26H29N2, 369.2331; found, 369.2331.
21.1 Hz), 74.5, 72.14, 72.06, 57.9, 57.8, 19.6, 19.5. IR (cm−1): 3052
(m), 3016 (m), 2988 (m), 2873 (w), 1654 (m), 1609 (m), 1449 (m),
1325 (s), 1287 (m), 738 (s), 640 (s), 593 (m). HRMS m/z: [M +
H]+ calcd for C15H21FNO, 250.1607; found, 250.1606.
[1-(4-Fluorophenyl)-2-propenyl]-thiomorpholine (4.3 br). Color-
1
less liquid, 82.3 mg (69.1%). H NMR (CDCl3): δ 7.32−7.27 (m,
2H), 7.03−6.97 (m, 2H), 5.85 (ddd, 3J = 17.1, 10.1, 8.6 Hz, 1H), 5.20
3
2
3
2
(1-Phenyl-2-propenyl)-thiomorpholine (3.6 br). Colorless liquid,
(dd, J = 17.1 Hz, J = 1.7 Hz, 1H), 5.16 (dd, J = 10.1 Hz, J = 1.7
1
69.6 mg (63.6%). H NMR (CDCl3): δ 7.43−7.28 (m, 4H), 7.28−
3
Hz, 1H), 3.81 (d, J = 8.6 Hz, 1H), 2.82−2.71 (m, 2H), 2.69−2.58
3
3
7.21 (m, 1H), 5.90 (ddd, J = 17.1, 10.0, 8.6 Hz, 1H), 5.22 (dd, J =
1
(m, 6H). 13C{1H} NMR (CDCl3): δ 163.1 (d, JC−F = 241.3 Hz),
2
3
2
17.1 Hz, J = 1.5 Hz, 1H), 5.15 (dd, J = 10.0 Hz, J = 1.5 Hz, 1H),
4
3
139.0, 137.6 (d, JC−F = 3.0 Hz), 129.6 (d, JC−F = 7.5 Hz), 117.5,
3
3.82 (d, J = 8.6 Hz, 1H), 2.86−2.72 (m, 2H), 2.72−2.57 (m, 6H).
115.4 (d, JC−F = 21.1 Hz), 74.0, 53.1, 28.5. IR (cm−1): 3095 (m),
2
13C{1H} NMR (CDCl3): δ 141.9, 139.4, 128.8, 128.2, 127.5, 117.3,
74.8, 53.2, 28.5. IR (cm−1): 3067 (m), 2991 (m), 2861 (m), 1641
(m), 1627 (m), 1450 (m), 1013 (s), 701 (s). HRMS m/z: [M + H]+
calcd for C13H18NS, 220.1160; found, 220.1156.
3058 (w), 3007 (m), 2973 (m), 2848 (w), 1642 (s), 1626 (m), 1322
(m), 1273 (s), 1131 (m), 873 (s), 751 (s), 649 (m). HRMS m/z: [M
+ H]+ calcd for C13H17FNS, 238.1066; found, 238.1056.
3-(Non-1-enyl)-2,6-dimethylmorpholine (5.2 br). Colorless liquid,
81.7 mg (68.4%). 1H NMR (CDCl3): δ 5.65 (ddd, 3J = 17.2, 10.3, 8.3
Hz, 1H), 5.16 (dd, 3J = 10.3 Hz, 2J = 1.8 Hz, 1H), 5.05 (dd, 3J = 17.2
2
3
Hz, J = 1.8 Hz, 1H), 3.66 (dqd, J = 10.6, 6.3, 2.2 Hz, 1H), 3.61
(dqd, 3J = 10.6, 6.3, 2.2 Hz, 1H), 2.79−2.72 (m, 1H), 2.69−2.59 (m,
2H), 1.89 (t, 3J = 10.6 Hz, 1H), 1.77 (t, 3J = 10.6 Hz, 1H), 1.67−1.55
[1-(4-Fluorophenyl)-2-propenyl]-1-methylpiperazine (4.1 br).
