Synthesis of Eight-Membered Nitrogen Heterocycles via a Heterogeneous PtI2-Catalyzed Cascade Cycloaddition Reaction of δ-Aminoalkynes with Electron-Deficient Alkynes

Article abstract of DOI:10.1002/adsc.201901644

A novel heterogeneous PtI₂-catalyzed cascade reaction of δ-aminoalkynes was developed for the synthesis of various eight-membered nitrogen heterocycles in excellent yields. The reaction proceeds via a hydration of δ-aminoalkynes and subsequent intramolecular cyclization and intermolecular addition as well as ring-expansion cascade reaction with another electron-deficient alkynes. This method has the advantages of simple operation and mild reaction conditions. And the simple PtI₂ with no any supports could be readily recycled through simple centrifugation without substantial loss of activity in 1,2-dichloroethane (DCE). The recyclability of PtI₂ may be ascribed to its insolubility in DCE. The reaction constitutes a formal [6+2]-cycloaddition. (Figure presented.).

Full text of DOI:10.1002/adsc.201901644

Title: Synthesis of Eight-Membered Nitrogen Heterocycles via a
Heterogeneous PtI2-Catalyzed Cascade Cycloaddition Reaction
of -Aminoalkynes with Electron-Deficient Alkynes
Authors: Lingyan Liu, Xinhong Li, Songmeng Wang, Hongkai Wang,
Weilin Wang, Weixing Chang, and li jing
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To be cited as: Adv. Synth. Catal. 10.1002/adsc.201901644
Link to VoR: http://dx.doi.org/10.1002/adsc.201901644

10.1002/adsc.201901644
Advanced Synthesis & Catalysis
FULL PAPER
DOI: 10.1002/adsc.201((will be filled in by the editorial staff))
Synthesis of Eight-Membered Nitrogen Heterocycles via a
Heterogeneous PtI2-Catalyzed Cascade Cycloaddition Reaction
of -Aminoalkynes with Electron-Deficient Alkynes
Xinhong Li,a Songmeng Wang,a Hongkai Wang,a Weilin Wang,a Lingyan Liu, a*
Weixing Chang,a Jing Lia,b*
a
the State Key Laboratory and Institute of Elemento-Organic Chemistry, College of Chemistry, Nankai Uiversity,
Tianjin 300071, P. R. China.
Phone: 022-23501410
E-mail: liulingyan@nankai.edu.cn; lijing@nankai.edu.cn.
Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Weijin Road 94#, Nankai District,
b
Tianjin 300071, P. R. China
Received: ((will be filled in by the editorial staff))
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/adsc.201######.((Please
delete if not appropriate))
Abstract. A novel heterogeneous PtI2-catalyzed cascade supports could be readily recycled through simple
reaction of δ-aminoalkynes was developed for the synthesis centrifugation without substantial loss of activity in 1,2-
of various eight-membered nitrogen heterocycles in excellent dichloroethane (DCE). The recyclability of PtI2 may be
yields. The reaction proceeds via a hydration of δ- ascribed to its insolubility in DCE. The reaction constitutes
aminoalkynes and subsequent intramolecular cyclization and a formal [6+2]-cycloaddition.
intermolecular addition as well as ring-expansion cascade
reaction with another electron-deficient alkynes. This
method has the advantages of simple operation and mild
reaction conditions. And the simple PtI2 with no any
Keywords: Eight-membered nitrogen heterocycles;
Cascade cyclization reaction; Heterogeneous PtI2-catalyzed;
δ-aminoalkynes; hydration
these methods somehow have some deficiencies, such
as unsatisfactory yields, long reaction time and the
limited substrates scope. Moreover, direct end-to-end
cyclization to make eight-membered ring are often
low yielding and the ring expansion strategy has been
shown to overcome this problem[4], although the
metal catalysts used are generally unrecyclable.
