Syn-Insertion of Alkynes into Gold-Phosphito Bonds: Stereoselectivity and Reversible Protodeauration

Article abstract of DOI:10.1021/acs.organomet.1c00283

The susceptibility of gold phosphito compounds to undergo alkyne insertion into gold-phosphorus bonds has been investigated. An electron-deficient alkyne (DMAD) underwent syn-insertion into the gold-phosphorus bond to generate a Z-vinylgold species, where

Full text of DOI:10.1021/acs.organomet.1c00283

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Article
Syn-Insertion of Alkynes into Gold−Phosphito Bonds:
Stereoselectivity and Reversible Protodeauration
Carly L. Masonheimer, Madeleine G. Atwood, Susan E. Hartzell, Erin A. Reph, Robert D. Pike,
and Robert A. Stockland, Jr.*
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ABSTRACT: The susceptibility of gold phosphito compounds to
undergo alkyne insertion into gold−phosphorus bonds has been
investigated. An electron-deficient alkyne (DMAD) underwent syn-
insertion into the gold−phosphorus bond to generate a Z-vinylgold
species, whereas electron-rich internal alkynes were unreactive. When
a P-chiral phosphinate was used as a probe, the protodeauration and
insertion steps were found to be stereospecific. In contrast to the insertion chemistry observed with DMAD, electron-deficient
terminal alkynes generated alkynylgold compounds and released secondary phosphites through a reversible protodeauration process.
diphenylacetylene.30 There are also examples of intramolecular
INTRODUCTION
■
anti-insertions into gold−heteroatom bonds. Bertrand and
The insertion of alkynes into metal-element bonds remains one
of the most valuable reactions in organometallic chemistry.
Hashmi reported anti-aminoauration31 and anti-phosphinoau-
ration of alkynylaniline derivatives.32
The intense interest in this area stems from the vast number of
applications this fundamental reaction has in small molecule1−6
It should be noted that treating a fluorogold species with 3-
and polymer chemistry.7−10 Furthermore, alkyne insertion
hexyne resulted in the reversible insertion of the alkyne into
the Au−F bond.33 An (E)-vinylgold compound was observed.
chemistry provides an atom-efficient approach to the synthesis
of vinylmetal species.11−16 Historically, gold compounds were
The proposed mechanism entailed the initial loss of the
fluoride, coordination of the hexyne to the gold center, and
anti-addition of the fluoride to the coordinated alkyne.
Reactions between electron-deficient alkynes and LAuX
species are complex and generate a range of vinylgold
compounds (Scheme 1). The regiochemistry and stereo-
chemistry of these reactions depend upon the identity of the
heteroatom and the supporting ligands. Several studies found
that phosphine ligands were not entirely innocent and
generated zwitterionic vinylgold compounds resulting from
insertion of the alkyne into the gold−ligand bond. Kuniyasu
and Kambe reported reactions between gold thiolate
complexes of the type (Ph3P)AuSAr and dimethyl acetylene-
dicarboxylate (DMAD).34 Vinylgold compounds were gen-
erated from the insertion of the alkyne into the Au−PR3 bond.
The Au−S bond was retained in these reactions. Bourissou
investigated terminal and internal alkynes’ reactivity with
silylgold compounds and discovered that DMAD underwent a
syn-insertion into the gold−silicon bond.35
thought to be unreactive toward this process. However, Teles’
pioneering work demonstrated that cationic gold compounds
activated alkynes toward nucleophilic attack through coordi-
nation of the π-system.17 This outer-sphere pathway generated
a vinylgold species and resulted in an overall anti-addition to
the alkyne. Following this work, a vast array of alkyne
functionalization reactions have been reported.18−27
In contrast, an inner-sphere alkyne insertion reaction
generates a formal syn-insertion product.28 The mechanism
of this process also entails initial coordination of the alkyne to
the gold; however, the next step is a migratory insertion of the
alkyne into the gold−element bond to generate the vinylgold
species. Despite the intense interest in this area, syn-insertions
are rare.28 Moreover, formal alkyne syn-insertions into well-
defined gold-heteroatom bonds are exceedingly rare.
With the hope of developing gold-catalyzed processes for the
preparation of functionalized alkenes, several research teams
investigated this process and found electron-rich internal
alkynes such as diphenyl acetylene and 4-octyne to be generally
unreactive toward syn-insertions, whereas electron-deficient
alkynes displayed a range of reactivity. Toste and Bergman
reported no reaction between amidogold compounds and
electron-rich internal alkynes, but an electron-poor alkene,
acrylonitrile, successfully inserted into the gold−nitrogen
bond.29 Nolan found that gold phenoxide compounds of the
type (NHC)Au-OAr were resistant toward the insertion of
Received: May 7, 2021
Published: July 5, 2021
https://doi.org/10.1021/acs.organomet.1c00283
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phosphito compounds, spectroscopic41−43 and computation-
al44 evidence suggests the bonding mode of [PO3R2]− groups
in 5−12 is consistent with a κ1-P(III) O-anionic phosphito
donor.45,46
Scheme 1. Syn-Insertions into Gold−Heteroatom
Bonds34,35
The structures of compounds 5 and 7 were determined by
single-crystal X-ray diffraction (Figures 1 and 2). The gold−
To gain insight into the susceptibility of gold phosphito
compounds to undergo alkyne insertion reactions, we have
investigated the reactivity of discrete species with a range of
internal and terminal alkynes and defined the key reaction
parameters for the design of a successful syn-insertion reaction.
Figure 1. Structure of 5. Thermal ellipsoids are displayed at 50%
probability, and hydrogens are omitted for clarity. Selected bond
distances (Å) and angles (deg): Au(1)−P(2) = 2.3065(5), Au(1)−
P(1) = 2.3470(4), P(2)−O(1) = 1.4833(14), P(2)−O(3) =
1.6131(13), P(2)−Au(1)−P(1) = 172.291(16), O(1)−P(2)−Au(1)
= 118.95(6), O(2)−P(2)−Au(1) = 108.29(5).
RESULTS AND DISCUSSION
■
Synthesis of Model Compounds. Several gold phosphito
complexes (5−12) were generated through protodeauration
reactions between arylgold precursors (1−4) and secondary
phosphites (Scheme 2).36−40 The bulky Buchwald and carbene
phosphorus bond distances are different in 5, with the Au−PR3
distance found to be the longer of the two (2.3065(5) vs
2.3470(4) Å). The P−Au−P angle deviates from linearity
(172.291(16)°), and the Au+−P−O− angle (118.95(6)°) is
larger than the two Au+−P−OEt angles (110.53(5)° and
108.29(5)°). The gold−carbon bond distances of the two
independent molecules of 7 are indistinguishable (2.054(4)
and 2.056(4) Å), whereas the C−Au−P angles are different
(177.76(12)° and 174.51(11)°) but do not deviate from
linearity as much as the P−Au−P angle found in 5. The Au−P
bond lengths found in 7 (2.2903(10) and 2.2929(10) Å) are
nearly identical to the corresponding bond lengths in 5,
suggesting that the trans-influence of the carbene and
phosphine ligands is comparable. Similar to 5, the Au+−P−
O− angles (122.5(1)°, 121.7(1)°) are significantly larger than
the two Au+−P−OEt angles (103.1(1)−110.5(1)°).
Scheme 2. Synthesis of Model Compounds
Compounds 5−12 are hygroscopic, and although crystals of
5 grew in an anhydrous state, three molecules of adventitious
water were found in the unit cell of 7. Two of these water
molecules link two molecules of 7 together through a
hydrogen-bonded chain, while the third hydrogen bonds to
only a single molecule of 7. No aurophilic interactions were
found in the packing of 5 or 7.
