Nickel-catalyzed indium(I)-mediated syn-selective propargylation of aldehydes

Article abstract of DOI:10.1002/ejoc.201201008

Low-valent indium(I)-mediated nickel-catalyzed propargylation of aldehydes is described. The nickel/indium(I)-mediated reaction of propargylic carbonates possessing different substitution patterns afforded syn-homopropargylic alcohols in high yields upon coupling with a variety of carbonyl compounds. Both the nickel catalyst and the phosphane ligands were found to play a crucial role in this transformation. The diastereoselectivity is strongly dependent on the ligand employed. A mechanism involving umpolung of the propargylnickel intermediates under the influence of low-valent indium is proposed to account for the dependence of the stereochemical characteristics of the phosphane ligands.

Full text of DOI:10.1002/ejoc.201201008

Job/Unit: O21008
/KAP1
Date: 03-09-12 12:00:12
Pages: 6
SHORT COMMUNICATION
DOI: 10.1002/ejoc.201201008
Nickel-Catalyzed Indium(I)-Mediated syn-Selective Propargylation of
Aldehydes
[a]
[a]
[a]
[a]
[a]
Tsunehisa Hirashita,* Yuuki Suzuki, Hiromitsu Tsuji, Yoshiki Sato, Kojiro Naito,
and Shuki Araki[
a]
Keywords: Indium / Nickel / Diastereoselectivity / C-C coupling / Alkynes
Low-valent indium(I)-mediated nickel-catalyzed proparg-
ylation of aldehydes is described. The nickel/indium(I)-me-
diated reaction of propargylic carbonates possessing dif-
ferent substitution patterns afforded syn-homopropargylic
alcohols in high yields upon coupling with a variety of carb-
onyl compounds. Both the nickel catalyst and the phosphane
ligands were found to play a crucial role in this transforma-
tion. The diastereoselectivity is strongly dependent on the
ligand employed. A mechanism involving umpolung of the
propargylnickel intermediates under the influence of low-
valent indium is proposed to account for the dependence of
the stereochemical characteristics of the phosphane ligands.
Introduction
corresponding homopropargylic alcohols with high syn
selectivity, which is opposite to Marshall propargylation
promoted by palladium catalysts.
Over the last decade, protocols involving the use of low-
valent indium with a catalytic amount of a transition metal
have been developed for organic synthesis.[ After the for-
mation of π-allylpalladium complexes by oxidative addition
1]
Results and Discussion
0
[2]
of Pd to allylic alcohol derivatives or by insertion of all-
enes to arylpalladium(II) compounds, transmetalation with
Propargylic mesylates and carbonates 1a–f were initially
In or In yields allylic indium reagents that react with carb- tested in the propargylation reaction (Scheme 1 and
I
0
onyl compounds to give the corresponding homoallylic Table 1). When propargyl mesylate (1a) and benzaldehyde
alcohols in high yields.[ Although the addition of allenyl/ were treated with InI in the presence of Ni(acac) (20 mol-
3]
2
propargylic metals with carbonyl compounds is an ex- %) and PPh (80 mol-%) in 1,3-dimethyl-2-imidazolidinone
3
tremely powerful method to prepare homopropargylic (DMI), a mixture of homoallenyl alcohol 2a and homo-
[
4]
alcohols, regioselective and stereoselective propargylation propargyl alcohol 3a was obtained in moderate yield
mediated by indium has received less attention than In-me- (Table 1, entry 1).
A
similar reaction catalyzed by
diated allylation.[ Propargylic indium reagents are pre- Pd(PPh ) selectively afforded 3a (Table 1, entry 2). The Pd-
5]
3
4
pared from propargylic halides by oxidative addition in a catalyzed reaction of mesylate 1b gave homoallenyl alcohol
manner similar to that of allylic indium reagents or re- 2b in 82% yield, although carbonate 1bЈ gave no product
ductive transmetalation from propargylic palladium com- (Table 1, entry 4). However, the Ni-catalyzed reaction of 1bЈ
0
pounds with InI or In . Marshall and co-workers studied proceeded rapidly to furnish 2b (61%) together with 3b
the InI-mediated propargylation of carbonyl compounds (30%; Table 1, entry 5). Substituents at the propargylic po-
extensively eventually to produce anti-homopropargylic sitionwerefoundtohaveacrucialeffectonthisreaction:benzylcarb-
alcohols with high selectivity.[ We explored a new method onates 1c and 1e underwent propargylation by both nickel
for the InI-mediated allylation of carbonyl compounds by and palladium catalysts to afford 3c and 3e (Table 1, en-
6]
[
7]
using π-allylnickel complexes, where allylic alcohols and tries 6, 7, 10, and 11). In contrast, propargylation with
[
8]
dienes serve as good precursors to the allylic reagents. We carbonates 1d and 1f bearing a methyl group at the prop-
describe herein that the Ni-catalyzed InI-mediated reaction argylic carbon atom proceeded only in the presence of the
of propargyl alcohol derivatives with aldehydes gives the nickel catalyst to give 3d and 3f in high yields (Table 1,
entries 8, 12 vs. 9, 13).