1
Colorless liquid, 77.9 mg (68.3%). H NMR (CDCl3): δ 7.36−7.27
(m, 2H), 7.04−6.93 (m, 2H), 5.87 (ddd, 3J = 17.1, 10.0, 8.8 Hz, 1H),
3
5.21 (dd, 3J = 10.0 Hz, 2J = 1.1 Hz, 1H), 5.09 (dd, 3J = 17.1 Hz, 2J =
(m, 1H), 1.43−1.33 (m, 1H), 1.33−1.17 (m, 8H), 1.13 (t, J = 6.3
Hz, 6H), 0.92−0.81 (m, 3H). 13C{1H} NMR (CDCl3): δ 138.0,
117.9, 72.4, 72.2, 69.0, 57.6, 55.2, 32.1, 31.8, 29.7, 26.6, 23.0, 19.60,
19.59, 14.4. IR (cm−1): 2854 (m), 2781 (m), 2719 (w), 1527 (s),
1448 (m), 1208 (m), 968 (s), 823 (m), 718 (s). HRMS m/z: [M +
H]+ calcd for C15H30NO, 240.2327; found, 240.2316.
3
1.1 Hz, 1H), 3.63 (d, J = 8.8 Hz, 1H), 2.72−2.14 (br, 8H), 2.27 (s,
1
3H). 13C{1H} NMR (CDCl3): δ 162.6 (d, JC−F = 170.4 Hz), 140.2,
138.1 (d, 4JC−F = 3.0 Hz), 129.7 (d, 3JC−F = 7.5 Hz), 116.8, 115.7 (d,
2JC−F = 21.1 Hz), 74.5, 55.6, 51.5, 46.3. IR (cm−1): 3103 (m), 3074
(m), 3016 (w), 2850 (m), 1665 (s), 1607 (s), 1448 (m), 1407 (m),
H
DOI: 10.1021/acs.organomet.9b00025
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
2.57 (m, 3H), 2.51−2.45 (m, 2H), 2.09−1.97 (m, 1H), 1.78−1.72
(m, 1H). 13C{1H} NMR (CDCl3): δ 142.3, 137.1, 128.5, 128.4,
125.8, 118.3, 68.1, 67.3, 50.1, 33.3, 32.4. IR (cm−1): 3041 (m), 3019
(w), 2965 (m), 2902 (m), 2853 (m), 1642 (m), 1615 (m), 1393 (m),
1315 (m), 1173 (m), 782 (m), 711 (s), 597 (s). HRMS m/z: [M +
H]+ calcd for C15H22NO, 232.1701; found, 232.1693.
3-(Non-1-enyl)-thiomorpholine (5.3 br). Colorless liquid, 80.1 mg
1
3
(71.2%). H NMR (CDCl3): δ 5.67 (ddd, J = 17.1, 10.2, 8.6 Hz,
1H), 5.15 (dd, 3J = 10.2 Hz, 2J = 1.6 Hz, 1H), 5.04 (dd, 3J = 17.1 Hz,
3
2J = 1.6 Hz, 1H), 2.93−2.80 (m, 2H), 2.76 (dt, J = 8.6 Hz, 5.2 Hz,
1H), 2.72−2.56 (m, 6H), 1.60−1.51 (m, 1H), 1.45−1.35 (m, 1H),
1.32−1.17 (m, 8H), 0.87 (t, 3J = 6.9 Hz, 3H). 13C{1H} NMR
(CDCl3): δ 137.4, 117.6, 69.6, 52.0, 32.1, 31.8, 29.6, 28.7, 26.8, 23.0,
14.4. IR (cm−1): 2959 (m), 2924 (s), 2855 (m), 2806 (m), 1637 (s),
1450 (m), 1382 (m), 1107 (m), 920 (s), 699 (s). HRMS m/z: [M +
H]+ calcd for C13H26NS, 228.1786; found, 228.1780.