Reactivity of Model Compounds. The reactivity of the
model compounds toward alkyne insertion was investigated
using a range of alkynes (Table 1). When electron-rich alkynes
such as diphenylacetylene or 5-decyne were used, no insertion
products were observed with 5−12. Prolonged stirring (1 wk,
80 °C) or increasing the temperature (110 °C) led to
decomposition and the formation of intractable mixtures.
Increasing the amount of the alkyne to 100 equiv was also
unsuccessful at 80 or 110 °C.
ligands were selected to minimize reversible ligand redis-
tribution reactions commonly observed with gold phosphito
compounds.37,39 Both cyclic and acyclic phosphites afforded
high yields of the target gold compounds. Compounds 5−12
were isolated as powders and exhibited a resonance for the
P(O)(OR)2 fragment in the 31P NMR spectrum between δ
−
2
111 and 121 ppm with JPP between 473 and 491 Hz for 5, 6,
Several functionalized alkynes were screened for activity
toward the insertion reaction (Table 1). Heating suspensions
9, and 10. While two bonding modes are known for metal
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ancillary ligand attached to the gold as well as the phosphite.
Substrates bearing bulky phosphine or carbene ligands (6, 8,
10, 12) were unreactive, and starting materials were recovered
after heating (80 °C, 48 h). When the temperature was
increased (110 °C), decomposition and the formation of
intractable mixtures were observed. The substrates containing
cyclic phosphites also generated mixtures, and vinylgold
compounds could not be isolated.
In contrast, substrates bearing smaller supporting ligands
and an acyclic phosphite (5, 7) afforded vinylgold compounds
(13, 14, Table 1). Monitoring the reaction of 7 with DMAD
by 31P NMR spectroscopy revealed the clean conversion of the
gold phosphito compound (7, δ 112.3 ppm) into the vinylgold
species (14, δ 18.3 ppm). The transformation of the metal
phosphite into a phosphonate was easy to follow since there
was a 94 ppm change in the chemical shift of the
−P(O)(OEt)2 fragment. In contrast with several previous
reports describing the reactivity of (R3P)AuX compounds with
activated alkynes, DMAD exclusively inserted into the Au−
phosphito bond.34,35 No insertion of DMAD into the Au−
carbene bond was observed.
Monitoring the formation of 13 from 5 yielded similar
observations. Clean insertion into the gold−phosphito bond
was observed, and no intermediates or insertion into the gold−
phosphine bond were found. Of note was the observation of a
4JPP of 14.6 Hz in the JohnPhos ligated vinylgold species (13).
Two electron-withdrawing groups were required for a
successful insertion reaction. Treating 5−12 with methyl
phenylpropiolate (Ph-CCCO2Me, 4−100 equiv) resulted in
recovered starting materials (80 °C, 48 h). Prolonged stirring
or increasing the temperature to 110 °C resulted in
decomposition. These observations are in contrast with the
syn-insertion into Au−Si bonds that Bourissou observed when
(Ph3P)AuSiPh3 was treated with methyl phenylpropiolate.49
The structures of 13 and 14 were determined by single-
crystal X-ray crystallography and revealed the syn-insertion of
DMAD into the gold phosphorus bonds of 5 and 7 (Figure 3,
Table 2), resulting in a Z-configuration. The alkene geometry
deviates from planarity in 13 and 14, as evidenced by the
torsion angles (Table 2). There were no aurophilic interactions
in the structures of 13 or 14.
Figure 2. Structure of 7. Thermal ellipsoids are displayed at 50%
probability, and the hydrogens as well as water molecules are omitted
for clarity. Selected bond distances (Å) and angles (deg): Au(1)−
C(1) = 2.056(4), Au(1)−P(1) = 2.2903(10), P(1)−O(1) = 1.481(3),
P(1)−O(3) = 1.621(3), C(1)−Au(1)−P(1) = 177.76(12), O(1)−
P(1)−Au(1) = 121.74(14), N(1)−C(1)−Au(1) = 124.7(3), N(2)−
C(1)−N(1) = 109.7(4).
a
Table 1. Alkyne Insertion into Gold−Phosphorus Bonds
The stereochemistry of the protodeauration and insertion
reactions was investigated using a P-chiral phosphinate,
(RP)(−)menthyl phenylphosphinate.50−55 Treatment of
(SIMes)AuPh or (JohnPhos)AuPh with the phosphinate
generated high yields of the metal phosphinito species through
a protodeauration reaction (eqs 1 and 2).36 The reaction was
a
Reaction conditions: 5−12 (0.13−0.16 mmol) in toluene (1.0 mL)
b
c
unless specified. Based upon isolated material. The reaction was
heterogeneous due to the low solubility of dppaOO in toluene. 1.6
mmol of 5 was used along with 5.0 mL of toluene. 1.6 mmol of 7 was
d
e
used along with 5.0 mL of toluene.
of bis(diphenylphosphino)acetylene dioxide (dppaOO)47 with
5−12 resulted in recovered starting materials after stirring for a
week at 80 °C, whereas heating to 110° resulted in
decomposition. Similarly, tetraethyl-acetylenedicarboxamide48
was unreactive toward the insertion reaction at lower
temperatures, and heating 5−12 with an excess of the
dicarboxamide to 110 °C resulted in the formation of
intractable mixtures.
stereospecific, as evidenced by NMR spectroscopic data. It is
worth noting that 15 and 16 are configurationally stable, and
no epimerization was observed upon heating to 110 °C.
X-ray quality crystals of 15 were obtained by simply cooling
the crude reaction mixture (Figure 4). Analysis of this structure
Analogous reactions using an electron-deficient alkyne
(DMAD) afforded a range of products depending on the
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Table 2. Selected Bond Distances (Å) and Angles (deg) for
the Syn-Insertion Products (13, 14)
13
14
distances
Au−L
2.2986(11)
2.060(4)
1.353(6)
1.807(4)
1.470(3)
2.020(2)
2.041(3)
1.347(4)
1.808(3)
1.465(2)
Au−C
CC
C−P
PO1
angles
L−Au−C1
Au−C1C2
C1C2−P
C2−P−O1
torsion angles
Au−C1C2−P
Au−C1C2−C4
C3−C1C2−C4
C3−C1C2−P
168.74(13)
127.6(3)
120.9(3)
174.46(10)
131.8(2)
124.6(2)
113.37(19)
112.17(12)
8.4(6)
168.3(3)
5.9(6)
2.7(4)
179.86(19)
0.8(4)
177.3(3)
176.31(19)
Figure 3. Structures of alkyne insertion products (13, 14). Thermal
ellipsoids are displayed at 50% probability, and the hydrogens are
omitted for clarity.
revealed that the protodeauration occurred with retention of
the configuration. This structure also sheds light on our recent
report regarding the stereospecific protodeauration and
transmetalation reactions between gold and palladium.36
Similar to the reactions of 5 and 7 with DMAD, treatment of
16 with DMAD afforded a vinylgold compound (17, eq 3). It
Figure 4. Structure of 15. Hydrogen atoms are omitted, and thermal
ellipsoids are displayed at 50% probability. Selected bond distances
(Å) and angles (deg): Au(1)−P(1) = 2.297(3), Au(1)−C(17) =
2.090(10), P(1)−O(1) = 1.508(7), P(1)−O(2) = 1.620(7), C(17)−
Au(1)−P(1) = 175.7(3), O(1)−P(1)−Au(1) = 121.0(3), O(1)−
P(1)−O(2) = 111.0(4), O(1)−P(1)−C(1) = 109.0(5).
