1,1-carboboration reactions of strongly electrophilic 2-borylethyl thioethers

Article abstract of DOI:10.5560/ZNB.2014-4190

The RSCH₂CH₂B(C₆F₅)₂ boranes 3a (R = Ph) and 3b (R = Et) were in situ generated by HB(C₆F₅)₂ hydroboration of the respective vinylthioethers. Their treatment with R

Full text of DOI:10.5560/ZNB.2014-4190

1,1-Carboboration Reactions of Strongly Electrophilic 2-Borylethyl
Thioethers
Christina Eller, Bastian Billmann, Constantin G. Daniliuc$, Gerald Kehr, and
Gerhard Erker
Organisch-chemisches Institut der Westfälischen Wilhelms-Universität Münster, Corrensstraße
40, 48149 Münster, Germany
$ X-Ray crystal structure analyses
Reprint requests to Prof. Dr. G. Erker. Fax: +49-251-8336503. E-mail: erker@uni-muenster.de
Z. Naturforsch. 2014, 69b, 1357 – 1364 / DOI: 10.5560/ZNB.2014-4190
Received August 22, 2014
Dedicated to Professor Hubert Schmidbaur on the occasion of this 80th birthday
The RSCH2CH2B(C6F5)2 boranes 3a (R = Ph) and 3b (R = Et) were in situ generated by
HB(C6F5)2 hydroboration of the respective vinylthioethers. Their treatment with R1−C≡C–
SiMe3 acetylenes resulted in clean 1,1-carboboration to give the respective RSCH2CH2-substituted
alkenylboranes 4 (3 examples). Likewise, the reagents 3 underwent 1,1-carboboration with the
acetylenes Ar2P–C≡C–SiMe3 to give the tetrasubstituted alkenylboranes 6, featuring a geminal pair
of RSCH2CH2/B(C6F5)2 substituents at one carbon atom and the Me3Si/PAr2 pair at the other
(3 examples). The compounds 6 feature an internal B···P interaction. The conceptually related
Mes2PCH2CH2B(C6F5)2 borane (2) does not undergo 1,1-carboboration with ArS–C≡C–SiMe3 but
forms the 1,2-P/B-FLP addition product 7 to the acetylene instead. Compounds 4a, 4c, 6a, and 7
were characterized by X-ray diffraction.
Key words: Boron, Sulfur, Alkenylboranes, Frustrated Lewis Pairs (FLPs)
Introduction
mation of the dienylborane 1a by the selective
transfer of an alkenyl group from boron to the
The 1,1-carboboration of suitable alkynes is a good acetylenic carbon [17] and the synthesis of a dou-
method for synthesizing alkenylboranes [1 – 3]. The bly PAr2-substituted “frustrated Lewis pair” 1b by
method is especially well suited for making alkenyl- CH2–CH2–PMes2 transfer [18]. We have now em-
boranes with bulky substitution patterns [4]. The early ployed a small series of RSCH2CH2-substituted bo-
development of this reaction (“Wrackmeyer reaction”) ranes as reagents carrying out the 1,1-carboboration
relied on metal-containing migrating substituents on reactions of two trimethylsilyl-substituted alkynes.
the alkyne (SiMe3, SnR3, PbR3 and a few oth-
ers) [5 – 8]; lately the use of very electrophilic bo-
ranes containing the B(C6F5)2 group greatly widened
the scope of the 1,1-carboboration reaction [9, 10],
now featuring H [11] and even alkyl or aryl groups
as migrating substituents [12]. It had been shown that
PAr2 [13] and even SR groups [14] migrated in these
“advanced” 1,1-carboboration reactions, which made
it a useful tool for e. g. phosphole [15] and even borole
synthesis [16].
We had recently shown that the 1,1-carboboration
reaction can be used for attaching functional groups
at the newly formed alkenylborane. Two typical ex-
amples are depicted in Scheme 1, namely the for- Scheme 1.
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C. Eller et al. · 1,1-Carboboration Reactions
Scheme 2.