[
a] Graduate School of Engineering, Nagoya Institute of
The stereochemical outcome of this propargylation was
confirmed by the reaction of 1d with cyclohexanecarbal-
dehyde, which gave homopropargylic alcohol 3g selectively
with a 93:7 ratio of diastereomers. The configuration of the
major diastereomer was determined to be syn by compari-
Technology,
Gokiso-cho, Showa-ku, Nagoya 466-8555, Japan
Fax: +81-52-735-5206
E-mail: hirasita@nitech.ac.jp
Homepage: http://www.nitech.ac.jp/
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201201008.
[
9]
son with an authentic sample. A similar reaction per-
Eur. J. Org. Chem. 0000, 0–0
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T. Hirashita, Y. Suzuki, H. Tsuji, Y. Sato, K. Naito, S. Araki
Table 2. Reaction of propargylic carbonate 1d with benzaldehyde.[a]
SHORT COMMUNICATION
Entry
Ligand
Yield [%] (syn/anti)[b]
Pd
Ni
Scheme 1. Propargylic mesylates and carbonates for propargyl-
ation.
1
2
3
4
5
6
7
8
9
PPh
PPh
PPh
PPhCy
PCy
P(p-MePh)
P(p-MeOPh)
P(p-CF Ph)
3
3
2
82 (64:36)
Ͼ99 (62:38)[
25 (67:33)
NR
96 (87:13)[c]
d]
Cy
2
76 (95:5)
39 (64:36)
33 (71:29)
97 (72:28)
Ͼ99 (58:42)
trace
3
NR
3
96 (74:26)
89 (78:22)
NR
NR
94 (77:23)
Table 1. Reaction of derivatives of propargylic alcohol with benzal-
3
[
a]
dehyde.
3
3
P(o-MePh)
dppf
3
NR
Entry
1
Catalyst[b]
Time
Yield [%][c]
1
1
1
1
0
1
2
3
100 (37:63)
Ͼ99 (80:20)
93 (52:48)
[h]
2
3
[e]
dpe-phos
89 (89:11)
1
2
1a
1a
1b
1bЈ
1bЈ
1c
1c
1d
1d
1e
1e
1f
Ni
Pd
Pd
Pd
Ni
Ni
Pd
Ni
Pd
Ni
Pd
Ni
Pd
1
8
3
24
2
3
4
4
22
3
3
2
2a: 9
3a: 46
Ͼ99 (87:13)[
NR
e]
0
3a: 22
[
d]
14
P(2-furyl)3
IPr
none
trace
NR
3
4
5
6
7
8
9
1
1
1
1
2b: 82
0
2b: 61
0
0
1
1
5
6
NR
NR
NR[
d]
3b: 30
c]
0
0
0
0
0
0
0
0
3c: 69 (62:38)[
3c: 100 (56:44)
3d: 90 (82:18)[
0
[a] Pd: Pd(OAc)
2
(5 mol-%), monodentate ligand (20 mol-%) or bi-
(10 mol-%), monodentate
[c]
dentate ligand (10 mol-%); Ni: Ni(acac)
ligand (40 mol-%) or bidentate ligand (20 mol-%). [b] Yield and dr
values were determined by H NMR spectroscopy with 1,4-dime-
thoxybenzene as a standard. [c] Isolated yield. [d] Pd(acac)
2
e]
1
c]
c]
0
1
2
3
3e: 91 (100:0)[
2
was
[
3e: 92 (63:37)
used as the catalyst. [e] In DMI.