Protodeauration between the vinylgold species and a
secondary phosphite would be the step in a catalytic cycle
that forms the vinyl phosphonate and regenerates the gold
phosphito species. Treatment of 13 with HP(O)(OEt)2 does
indeed generate 5 and the vinyl phosphonate (90 °C, 20 h).
However, the development of a catalytic process was hindered
by the observation that an uncatalyzed double-addition
reaction occurs between DMAD and HP(O)(OEt)2 (2
should be noted that the reactivity of 16 toward insertion was
sluggish compared to 5 or 7, and only moderate conversion
was observed. After heating for 48 h at 80 °C, 45% of 16
1
remained unreacted. Monitoring the reaction by H and 31P
NMR spectroscopy revealed the emergence of a single set of
4
signals for 17 (31P δ: 63.6, 29.0; JPP = 12.3), confirming that
the reaction was stereospecific at phosphorus.
equiv) under the insertion conditions (80 °C, 2 days).56
A
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successful catalytic approach needs to circumvent this
background reaction.
Scheme 3. Regioselective Insertion of Terminal Alkynes
into Gold−Silicon Bonds
To this end, we investigated the possibility of replacing the
protodeauration step with iodination in order to eliminate the
need for the secondary phosphite. This alternative approach
would convert the vinylgold intermediate into an iodovinyl
phosphonate and an iodogold species. The latter could be
transformed into a gold phosphito species through trans-
metalation with M[P(O)R2].57 Treatment of 13 with I2
afforded (JohnPhos)AuI and a (Z)-β-iodo-vinylphosphonate
(18) under mild conditions (eq 4).58
Although the reaction using discrete species was successful,
the development of a catalytic process was prevented by the
observation that iodine reacts rapidly with 5 to generate
(JohnPhos)AuI and IP(O)(OEt)2 (eq 5).59 As a result, any
gold phosphito intermediates would be rapidly consumed by
iodine prior to alkyne insertion.
rich alkynes, the reaction highly favored the metal phosphite.40
In contrast, significant amounts of the alkynylgold species were
observed when electron-deficient alkynes were used. Although
the focus of this work was insertion chemistry, this chemistry is
noteworthy since examples of reversible protodeauration at
gold(I) are rare.62
Building on these observations, a preparative method was
devised for converting metal phosphito species into
alkynylgold compounds. The scope of this process was
investigated using the remainder of the gold phosphito
compounds (Scheme 4). When methyl propiolate was used
as a representative electron-deficient alkyne, compounds 5−8
were successfully converted into alkynylgold species (19−22)
We were able to increase the scale of the iodination reaction.
Treatment of a 1.00 g sample of 13 (1.29 mmol) with iodine
afforded 18 in 89% yield. Although a process that is
stoichiometric in gold is generally not desirable, it should be
noted that the gold is not sacrificial in this reaction. The gold
was recovered as (JohnPhos)AuI (93%) and used in
subsequent reactions.
Reactivity of Terminal Alkynes. The reactivity of
terminal alkynes was also investigated. Previous reports
found that the regioselectivity of the insertion reaction was
sensitive to the supporting ligand attached to the gold.
Bourissou found that methyl propiolate regioselectively
inserted into the gold−silicon bond of (Ph3P)AuSiMe2Ph to
generate a vinylgold species with a β-carboxylate fragment.35,49
Subsequent work revealed that changing the supporting ligand
to an N-heterocyclic carbene reversed the regioselectivity of
the insertion reaction (Scheme 3).60 Ananikov reported the
acetic acid promoted insertion of methyl propiolate into the
gold−phosphorus bond of gold thiolate compounds (Scheme
3).61
Scheme 4. Synthesis of Alkynylgold Species from Gold
Phosphites
To probe the reactivity of terminal alkynes toward the
insertion reaction, a model gold phosphito compound (5) was
treated with terminal alkynes. Adding 1-hexyne to 5 (80 °C for
48 h) resulted in the recovery of starting materials. No
insertion products were observed. Switching to an electron-
deficient alkyne (methyl propiolate) did not generate insertion
products; however, analysis of the reaction mixture revealed
the presence of an alkynylgold species ((JohnPhos)AuC
CCO2Me) and diethylphosphite. Instead of alkyne insertion,
protodeauration occurred to generate the alkynylgold species
along with a secondary phosphite (eq 6).
The protodeauration reaction was found to be reversible and
influenced by the nature of the terminal alkyne. For electron-
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in moderate to good isolated yields. Even gold phosphito
compounds containing bulky carbene or dialkylbiaryl ligands
were successfully transformed using 5 equiv of the alkyne.
Since the alkynylation reaction proceeded under base-free
conditions, this process could be a practical approach to the
synthesis of alkynylgold compounds bearing base-sensitive
groups.63,64
Cooling the reaction mixture containing 10 and H3PO3
afforded X-ray quality crystals of a H3PO3 adduct. The
phosphorous acid interacts with 10 by forming hydrogen
bonds with the phosphito oxygen (Figure 5). The oxygen−
The stereochemical outcome of this reversible protodeaura-
tion reaction was investigated using a P-chiral gold phosphite
(16). Treatment of 16 with methyl propiolate (eq 7) afforded
19, as well as (RP)(−)menthyl phenylphosphinate. Thus, the
protodeauration was found to be stereospecific and proceed
with retention of the configuration. No epimerization of the
phosphorus stereocenter was observed. It should be noted that
the reaction of the phenylgold precursor (1) with secondary
phosphites and (RP)(−)menthyl phenylphosphinate was not
reversible.
Inspired by Ananikov’s report on the synthesis of gem-
vinylgold thiolate complexes through the treatment of gold
thiolates with methyl propiolate in the presence of carboxylic
acids,61 the effect of benzoic acid on the protodeauration
reaction was investigated. No protodeauration was observed
between 5 and benzoic acid (80 °C, 6 days). Adding methyl
propiolate to this reaction (1:1−1:5 equiv) led to mixtures of 5
and 19 after heating (80 °C, 24 h). Using an excess of benzoic
acid (1:10) significantly suppressed the alkynylation reaction,
and unreacted 5 was the major species found in the crude
reaction mixture. No vinylgold compounds were found in these
reactions. Because of the observation that benzoic acid
hydrogen bonds to 5, it is reasonable to predict that an excess
of benzoic acid will sequester the [Au+]P-O− group and
prevent the alkynylation reaction.
Figure 5. Structure of dimerized 10·H3PO3. Thermal ellipsoids are
displayed at 50% probability, and the hydrogens are omitted for
clarity. Selected bond distances (Å) and angles (deg). Au(1)−P(1) =
2.2878(7), Au(1)−P(2) = 2.3261(7), P(1)−O(1) = 1.504(2), P(1)−
Au(1)−P(2) = 171.53(2), O(1)−P(1)−O(2) = 112.82(12), O(1)−
P(1)−Au(1) = 115.28(9). Hydrogen bonding: O(4)−O(1) =
2.476(3), O(5)−O(6) = 2.527(4), P(1)−O(1)−O(4) = 131.7(3),
P(3)−O(6)−O(5) = 129.2(2).