This made the respective RS–CH2CH2-substituted nated PhS···B structural feature in compound 4a. This
alkenylboranes readily available. Their preparation and was confirmed by the X-ray crystal structure analysis
characterization will be described in this article.
of compound E-4a (see Fig. 1 and Table 3). It shows
that the borane reagent 3a has added to the Me3Si-
C≡ carbon atom of the acetylene reagent and induced
migration of the SiMe3 group to its adjacent ≡C-Ph
Results and Discussion
We had previously described the reaction of acetylenic carbon atom to make room for the PhS–
phenyl vinylsulfide with Piers’ borane [HB(C6F5)2]. CH2–CH2- substituent for its migration from boron to
It gave the anti-Markovnikov hydroboration prod- carbon. The formation of the final product 4a then ap-
uct 3a of the vinylsulfide functionality. The prod- parently profits from some internal stabilization by Ph-
uct 3a turned out to show an extremely low solu- S···B coordination.
bility; it is probably oligomeric, but it was amply
The in situ-formed S/B FLP 3a was similarly
identified by the formation of a variety of addition trapped by 1-trimethylsilylhexyne to selectively give
products and derivatives [19]. We have now gener- the 1,1-carboboration product 4b. The reaction was
ated the oligomeric S/B frustrated Lewis pair 3a in carried out directly in [D8]toluene, and the product was
situ from PhS-vinyl and HB(C6F5)2. After stirring the not isolated but characterized from the reaction mix-
suspension for 30 min at r. t. in toluene we added ture. The NMR analysis showed that the major isomer
phenyl(trimethylsilyl)acetylene and stirred the mixture was formed that had similar NMR data as compound
overnight at 80 ◦C. Workup gave the product 4a as 4a (see Table 1).
a colorless solid in 58% yield. The product was char-
We have also treated ethyl vinylsulfide with
acterized by C, H elemental analysis, by NMR spec- HB(C6F5)2. The resulting suspension of the pre-
troscopy and X-ray diffraction. This identified it as
Table 1. Selected spectroscopic data of compounds 4a–c.
a 1,1-carboboration product of the borane 3a with this
acetylene. There are two stereoisomers possible, but
we have only found one major isomer which was iden-
tified as the E-4a by NMR spectroscopy and X-ray
diffraction (see Scheme 2 and Fig. 1).
Compound
R[S]
4aa
Ph
Ph
4bb
Ph
n-C4H9
4ca
C2H5
Ph
R1
δ
δ
δ
δ
13C1
13C2
13C3
13C4
148.1
158.4
42.3
38.2
3.05
3.17
8.4
144.4
156.4
38.7
37.3
2.94
2.55
10.5
−6.8
8.4
146.7
158.4
38.9
34.1
2.69
Compound 4a shows the typical 13C NMR low-field
resonance of an alkenylborane = C2–[B] carbon atom
(see Table 1). It features an 11B NMR signal in the
δ1H(3)
δ1H(4)
δ
δ
2.75
1.6
range of a tetracoordinated borane. Consistently, we
11B
19
observed a ∆δ
F
m,p
chemical shift difference of the
29Si
−8.6
−8.9
borane-bound C6F5 pair of substituents in an interme-
diate range between typical 3- and 4-coordinate values.
Taken together these data point to a weakly coordi-
19
∆δ
F
m,p
8.1
8.2/7.3
a
In CD2Cl2, 299 K; b in C7D8, 299 K.
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C. Eller et al. · 1,1-Carboboration Reactions
1359
Fig. 1. A view of the molecular structure of the 1,1-
carboboration product 4a (displacement ellipsoids are shown
at the 50% probability level; H atoms as spheres with arbi-
trary radii).