3f: 98 (96:4)[
e]
1f
23
0
[
(
[
(
a] All reactions were conducted with 1 (0.50 mmol), benzaldehyde
0.25 mmol), Ni or Pd catalyst, and InI (0.50 mmol) in DMI at r.t.
b] Pd: Pd(PPh (10 mol-%); Ni: Ni(acac) (20 mol-%) and PPh
80 mol-%). [c] Determined by H NMR spectroscopy. [d] The reac-
When PPh was used as a ligand in the Pd-catalyzed re-
action, 3d was obtained with moderate selectivity, whereas
the Ni-catalyzed reaction gave 3d with high syn selectivity
3
3
)
4
2
3
1
(
Table 2). This syn selection is not attributable to the acetyl-
tion was performed on 0.30-mmol scale. [e] Determined by GC
analysis of the corresponding acetates.
acetonate ligand because Pd(acac) showed no effect on the
2
diastereoselectivity (Table 2, entry 2). Aromatic substituents
on the phosphane atom are crucial for promoting the reac-
tion; replacing the phenyl groups by cyclohexyl groups led
to erosion of the yields and the selectivities (Table 2, en-
tries 3–5). Introducing a methyl or a methoxy group at the
para position affected both the Pd-catalyzed and Ni-cata-
lyzed reactions in an opposite manner (Table 2, entries 6
and 7). An increase in the syn selectivity was found in the
former and a large decrease in the diastereoselectivity was
observed in the latter, in particular for P(o-MeOC H ) .
formed with propargylic bromide 1dЈ and metallic indium
afforded the anti adduct selectively (Scheme 2).
6
4 3
The introduction of a CF group at the para position or a
3
methyl group at the ortho position suppressed the proparg-
ylation completely (Table 2, entries 8 and 9). A bidentate
ligand exerted markedly different effects on the two reac-
tions (Table 2, entries 10–13). The use of diphenylphos-
phanylferrocene (dppf) and dpe-phos (bis[2-(diphenylphos-
phanyl)phenyl] ether) improved the selectivity of the Pd-cat-
alyzed reaction. However, when dppf was used in the Ni-
catalyzed reaction, the anti isomer prevailed slightly
Scheme 2. Divergent diastereoselective propargylation.
The results showed that the limitations of the Pd-cata- (Table 2, entry 10), and the Ni-catalyzed reaction with dpe-
lyzed reaction were simply overcome by changing the sol- phos showed almost no diastereomeric selectivity (Table 2,
vent. In THF, even non-benzylic propargylic carbonates entry 12). The reactions performed in DMI (Table 2, en-
were useful in the reaction. Therefore, we next examined tries 11 and 13) caused recovery of the syn selectivity similar
the effects of ligands on the stereoselectivity of the reaction to that of entry 8 in Table 1. 2-Furylphosphane and a N-
of 1d with benzaldehyde (Table 2).
heterocyclic carbene ligand were not operative under the
2
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I
Ni-Catalyzed In -Mediated syn-Selective Propargylation of Aldehydes
conditions for this reaction (Table 2, entries 14 and 15).
The strong effect of the ligand on the diastereoselectivity
Both Pd(acac) and Ni(acac) without phosphane ligands shown in Table 2 might imply that the allenyl/propargyl
2
2
were found to be inactive (Table 2, entry 16).
nickel reagents react directly with benzaldehyde and InI
II
Because the highest syn selectivity was observed in the simply acts as a reducing agent for the Ni catalyst. To
case with PPh , a series of Ni-catalyzed reactions of prop- elucidate this possibility, reaction with a stoichiometric
3
argylic carbonates with carbonyl compounds was next ex- amount of Ni(cod) was conducted in the absence of InI
2
amined in the presence of PPh (Table 3). The reactions of (Scheme 3). The reaction did not proceed in the presence of
3
1
d with cyclohexanecarbaldehyde afforded 3g in good yield an indium(III) salt, which is thought to be formed in situ
I
with a ratio similar to that of benzaldehyde. The reactions during the oxidative process of In . In contrast, reaction
of 1d with p-anisaldehyde or aliphatic aldehydes gave the with a catalytic amount of Ni(cod) (10 mol-%) and InI
2
corresponding homopropargylic alcohols 3h–j in good (100 mol-%) gave the corresponding alcohol 3d in good
yields with high syn selectivity. When α-phenyl-substituted yield.
carbonate 1g was subjected to coupling with benzaldehyde,
3
k was obtained with syn selectivity. Substituents at the
acetylenic terminus did not affect this tendency: carbonates
h and 1i afforded 3l and 3m in good yields while main-
1
taining high levels of syn selectivity. The reaction of 1i with
ortho- and para-hydroxybenzaldehydes gave 3n and 3o, indi-
cating that the phenolic hydroxy group neither deterred the
reaction nor affected the selectivity. Upon coupling of 1i
with acetophenone, the predominant formation of syn-3p
and an increase in the syn selectivity in DMI were also ob-
served. When carbonate 1j with a free acetylenic hydrogen
atom was subjected to the conditions, the corresponding
homopropargylic alcohol 3q was obtained accompanying
its hydrogenated product.