Since benzoic acid was unable to promote the insertion
reaction, a stronger acid, H3PO3, was screened. The addition of
H3PO3 (1 equiv) to solutions of 5−12 along with methyl
propiolate (50 °C, 24 h) did not promote the insertion
reaction. Monitoring the reactions using 31P NMR spectros-
copy revealed broadening of the resonance for the −P(O)-
(OR)2 fragment due to hydrogen bonding between the metal
phosphite and H3PO3 (eq 8), but no insertion or
oxygen bond distance is 2.476(3) Å, and the PO···H−O angle
is 171(7)°. Two molecules of H3PO3 are connected through
hydrogen bonds as well, which results in the linkage of two
molecules of 10 through the dimerized H3PO3. Analysis of the
extended structure reveals that the H3PO3 resides in channels
surrounded by molecules of 10. The two Au−P bond lengths
are 2.2878(7) and 2.3261(7) Å, with the phosphine−gold
bond being the longer of the two. The P−O− distance is longer
(1.504(2) Å) than similar complexes which could be due to
hydrogen bonding of the phosphorus acid.
1
protodeauration products were observed in the H or 31P
NMR spectra.
To evaluate the ability of H3PO3 to cleave the gold−
phosphorus bond, separate experiments were carried out
between 5−12 and H3PO3. While the coordination of the acid
to the metal phosphite was evident in the 31P NMR spectrum,
no cleavage of the gold−phosphorus bond was observed from
these control reactions.
In conclusion, electron-deficient internal alkynes insert into
the Au−P bonds of gold phosphito compounds to generate
(Z)-vinylgold species. When a P-chiral phosphinate was used
as a model system, the protodeauration and alkyne insertion
reactions were found to be stereospecific. In contrast to these
findings, terminal alkynes did not show any propensity toward
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H, 6.52. Found: C, 59.85; H, 6.61. 1H (CDCl3, 25 °C): δ 7.39 (t, 2H,
J = 7.7, ArH), 7.23 (d, 4H, J = 7.7, ArH), 6.99 (m, 4H, Ar-H), 6.82 (t,
1H, J = 7.0, ArH), 4.01 (s, 4H, −CH2N−), 3.17 (sept, 4H, J = 6.8,
−CH−), 1.50 (d, 12H, J = 6.8, −Me), 1.37 (d, 12H, J = 6.9, −Me).
13C{1H} (CDCl3, 25 °C): δ 216.7 (s, carbene C), 170.2 (s, quat),
146.9 (s, quat), 140.6 (s, ArCH), 134.9 (s, quat), 129.5 (s, ArCH),
126.7 (s, ArCH), 124.4 (s, ArCH), 124.3 (s, ArCH), 53.9 (s,
−CH2N−), 29.1 (s, −CH−), 25.2 (s, −Me), 24.2 (s, −Me).
Preparation of Gold Phosphites. General Method B. A 10
mL vial was charged in air with the arylgold precursor, secondary
phosphite (1 equiv, if it is a solid), and a magnetic stirring bar. The
vial was capped, and the atmosphere was exchanged for nitrogen on a
manifold. The secondary phosphite (1 equiv, if it is a liquid) was
added by syringe along with toluene (8 mL). The reaction was stirred
for 18 h at the desired temperature. The volatiles were removed under
vacuum, and the gold phosphites were separated from the solid
residue by column chromatography. Chromatography details: flash
(N2 pressure), 75 g of basic Al2O3 per gram of crude gold phosphite,
EtOAc:MeOH (gradient 100:0−90:10). After removal of the volatiles,
the residue was dissolved in CH2Cl2 and dried over MgSO4.
Filtration, concentration, and drying overnight under vacuum afforded
the (5−12) as white solids. If desired, the gold phosphites can be
recrystallized by cooling a saturated EtOAc solution to −30 °C.
Preparation of (JohnPhos)Au(P(O)(OEt)2) (5). The title compound
was prepared following general method B using (JohnPhos)AuPh
(1.000 g, 1.75 mmol) and diethylphosphite (0.225 mL, 1.75 mmol).
After heating at 70 °C for 18 h, purification by column
chromatography (Rf = 0.22, EtOAc:MeOH 90:10) afforded the title
compound as a white solid (1.02 g, 92%).40
insertion. Instead, terminal alkynes participated in a reversible
protodeauration reaction with the gold phosphito species to
generate alkynylgold compounds and free phosphite.
EXPERIMENTAL SECTION
■
General Considerations. All reactions were carried out under a
nitrogen atmosphere unless specified. Solvents were dried using CaH2
or a Grubbs-type solvent purification system and distilled prior to use.
The chlorogold precursors (JohnPhos)AuCl,65 (tBuXPhos)AuCl,66
(SIMes)AuCl,67 and (SIPr)AuCl67) as well as tetraethyl-acetylenedi-
carboxamide48 and bis(diphenylphosphino)acetylene dioxide47 were
prepared following literature procedures. The arylgold precursors
were prepared following variations of literature procedures as
described below.68−72 The remaining reagents were obtained from
commercial sources and used as received. CDCl3 was dried over CaH2
and distilled immediately prior to use while C6D6 was dried over
activated molecular sieves (3 Å) and filtered through a 5 μm filter
1
prior to use. H NMR chemical shifts were determined by reference
to residual nondeuterated solvent resonances, and 13C{1H} chemical
shifts were determined by reference to deuterated solvent resonances.
Coupling constants are given in hertz. 31P{1H} NMR spectra were
referenced to external H3PO4 (0 ppm). 1H and 13C NMR resonances
were assigned through analysis of 1D and 2D experiments. Elemental
analyses were determined by Midwest Microlabs.
Preparation of Arylgold Precursors. General Method A. A
vial (30 mL) was charged with LAuCl, PhB(OH)2 (2 equiv), Cs2CO3
(2 equiv), and a magnetic stirring bar (in air). The vial was capped,
and the atmosphere was exchanged for nitrogen using a vacuum
manifold. After injecting isopropanol by syringe, the vial was placed in
an aluminum block heater at 55 °C and stirred for 24 h. The arylgold
compounds were separated from the solid residue by column
chromatography. Chromatography details: flash (N2 pressure), 35−
40 g of SiO2 (NEt3 treated) per gram of crude arylgold compound,
hexane:EtOAc (gradient 100:0−75:25). After removal of the volatiles,
the residue was dissolved in CH2Cl2 and dried over MgSO4.
Filtration, concentration, and drying overnight afforded the (1−4)
as white solids. If desired, 1−4 can be recrystallized by cooling
saturated EtOAc solutions to −30 °C.
Preparation of (tBuXPhos)Au(P(O)(OEt)2) (6). The title compound
was prepared following general method B using (tBuXPhos)AuPh
(1.00 g, 1.43 mmol) and diethylphosphite (0.184 mL, 1.43 mmol).
After heating at 70 °C for 18 h, purification by column
chromatography (Rf = 0.30, EtOAc:MeOH 90:10) afforded the title
compound as a white solid (0.99 g, 91%).40
Preparation of (SIMes)Au(P(O)(OEt)2) (7). The title compound was
prepared following general method B using (SIMes)AuPh (1.00 g,
1.72 mmol) and diethylphosphite (0.222 mL, 1.72 mmol). After
heating at 85 °C for 18 h, purification by column chromatography (Rf
= 0.34, EtOAc:MeOH 90:10) afforded the title compound as a white
solid (0.91 g, 83%).40
Preparation of (JohnPhos)AuPh (1). The title compound was
prepared following general method A using (JohnPhos)AuCl (2.00 g,
3.77 mmol), PhB(OH)2 (0.919 g, 7.54 mmol), Cs2CO3 (2.46 g, 7.55
mmol), and isopropanol (20 mL). After purification by column
chromatography (Rf = 0.52, hexane:EtOAc 70:30), the title
compound was isolated as a white solid (1.56 g, 72%).72
Preparation of (SIPr)Au(P(O)(OEt)2) (8). The title compound was
prepared following general method B using (SIPr)AuPh (1.00 g, 1.50
mmol) and diethylphosphite (0.194 mL, 1.51 mmol). After heating at
85 °C for 18 h, purification by column chromatography (Rf = 0.36,
EtOAc:MeOH 90:10) afforded the title compound as a white solid
(0.94 g, 86%). Anal. Calcd for C31H48AuN2O3P: C, 51.38; H, 6.68.