Fig. 2. A view of the molecular structure of the 1,1-
carboboration product 4c (displacement ellipsoids are shown
at the 50% probability level; H atoms as spheres with
arbitrary radii).
sumably oligomeric hydroboration product (3b, adduct 5 (Scheme 3). It was characterized in situ by
see Scheme 2) was subsequently treated with NMR (11B: δ = −8.7; 31P: δ = −1.1; 29Si: δ −14.0;
phenyl(trimethylsilyl)acetylene (80 ◦C, overnight, ∆δ19F m,p = 6.0 ppm; for further details including the
toluene) to give the 1,1-carboboration product 4c as depicted NMR spectra see the Supporting Information
a colorless solid, isolated in 66% yield (characterized available online; see note at the end of the paper
by C, H elemental analysis, by NMR spectroscopy, for availability). We then generated compound 3a in
and by X-ray diffraction). It shows the typical spec- situ in toluene (r. t., 60 min) and treated the resulting
troscopic and structural features of the C3-bridged suspension with Ph2P–C≡C–SiMe3 (80 ◦C overnight).
internally S···B-coordinated S/B FLP product (see Workup eventually gave the product 6a as a colorless
Tables 1 and 3 and Fig. 2).
powder in 36% yield (Scheme 3). Single crystals of
We then treated the in situ-generated sys- compound 6a suitable for its characterization by X-ray
tem 3a with a small series of diarylphosphino- diffraction were obtained by slow crystallization from
(trimethylsilyl)acetylenes [aryl = phenyl (a), o-tolyl pentane at −32 ◦C. The X-ray crystal structure analy-
(b), mesityl (c)]. The reaction of 3a with Ph2P– sis has confirmed that the product 6a had been formed
C≡C–SiMe3 at r. t. (10 min) in CD2Cl2 gave the P/B by a selective 1,1-carboboration reaction (see Fig. 3).
Scheme 3.
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C. Eller et al. · 1,1-Carboboration Reactions
Table 2. Selected spectroscopic data of compounds 6a–ca.
Compound
6ab
6bb
6cb
PAr2
PPh2
P(o-tol)2
PMes2
δ
13C1
139.1
27.2
205.6
40.2
50.0
32.8
3.12
2.88
−6.7
−10.8
6.9
140.0
27.1
202.1
40.9
52.3
33.0
3.04
2.91
−2.7
−10.9
6.0
144.8
24.2
196.5
40.4
51.8
32.6
2.99
2.83
0.5
1JPC
δ
13C2
C3
3JPC
δ
13C4
δ1H(3)
δ1H(4)
δ
δ
11B
29Si
−10.0
2JPSi
7.4
19
∆δ
F
6.5
6.4
5.8
m,p
a
Chemical shifts as δ values in ppm, J in Hz; b in CD2Cl2, 299 K.
Fig. 3. A view of the molecular structure of the 1,1-
carboboration product 6a (displacement ellipsoids are shown
at the 30% probability level; H atoms as spheres with arbi-
trary radii).
Table 3. Selected structural data of compounds 4a, 4c, and
6aa.
Compound
R[S]
4a
Ph
Ph
4c
C2H5
Ph
6a
Ph
R1
PPh2
It shows that both the B(C6F5)2 group and its former
PhSCH2–CH2 substituent are now formally attached
at the former acetylenic carbon atom C2. We assume
that it was the SiMe3 group that had consequently
migrated along the acetylenic core C2 framework to
become attached at C1, geminally oriented to the PPh2
substituent. The tetracoordinated C=C double bond
of the product 6a is found E-configurated. It features
a marked B···P interaction (see Fig. 3).
C1–C2
C2–C3
C3–C4
B1–S1
B1–P1
1.353(2)
1.523(2)
1.526(2)
2.169(2)
–
359.7
360.0
351.4
1.346(3)
1.522(3)
1.522(3)
2.112(2)
–
360.0
359.9
348.3
1.359(3)
1.510(3)
1.533(3)
–
2.030(3)
359.5
360.0
346.7
10.0(2)
−167.1(2)
Σ∠C1R1SiC
Σ∠C2CCB
Σ∠B1CCC
R1–C1–C2–B1
C2–C3–C4–S1
178.6(1)
−37.4(1)
−175.7(2)
−46.5(2)
a
The NMR features indicate an analogous structure
of compound 6a in solution (CD2Cl2, 299 K, see Ta-
ble 2). It features typical heteroatom NMR data of
Bond lengths in Å and angles in deg.
an internal B–P-coordinated system. The 11B NMR to learn whether the carboboration of the acetylene
19
chemical shift and the ∆δ
F
m,p
NMR chemical shift by the P/B system 2 can be achieved. The reaction
difference at the C6F5 substituents indicate a stronger was performed in pentane (r. t., 18 h) to eventually
internal Lewis acid and Lewis base interaction in the give the product 7 which we isolated in 47% yield as
P/B compound 6a than it was observed for the related a colorless powder. Compound 7 was characterized by
S/B systems 4 (see above).
