Rhodium(I)-catalyzed arylation of β-chloro ketones and related derivatives through domino dehydrochlorination/conjugate addition

Article abstract of DOI:10.1002/adsc.201200821

Highly efficient arylations of β-chloro ketones and their ester and amide derivatives were achieved by means of domino dehydrochlorination/Rh(I)- catalyzed conjugate addition. In situ generated vinyl ketones and their analogues were identified as the reaction intermediates. The present synthetic protocol provides a concise route to (chiral) β-aryl ketones, esters, and amides. Copyright

Full text of DOI:10.1002/adsc.201200821

UPDATES
DOI: 10.1002/adsc.201200821
Rhodium(I)-Catalyzed Arylation of b-Chloro Ketones and
Related Derivatives through Domino Dehydrochlorination/
Conjugate Addition
Quanbin Jiang,a Tenglong Guo,a Qingfu Wang,a Ping Wu,a and Zhengkun Yua,b,*
a
Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian, Liaoning 116023,
Peopleꢀs Republic of China
Fax : (+86)-411-8437-9227; e-mail: zkyu@dicp.ac.cn
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, CAS, 354 Fenglin Road,
b
Shanghai 200032, Peopleꢀs Republic of China
Received: September 12, 2012; Revised: March 20, 2013; Published online: && &&, 0000
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/adsc.201200821.
Abstract: Highly efficient arylations of b-chloro ke-
tones and their ester and amide derivatives were
achieved by means of domino dehydrochlorination/
Rh(I)-catalyzed conjugate addition. In situ generat-
ed vinyl ketones and their analogues were identified
as the reaction intermediates. The present synthetic
protocol provides a concise route to (chiral) b-aryl
ketones, esters, and amides.
nation to result in other undesired reactions. How-
AHCTUNGTREGeNNUN ver, the consequence of such a b-hydride elimination
process may be applied in a domino reaction se-
quence[10] to accomplish an indirect cross-coupling.
Although nickel compounds have always been used
as the effective catalysts for alkyl halide-involving
cross-couplings, other transition metals have recently
been reported.[7–9,11] In this aspect, a palladium-cata-
lyzed one-pot, two-step procedure, i.e., hydrolysis/de-
hydrochlorination/Heck coupling of chloroethanesul-
fonyl chloride with iodoarenes, was realized to pre-
pare styrene sulfonate salts [Scheme 1 (b)].[11] During
Keywords: arylation; b-chloro ketones; domino re-
3
À
actions; rhodium(I); sp C Cl bond cleavage
Activated alkyl chlorides have been used as electro-
philes in cross-coupling processes.[1] Recently, carbon-
carbon cross-couplings involving the cleavage of unac-
3
À
tivated sp C Cl bonds have become more and more
attractive.[2] Fu et al. reported nickel-catalyzed Suzuki
reactions of unactivated alkyl chlorides with 9-BBN-
alkyls.[3,4] Unactivated secondary alkyl chlorides also
underwent the same type of reactions,[5] in which an
amino-directing group was required [Scheme 1 (a)].[5b]
With bimetallic nickel/copper catalysts, Hu et al. es-
tablished the cross-coupling reactions of unactivated
alkyl halides with terminal alkynes[6a] and hetero-
ACHTUNGTRENNUNG
arenes,[6b] respectively. Chlorocycloheptane was re-
ported to couple with lithium arylborates.[7] Unacti-
vated chlorides have also been documented for Ne-
gishi reactions.[8] In the presence of the Grignard re-
agent cyclohexylmagnesiun chloride, unactivated alkyl
À
chlorides were utilized for arene C H functionaliza-
tion.[9]
The major problem of alkyl halide-involving cross-
coupling reactions is that the halide substrate or inter-
mediate generated in situ undergoes b-hydride elimi- Scheme 1. sp C Cl cleavage of alkyl chlorides.
3
À
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Quanbin Jiang et al.
Table 1. Screening of conditions for the reaction of 3-chloropropiophenone (1a) and phenylboronic acid (2a).[a]
UPDATES
Entry
Catalyst/
N
Ligand/
A
Ratio 3a:4
Yield of 3a [%][b]
1[c]
2
N
G
(Æ)-BINAP/5
(Æ)-BINAP/5
(Æ)-BINAP/5
(Æ)-BINAP/5
(Æ)-BINAP/5
(Æ)-BINAP/5
(Æ)-BINAP/2.5
(Æ)-BINAP/5
PPh3/10
dppe/5
dppp/5
dppb/5
–
>99:1
>99:1
73:27
>99:1
>99:1
>99:1
99:1
95:5
93:7
93:7
93:7
99:1
99:1
96:4
92:8
92:8
>99:1
43
88
69
69
68
97
82
91
75
69
80
83
88
85
86
82
99
3[d]
4
5
6
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
T
N
E
T
E
E
T
E
R
A
7
8[d]
9
10
11
12
13
14[e]
15[f]
16[g]
17[h]
(Æ)-BINAP/5
(Æ)-BINAP/5
(Æ)-BINAP/5
(Æ)-BINAP/5
[a]
molar ratio of 3a:4 was determined by GC analysis.