Found: C, 51.59; H, 6.57. 1H (CDCl3, 25 °C): δ 7.38 (t, 2H, J = 7.8,
ArH), 7.22 (d, 4H, J = 7.8, ArH), 4.06 (s, 4H, −NCH2−), 3.36 (m,
4H, −OCH2−), 3.03 (sept, 4H, J = 6.8, −CH−), 1.39 (d, 12H, J =
6.8, −Me), 1.33 (d, 12H, J = 6.9, −Me), 0.89 (t, 6H, J = 7.0, −Me).
13C{1H} (CDCl3, 25 °C): δ 216.6 (d, J = 168.2, carbene C), 146.8 (s,
quat), 133.7 (s, quat), 130.1 (s, ArCH), 124.7 (s, ArCH), 57.1 (s,
−OCH2−), 54.0 (d, J = 5.8, −NCH2−), 29.2 (s, −CH−), 25.3 (s,
−Me), 24.3 (s, −Me), 16.7 (d, J = 7.8, −Me). 31P{1H} (CDCl3, 25
°C): δ 111.6 (s).
Preparation of (tBuXPhos)AuPh (2). The title compound was
prepared following general method A using (tBuXPhos)AuCl (2.00 g,
3.04 mmol), PhB(OH)2 (0.742 g, 6.09 mmol), Cs2CO3 (1.98 g, 6.08
mmol), and isopropanol (20 mL). After purification by column
chromatography (Rf = 0.70, hexane:EtOAc 70:30), the title
compound was isolated as a white solid (1.61 g, 76%).72
Preparation of (SIMes)AuPh (3). The title compound was prepared
following general method A using (SIMes)AuCl (2.00 g, 3.71 mmol),
PhB(OH)2 (0.905 g, 7.42 mmol), Cs2CO3 (2.42 g, 7.43 mmol), and
isopropanol (20 mL). After purification by column chromatography
(Rf = 0.26, hexane:EtOAc 70:30), the title compound was isolated as
a white solid (1.41 g, 65.4%). Anal. Calcd for C27H31AuN2: C, 55.86;
Preparation of (JohnPhos)Au(P(O)Pin) (9). The title compound
was prepared following general method B using (JohnPhos)AuPh
(0.500 g, 0.873 mmol) and HP(O)Pin (0.144 g, 0.877 mmol). After
heating at 70 °C for 18 h, purification by column chromatography (Rf
= 0.30, EtOAc:MeOH 90:10) afforded the title compound as a white
solid (0.49 g, 85%).40
1
H, 5.38. Found: C, 55.97; H, 5.44. H (CDCl3, 25 °C): δ 7.02 (m,
4H, ArH), 6.97 (s, 4H, ArH), 6.84 (t, 1H, J = 7.0, ArH), 3.94 (s, 4H,
−CH2N−), 2.39 (s, 12H, −Me), 2.32 (s, 6H, −Me). 13C{1H}
(CDCl3, 25 °C): δ 216.2 (s, carbene C), 169.6 (s, quat), 140.6 (s,
ArCH), 138.3 (s, quat), 135.9 (s, quat), 135.5 (s, quat), 129.6 (s,
ArCH), 126.8 (s, ArCH), 124.7 (s, ArCH), 51.0 (s, −CH2N−), 21.2
(s, −Me), 18.3 (s, −Me).
Preparation of (tBuXPhos)Au(P(O)Pin) (10). The title compound
was prepared following general method B using (tBuXPhos)AuPh
(0.500 g, 0.716 mmol) and HP(O)Pin (0.118 g, 0.719 mmol). After
heating at 70 °C for 18 h, purification by column chromatography (Rf
= 0.41, EtOAc:MeOH 90:10) afforded the title compound as a white
solid (0.50 g, 89%).36
Preparation of (SIPr)AuPh (4). The title compound was prepared
following general method A using (SIPr)AuCl (2.00 g, 3.21 mmol),
PhB(OH)2 (0.783 g, 6.42 mmol), Cs2CO3 (2.09 g, 6.41 mmol), and
isopropanol (20 mL). After purification by column chromatography
(Rf = 0.74, hexane:EtOAc 70:30), the title compound was isolated as
a white solid (1.45 g, 68.4%). Anal. Calcd for C33H43AuN2: C, 59.63;
Preparation of (SIMes)Au(P(O)Pin) (11). General Method B was
followed using (SIMes)AuPh (0.500 g, 0.861 mmol) and HP(O)Pin
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(0.142 g, 0.865 mmol). After heating at 85 °C for 18 h, purification by
column chromatography (Rf = 0.17, EtOAc:MeOH 95:5) afforded the
title compound as a white solid (0.38 g, 66%). Anal. Calcd for
cooling the crude reaction mixture (0 °C). Anal. Calcd for
1
C31H42AuN2O7P: C, 47.58; H, 5.41. Found: C, 47.32; H, 5.41. H
(CDCl3, 25 °C): δ 6.94 (s, 4H, ArH), 3.94 (s, 4H, −NCH2−), 3.72
(m, 4H, −OCH2−), 3.59 (s, 3H, −OMe), 3.47 (s, 3H, −OMe), 2.33
(s, 12H, −Me), 2.29 (s, 6H, −Me), 1.10 (t, 6H, J = 7.0, −Me).
13C{1H} (CDCl3, 25 °C): δ 209.7 (d, J = 5.2, carbene C), 195.3 (d, J
= 23.6, quat), 176.2 (d, J = 35.6, quat), 166.5 (d, J = 24.3, quat), 138.6
(s, quat), 136.0 (s, quat), 135.0 (s, quat), 129.6 (s, ArCH), 129.2 (d, J
= 196.2, quat), 61.9 (d, J = 5.2, −OCH2−), 51.8 s, −OMe), 51.1 (s,
−CH2N−), 21.2 (s, −Me), 18.1 (s, −Me), 16.5 (d, J = 6.2, −Me).
31P{1H} (CDCl3, 25 °C): δ 18.3 (s).
1
C27H38AuN2O3P: C, 48.65; H, 5.75. Found: C, 48.68; H, 5.59. H
(CDCl3, 25 °C): δ 6.92 (s, 4H, ArH), 3.96 (s, 4H, −NCH2−), 2.29
(s, 18H, −Me), 1.24 (s, 6H, −Me), 0.91 (s, 6H, −Me). 13C{1H}
(CDCl3, 25 °C): δ 214.3 (d, J = 178.0, carbene C), 139.0 (s, quat),
135.6 (s, quat), 134.5 (s, quat), 129.9 (s, ArCH), 83.4 (d, J = 4.6,
quat), 51.2 (d, J = 5.8, −NCH2−), 25.3 (d, J = 2.7, −Me), 24.7 (d, J =
5.4, −Me), 21.1 (s, −Me), 18.1 (s, −Me).31P{1H} (CDCl3, 25 °C): δ
120.5 (s).