C, H elemental analysis, by X-ray diffraction and by
We also prepared the closely related P/B prod- NMR spectroscopy. The X-ray crystal structure analy-
ucts 6b [P(o-tolyl)2] and 6c (PMes2) by the 1,1- sis (single crystals were obtained by slow evaporation
carboboration reactions of the in situ-generated S/B of a pentane solution at −32 ◦C) revealed that the prod-
system 3a with (o-tolyl)2P–C≡C–SiMe3 or Mes2P– uct in this case was not formed by 1,1-carboboration,
C≡C–SiMe3 and isolated the products in 48% (6b) but the alkyne had added to the pair of heteroatoms
and 34% (6c) yield. Both compounds showed similar of the P/B FLP 2 to form the respective six-membered
NMR spectra to those of 6a (see Table 2) indicating heterocycle (see Scheme 4 and Fig. 4). This is a typical
similar structures with internal P···B coordination (for FLP addition product [20].
details see Table 2 and the Supporting Information).
The X-ray crystal structure analysis characterized
Eventually we treated the P/B FLP 2 (see compound 7 as a zwitterionic phosphonium cation type
Scheme 1) with the acetylene (p-tolyl)S–C≡C–SiMe3 with an internal borate anion formed by regioselective
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C. Eller et al. · 1,1-Carboboration Reactions
1361
Scheme 4.
series of trimethylsilyl-substituted alkynes to give the
respective tetrasubstituted alkenylboranes 4 and 6. In
these cases it is the RS–CH2CH2- substituent at the
boron atom that selectively migrates from boron to car-
bon during the multi-rearrangement process. Quite sur-
prisingly, only single geometric isomers of the com-
pounds 4 were obtained, a reaction behavior that was
markedly different from many of our earlier reported
examples that were stereo-unselective [11]. At this
time we do not have an ample explanation for this be-
havior. In the phosphorus-containing examples 6 it is
probably the formation of the marked B–P interaction
in the product that determines the selective formation
of the E-alkenyl boranes. It seems that the formation of
Fig. 4. Molecular structure of compound 7 (displacement el- the addition product 7 marks a limiting situation where
lipsoids are shown at the 30% probability level; H atoms
FLP addition to the alkyne has become favored over
as spheres with arbitrary radii). Selected bond lengths
1,1-carboboration.
(Å) and angles (deg): P1–C1 1.815(2), C1–C2 1.532(4),
Our examples of the selective formation of
C2–B1 1.646(4), B1–C4 1.667(4), C4–C3 1.351(3), C3–
the RS–CH2CH2-substituted alkenylboranes by 1,1-
carboboration extends the scope of this method. It had
been shown that related alkenylboranes obtained by
the “advanced” B(C6F5)2-containing variation can un-
dergo cross-coupling reactions to form the respective
P1 1.822(2); C2–B1–C4 109.3(2), C41–B1–C51 111.0(2),
C1–P1–C3 106.3(1), C11–P1–C21 109.2(1), C3–S1–C31
106.0(1), P1–C1–C2–B1 −71.1(2), P1–C3–C4–B1 1.7(3),
C3–P1–C1–C2 42.5(2).
alkyne addition to the P/B FLP 2. The phosphonium boron-free organic follow-up products easily. Other
moiety shows a distorted tetrahedral coordination geo- highly substituted alkenylboranes obtained by this
metry at phosphorus. Hindered rotation of the mesityl method had been used as selective Lewis acid com-
1
and C6F5 substituents gave rise to the H NMR ob- pounds in catalytic metal-free FLP hydrogenation re-
servation of two pairs of diastereotopic methylene hy- actions of electron-poor alkenes and alkynes.
drogen atoms of the bridging [P]–CH2–CH2–[B] ethy-
lene moiety (for details see the Supporting Informa-
tion). Compound 7 shows a typical borate 11B NMR
signal at δ = −12.4 ppm and a typical phosphonium
31P NMR signal at δ = 5.1 ppm.