Scheme 3. Propargylation with stoichiometric and catalytic
amounts of Ni catalyst.
Recently, allylindium reagents having a square pyramidal
geometry with apical phosphane ligands were isolated and
[
10]
fully characterized by X-ray analysis.
These isolable all-
Table 3. Propargylation of aldehydes with 1d and 1g–j.
ylindium compounds were prepared by the addition of the
phosphane ligands to the allylic indium compounds. We
next examined the possibility that a similar coordination of
the phosphanes to the allenylindium reagents is responsible
for the capricious characteristics of these propargylations.
Consequently, the allenyl/propargylindium reagent, pre-
pared from 1dЈ and metallic indium, was allowed to react
with benzaldehyde in the presence or absence of PPh3
(Scheme 4). The In-mediated propargylation gave 3d in
good yield with almost 1:1 diastereomeric ratio after 5 h,
although a lowered yield with bias to the syn isomer was
observed after 1 d, indicating that selective decomposition
of the anti isomer occurred, as found in crotylation reac-
[
11]
tions.
This decay was suppressed by PPh : 3d was ob-
3
tained in 71% yield with a slight bias to the syn isomer.
These observations were informative but insufficient to ac-
count for the syn selectivity.
3
Scheme 4. Effects of PPh on the allenyl/propargylindium reagent.
1
[
a] Figures in parentheses show a syn/anti ratio determined by H
Considering the results described previously, we raise an
important question: why did the phosphane ligands affect
NMR spectroscopy. [b] Yield determined by NMR spectroscopy.
c] syn-2-Methyl-1-phenylbut-3-en-1-ol was obtained (12%).
[
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T. Hirashita, Y. Suzuki, H. Tsuji, Y. Sato, K. Naito, S. Araki
SHORT COMMUNICATION
the stereochemical outcome of the propargylation? The Acknowledgments
phosphane ligands might no longer be able to exist on the
allenyl/propargyl indium reagents provided that the trans-
This work was partially supported by a Grant-in-Aid for Scientific
Research from the Ministry of Education, Science, Sports and Cul-
mechanism of the palladium-catalyzed umpolung allyl- ture, Japan (No. 14340195).
metalation is completed. In connection with our study, the
[
12]
[13]
ation
and propargylation
using Et Zn or Et B might
2 3
be helpful for understanding the present reaction. Recently,
η -allylpalladium species are proposed as intermediates for
the enantioselective allylations that cannot be reconciled
1
[1] a) S. Araki, T. Hirashita in Main Group Metals in Organic Syn-
thesis Vol. 1 (Eds.: H. Yamamoto, K. Oshima), Wiley, New
York, 2004, pp. 323–386; b) S. Araki, T. Hirashita in Compre-
hensive Organometallic Chemistry III (Eds.: R. Crabtree, M.
Mingos), Elsevier, Oxford, 2007, pp. 649–751.
with the initially proposed mechanism involving allylic zinc
or allylic boron reagents through transmetalation.[
14,15]
Di-
metallic Pd–Zn complexes have also been proposed for [2] a) J. A. Marshall, L. M. McNulty, D. Zou, J. Org. Chem. 1999,
propargylation by a computational study.[
16]
64, 5193–5200; b) S. Araki, T. Kamei, T. Hirashita, H. Yama-
mura, M. Kawai, Org. Lett. 2000, 2, 847–849.
A similar
mechanism based on the umpolung of the propargylnickel
intermediates under the influence of low-valent indium is
apparently a plausible explanation for the present reaction.
The preferred stereochemical mode of propargylation
[
3] a) U. Anwar, R. Grigg, M. Rasprini, V. Savic, V. Sridharan,
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with allenyl/propargyl metals depends on the intrinsic prop-
erties of the counter metal and the circumstances.[
17,18]
Al-
though
a general approach to anti-homopropargylic
alcohols, including the Pd-catalyzed InI-mediated proparg-
ylation, has been well established, little is known about
accessing syn isomers. The present propargylation provides
a facile and efficient route to these compounds by using
only nickel catalysts instead of palladium catalysts, which
give the anti isomers predominantly.
2
005, 3071–3073; i) R. Grigg, S. McCaffrey, V. Sridharan,
C. W. G. Fishwick, C. Kilner, S. Korn, K. Bailey, J. Blacker,
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haran, Tetrahedron 2008, 64, 8177–8181.
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[
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In summary, we have developed the InI-mediated syn-
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pargyl carbonates in the presence of Ni catalysts. The pres-
ent Ni-catalyzed propargylation proved to have a different
5
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0
nature than either the In -mediated or the Pd-catalyzed InI-
[
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mediated reactions. Further applications of this propargyl-
ation reaction are currently under study.