Therefore, it is still desirable to explore a simple,
mild, and efficient synthetic method for the
Introduction
Medium-sized rings heterocyclic compounds are
ubiquitous building blocks in natural products and
pharmaceuticals, and eight-membered nitrogen
heterocycles have been found to exhibit unique
biological activities (Figure 1).[1] Organic synthesis
chemists have paid more attention to develop
effective methodologies for the construction of eight-
membered nitrogen heterocycles in recent decade,
despite their intrinsically unfavorable entropic and
enthalpic factors.[2] Among them, transition metal
catalyzed cycloadditions are the most attractive
methods to construct medium-sized ring systems.[3]
For example, Rovis's group described a rhodium-
catalyzed asymmetric [4+2+2] cycloaddition of
dienyl isocyanates and terminal alkynes to afford
bicyclo[6.3.0] azocine derivatives (Scheme 1, eq.1).[3a]
construction
of
eight-membered
nitrogen
heterocycles in chemical and drug development.
Figure 1. Biologically active natural products containing
azocine skeletons.
Louie and co-workers reported
a Ni/P(p-tol)3
catalyzed intermolecular cycloaddition between 1,3-
dienes and 3-azetidinones/3-oxetanones to construct
the eight-membered nitrogen heterocycles (Scheme 1,
eq.2).[3b] Ma et. al developed [Cp*RhCl2]2-catalyzed
As a continuous work on the homopropargylic
amines (β-aminoalkynes) of our research group,[5] we
herein developed a heterogeneous PtI2-catalyzed
cascade cycloaddition reaction of δ-aminoalkynes
and electron-deficient alkynes without the need of
[4+2+2]-cyclization
between
N-pivaloyloxy
benzamides and 1,6-allene-enes to form the eight-
membered lactams (Scheme 1, eq.3).[3c] Nevertheless,
1
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10.1002/adsc.201901644
Advanced Synthesis & Catalysis
additional supports (Scheme 1, eq.4). To the best of
our knowledge, it is unprecedent that this simple
platinum halides are used as heterogeneous catalysts
in such reactions. Previous simple transition metal
catalyzed reactions are most homogeneous reaction,
whereas for the heterogeneous reactions, the
supported metal catalysts are usually involved, such
as carbon, silica gel, Al2O3, Fe2O3, molecular sieves,
or polymer supports.[6] Moreover, as shown in the
literature [7], this rare strategy of synthesizing 8-
membered ring via a cascade reaction, involving
cyclisation of a linear molecule and in situ ring
expansion of 6-b-4 fused rings to 8-membered rings,
has many advantages over the traditional direct end-
to-end cyclization, such as offering excellent yields,.
the amount of Ph3PAuCl to 2.5 mol% nor employing
Ph3PAuNTf2 as a catalyst enhanced the yield (entries
9 and 10). Examination of other solvents revealed
that 1,2-dichloroethane (DCE) gave the best yield at
100 °C (entries 11–13). Intrigued by this result, we
retested
the
catalyst
previously
screened
(Ph3PAuNTf2, CuOTf, AgOAc, and PtI2) in DCE at
100 °C (entries 14-17) and were surprised to find that
a 99% yield of 3aa could be obtained in the reaction
of 1a and 2a in DCE in the presence of 10 mol% PtI2.
Moreover, the yield was maintained even when the
amounts of PtI2 and diethyl but-2-ynedioate 2a were
decreased to 2.5 mol% and 1.1 equiv., respectively
(entries 18 and 19). In summary, these experiments
revealed that the optimal conditions involved the use
of 2.5 mol% PtI2 and 1.1 equiv. of 2a in DCE (0.1 M)
at 100 °C.