Experimental Section
All syntheses involving air- and moisture-sensitive com-
pounds were carried out using standard Schlenk-type glass-
ware (or in a glove box) under an atmosphere of argon.
The phosphanes were synthesized according to a modified
literature procedure [21]. Bis(pentafluorophenyl)borane was
synthesized according to a modified literature procedure [22,
23]. Phenylvinylsulfide and ethylvinylsulfide were purchased
from Sigma Aldrich and TCI.
Conclusion
The scope of the 1,1-carboboration reaction seems
to be steadily increasing. With this study we
have shown that we can use in situ-generated R2-
B(C6F5)2 FLPs with thioether-containing substituents
[R2 = PhSCH2CH2 or EtSCH2CH2] as reagents un-
Preparation of compound 4a
Bis(pentafluorophenyl)borane (56.1 mg, 0.162 mmol,
dergoing the 1,1-carboboration reaction with a small 1.0 eq.) in toluene (5 mL) was added to a solution of
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C. Eller et al. · 1,1-Carboboration Reactions
phenylvinylsulfide (22.1 mg, 0.162 mmol, 1.0 eq.) in toluene tained by slow evaporation of a dichloromethane solution of
(5 mL) to give a colorless suspension, which was stirred compound 4c at −32 ◦C. – C27H23BF10SSi: calcd. C 53.30
for 30 min at room temperature. Thereafter trimethylsilyl- H 3.81; found C 53.10 H 3.51. – 1H NMR (600 MHz, 299 K,
phenylacetylene (28.3 mg, 31.8 µL, 0.162 mmol, 1.0 eq.) CD2Cl2): δ = 7.29 (m, 2H, m-Ph), 7.15 (m, 1H, p-Ph), 6.92
was added, and the light-yellow reaction mixture was stirred (m, 2H, o-Ph), 2.75 (br, 2H, SCH2), 2.69 (m, 2H, CH2),
at 80 ◦C for overnight. Subsequently all volatiles were 2.18 (q, JHH = 7.4 Hz, 2H, CH2Et), 1.25 (t, JHH = 7.4 Hz,
3
3
removed in vacuo, and pentane (5 mL) was added to the 3H, CHE3t), −0.44 ppm (s, JSiH = 6.6 Hz, 9H, SiCH3).
2
yellow residue. Then, immediately after the addition of
–
13C{1H} NMR (151 MHz, 299 K, CD2Cl2): δ = 158.4
1
pentane (5 mL), all volatiles were removed in vacuo, and (br, BC=), 149.3 (i-Ph), 149.1 (dm, JFC ∼ 240 Hz, C6F5),
