Synthesis of peri -substituted (Naphthalen-1-yl)phosphine ligands by rhodium(I)-Catalyzed phosphine-directed C-H arylation

Article abstract of DOI:10.1021/acs.orglett.8b00305

A novel protocol for effective rhodium(I)-catalyzed C-H arylation of tertiary phosphines has been devised. It is amenable to a wide range of substrates and gives the products in moderate to high yields. This strategy provides a simple and efficient route to peri-substituted (naphthalen-1-yl)phosphines.

Full text of DOI:10.1021/acs.orglett.8b00305

Letter
Cite This: Org. Lett. XXXX, XXX, XXX−XXX
pubs.acs.org/OrgLett
Synthesis of peri-Substituted (Naphthalen-1-yl)phosphine Ligands by
Rhodium(I)-Catalyzed Phosphine-Directed C−H Arylation
†
,§
†,§
‡
†
†
†
,†
Xue Luo, Jia Yuan, Chang-Duo Yue, Zi-Yang Zhang, Jian Chen, Guang-Ao Yu,*
,
and Chi-Ming Che*
†Key Laboratory of Pesticide & Chemical Biology, Ministry of Education, and Chemical Biology Center, College of Chemistry,
Central China Normal University, Wuhan 430079, People’s Republic of China
‡
State Key Laboratory of Synthetic Chemistry, and Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong
Kong, China
*
S Supporting Information
ABSTRACT: A novel protocol for effective rhodium(I)-
catalyzed C−H arylation of tertiary phosphines has been
devised. It is amenable to a wide range of substrates and gives
the products in moderate to high yields. This strategy provides
a simple and efficient route to peri-substituted (naphthalen-1-
yl)phosphines.
a
peri-Substituted naphthalenes display unique geometry. The
natural geometry of naphthalene is planar, with all angles close
to 120°, which results in the “ideal” peri distance of ca. 2.5 Å.
The peri-distance is the intermediate between ortho- and bay-
region distances (Figure 1). This unique geometry makes them
potentially applicable in electroluminescent materials and
Table 1. Screening of the Reaction Conditions
1
b
organic transformations. Tertiary phosphines remain the
entry
catalyst (mol %)
base
temp (°C)
conv (%)
most widely used ligands in organometallic chemistry and
catalysis, because their electronic and steric properties are more
easily modified than those of other ligands. Among them,
naphthalene-1,8-diyl phosphines have received increasing
attention in recent decades, owing to their utility as rigid
1
2
3
4
5
6
7
8
9
[Rh(cod)Cl] (2.5)
tBuOLi
tBuONa
tBuOK
tBuOLi
tBuOLi
tBuOLi
tBuOLi
tBuOLi
tBuOLi
tBuOLi
tBuOLi
none
140
140
140
140
140
140
140
140
110
70
95
77
85
67
12
21
<3
2
[Rh(cod)Cl] (2.5)
2
2
[Rh(cod)Cl] (2.5)
2
[Cp*RhCl ] (2.5)
2
2
Ru(cod)Cl (5)
2
bidentate C symmetric ligands in organometallic complexes
Pd(OAc) (5)
3
2
(Figure 1). However, modification of the backbones of such
[Ir(cod)Cl] (2.5)
2
[Rh(cod)Cl] (1.0)
81
2
c
[Rh(cod)Cl] (2.5)
95 (82 )
2
10
11
12
[Rh(cod)Cl] (2.5)
71
0
2
none
140
140
[Rh(cod)Cl] (2.5)
7
2
a
Reaction conditions: 1a (0.3 mmol), bromobenzene (0.3 mmol),
base (0.9 mmol), and [Rh(cod)Cl] in toluene (1.5 mL) for 24 h
2
b
31
c
under nitrogen. Based on P NMR. Isolated yield.
ligands with different substituents currently requires the use of
strong bases and multistep synthesis, especially in the case of 8-
substituted (naphthalen-1-yl)phosphines, limiting their appli-
1
,3
Figure 1. Comparison of the geometries of peri-substitution in
naphthalenes, ortho-substitution in benzenes, and bay-region-disub-
stitution in phenanthrenes. General formulas of naphthalene-1,8-diyl
ligands and their metal complexes are shown at the bottom. E =
heavier pnictogen (P, As, Sb, Bi) or chalcogen (S, Se, Te); E′ = any p-
block element; M = transition metal.
cations. The development of efficient and concise protocols
for the synthesis of various naphthalene-1,8-diyl phosphine
derivatives remains a challenge.
Received: January 28, 2018
©
XXXX American Chemical Society
A
DOI: 10.1021/acs.orglett.8b00305
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
Scheme 1. Rh-Catalyzed Arylation of (Naphthalen-1-
yl)phosphines with Different Aryl and Heteroaryl
,
a b
Bromides
Figure 2. Ortep drawings of 2a, 6a, 15b, and 24a with 30% ellipsoid
probability. Hydrogen atoms and solvent molecule have been omitted
for clarity.