Table 1. Optimization of conditions for the formation of
eight-membered nitrogen heterocycle 3aaa)
Entry Catalyst (mol%)
Solvent
DMF
DMF
DMF
DMF
T (C)
80
t (h) Yieldb)
1
2
3
4
CuOTf (20)
4
4
4
2
30
30
68
73
AgOAc (20)
80
PtI2 (10)
80
Ph3PAuCl (5)
80
(2,4-di-t-BuC6H3O)3P
AuCl (5)
5
DMF
80
3
59c)
6
7
8
9
(4-CF3Ph)3PAuCl (5)
BINAP(AuCl)2 (5)
JohnphosAuCl (5)
Ph3PAuCl (2.5)
DMF
DMF
DMF
DMF
DMF
PhMe
dioxane
DCE
120
120
120
80
3
3
3
2
4
4
4
4
4
4
4
4
4
4
53c)
59c)
70c)
76
80c)
10 Ph3PAuNTf2 (2.5)
11 Ph3PAuCl (2.5)
12 Ph3PAuCl (2.5)
13 Ph3PAuCl (2.5)
14 Ph3PAuNTf2 (2.5)
15 CuOTf (20)
16 AgOAc (20)
17 PtI2 (10)
80
100
100
100
100
100
100
100
100
100
92c) (88)
78c)
94c) (88)
95c) (94)
65c)
Scheme 1. The constuction of eight-membered nitrogen
heterocycles.
DCE
DCE
DCE
65c)
Results and Discussion
DCE
99
18 PtI2 (5)d)
19 PtI2 (2.5)d)
DCE
99
In our initial study, we carried out some screening
experiments on the reaction of -aminoalkyne 1a
with 2 equiv. of diethyl but-2-ynedioate (2a) in N, N-
dimethylformamide (DMF) (Table 1). When CuOTf
or AgOAc was used as a catalyst, the reaction gave
the tetrahydroazocine 3aa in low yield at 80 °C for 4
h (entries 1 and 2). Switching to use PtI2 and
Ph3PAuCl increased the yields of 3aa to 68% and
73%, respectively (entries 3 and 4). Gold(I) catalysts
with various phosphine ligands—(2,4-di-t-BuPhO)3P,
(4-CF3Ph)3P, BINAP, and Johnphos—were further
investigated and no obvious improved yield was
observed even when the reaction temperature was
increased to 120 °C (entries 5-8). Neither decreasing
DCE
99
a) Standard procedure: A Schlenk tube was charged with catalyst,
δ-aminoalkyne 1a (17.3 mg, 0.1 mmol), solvent (1.0 mL), and
diethyl but-2-ynedioate (2a) (0.2 mmol, 32 L, 2.0 equiv.) in that
order, and the mixture was stirred under the specified reaction
conditions and monitored by thin-layer chromatography.
Abbreviations: DMF = N, N-dimethylformamide, BINAP =
(+/−)-2,2'-bis(diphenyl- phosphino)-1,1'-binaphthy, Johnphos =
b)
2-(di-t-butylphosphino) biphenyl, DCE = 1,2-dicloroethane.
Isolated yields are provided, unless otherwise stated. c) The yields
were determined by 1H NMR spectroscopy with 1,3,5-
trimethoxylbenzene as an internal standard. d) The amount of 2a
was 1.1 equiv..
2
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10.1002/adsc.201901644
Advanced Synthesis & Catalysis
In the above described experiments, we observed
that the PtI2, a black powder, was insoluble in DCE
for the duration of the process (Figure 2).
Figure 2. Picture of solubility of catalyst. (a) PtI2 (6.7 mg,
2.5 mol%) was added initially to a Schlenk tube. (b) 1a
(103.8 mg, 0.6 mmol), 2a (106 L, 0.66 mmol, 1.1 equiv.),
and DCE (6 mL) were subsequently added into the tube.
(c) The reaction mixture was heated at 100 C for 1 h. (d)
The reaction mixture was standed for 6 h after reaction
completion.
To determine whether the PtI2 catalyst was in fact
recyclable, we conducted the hot-filtration
experiments.[8] In detail, after completion of the
reaction, the mixture was hot-filtered through a small
kieselguhr column, and the filtrate was then analyzed
by inductively coupled plasma optical emission
spectrometry. The analyzed results showed that the
PtI2 content in the filtrate was less than 0.2% (<2.3
g), indicating that catalyst was almost recoverable.