3-(5-Phenyl-pent-1-enyl)-2,6-dimethylmorpholine (7.2 br). Col-
1
orless liquid, 96.7 mg (74.3%). H NMR (CDCl3): δ 7.36−7.23 (m,
2H), 7.23−7.08 (m, 3H), 5.71 (ddd, 3J = 17.2, 10.3, 8.8 Hz, 1H), 5.25
3
2
3
2
(dd, J = 10.3 Hz, J = 1.7 Hz, 1H), 5.14 (dd, J = 17.2 Hz, J = 1.7
Hz, 1H), 3.72 (dqd, 3J = 10.0, 6.3, 2.4 Hz, 1H), 3.65 (dqd, 3J = 10.0,
6.3, 2.4 Hz, 1H), 2.83−2.71 (m, 2H), 2.71−2.64 (m, 1H), 2.62 (d, 3J
= 11.2 Hz, 1H), 2.60−2.52 (m, 1H), 2.01−1.94 (m, 1H), 1.99 (t, 3J =
3
10.6 Hz, 1H), 1.83 (t, J = 10.6 Hz, 1H), 1.77−1.74 (m, 1H), 1.18
3-(Hept-1-enyl)-2,6-dimethylmorpholine (6.1 br). Colorless
liquid, 77.9 mg (73.4%). 1H NMR (CDCl3): δ 5.63 (ddd, 3J =
17.2, 10.1, 9.0 Hz, 1H), 5.15 (dd, 3J = 10.1 Hz, 2J = 1.8 Hz, 1H), 5.04
(dd, 3J = 6.3 Hz, 4J = 2.4 Hz, 6H). 13C{1H} NMR (CDCl3): δ 142.7,
137.4, 128.7, 128.6, 126.0, 118.5, 72.4, 72.2, 68.3, 57.7, 54.6, 33.7,
32.8, 19.59, 19.56. IR (cm−1): 3027 (m), 2997 (w), 2972 (m), 2856
(m), 1661 (m), 1603 (m), 1416 (m), 1371 (s), 1267 (m), 874 (m),
735 (s), 606 (m). HRMS m/z: [M + H]+ calcd for C17H26NO,
260.2014; found, 260.2007.
3
2
(dd, J = 17.2 Hz, J = 1.8 Hz, 1H), 3.73−3.63 (m, 1H), 3.63−3.54
2
3
(m, 1H), 2.74 (dd, J = 11.3 Hz, J = 1.7 Hz, 1H), 2.70−2.58 (m,
2H), 1.89 (t, 3J = 10.6 Hz, 1H), 1.77 (t, 3J = 10.6 Hz, 1H), 1.66−1.54
(m, 1H), 1.44−1.33 (m, 1H), 1.33−1.23 (m, 3H), 1.23−1.16 (m,
1H), 1.11 (dt, 3J = 6.6 Hz, 4J = 1.8 Hz, 6H), 0.87 (t, 3J = 7.2 Hz, 3H).
13C{1H} NMR (CDCl3): δ 138.0, 117.9, 72.4, 72.1, 69.0, 57.6, 55.2,
31.5, 28.9, 23.1, 19.594, 19.585, 14.4. IR (cm−1): 2976 (m), 2948 (w),
2879 (m), 2835 (m), 1637 (m), 1379 (m), 1257 (s), 1093 (m), 827
(m), 650 (m), 619 (s). HRMS m/z: [M + H]+ calcd for C13H26NO,
212.2014; found, 212.2008.