pentane (5 mL) was added again to finally give a colorless 146.7 (=CSi), 140.9 (dm, 1JFC ∼ 250 Hz, C6F5), 137.7 (dm,
precipitate. The supernatant solution of the suspension 1JFC ∼ 250 Hz, C6F5), 128.3 (m-Ph), 127.4 (br, o-Ph), 125.1
was removed, and the colorless solid was dried in vacuo (p-Ph), 116.7 (br, i-C6F5), 38.9 (CH2), 34.1 (SCH2), 30.2
to give compound 4a (61.4 mg, 0.094 mmol, 58%) as (CHE2t), 12.8 (CH3Et), 0.2 ppm (1JSiC = 52.3 Hz, SiCH3). –
a colorless powder. Crystals suitable for the X-ray crystal 11B{1H} NMR (192 MHz, 299 K, CD2Cl2): δ = 1.6 ppm
structure analysis were obtained by slow evaporation of (ν1/2 ∼ 350 Hz). – 19F NMR (564 MHz, 299 K, CD2Cl2):
a dichloromethane solution of compound 4a at −32 ◦C. – δ = −126.3, −127.9, −129.5 (each br, Σ4F, o-C6F5),
C31H23BF10SSi: calcd. C 56.72 H 3.53; found C 56.33 H −156.0, −156.9 (each br, each 1F, p-C6F5), −164.2 ppm
1
19
3.33. – H NMR (500 MHz, 299 K, CD2Cl2): δ = 7.35 (m, (br, 4F, m-C6F5), [∆δ
F
= 8.2/7.3]. – 29Si{1H} DEPT
m,p
1H, p-PhS), 7.31 (m, 2H, m-Ph), 7.23 (m, 2H, m-PhS), 7.17 (119 MHz, 299 K, CD2Cl2): δ = −8.9 ppm (ν1/2 ∼ 1 Hz)
(m, 1H, p-Ph), 7.11 (m, 2H, o-PhS), 6.96 (m, 2H, o-Ph),
Preparation of compound 6a
3.17 (m, 2H, SCH2), 3.05 (m, 2H, CH2), −0.42 ppm (s,
2JSiH = 6.6 Hz, 9H, SiCH3). – 13C{1H} NMR (125 MHz,
Bis(pentafluorophenyl)borane (56.1 mg, 0.162 mmol,
299 K, CD2Cl2): δ = 158.4 (br, BC=), 149.4 (i-Ph), 148.9
1.0 eq.) in toluene (2 mL) was added to a solution of
1
(dm, JFC ∼ 240 Hz, C6F5), 148.1 (br, = CSi), 141.0 (dm,
phenylvinylsulfide (22.1 mg, 0.162 mmol, 1.0 eq.) in
1
1JFC ∼ 250 Hz, C6F5), 137.5 (dm, JFC ∼ 250 Hz, C6F5),
toluene (10 mL) to give a suspension which was stirred
for 1 h at room temperature. Thereafter diphenylphos-
phino(trimethylsilyl)acetylene
130.7 (p-PhS), 130.5 (i-PhS), 130.0 (o-PhS), 129.5 (m-PhS),
128.4 (m-Ph), 127.3 (o-Ph), 125.2 (p-Ph), 116.9 (br, i-
(45.7 mg,
0.162 mmol,
C6F5), 42.3 (CH2), 38.2 (SCH2), 0.2 ppm (1JSiC = 52.3 Hz,
SiCH3). – 11B{1H} NMR (160 MHz, 299 K, CD2Cl2):