[b]
[c]
[d]
[e]
[f]
Isolated yields.
2a (0.5 mmol).
Water (0.2 mL) was added.
In toluene.
In THF.
At 508C.
[g]
[h]
At 808C.
3
À
our ongoing study on sp C Cl bond activation/cleav-
RhClACTHGUNTRENNU(G PPh3)3 was found to be the most efficient cat-
age, we envisioned that hydrochloride might be elimi- alyst with (Æ)-BINAP as the suitable ligand (Table 1,
nated from b-chloro ketones by a base to form the entries 1–12). With 5 mol% catalyst loading, 3a was
corresponding a,b-unsaturated ketones which subse- obtained in 97% yield (Table 1, entry 6). The reaction
quently undergo catalytic conjugate addition, afford- also proceeded under ligand-free conditions (Table 1,
ing indirect cross-coupling products. Herein, we entry 13). In toluene or THF or at 508C, the reaction
report an efficient Rh(I)-catalyzed domino dehydro- was less efficient (Table 1, entries 14–16), whereas ele-
chlorination/conjugate addition process for the aryla- vating the temperature to 808C resulted in the desired
tion of b-chloro ketones and their ester and amide de- product in 99% yield (Table 1, entry 17). Compound 4
3
À
rivatives via sp C Cl bond cleavage [Scheme 1 (c)].
was detected as the minor product and its formation
Initially, the reaction of 3-chloropropiophenone will be discussed in the mechanism context.
(1a) and phenylboronic acid (2a) in a 1:1 molar ratio
The synthetic protocol was then extended to the re-
was carried out in dioxane at 608C [Eq. (1), Table 1]. actions of 1a with various boronic acids (2) under the
In the presence of K3PO4 base and 2.5 mol% optimal conditions [Eq. (2), Table 2]. Arylboronic
A
E
desired product 3a was formed in 43% yield within substituent reacted with 1a to form the desired prod-
20 h (Table 1, entry 1). Increasing the amount of 2a to ucts 3b–f in 94–98% yields (Table 2, entries 2–6), and
2.0 equiv. led to 3a in 88% isolated yield (Table 1, the steric hindrance from a 2-methoxy group on the
entry 2). Addition of water was detrimental to the re- aryl ring of 2g lessened the reaction efficiency, pro-
action (Table 1, entry 3), while Rh(I)-catalyzed 1,4- ducing 3g in 73% yield (Table 2, entry 7). The reac-
addition reactions of enones usually require the in- tion of 1a with electron-withdrawing group-substitut-
volvement of water.[12]
products, i.e., 3h–l (91–97%) (Table 2, entries 8–12).
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Rhodium(I)-Catalyzed Arylation of b-Chloro Ketones and Related Derivatives
Table 2. Reactions of 1a with arylboronic acids 2.[a]
ating 3p–s in 69–99% yields (Table 2, entries 16–19).
3-Pyridylboronic acid (2t) did not show any reactivity,
and only the product 5 (53%) was collected from the
reaction of 2t with 1a [Table 2, entry 20 and Eq. (3)].
Compound 5 is considered to be product from the
domino dehydrochlorination/dimerization sequence of
substrate 1a under the stated conditions.[13,14] Di- and
trisubstituted arylboronic acids 2u and 2v reacted
with 1a to afford 3t and 3u in 85% and 87% yields
(Table 2, entries 21 and 22), respectively. The desired
product such as 3h could be further functionalized
through a Suzuki cross-coupling protocol, providing
b-carbonyl-bearing biaryl 3v [Eq. (4)].
Next, the substrate scope was explored by using
functionalized b-carbonylalkyl chlorides and various
arylboronic acids as the substrates [Table 3 and Eq.
(5)]. b-Carbonylalkyl chlorides are commercially
available or were prepared by the Friedel–Crafts reac-
tions of chlorides with the corresponding arenes (see
the Supporting Information for details). At 808C, the
reactions of substituted 3-chloropropiophenones effi-
ciently proceeded to form the desired products 6a–n
in excellent yields (88–98%) with tolerance of methyl,
methoxy, chloro and fluoro as the substituents. Only
in the reactions between two 4-electron-withdrawing
group-substituted substrates were the products, i.e.,
6i, 6j and 6m, obtained in lower yields (80–86%).