Scheme 2. Rh-Catalyzed Arylation of (Naphthalen-1-
,
a b
yl)phosphines with Aryl and Heteroaryl Chlorides
a
Reaction conditions: 1a (1 mmol), aryl or heteroaryl bromide (1
mmol), tBuOLi (3 mmol), and [Rh(cod)Cl]2 (0.025 mmol) in
b
toluene (5 mL) at 110 °C for 24 h under nitrogen. Isolated yield.
c
1
50 °C.
In recent decades, direct functionalization of C−H bonds has
a
been recognized as a powerful tool for the construction of
functionalized molecules due to its fewer steps and high atom
Reaction conditions: 1a (1 mmol), aryl or heteroaryl chloride (1
mmol), tBuOLi (3 mmol), and [Rh(cod)Cl]2 (0.025 mmol) in
4
b
economy. However, monophosphines are generally difficult to
toluene (5 mL) at 150 °C for 24 h under nitrogen. Isolated yield.
functionalize through metal-catalyzed C−H bond activation,
because their chelating properties may result in poisoning of
the active metal catalyst. Consequently, only a couple of
5
expected product 2a with 95% conversion in the presence of
catalytic systems based on palladium and rhodium have been
2.5 mol % [Rh(cod)Cl] and 3 equiv of tBuOLi at 140 °C for
2
6
reported, employing FcP(tBu) (Fc = ferrocenyl) and biaryl-
24 h (Table 1, entry 1). Other bases, such as tBuONa and
tBuOK, were also found to promote the reaction, but tBuOLi
was somewhat superior in terms of product yield (Table 1,
entries 2 and 3). As an alternative rhodium complex,
[Cp*RhCl ] was also found to promote the reaction, giving
2
7
based phosphines as starting materials. Meanwhile, a few well-
defined cyclomethylated complexes containing (naphthalen-1-
8
yl)phosphine have been prepared by C−H bond activation.
These reports provide a better understanding of the mechanism
of such transformations and have led to the design of new
2
2
a moderate conversion (Table 1, entry 4). In contrast, other
8
,9
functionalized molecules and catalysts. Herein, we report the
rhodium(I)-catalyzed P-directed C−H arylation of (naphtha-
len-1-yl)phosphines to give a series of 8-substituted derivatives.
Initially, we studied C−H arylation of readily available 1-
naphthalenyldiphenylphosphane (1a) with bromobenzene as a
model reaction. As shown in Table 1, the reaction gave the
transition metal complexes, such as [Ru(cod)Cl ], [Ir(cod)-
2
Cl] , and Pd(OAc) , gave the expected product only in very
2
2
low substrate conversions (Table 1, entries 5−7). The reaction
temperature could be reduced to 110 °C without affecting the
reactivity, but a further reduction to 70 °C led to only moderate
conversions (Table 1, entries 9 and 10). The expected product
B
DOI: 10.1021/acs.orglett.8b00305
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
Scheme 3. Rh-Catalyzed Arylation of (Naphthalen-1-
yl)phosphine Derivatives with Aryl Bromides
Scheme 4. Proposed Mechanism
,
a b
a
Reaction conditions: 1a (1 mmol), aryl or heteroaryl chloride (1
mmol), tBuOLi (3 mmol), and [Rh(cod)Cl]2 (0.025 mmol) in
b
c
toluene (5 mL) at 150 °C for 24 h under nitrogen. Isolated yield. At
110 °C
gave the respective products in yields of 90% (12a), 52% (13a),
9% (14a), 76% (15a), and 50% (15b) (Figure 2). Whereas
the reaction with 1-bromo-3,5-dimethylbenzene gave 86% of
7a, an attempted reaction with 1-bromo-2,4-dimethylbenzene
8
1
did not yield any of 18a, indicating a pronounced steric effect
on the reaction. It was noted that heteroaryl bromides were also
amenable to the C−H arylation and gave the respective
products in moderate to high yields (19a−23a, 40−84%).
To further extend the reaction scope, we examined the scope
in terms of aryl and heteroaryl chlorides (Scheme 2). 1-Chloro-
4-methylbenzene reacted with compound 1a to afford the
expected product 4a in only 40% yield. Moreover, it was found
that some heteroaryl chlorides reacted smoothly to afford the
corresponding products in moderate yields (24a−27a and 24b,
36−77%). However, an attempted reaction with 3-chlorothio-
phene did not proceed. Moreover, the reactions of (naph-
thalen-1-yl)phosphine derivatives with aryl bromides were also
surveyed (Scheme 3). (2-Methylnaphthalen-1-yl)diphenyl-
phosphane, (4-methoxynaphthalen-1-yl)diphenylphosphane,
and anthracen-9-yldiphenylphosphane were also successful in
the C−H arylation to give the corresponding products in
moderate to high yields (29a−34a, 27−96%).