In addition, we conducted several other experiments
to confirm the significance and reusability of the
catalyst. In the presence of 2.5 mol% PtI2, 1a was
allowed to react with 2a in DCE at 100 °C for 30 min
(Figure 3a-I, point A, 40% conversion); then the
reaction mixture was rapidly hot-filtered, and the
filtrate was reheated to 100 °C and maintained at that
temperature for an additional 3.5 h. During this
period (Figure 3a-II, point B), no additional
conversion was detected. However, if another 2.5
mol% PtI2 was added to the reaction mixture, the
conversion of reation began to increase again, and a
99% yield of the product was obtained after an
another 3.5 h at 100 °C (Figure 3a-III, point C).
Figure 3. (a) Hot-filtration experiments. All yields were
determined by 1H NMR spectroscopy of the crude products
with 1,3,5-trimethoxylbenzene as an internal standard.
Phase I: 2.5 mol% PtI2, 0.5 h; phase II: no PtI2 (hot-
filtered), 3.5 h; phase III: 2.5 mol% PtI2, 3.5 h. (b)
Assessment of catalyst stability under batch conditions: -
aminoalkyne 1a (34.6 mg, 0.2 mmol) was allowed to react
with diethyl but-2-ynediote (2a, 35 mL, 0.22 mmol) in
DCE (2 mL) at 100 °C for 8 h in the presence of 2.5 mol%
PtI2 (2.2 mg, 0.005 mmol). Between runs, the PtI2 was
separated by centrifugation, and then used in the next run
(runs 1–4). (c) Comparison of powder X-ray diffraction
patterns of PtI2 before run 1 and after run 4.
We also evaluated the stability of the catalyst.[9] In
a reaction of -aminoalkyne 1a (0.2 mmol) and
diethyl but-2-ynedioate (2a, 0.22 mmol) catalyzed by
2.5 mol% PtI2 (2.2 mg), the catalyst could be
recovered by simple centrifugation and reused three
times with only a small decrease in the yield of 3aa
(Figure 3b, runs 1–4). Under these kinetically
controlled conditions, the changes in the apparent rate
constant in the consecutive runs reflect the extent of
catalyst deactivation. The catalyst stability was
confirmed by comparison of its powder X-ray
diffraction patterns before run 1 and after run 4
(Figure 3c). Summarily, the PtI2 was considered as a
recyclable catalyst in this reaction, as mainly ascribed
to the poor solubility of the catalyst PtI2 in DCE.
Using the optimized reaction conditions (Table 1,
entry 19), we evaluated a series of δ-aminoalkynes 1
and electron-deficient alkynes 2 (Table 2). Various
3
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10.1002/adsc.201901644
Advanced Synthesis & Catalysis
N-aryl-substituted δ-aminoalkynes 1 were suitable
substrates for reactions with 2a, delivering the
corresponding eight-membered nitrogen heterocycles
(3aa–3ka) in 76–99% yields. Moreover, substrates
bearing with electron-donating substituents (3ba–3fa)
on the N-aryl ring generally gave higher yields than
those with electron-withdrawing substituents (3ga–
3ja). Unfortunately, N-tosyl aminoalkyne 1l failed to
react with 2a even at 150 °C for 8 h. This
phenomenon may be explained that the strong
electron-withdrawing ability of N-Ts protecting group
reduced the nucleophilicity of nitrogen atom, and
then inhibited the intermolecular nucleophilic
addition cyclization. Interestingly, δ-aminoalkyne 1m
(X = O) afforded a 68% yield of 3ma. Moreover,
reaction of an internal aminoalkyne with a methyl
(1n) or phenyl group (1o) could also produce 3na and
3oa in good yields. In contrast, N-benzyl-substituted
aminoalkyne 1p gave only acyclic product 4pa,
which did not further undergo intramolecular enyne-
cyclization even at increased temperature. We
surmised that the electron-riched nitrogen attached to
benzyl group of 1p preferred to undergo the
intermolecular nucleophilic addition with electron-
deficient alkyne 2a, instead of forming the enamine
intermediate via hydration of 1p. When dimethyl but-
2-ynedioate (2b) was used as the alkyne,
tetrahydroazocine 3ab and oxa-tetrahydroazocine
3mb were obtained in 99% and 63% yields,
respectively. Notably, unsymmetrical electron-
deficient alkyne 2c was also a good substrate, giving
regioselective 3ac and 3mc in 99% and 69% yields,
respectively. And the regioselectivity of the reaction