Naphthyl-based 3-chloro ketone reacted with 1a to
form 6o in 99% yield. The thienyl, furyl, pyrrolyl and
indolyl derivatives of 1a also exhibited excellent reac-
tivity and their reactions efficiently afforded the de-
sired products 6p–v. b-Chloro ester and amide deriva-
tives also underwent the same type of reactions, fur-
nishing the corresponding products 6w–z (68–85%
from the esters) and 6z1–z4 (65–81% from the
amides) in good to moderate yields. Aliphatic 1-chlor-
opentan-3-one behaved very well to give the desired
product 6z5 in 94% yield, whereas 3-chlorocyclohexa-
Entry
R1 (2)
Product (3)
Yield [%][b]
1
2
3
4
5
6
7
8
C6H5 (2a)
3a
3b
3c
3d
3e
3f
3g
3h
3i
3j
3k
3l
3m
3n
3o
3p
3q
3r
97
95
98
96
94
94
73
94
91
97
96
94
65
64
99
87
98
69
99
53
85
87
4-MeC6H4 (2b)
3-MeC6H4 (2c)
2-MeC6H4 (2d)
4-MeOC6H4 (2e)
3-MeOC6H4 (2f)
2-MeOC6H4 (2g)
4-ClC6H4 (2h)
4-MeO2CC6H4 (2i)
4-FC6H4 (2j)
4-CF3C6H4 (2k)
3-CF3C6H4 (2l)
3-NO2C6H4 (2m)
4-OHCC6H4 (2n)
4-t-BuC6H4 (2o)
2-naphthyl (2p)
1-naphthyl (2q)
2-furyl (2r)
9
10
11
12
13[c]
14[d]
15[d]
16
17
18
19
20
21
22
3-thienyl (2s)
3-pyridyl (2t)
3,4-F2C6H3 (2u)
3,4,5-F3C6H2 (2v)
3s
5[e]
3t
3u
[a]
Reaction conditions: 1a (0.5 mmol), 2 (1.0 mmol), K3PO4
(1.0 mmol), dioxane (2 mL), 608C, 20 h, 0.1 MPa N2.
Isolated yields.
[b]
[c]
[d]
[e]
At 808C.
2n or 2o (1.5 mmol), K3PO4 (1.5 mmol), 808C, 30 h.
See Eq. (3).
For less reactive 3-nitro-, 4-formyl- and 4-tert-butyl- none only showed a poor reactivity to form 6z6
phenylboronic acids 2m–o, their reactions with 1a had (25%). Surprisingly, 3-methyl-3-chloropropiophenone
to be performed at an elevated temperature, i.e., efficiently reacted with 2a, producing 6z7 in 97%
808C, or at 808C over a longer reaction time (Table 2, yield.
entries 13–15). Naphthyl-, 2-furyl- and 3-thienylboron-
In a fashion similar to the functionalization of 3h,
ic acids underwent the same type of reactions, gener- product 6j was further transformed to 6z8 [Eq. (6)],
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UPDATES
Table 3. Reactions of b-chloro ketones and their ester and amide derivatives (1) with arylboronic acids
(2).[a,b]
[a]
Conditions: 1 (0.5 mmol), 2 (1.0 mmol), K3PO4 (1.0 mmol), dioxane (2 mL), 808C, 20 h, atmospheric N2.
Isolated yields.
At 608C.
At 1008C.
[b]
[c]
[d]
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Rhodium(I)-Catalyzed Arylation of b-Chloro Ketones and Related Derivatives
demonstrating a potential application of the present its polymerization. Under the catalytic conditions 5
synthetic methodology. The competition reactions of was only formed in 24% yield from dimerization of
1a with 2e and 2h or 2a with 1b and 1g, afforded 3e the in-situ generated 7 [Eq. (8)], also revealing self-
and 3h or 6a and 6g in a 1:3 or 1:1 molar ratio (see polymerization of 7 during the reaction.
the Supporting Information), respectively, revealing
Treatment of 7 with 2a formed 3a as the major
an obvious substituent effect from substrates 2. An product and 4 as the minor product [Eq. (9)]. Forma-
electron-donating substituent on the aryl ring of an tion of 4 was confirmed by the controlled reaction of
arylboronic acid decreased the efficiency of the reac- 5 with 2a [Eq. (10)], in which a base played a crucial
tion, while the substituent on the aryl ring of the alkyl role in the product yield. These results reveal that in-
chloride substrate did not obviously affect formation termediate 7 is more reactive than 5, and such a reac-
of the desired product. Because a,b-unsaturated car- tivity difference of the reaction intermediates con-
bonyls are usually susceptible to heating and air trolled the product selectivity.