3-(5-Phenyl-pent-1-enyl)-thiomorpholine (7.3 br). Colorless
1
liquid, 81.8 mg (65.9%). H NMR (CDCl3): δ 7.34−7.23 (m, 2H),
7.22−7.12 (m, 3H), 5.75 (ddd, 3J = 17.2, 10.3, 8.7 Hz, 1H), 5.22 (dd,
2
3
2
3J = 17.2 Hz, J = 1.8 Hz, 1H), 5.09 (dd, J = 10.3 Hz, J = 1.8 Hz,
1H), 2.93−2.86 (m, 2H), 2.83 (dd, 3J = 14.5 Hz, 8.4 Hz, 1H), 2.73−
2.56 (m, 8H), 1.97−1.92 (m, 1H), 1.81−1.62 (m, 1H). 13C{1H}
NMR (CDCl3): δ 142.3, 136.5, 128.5, 128.3, 125.8, 117.8, 68.3, 51.6,
33.3, 32.6, 28.4. IR (cm−1): 3075 (m), 3019 (m), 2956 (w), 2823
(m), 1638 (m), 1621 (m), 1395 (m), 1327 (m), 1193 (m), 790 (m),
673 (m), 629 (s). HRMS m/z: [M + H]+ calcd for C15H22NS,
248.1473; found, 248.1467.
3-(Hept-1-enyl)-thiomorpholine (6.2 br). Colorless liquid, 69.3
mg (69.2%). 1H NMR (CDCl3): δ 5.66 (ddd, 3J = 17.2, 10.2, 8.7 Hz,
1H), 5.14 (dd, 3J = 10.2 Hz, 2J = 1.8 Hz, 1H), 5.02 (dd, 3J = 17.2 Hz,
3
2J = 1.8 Hz, 1H), 2.91−2.82 (m, 2H), 2.74 (dt, J = 8.7 Hz, 5.1 Hz,
1H), 2.72−2.55 (m, 6H), 1.63−1.53 (m, 1H), 1.48−1.35 (m, 1H),
1.35−1.17 (m, 4H), 0.86 (t, 3J = 7.2 Hz, 3H). 13C{1H} NMR
(CDCl3): δ 137.4, 117.6, 69.7, 52.0, 31.6, 29.1, 28.8, 23.1, 14.4. IR
(cm−1): 2983 (m), 2926 (w), 2884 (m), 2813 (m), 1603 (m), 1278
(m), 1192 (s), 947 (m), 797 (s), 704 (s), 583 (m). HRMS m/z: [M +
H]+ calcd for C11H22NS, 200.1473; found, 200.1467.
ASSOCIATED CONTENT
* Supporting Information
■
S
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.9b00025.
NMR spectra for all newly reported compounds and
conversion versus time data for four additional substrate
combinations (PDF)
Crystal data including bond lengths and angles for the
mesityl-substituted catalyst (TXT)
3-(5-Phenyl-pent-1-enyl)-morpholine (7.1 br). Colorless liquid,
1
Accession Codes
83.1 mg (71.6%). H NMR (CDCl3): δ 7.33−7.28 (m, 2H), 7.23−
3
3
CCDC 1891646 contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge
via www.ccdc.cam.ac.uk/data_request/cif, or by emailing
7.19 (m, 3H), 5.77 (ddd, J = 17.2, 10.3, 9.0 Hz, 1H), 5.28 (dd, J =
2
3
2
10.3 Hz, J = 1.7 Hz, 1H), 5.15 (dd, J = 17.2 Hz, J = 1.7 Hz, 1H),
3.78−3.69 (m, 4H), 2.81−2.77 (m, 1H), 2.74−2.69 (m, 1H), 2.64−
I
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data_request@ccdc.cam.ac.uk, or by contacting The Cam-
bridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
AUTHOR INFORMATION
Corresponding Author
*E-mail: Joseph.Schmidt@utoledo.edu. Phone: 419-530-1512.
Fax: 419-530-4033.
■
ORCID
Joseph A. R. Schmidt: 0000-0003-3019-0055
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by the National Science Foundation
under CHE-0841611 and The University of Toledo via
Summer Research Fellowship (J.A.R.S.).
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