can be attributed to stronger electron-withdrawing
ability of trifluoromethyl group than that of ester
group (CO2Et). The absolute configurations of 3aa
and 3mc were unambiguously confirmed by X-ray
single-crystal diffraction analysis (Figures S1 and
a)
Standard procedure: A Schlenk tube was charged with
PtI2 (1.1 mg, 0.0025 mmol, 2.5 mol%), -aminoalkyne 1
(0.1 mmol), DCE (1.0 mL), and alkynyl ester 2 (0.11
mmol, 1.1 equiv.) in that order, and the mixture was stirred
at 100 °C for 4 h under argon and monitored by TLC.
Isolated yields are given. N.R. = no reaction.
reaction mixture was stirred at 150 °C for 8 h.
b)
The
The
c)
reaction was conducted at 120 °C for 5 h in the presence of
PtI2 (2.3 mg, 0.005 mmol, 5 mol%). The reaction was
d)
conducted step-by-step. A Schlenk tube was charged with
PtI2 (2.3 mg, 0.005 mmol, 5 mol%), -aminoalkyne 1o (0.1
mmol) and DCE (1.0 mL), the mixture was stirred at 100
°C for 24 h under argon, then alkynyl ester 2a (0.11 mmol,
1.1 equiv.) was injected to the mixture for another 4 h at
100 °C. e) The reaction was conducted at room temperature
for 1 h.
A gram-scale reaction of 1a (3 mmol) and 2a (3.3
mmol) produced 3aa in 99% yield in the presence of
PtI2 (2.5 mol%) at 100 °C for 4 h in DCE (Scheme 2).
S2).[10
]
Table 2. PtI2-catalyzed cascade reactions of -amino
alkynes 1 and electron-deficient alkynes 2.a)
Scheme 2. Gram-scale reaction.
To gain insight into the mechanism of this cascade
reaction, we conducted several control experiments.
First, we found that subjecting -aminoalkyne 1a to
the standard conditions in the absence of alkyne 2a
gave hydration product I in 99% yield, whereas no
reaction occurred in the absence of PtI2 catalyst
(Scheme 3, eq.1). Isolation of aminoketone I and
subsequent reaction with diethyl but-2-ynedioate (2a)
delivered a 99% and 64% yields of tetrahydroazocine
3aa in the presence or absence of PtI2 for the same
reaction time (Scheme 3, eq.2). These results
demonstrated that the PtI2 was requisite to the
hydration of -aminoalkyne 1a. To confirm that the
4
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10.1002/adsc.201901644
Advanced Synthesis & Catalysis
hydration product was involved in the reaction, we
added either 4Å molecular sieves or water (0.5 to 55
equiv) to the reaction mixture and found that the yield
of 3aa was lower in the presence of 4Å molecular
sieve (Scheme 3, eq.3), and a small amount of water
added had no obvious deleterious effect on the
reaction outcome, while a large amount of water
would complicate the reaction system and
significantly reduce the yield of product (Scheme 3,
eq.4). Taken together, we surmised that a trace
amount of water in the system was conducive to the
reaction. And the source of water may come from the
materials and DCE solvent as well as during the
course of feeding in the air. Moreover, the
determination of moisture content has been done by
titration experiments, the results showed that the total
water content was 100 ppm (about 0.1 mg H2O) for
the reaction system (0.1 mmol 1a and 1 mL DCE), it
may not enough to achieve completely hydration of
the alkynes. Nevertheless, the aminoketone was then
transformed to the cycloenamine with the elimination
of one molecular H2O. In other words, the whole
reaction needs only trace amount of water to undergo
the hydration of alkyne concomitant with the
formation of high reactive cycloenamine and
subsequent transformation. Additionally, in the
absence of PtI2 catalyst, the reaction of 1a and 2a
afford a intermolecular hydroamination product 5 in
20% yield with most substrate remained and with no
3aa produced (Scheme 3, eq.5). This result further
indicates that PtI2 mainly accelerates the hydration of
aminoalkyne and the formation of enamine
intermediate, has no significant promotion of
subsequent intermolecular nucleophilic addition
reaction.[11] Fortunately, the reaction of aminoketone I
with 2a was conducted at 20 C to afford the
intermediate IV, which was isolated by column
chromatography (neutral alumina), and the sructure
was confirmed by NMR spectra.[12]
Scheme 3. Controlled experiments.