Preparation of (SIPr)Au(P(O)Pin) (12). The title compound was
prepared following general method B using (SIPr)AuPh (0.500 g,
0.752 mmol) and HP(O)Pin (0.124 g, 0.755 mmol). After heating at
85 °C for 18 h, purification by column chromatography (Rf = 0.30,
EtOAc:MeOH 95:5) afforded the title compound as a white solid
(0.39 g, 69%). Anal. Calcd for C33H50AuN2O3P: C, 52.80; H, 6.71.
Found: C, 52.65; H, 6.59. 1H (CDCl3, 25 °C): δ 7.39 (t, 2H, J = 7.7,
ArH), 7.23 (d, 4H, J = 7.7, ArH), 4.02 (s, 4H, −NCH2−), 3.03 (sept,
4H, J = 6.9, −CH−), 1.42 (d, 12H, J = 6.8, −Me), 1.33 (d, 12H, J =
6.8, −Me), 1.19 (s, 6H, −Me), 0.71 (s, 6H, −Me). 13C{1H} (CDCl3,
25 °C): δ 214.5 (d, J = 176.5, carbene C), 146.6 (s, quat), 133.9 (s,
quat), 130.2 (s, ArCH), 124.8 (s, ArCH), 83.4 (d, J = 4.8, quat), 54.1
(d, J = 6.1, −NCH2−), 29.2 (s, −CH−), 25.5 (s, −Me), 25.3 (d, J =
2.6, −Me), 24.9 (d, J = 5.3, −Me), 24.2 (s, −Me). 31P{1H} (CDCl3,
25 °C): δ 119.0 (s).
Preparation of Vinylgold Compounds: General Method C. A
vial (10 mL) was charged (in air) with a gold phosphito compound
and a magnetic stirring bar. The atmosphere was exchanged for
nitrogen on a vacuum manifold, and DMAD was injected along with
toluene. The vial was heated in an aluminum block heater at the
desired temperature until consumption of the gold precursor was
complete (31P NMR). The volatiles were removed, and the title
compound was separated by column chromatography. Chromatog-
raphy details: flash (N2 pressure), 50 g of SiO2 (NEt3 treated) per
gram of crude vinylgold compound, EtOAc:MeOH (gradient 100:0−
90:10). After removal of the volatiles, the residue was dissolved in
CH2Cl2 and dried over MgSO4. Filtration, concentration, and drying
overnight under vacuum afforded the vinylgold compounds as waxy
solids.
Preparation of (Sp)-(SIMes)Au(P(O)Ph((−)O-Men)) (15). The title
compound was prepared following general method B using 7 (1.000
g, 1.72 mmol) and (Rp)-HP(O)Ph((−)O-Men) (0.483 g, 1.72 mmol,
dr > 90:1). After stirring at 100 °C for 24 h, the title compound was
isolated by column chromatography (Rf = 0.34, EtOAc:MeOH 95:5)
as a white solid (0.98 g, 73%, dr > 90:1). Anal. Calcd for
1
C37H50AuN2O2P: C, 56.77; H, 6.44. Found: C, 56.40; H, 6.06. H
(CDCl3, 25 °C): δ 7.26 (dd, 2H, J = 12.7, 7.5, o-C6H5), 7.20 (t, 1H, J
= 7.4, p-C6H5), 7.13 (t, 2H, J = 7.5, m-C6H5), 6.97 (s, 2H, ArH), 6.92
(s, 2H, ArH), 4.00 (s, 4H, −NCH2−), 3.74 (m, 1H, −OCH−), 2.34
(s, 6H, −Me), 2.31 (s, 6H, −Me), 2.30 (s, 6H, −Me), 2.22 (m, 1H,
−CH2−), 1.84 (septd, 1H, J = 7.0, 2.9, −CH−), 1.53 (m, 2H,
−CH2−), 1.19 (m, 1H, −CH−), 1.07 (m, 2H, −CH−, −CH2−), 0.82
(d, 3H, J = 6.0, -Me), 0.76 (m, 2H, −CH2−), 0.72 (d, 3H, J = 7.0,
−Me), 0.59 (d, 3H, J = 7.0, −Me). 13C{1H} (CDCl3, 25 °C): δ 217.5
(d, J = 143.0, carbene C), 146.4 (d, J = 73.9, quat), 139.1 (s, quat),
135.8 (s, quat), 135.7 (s, quat), 134.5 (s, quat), 129.90 (s, ArCH),
129.85 (s, ArCH), 129.76 (d, J = 16.6, ArCH), 128.9 (d, J = 1.9,
ArCH), 127.4 (d, J = 11.6, ArCH), 78.3 (s, −OCH−), 51.3 (d, J =
4.8, −NCH2−), 48.7 (d, J = 8.7, −CH−), 44.3 (s, −CH2−), 34.7 (s,
−CH2−), 31.8 (s, −CH−), 24.5 (s, −CH−), 23.4 (s, −CH2−), 22.1
(s, −Me), 21.2 (s, −Me), 21.0 (s, −Me), 18.2 (s, −Me), 18.1 (s,
−Me), 16.8 (s, −Me). 31P{1H} (CDCl3, 25 °C): δ 119.1 (s).
Preparation of (Sp)-(JohnPhos)Au(P(O)Ph((−)O-Men)) (16). The
title compound was prepared following general method B using 5
(1.00 g, 1.75 mmol) and (Rp)-HP(O)Ph((−)O-Men) (0.490 g, 1.75
mmol, dr > 90:1). After stirring at 115 °C for 18 h, the title
compound was isolated by column chromatography (Rf = 0.46,
EtOAc:MeOH 90:10) as a white solid (1.16 g, 86%, dr > 90:1).36
Preparation of (Z)-(JohnPhos)Au(MeO2CCO2Me)(P(O)Ph(O-
Men)) (17). The title compound was prepared following general
method C using 16 (0.500 g, 0.645 mmol) and DMAD (0.317 mL,
2.58 mmol, 4 equiv). After stirring at 80 °C for 48 h, the title
compound was isolated by column chromatography (Rf = 0.44,
EtOAc:hexane 70:30) as a white waxy solid (0.26 g, 44%, dr > 90:1).
Anal. Calcd for C42H57AuO6P2: C, 55.02; H, 6.27. Found: C, 54.54;
Preparation of (Z)-(JohnPhos)Au(MeO2CCO2Me)(P(O)(OEt)2)
(13). The title compound was prepared following general method C
using 5 (1.00 g, 1.58 mmol) and DMAD (0.778 mL, 6.33 mmol, 4
equiv). The reaction mixture was stirred at 80 °C for 48 h. Following
purification by column chromatography (Rf = 0.28, hexane:EtOAc
40:60), the title compound was isolated as a pale-yellow wax (1.03 g,
84%). Crystals of 13 that were suitable for X-ray diffraction were
grown by cooling a saturated hexane/EtOAc solution (−30 °C). Anal.