during their preparation and storage, the present
work has provided a concise protocol for the in-situ shortening the reaction time to 1 h to achieve an in-
preparation of this category of compounds. complete conversion of 1a (70%), the intermediate
By lowering the catalyst loading to 1 mol% and
In order to investigate the reaction pathway, con- species, i.e., 7, was detected to be formed from the in-
1
trol experiments were performed. Using K3PO4 base situ dehydrochlorination of 1a by H NMR analysis of
under heating, 1a was dehydrochlorinated to phenyl the reaction mixture of 1a with 2a [Eq. (11)]. Water
vinyl ketone (7)[15] [Eq. (7)]. At 808C over a period of necessary for the hydrolysis step in the catalytic cycle
20 h compound 7 could not remain unchanged due to presumably came from the interaction of boronic
acids and K3PO4 base.[16,17] Under the same conditions,
chloroethyl phenyl sulfone could only be converted to
phenyl vinyl sulfone which was inert to boronic
acids[18] and chloroethyl phenyl ether showed no reac-
tivity, which suggests the directing effect of the oxo
3
[19]
À
functionality in 1 on the sp C Cl bond cleavage.
Thus, the reaction pathway of 1 with 2 can be depict-
ed by a domino reaction sequence involving base-
mediated dehydrochlorination of 1 to form an a,b-un-
saturated carbonyl intermediate/Rh(I)- catalyzed con-
jugate addition of boronic acid 2 to the carbonyl inter-
mediate.
Intrigued by the successful synthesis of 6z7 from
the reaction of 3-methyl-3-chloropropiophenone with
2a, (+)-6z7 was also prepared in 97% yield with 85%
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Quanbin Jiang et al.
UPDATES
ee by using RhCl(CO)ACHTUNGTRENNUNG
ence of a chiral phosphine ligand, i.e., (S)-H8-BINAP ated a,b-unsaturated carbonyls through b-sp3 C Cl
(see the Supporting Information for a screening of bond cleavage.
conditions). Under the same conditions, the substrate
À
scope was examined and the chiral arylation products
8a–j were efficiently synthesized (Table 4). b-Methyl
functionality did not affect the reaction efficiency and
Experimental Section
in most of the cases, the desired chiral products were
obtained in >93% yields with up to 92% enantiose-
lectivity. The ortho substituent on the aryl moiety of
boronic acids 2 improved the enantiopurity of chiral
Typical Procedure for the Reactions of b-Carbonyl-
alkyl Chlorides (1) with Arylboronic Acids (2):
Synthesis of 3a
Under a nitrogen atmosphere, a mixture of RhClACHTUNGTRENNUNG(PPh3)3
products (+)-8d and (+)-8j.
(23 mg, 0.025 mmol), (Æ)-BINAP (16 mg, 0.025 mmol),
K3PO4 (212 mg, 1.0 mmol) in dioxane (1 mL) was stirred at
room temperature for 15 min and followed by addition of
phenylboronic acid (2a) (122 mg, 1.0 mmol), and 3-chloro-
propiophenone (1a) (84 mg, 0.5 mmol) in dioxane (1 mL).
The resultant mixture was stirred at 608C for 20 h. After
In conclusion, the highly efficient arylation of b-
chloro ketones and their ester and amide derivatives
was realized by means of domino dehydrochlorina-
tion/Rh(I)-catalyzed conjugate addition. This synthet-
ic protocol has exhibited its potential application in
Table 4. Asymmetric reactions of 3-chloro-1-butan-1-one (1) with arylboronic acids (2).[a–c]
[a]
Reaction conditions: 1 (0.25 mmol), 2 (0.5 mmol), K3PO4 (0.5 mmol), dioxane (2 mL), 808C, 20 h, at-
mospheric N2.
Isolated yields.
[b]
[c]
The ee values were determined by chiral HPLC using an Ad-H column.
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Rhodium(I)-Catalyzed Arylation of b-Chloro Ketones and Related Derivatives
being cooled to ambient temperature, all the volatiles were
removed under reduced pressure. The resulting residue was
purified by flash silica gel column chromatography (eluent:
petroleum ether (60–908C)/Et2O=40:1, v/v) to afford 3a as
a white solid; yield: 102 mg (97%).
kin, V. Proust, X. L. Hu, Angew. Chem. 2010, 122,
3125–3128; Angew. Chem. Int. Ed. 2010, 49, 3061–3064.
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We are grateful to the 973 Program (2009CB825300) and the
National Natural Science Foundation of China (21272232)
for financial support of this research.
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UPDATES
8 Rhodium(I)-Catalyzed Arylation of b-Chloro Ketones and
Related Derivatives through Domino Dehydrochlorination/
Conjugate Addition
Adv. Synth. Catal. 2013, 355, 1 – 8
Quanbin Jiang, Tenglong Guo, Qingfu Wang, Ping Wu,
Zhengkun Yu*
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