Figure 4. IR spectrum of aminoketone I in toluene: (a)
Without molecular sieve. (b) With 5 Å molecular sieve
after 12 h at 120 C.
Besides, we added 5Å molecular sieve to the
aminoketone I in toluene, found that both the NH
stretching vibration (3381 cm-1) and the carbonyl
stretching vibration (1706 cm-1) of aminoketone I
nearly disappeared in IR spectroscopy, as well as
with the appearance of new weak enamine
deformation vibration (1599 cm-1). It was inferred
that cycloenamine intermediate II was generated
(Figure 4).[13]
On the basis of the above all experiments, we
proposed a possible mechanism shown in Scheme 4.
In the presence of PtI2, -aminoalkyne 1a is hydrated
to generate aminoketone intermediate I (path a),
which is subsequently transformed to enamine
intermediate II via intramolecular cyclocondensation
and deprotonation reactions. The Intermediate II
undergoes an intermolecular nucleophilic addition
reaction with electron-deficient alkyne 2a to generate
intermediate III, and a concomitant intramolecular
cyclization reaction gives fused cyclobutene
intermediate IV. This intermediate is readily
converted to eight-membered nitrogen heterocycle
3aa via ring expansion,[14] owing to the highly
strained skeleton and sterically bulky substituents of
IV. It should be noted that the direct intramolecular
6-exo-dig hydroamination cyclization of 1a to give
intermediate II (path b) cannot be ruled out.
5
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10.1002/adsc.201901644
Advanced Synthesis & Catalysis
evidences, namely, hydration of the δ-aminoalkynes
and
subsequent
intramolecular
cyclization-
intermolecular nucleophilic addition-intramolecular
cycloaddition-ring expansion cascade sequence was
involved in this reaction. This method provides a
novel strategy for the construction of medium-sized
ring. In addition, product 3ab could be used as a
starting material for the synthesis of fluorescent
molecule 6. Further functionalization transformation
of products is on progress in our group.
Experimental Section
Scheme 4. Possible reaction mechanism.
General Method for the Synthesis of product 3
To a dried Schlenk tube was added PtI2 (1.2 mg, 2.5 mol%),
different -aminoalkynes 1 (0.1 mmol), alkynylesters 2
(0.11 mmol, 1.1 equiv.) and DCE (1 mL) were sequentially
added under Ar atmosphere, the mixture was stirred at
100 C until -aminoalkynes 1 disappear (monitored by
TLC). Then filtered, the filtrate was concentrated in vacuo
to give the residue, which was purified by column
chromatography with gradient elution (Silica gel,
petroleum ether : ethyl acetate = 10 : 1) to give the final
products 3.
Acknowledgements
We are grateful for financial support from the National Key
Research and Development Program of China (no.