Calcd for C30H43AuO7P2: C, 46.52; H, 5.60. Found: C, 46.27; H,
1
H, 6.26. H (CDCl3, 25 °C): δ 7.90 (m, 3H, ArH), 7.43 (m, 6H,
1
ArH), 7.29 (m, 1H, ArH), 7.22 (m, 1H, ArH), 7.16 (br d, 1H, J = 7.6
ArH), 7.10 (m, 2H, ArH), 4.22 (m, 1H, −CH−), 3.67 (s, 3H,
−OMe), 3.49 (s, 3H, −OMe), 2.20 (m, 1H, −CH2−), 2.12 (dsept,
1H, J = 7.0, 1.9, −CH−), 1.61 (m, 2H, −CH2−), 1.46 (d, 9H, J =
15.0, −Me), 1.39 (d, 9H, J = 14.8, −Me), 1.35 (m, 2H, −CH−), 1.14
(m, 1H, −CH2−), 0.95 (m, 1H, −CH2−), 0.86 (d, 3H, J = 7.1, −Me),
0.83 (m, 1H, −CH2−), 0.81 (d, 3H, J = 6.5, −Me), 0.74 (d, 3H, J =
6.9, −Me). 13C{1H} (CDCl3, 25 °C): δ 202.6 (dd, J = 95.7, 23.6,
quat), 176.2 (d, J = 31.2, quat), 166.4 (dd, J = 23.0, 9.0, quat), 150.6
(d, J = 15.4, quat), 141.9 (d, J = 6.3, quat), 136.1 (d, J = 141.5, quat),
134.6 (s, ArCH), 133.0 (d, J = 7.1, ArCH), 131.5 (d, J = 10.4, ArCH),
131.1 (d, J = 145.9, quat), 130.9 (d, J = 2.9, ArCH), 130.1 (d, J = 2.1,
ArCH), 129.2 (s, ArCH), 129.1 (s, ArCH), 128.9 (s, ArCH), 128.7
(s, ArCH), 127.8 (d, J = 36.2, quat), 127.7 (d, J = 13.3, ArCH), 127.4
(s, ArCH), 126.5 (d, J = 5.5, ArCH), 76.4 (d, J = 7.1, −CH−), 51.3
(s, −OMe), 50.9 (s, −OMe), 48.9 (d, J = 6.6, −CH−), 43.8 (s,
−CH2−), 37.5 (d, J = 21.3, quat), 37.4 (d, J = 20.6, quat), 34.4 (s,
−CH2−), 31.8 (s, −CH−), 30.9 (d, J = 7.1, −Me), 25.2 (s, −CH−),
22.9 (s, −CH2−), 22.1 (s, −Me), 21.4 (s, −Me), 15.8 (s, −Me).
31P{1H} (CDCl3, 25 °C): δ 63.6 (d, J = 12.3, −PR3), 29.0 (d, J = 12.3,
−P(O)−).
5.81. H (CDCl3, 25 °C): δ 7.87 (t, 1H, J = 7.2, ArH), 7.44 (m 2H,
ArH), 7.39 (t, 2H, J = 7.5, ArH), 7.31 (t, 1H, J = 7.4, ArH), 7.23 (m,
1H, ArH), 7.17 (d, 2H, J = 7.5, ArH), 4.08 (m, 4H, −OCH2−), 3.68
(s, 3H, −OMe), 3.67 (s, 3H, −OMe), 1.40 (d, 18H, J = 15.0, −Me),
1.30 (t, 6H, J = 7.1, −Me). 13C{1H} (CDCl3, 25 °C): δ 201.8 (dd, J =
95.9, 25.3, quat), 175.5 (d, J = 36.3, quat), 166.4 (dd, J = 23.7, 8.7,
quat), 150.5 (d, J = 15.4, quat), 142.0 (d, J = 6.1, quat), 134.6 (s,
ArCH), 133.0 (d, J = 7.3, ArCH), 130.2 (d, J = 2.1, ArCH), 129.1 (s,
ArCH), 128.9 (s, ArCH), 127.9 (d, J = 200.9, quat), 127.6 (d, J =
36.9, quat), 127.5 (s, ArCH), 126.5 (d, J = 5.6, ArCH), 61.8 (d, J =
5.4, −OCH2−), 51.9 (s, −OMe), 51.0 (s, −OMe), 37.4 (d, J = 21.2,
−Me), 30.8 (d, J = 7.1, −Me), 16.5 (d, J = 6.7, −Me). 31P{1H}
(CDCl3, 25 °C): δ 63.0 (d, J = 14.6, −PR3), 18.8 (d, J = 14.6,
−P(O)(OEt)2).
Preparation of (Z)-(SIMes)Au(MeO2CCO2Me)(P(O)(OEt)2) (14).
The title compound was prepared following general method C using 7
(1.00 g, 1.56 mmol) and DMAD (0.768 mL, 6.25 mmol). The
reaction mixture was stirred at 80 °C for 48 h. Following purification
by column chromatography (Rf = 0.24, 100% EtOAc), the title
compound was isolated as a pale-yellow waxy solid (0.93 g, 76%).
Crystals of 14 that were suitable for X-ray diffraction were grown by
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Preparation of (Z)-(MeO2C)(I)CC(CO2Me)(P(O)(OEt)2) (18). A
vial (10 mL) was charged with 13 (1.00 g, 1.29 mmol), iodine (0.328
g, 1.29 mmol), and a stirring bar. The atmosphere was exchanged for
nitrogen, and toluene (5 mL) was injected by syringe. After stirring
(12 h, 25 °C), the volatiles were removed under vacuum, and the
residue was dissolved in a minimal amount of hot ethyl acetate. The
solution was filtered through Celite and allowed to cool to room
temperature. Crystals of JohnPhosAuI formed after 24 h and were
separated. The ethyl acetate was evaporated, and the title compound
was isolated by column chromatography (Rf = 0.67, EtOAc) as a light
tan oil (0.48 g, 89%). A small amount of JohnPhosAuI was also
isolated from the column, and combining the two JohPhosAuI
samples afforded 0.75 g (93%) of the iodogold compound. Anal.
Calcd for C10H16IO7P: C, 29.58; H, 3.97. Found: C, 29.58; H, 4.17.
1H (CDCl3, 25 °C): δ 4.22 (m, 4H, −CH2−), 3.83 (s, 3H, −OMe),
Preparation of (SIMes)Au(CCCO2Me) (21). The title compound
was prepared following general method D using (7) (0.500 g, 0.781
mmol) and methyl propiolate (0.347 mL, 3.90 mmol, 5 equiv). After
heating at 85 °C for 18 h, purification by column chromatography (Rf
= 0.28, hexane:EtOAc 70:30) afforded the title compound as a white
solid (0.32 g, 70%).40
Preparation of (SIPr)Au(CCCO2Me) (22). The title compound
was prepared following general method D using (8) (0.630 g, 0.869
mmol) and methyl propiolate (0.387 mL, 4.35 mmol, 5 equiv). After
heating at 85 °C for 18 h, purification by column chromatography (Rf
= 0.39, hexane:EtOAc 70:30) afforded the title compound as a white
solid (0.46 g, 79%). Anal. Calcd for C31H41AuN2O2: C, 55.52; H,
6.16. Found: C, 55.47; H, 6.06. 1H (CDCl3, 25 °C): δ 7.41 (t, 2H, J =
7.7, ArH), 7.23 (d, 4H, J = 7.7, ArH), 4.01 (s, 4H, −NCH2−), 3.57 (s,
3H, −OMe), 3.03 (sept, 4H, J = 6.8, −CH−), 1.40 (d, 12H, J = 6.8,
−Me), 1.33 (d, 12H, J = 6.9, −Me). 13C{1H} (CDCl3, 25 °C): δ
209.6 (s, carbene C), 154.1 (s, quat), 146.7 (s, quat), 134.02 (s, quat),
133.95 (s, quat), 130.1 (s, ArCH), 124.7 (s, ArCH), 93.3 (s, quat),
53.9 (s, −NCH2−), 51.9 (s, −OMe), 29.1 (s, −CH−), 25.4 (s, −Me),
24.2 (s, −Me).