δ = 8.4 ppm (ν1/2 ∼ 400 Hz). – 19F NMR (470 MHz,
299 K, CD2Cl2): δ = −127.2 (br, 2F, o-C6F5), −156.4
1.0 eq.) was added. The brownish/yellow reaction mixture
was stirred at 80 ◦C for overnight. After cooling to room
temperature all volatiles were removed in vacuo, and the
obtained residue was dissolved in pentane (3 mL). Then
all volatiles were removed in vacuo, and the resulting
residue was dissolved in hexane (3 mL). The hexane
solution was stored at −32 ◦C and after 4 days a colorless
precipitate was formed. The precipitate was collected and
dried in vacuo to give compound 6a (44.0 mg, 0.058 mmol,
3
(tm, JFF = 20.5 Hz, 1F, p-C6F5), −164.5 ppm (m, 2F,
19
m-C6F5), [∆δ
F
m,p
= 8.1]. – 29Si{1H} DEPT (99 MHz,
299 K, CD2Cl2): δ = −8.6 ppm (ν1/2 ∼ 2 Hz).
Preparation of compound 4c
Bis(pentafluorophenyl)borane (80.0 mg, 0.231 mmol, 36%) as a colorless powder. Crystals suitable for the
1.0 eq.) was dissolved in toluene (2 mL) and added to a so- X-ray crystal structure analysis were obtained by slow
lution of ethylvinylsulfide (20.4 mg, 0.231 mmol, 1.0 eq.) evaporation of a pentane solution of compound 6a at
in toluene (10 mL). After the resulting suspension was −32 ◦C. – C37H28BF10PSSi: calcd. C 58.18 H 3.69;
stirred for 30 min trimethylsilylphenylacetylene (40.3 mg, found C 58.67 H 3.46. – 1H NMR (500 MHz, 299 K,
0.231 mmol, 1.0 eq.) was added. The brownish reaction CD2Cl2): δ = 7.50 (m, 2H, p-PhP), 7.38 (m, 4H, m-PhP),
mixture was stirred at 80 ◦C for overnight. Then all volatiles 7.31 (m, 4H, o-PhP), 7.27 (m, 2H, m-PhS), 7.24 (m, 2H,
were removed in vacuo, and the obtained residue was o-PhS), 7.19 (m, 1H, p-PhS), 3.12 (m, 2H, CH2), 2.88 (m,
2
extracted with pentane (5 mL) to give a colorless precipitate. 2H, SCH2), 0.10 ppm (s, JSiH = 6.7 Hz, 9H, SiCH3). –
The supernatant solution of the suspension was removed, and 13C{1H} NMR (126 MHz, 299 K, CD2Cl2): δ = 205.6 (br,
1
the residue was dried in vacuo to give the compound 4c as BC=), 147.9 (dm, JFC =∼ 240 Hz, C6F5), 140.0 (dm,
1
a colorless powder (66.2 mg). The supernatant solution was 1JFC =∼ 250 Hz, C6F5), 139.1 (d, JPC = 27.2 Hz, = CP),
1
stored at −32 ◦C for 3 d to give a colorless solid (27.0 mg). 137.3 (dm, JFC =∼ 250 Hz, C6F5), 136.2 (i-PhS), 132.3
2
4
The two solid fractions were combined to give compound 4c (d, JPC = 9.1 Hz, o-PhP), 131.8 (d, JPC3 = 2.7 Hz, p-PhP),
(93.2 mg, 0.153 mmol, 66%) as a colorless powder. Crystals 130.1 (o-PhS), 129.2 (m-PhS), 129.1 (d, JPC = 10.3 Hz, m-
suitable for the X-ray crystal structure analysis were ob- PhP), 126.9 (d, 1JPC = 39.3 Hz, i-PhP), 126.7 (p-PhS), 116.9
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C. Eller et al. · 1,1-Carboboration Reactions
1363
2
(br, i-C6F5), 40.2 (br d, 3JPC = 50.0 Hz, CH2), 32.8 (SCH2), (br, BC=), 144.7 (d, JPC = 7.2 Hz, o-Mesb), 144.3 (d,
0.1 ppm (d, JSiC = 53.3 Hz, JPC = 2.2 Hz, SiCH3). – 2JPC = 7.6 Hz, o-Mesa), 142.4 (d, JPC = 7.9 Hz, p-Mesb),
1
3
4
11B{1H} NMR (160 MHz, 299 K, CD2Cl2): δ = −6.7 ppm 142.3 (d, 4JPC = 7.8 Hz, p-Mesa), 141.8 (d, 2JPC = 12.9 Hz,
(ν1/2 ∼ 200 Hz). – 19F NMR (470 MHz, 299 K, CD2Cl2): o’-Mesb), 140.5 (d, 2JPC = 10.0 Hz, o’-Mesa), 135.1 (p-Tol),
3
134.4 (i-Tol), 132.3 (d, JPC = 10.6 Hz, m-Mesa), 132.2 (d,
δ = −130.1 (m, 2F, o-C6F5), −158.4 (t, 3JFF = 20.2 Hz, 1F,
3
3JPC = 10.3 Hz, m-Mesb), 131.9 (d, JPC = 10.8 Hz, m’-
19
p-C6F5), −164.9 ppm (m, 2F, m-C6F5), [∆δ
F
m,p
= 6.5]. –
3
Mesa), 131.7 (d, JPC = 11.2 Hz, m’-Mesb), 128.5 (m-Tol),
29Si{1H} DEPT (99 MHz, 299 K, CD2Cl2):δ = −10.8 ppm
1
127.4 (o-Tol), 125.1 (d, JPC = 76.3 Hz, i-Mesa), 120.5 (d,
2
(d, JPSi = 6.9 Hz). – 31P{1H} NMR (202 MHz, 299 K
1
1JPC = 76.6 Hz, i-Mesb), 117.0 (d, JPC = 58.8 Hz, PC=)t,
CD2Cl2): δ = 14.3 ppm (ν1/2 ∼ 100 Hz).