Figure 3. Ortep drawings of 35 (left) and 39 (right) with 30%
ellipsoid probability. Hydrogen atoms and solvent molecule have been
omitted for clarity.
was scarcely observed in the absence of either [Rh(cod)Cl] or
2
tBuOLi (Table 1, entries 11 and 12).
Having established the optimal conditions using [Rh(cod)-
Cl] as a precatalyst, various aryl and heteroaryl bromides were
2
examined with 1-naphthalenyldiphenylphosphane (1a) and 1-
naphthalenyldicyclohexylphosphane (1b) (Scheme 1). Most of
the reactions with aryl bromides furnished the corresponding
C−H arylation products in moderate to high yields (52−90%).
Substrates bearing electron-donating groups on their aryl rings,
such as OMe, Me, 1,3-dioxolanyl, and iPr, gave the
corresponding products in 81% (3a), 84% (4a), 83% (11a)/
86% (11b), and 87% (16a) yields, respectively. The reaction
has also been shown to be tolerant to aromatic halides (Cl) and
To gain a better understanding of the catalytic cycle, studies
were conducted to shed light on the mechanism. The reaction
rings bearing electron-withdrawing groups (CF , COPh, and
3
CH CN), giving the respective products in moderate to high
yields (5a−8a and 8b, 61−80%). However, 4-bromoaniline and
of [Rh(cod)Cl] with 5 equiv of 1a and bromobenzene in the
2
2
presence of tBuOLi was monitored by ESI-MS. The results
indicate the involvement of intermediates I, II, and V,
consistent with C−H bond activation by Rh(I) (Figure S1;
see the Supporting Information(SI)). However, only complex
35 (Figure 3) could be easily obtained in 90% yield by the
4
-bromobenzaldehyde did not react with compound 1a.
Additionally, 9-bromophenanthrene, 9-bromoanthracene, 2-
bromo-9,9-dihexyl-9H-fluorene, 9-(4-bromophenyl)-9H-carba-
zole, and 2-bromo-9H-fluoren-9-one were also effective and
C
DOI: 10.1021/acs.orglett.8b00305
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
Table 2. Au-Catalyzed Hydration of 4-Phenylbut-3-yn-2-
one
groups, starting from the parent scaffolds. Efforts to discover
new organometallic complexes containing naphthalenyl-
phosphine ligands, and to expand their catalytic applications,
are currently underway.
,
ab
ASSOCIATED CONTENT
Supporting Information
■
*
S
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.or-
glett.8b00305.
Experimental procedures, additional experimental data,
and compounds characterization data (PDF)
Accession Codes
CCDC 1589200−1589201, 1589213, 1589217−1589218, and
1
817663 contain 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 data_
request@ccdc.cam.ac.uk, or by contacting The Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CB2
1
EZ, UK; fax: +44 1223 336033.
b
entry
[Au]
conv (%)
ton
AUTHOR INFORMATION
Corresponding Authors
1
2
3
4
5
6
36
37
38
39
40
41
41
54
56
65
34
44
2050
2700
2800
3250
1700
2200
■
*
*
E-mail: yuguang@mail.ccnu.edu.cn.
E-mail: cmche@hku.hk.
ORCID
a
Reaction conditions: 4-phenylbut-3-yn-2-one (1.0 mmol), catalyst
Guang-Ao Yu: 0000-0001-8942-0893
Chi-Ming Che: 0000-0002-2554-7219
Author Contributions
(
(
0.02 mol %), AgSbF (0.03 mol %), EtOH (0.5 equiv), and HOTf
0.9 mol %) in CPME (cyclopentyl methyl ether, 1.0 mL) at 110 °C
6
b
1
for 36 h under nitrogen. Determined by H NMR.
§
X.L. and J.Y. contributed equally.
Notes
reaction of [Rh(cod)Cl]2 with 1a in CH Cl at room
2
2
temperature. Attempts to isolate other intermediates have
been unsuccessful, probably as a result of their instability. On
the basis of the experimental results, a proposed mechanism for
the catalytic reaction is shown in Scheme 4. Initially, Rh(I)
intermediate II is proposed to be generated by the reaction of
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
The authors would like to thank the National Natural Science
Foundation of China (Nos. 21472060, 21772058, and
[
Rh(cod)Cl] with 1-naphthalenylphosphane in the presence of
2
2
1072071), the 111 Project B17019, and self-determined
base. The aryl halide then reacts with Rh(I) intermediate II by
oxidative addition to yield Rh(III) intermediate III, which
subsequently undergoes reductive elimination, intramolecular
C−H bond activation, and coordination, to liberate the product
and regenerate Rh(I) intermediate II.
Finally, we examined the hydration of 4-phenylbut-3-yn-2-
research funds of CCNU from the colleges’ basic research
and operation of MOE (Nos. CCNU17QN0021,
CCNU17CG0011, and CCNU17KYZHSY07).
4
,10
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