3.82 (s, 3H, −OMe), 1.37 (t, 6H, J = 7.1, −Me). 13C{1H} (CDCl3, 25
°C): δ 165.2 (d, J = 10.4, CO), 164.1 (d, J = 22.7, CO), 143.2
(d, J = 180.9, quat), 105.6 (s, quat), 64.0 (d, J = 5.8, −OCH2−), 54.3
(s, −OMe), 53.4 (s, −OMe), 16.4 (d, J = 6.5, −Me). 31P{1H}
(CDCl3, 25 °C): δ 7.0 (s).
Preparation of Alkynylgold Compounds. General Method
D. A vial (10 mL) was charged with a gold phosphito precursor and a
magnetic stirring bar. The vial was capped, and the atmosphere was
exchanged for nitrogen. Methyl propiolate (5 equiv) was injected by
syringe along with toluene (6 mL). After the reaction was complete,
the volatiles were removed, and the title compound was purified by
column chromatography. Chromatography details: flash (N2
pressure), 25 g of NEt3 treated SiO2 per gram of crude alkynylgold
compound, hexane:EtOAc (gradient 100:0−30:70). After removal of
the volatiles, the residue was dissolved in CH2Cl2 and dried over
MgSO4. Filtration, concentration, and drying overnight under vacuum
afforded the alkynylgold compounds as white solids. If desired, the
alkynylgold compounds can be recrystallized by cooling a saturated
hexane/EtOAc solution to −30 °C.
Preparation of (JohnPhos)Au(CCCO2Me) (19). The title
compound was prepared following general method D using (5)
(1.00 g, 1.58 mmol) and methyl propiolate (0.703 mL, 7.91 mmol, 5
equiv). After heating at 70 °C for 18 h, purification by column
chromatography (Rf = 0.37, hexane:EtOAc 70:30) afforded the title
compound as a white solid (0.66 g, 72%). Anal. Calcd for
C24H30AuO2P: C, 49.83; H, 5.23. Found: C, 49.93; H, 5.19. 1H
(CDCl3, 25 °C): δ 7.83 (t, 1H, J = 3.9, ArH), 7.48 (m, 5H, ArH),
7.27 (m, 1H, ArH), 7.11 (d, 2H, J = 7.6, ArH), 3.69 (s, 3H, −OMe),
1.37 (d, 18H, J = 15.0, −Me). 13C{1H} (CDCl3, 25 °C): δ 154.4 (d, J
= 2.9, quat), 150.3 (d, J = 15.0, quat), 142.2 (d, J = 6.2, quat), 138.2
(d, J = 129.4, quat), 134.3 (d, J = 1.0, ArCH), 133.1 (d, J = 7.1,
ArCH), 130.5 (d, J = 2.3, ArCH), 129.2 (s, ArCH), 129.1 (s, ArCH),
128.4 (s, ArCH), 127.0 (d, J = 41.3, quat), 126.8 (d, J = 6.2, ArCH),
91.9 (d, J = 22.0, quat), 51.9 (s, −OMe), 37.6 (d, J = 22.7, -quat),
31.0 (d, J = 6.9, −Me). 31P{1H} (CDCl3, 25 °C): δ 64.0 (s).
Preparation of (tBuXPhos)Au(CCCO2Me) (20). The title
compound was prepared following general method D using (6)
(0.423 g, 0.558 mmol) and methyl propiolate (0.248 mL, 2.79 mmol,
5 equiv). After heating at 70 °C for 18 h, purification by column
chromatography (Rf = 0.86, hexane:EtOAc 70:30) afforded the title
compound as a white solid (0.32 g, 81%). Anal. Calcd for
C33H48AuO2P: C, 56.25; H, 6.87. Found: C, 55.94; H, 6.81. 1H
(CDCl3, 25 °C): δ 7.85 (td, 1H, J = 7.6, 1.2, ArH), 7.46 (m, 2H,
ArH), 7.30 (ddd, 1H, J = 7.6, 4.6, 1.5, ArH), 7.12 (s, 2H, ArH), 3.67
(s, 3H, -OMe), 3.02 (sept, 1H, J = 6.9, −CH−), 2.33 (sept, 1H, J =
6.7, −CH−), 1.40 (d, 18H, J = 15.0, −Me), 1.35 (d, 6H, J = 6.9,
−Me), 1.30 (d, 6H, J = 6.8, −Me), 0.91 (d, 6H, J = 6.6, −Me).
13C{1H} (CDCl3, 25 °C): δ 154.4 (d, J = 2.9, quat), 149.9 (s, quat),
ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.organomet.1c00283.
■
sı
NMR spectra of all new compounds (PDF)
Accession Codes
CCDC 2080845−2080850 contain the supplementary crys-
tallographic 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 1EZ, UK; fax: +44 1223 336033.
AUTHOR INFORMATION
Corresponding Author
■
Robert A. Stockland, Jr. − Department of Chemistry, Bucknell
University, Lewisburg, Pennsylvania 17837, United States;
orcid.org/0000-0002-4351-6395; Email: rstockla@
bucknell.edu
Authors
Carly L. Masonheimer − Department of Chemistry, Bucknell
University, Lewisburg, Pennsylvania 17837, United States
Madeleine G. Atwood − Department of Chemistry, Bucknell
University, Lewisburg, Pennsylvania 17837, United States
Susan E. Hartzell − Department of Chemistry, Bucknell
University, Lewisburg, Pennsylvania 17837, United States
Erin A. Reph − Department of Chemistry, Bucknell University,
Lewisburg, Pennsylvania 17837, United States
Robert D. Pike − Department of Chemistry, The College of
William and Mary, Williamsburg, Virginia 23185, United
States; orcid.org/0000-0002-8712-0288
Complete contact information is available at:
https://pubs.acs.org/10.1021/acs.organomet.1c00283
Notes
The authors declare no competing financial interest.
148.6 (d, J = 15.5, quat), 145.8 (s, quat), 139.1 (d, J = 129.8, quat),
135.6 (d, J = 5.2, quat), 135.3 (d, J = 1.7, ArCH), 134.8 (d, J = 7.9,
ArCH), 130.1 (d, J = 2.0, ArCH), 129.2 (d, J = 38.6, quat), 126.5 (d, J
= 6.2, ArCH), 122.2 (s, ArCH), 91.7 (d, J = 22.5, quat), 51.8 (s,
−OMe), 38.2 (d, J = 23.6, quat), 33.9 (s, −Me), 31.5 (d, J = 6.7,
−Me), 31.0 (s, −CH−), 26.4 (s, −Me), 24.0 (s, −Me), 23.2 (s,
−Me). 31P{1H} (CDCl3, 25 °C): δ 63.4 (s).
ACKNOWLEDGMENTS
■
The authors acknowledge the National Science Foundation for
generous support of this work (CHE-1955190, CHE-1300088)
as well as the funds to purchase the NMR spectrometer (CHE-
0521108) and are indebted to NSF (CHE-0443345) and the
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(21) Furstner, A. Gold Catalysis for Heterocyclic Chemistry: A
̈
College of William and Mary for the purchase of the X-ray
equipment. The authors thank the Clare Boothe Luce
Foundation for research fellowships to C.L.M. and M.G.A.
and Bucknell University for a Scholarly Development Grant to
R.A.S. The authors thank Michael Krout and Tim Strein for
helpful discussions.
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