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8214–8219; c) J. A. Marshall, H. R. Chobanian, J. Org. Chem.
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[9] K. Furuta, M. Ishiguro, R. Haruta, N. Ikeda, H. Yamamoto,
Typical Experimental Procedure: To a mixture of Ni(acac)
pared by heating Ni(acac) ·2H O (15 mg, 0.05 mmol) under re-
duced pressure, was added PPh (53 mg, 0.2 mmol), indium(I) iod-
2
, pre-
2
2
[
3
ide (121 mg, 0.50 mmol) in THF (1.0 mL), methyl 4-phenylbut-3-
yn-2-yl carbonate (1d; 90 μL, 0.50 mmol), and benzaldehyde
Bull. Chem. Soc. Jpn. 1984, 57, 2768–2776.
10] a) M. Yasuda, M. Haga, A. Baba, Eur. J. Org. Chem. 2009,
[
(26 μL, 0.25 mmol). The reaction mixture was stirred at room tem-
5
513–5517; b) M. Yasuda, M. Haga, A. Baba, Organometallics
perature under an atmosphere of argon for 1 d and then quenched
with dilute hydrochloric acid (1 m). The product was extracted with
diethyl ether and washed with aqueous saturated sodium hydrogen
carbonate, water, and brine. The organic layer was dried with anhy-
drous sodium sulfate, and the solvent was removed under reduced
pressure. The residue was purified by chromatography on silica gel
2009, 28, 1998–2000.
[
[
11] G. C. Lloyd-Jones, T. Russell, Synlett 1998, 903–905.
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787–789.
[
13] Y. Tamaru, S. Goto, A. Tanaka, M. Shimizu, M. Kimura, An-
(
(
EtOAc/hexane = 1:5) to give 2-methyl-1,4-diphenylbut-3-yn-1-ol
3d; 58 mg, 96%, syn/anti = 87:13).
gew. Chem. Int. Ed. Engl. 1996, 35, 879–880.
[14] G. P. Howell, A. J. Minnaard, B. L. Feringa, Org. Biomol.
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Supporting Information (see footnote on the first page of this arti-
cle): General methods, assignment of syn/anti isomers, experimen-
tal procedures, spectroscopic data of the products, and copies of
[
15] S.-F. Zhu, X.-C. Qiao, Y.-Z. Zhang, L.-X. Wang, Q.-L. Zhou,
Chem. Sci. 2011, 2, 1135.
[16] R. Álvarez, A. R. D. Lera, J. M. Aurrecoechea, A. Durana, Or-
ganometallics 2007, 26, 2799–2802.
1
the H NMR spectra.
4
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I
Ni-Catalyzed In -Mediated syn-Selective Propargylation of Aldehydes
[
17] a) E. Vrancken, H. Gérard, D. Linder, S. Ouizem, N. Alouane,
E. Roubineau, K. Bentayeb, J. Marrot, P. Mangeney, J. Am.
Chem. Soc. 2011, 133, 10790–10802 and references cited therein
b) M. Chen, W. R. Roush, J. Am. Chem. Soc. 2012, 134, 10947–
[18] Marshall propargylation normally gives anti-homopropargylic
alcohols upon coupling of a broad range of aldehydes; how-
ever, reaction of benzaldehyde afforded a nearly 1:1 mixture of
anti and syn adducts in agreement with the results shown in
Table 1. See ref.[
6a]
1
0952; c) Y. Sasaki, M. Sawamura, H. Ito, Chem. Lett. 2011,
40, 1044–1046; d) L. N. Guo, H. Gao, P. Mayer, P. Knochel,
Received: July 27, 2012
Chem. Eur. J. 2010, 16, 9829–9834.
Published Online: ᭿
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Date: 03-09-12 12:00:12
Pages: 6
T. Hirashita, Y. Suzuki, H. Tsuji, Y. Sato, K. Naito, S. Araki
SHORT COMMUNICATION
Propargylation
The Ni-catalyzed InI-mediated propargyl-
ation of carbonyl compounds gave the cor-
responding homopropargylic alcohols in
high yields with syn selectivity. Aromatic
phosphane ligands were found to play a
crucial role in this transformation.
T. Hirashita,* Y. Suzuki, H. Tsuji, Y. Sato,
K. Naito, S. Araki ............................ 1–6
Nickel-Catalyzed Indium(I)-Mediated syn-
Selective Propargylation of Aldehydes
Keywords: Indium / Nickel / Diastereoselec-
tivity / C-C coupling / Alkynes
6
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