1
3
29.0 (d, JPC = 41.6 Hz, PCH2), 24.9 (d, JPC = 5.4 Hz,
o’-CHM3 es,b), 24.5 (d, JPC = 3.4 Hz, o-CHMes,b), 23.4 (d,
3
Preparation of compound 7
3
3JPC = 4.7 Hz, o’-CHMes,a), 22.9 (br, o-CH3Mes,a), 20.7
3
Dimesitylvinylphosphane
(48.0 mg,
0.162 mmol,
(p-CHT3ol), 20.6 (p-CHM3 es,a), 20.3 (p-CH3Mes,b), 15.5 (br,
1.0 eq.) and bis(pentafluorophenyl)borane (56.1 mg,
0.162 mmol, 1.0 eq.) were dissolved in pentane (4 mL)
and stirred 30 min at room temperature. Then p-
tolyl[(trimethylsilyl)ethynyl]sulfide (35.7 mg, 0.162 mmol,
1.0 eq.) was added. Immediately the reaction mixture turned
yellow, and a colorless solid precipitated. Stirring of the
suspension was continued for overnight. Subsequently the
supernatant solution was removed, and the resulting residue
was washed with pentane (5 mL). The obtained colorless
solid was dried in vacuo to give compound 7 (65.5 mg,
0.076 mmol, 47%) as a colorless powder. Crystals suitable
for the X-ray crystal structure analysis were obtained
from a pentane solution of compound 7 at −32 ◦C. –
C44H42BF10PSSi: calcd. C 61.26 H 4.91; found C 59.45 H
4.45. – 1H NMR (500 MHz, 299 K, C6D6): δ = 6.82 (m,
t
BCH2), 3.1 ppm (SiCH3), [C6F5 not listed;
tentative
assignment]. – 11B{1H} NMR (160 MHz, 299 K, C6D6):
δ = −12.4 ppm (ν1/2 ∼ 60 Hz). – 19F NMR (470 MHz,
299 K, C6D6): δ = −124.0, −127.0, −128.4, −128.9
3
(each br, each 1F, o-C6F5), −160.29 (t), JFF = 20.8 Hz),
3
−160.34 (t, JFF = 21.1 Hz) (each 1F, p-C6F5), −164.1
(2F), −165.3 (1F), −165.6 ppm (1F) (each br, 4F, m-C6F5).
–
29Si{1H} DEPT (99 MHz, 299 K, C6D6): δ = −3.0 ppm
3
(dm, JPSi = 25.0 Hz). – 31P{1H} NMR (202 MHz, 299 K,
C6D6): δ = 5.1 ppm (ν1/2 ∼ 20 Hz 1 ppm).
Supporting information
Additional experimental and analytical details, crystal-
lographic data and pictures of spectra are given as Sup-
porting Information (33 pages) available online (DOI:
10.5560/ZNB.2014-4190).
CCDC 1020239 to 1020242 contain the supplementary
crystallographic data for this paper. These data can be ob-
tained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
4
2H, o-Tol), 6.65 (d, JPH = 2.3 Hz, 1H, m-Mesa), 6.43 (m,
4
2H, m-Tol), 6.38 (d, JPH = 2.9 Hz, 1H, m’-Mesa), 6.08
4
(s, 1H, m-Mesb), 5.87 (d, JPH = 3.2 Hz, 1H, m’-Mesb),
2.99 (s, 3H, o-CHM3 es,a), 2.89, 2.15 (each m, each 1H,
PCH2), 1.90 (s, 3H, p-CHMes,a), 1.89 (s, 3H, p-CH3Tol),
3
1.86 (s, 3H, o-CHM3 es,b), 1.85 (s, 3H, o’-CHM3 es,b), 1.76,
1.57 (each m, each 1H, BCH2), 1.66 (s, 3H, p-CHMes,b),
Acknowledgement
3
1.45 (s, 3H, o’-CHM3 es,a), 0.39 ppm (s, 9H, SiCH3). –
Financial support from the Deutsche Forschungsgemein-
13C{1H} NMR (126 MHz, 299 K, C6D6): δ = 226.0 schaft is gratefully acknowledged.
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