2017YFD0201404) and the National Natural Science Foundation
of China (no. 21873051), as well as from the Natural Science
Foundation of Tianjin City (no. 17JCZDJC37300). We also
acknowledge support from the Collaborative Innovation Center
of Chemical Science and Engineering (Tianjin).
Scheme 5. Transformation of tetrahydroazocine 3ab.
Finally, we disclosed that reaction of
tetrahydroazocine 3ab with commercially available
tetracyanoethene yielded tricyanovinylated aniline
derivative 6 rather than expected [4+2]-cycloadduct 7
(Scheme 5). Interesting, 6 possessed fluorescent
properties,[15] displaying different colors in various
polar solvents in daylight (Figure S4). The absorption
and emission spectra of 6 were measured in these
solvents (Figures S5 and S6, Tables S1 and S2), and
the results indicated that the absorption wavelength of
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A recyclable platinum-catalyzed cascade reactions
of δ-aminoalkynes and electron-deficient alkynes was
developed for the synthesis of tetrahydroazocines.
The recyclability of PtI2 catalyst was supported by
several experiments and confirmed by some
analytical determination, and the PtI2 catalyst could
be easily recovered by simple centrifugation and
reused without substantial loss of activity. This
highly efficient cascade reaction affords a variety of
eight-membered nitrogen heterocycles in excellent
yields. And a reasonable mechanism was proposed
based on some controll experiments and solid
[4] For recent papers that use ring expansion methods to
improve the efficiency of nitrogen containing medium-
sized rings, see: a) T. C. Stephens, W. P. Unsworth.
Synlett. 2020, 31, 133-146; b) J. R. Donald, W. P.
6
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10.1002/adsc.201901644
Advanced Synthesis & Catalysis
Unsworth, Chem. Eur. J. 2017, 23, 8780–8799; c) L.
[10] Crystal data for the compound 3aa: C20H25NO4,
MW 343.41, Monoclinic, C2/c, Final R indices [I>
2ó(I)], R1 = 0.0598, wR2 = 0.1540, R indices (all
data) R1 = 0.0769, wR2 = 0.1689, a = 30.391 (6) Å,
b = 8.1281 (16) Å, c = 17.670 (4) Å, V) 3684.9 (16)
A^3, T) 113 K, Z) 8. Reflections collected / unique:
4399/ 3475 [R(int) = 0.046], number of observations
[>2ó(I)] 4399, parameters) 246, Goodness-of-fit on
F^2) 1.085. Supplementary crystallographic data
G. Baud, M. A. Manning, H. L. Arkless, T. C.
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have
been
deposited
at
the
Cambridge
Crystallographic Data Center. CCDC 1834346.
Crystal data for the compound 3mc: C17H18F3NO3,
MW 341.32, monoclinic, P21/c, Final R indices [I>
2ó(I)], R1 = 0.0584, wR2 = 0.1875, R indices (all
data) R1 = 0.0900, wR2 = 0.1492, a = 8.4341 (8) Å, b
= 11.5843 (17) Å, c = 16.7267 (18) Å, V) 1605.6 (3)
A^3, T) 120 K, Z) 4. Reflections collected / unique:
7269/ 3706 [R(int) = 0.038], number of observations
[>2ó(I)] 2491, parameters) 219, Goodness-of-fit on
F^2) 0.91. Supplementary crystallographic data have
been deposited at the Cambridge Crystallographic
Data Center. CCDC 1941876.
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7
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10.1002/adsc.201901644
Advanced Synthesis & Catalysis
FULL PAPER
Synthesis
of
Eight-Membered
Nitrogen
Heterocycles via a Heterogeneous PtI2-Catalyzed
Cascade Cycloaddition Reaction of
Aminoalkynes with Electron-Deficient Alkynes
-
Adv. Synth. Catal. Year, Volume, Page – Page
Xinhong Li,a Songmeng Wang,a Hongkai Wang,a
Weilin Wang,a Lingyan Liu, a* Weixing Chang,a
Jing Lia,b*
8
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