Efficient preparation of apically substituted diamondoid derivatives

Article abstract of DOI:10.1055/s-0033-1338583

We present an effective three-step chromatography-free sequence for the preparation of apical monohydroxy derivatives of diamantane, triamantane, and [121]tetramantane from the corresponding bis-apical diols utilizing tert-butyldimethylsilyl chloride as t

Full text of DOI:10.1055/s-0033-1338583

PAPER
▌787
paper
Efficient Preparation of Apically Substituted Diamondoid Derivatives
Apically Substituted Diamondoids
Paul Kahl,a Boryslav A. Tkachenko,a Anatoliy A. Novikovsky,b Jonathan Becker,1,c Jeremy E. P. Dahl,d
Robert M. K. Carlson,d Andrey A. Fokin,*a,b Peter R. Schreiner*a
a
Institute of Organic Chemistry, Justus-Liebig University, Heinrich-Buff-Ring 58, 35392 Giessen, Germany
Fax +49(641)9934309; E-mail: prs@uni-giessen.de
b
Department of Organic Chemistry, Kiev Polytechnic Institute, pr. Pobedy 37, 03056 Kiev, Ukraine
E-mail: aaf@xtf.ntu-kpi.kiev.ua
c
Institute of Inorganic Chemistry, Justus-Liebig University, Heinrich-Buff-Ring 58, 35392 Giessen, Germany
d
Stanford University, Stanford Institute for Materials & Energy Science, 476 Lomita Mall, Stanford, CA 94305, USA
Received: 30.11.2013; Accepted: 13.12.2013
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Abstract: We present an effective three-step chromatography-free
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sequence for the preparation of apical monohydroxy derivatives of
diamantane, triamantane, and [121]tetramantane from the corre-
sponding bis-apical diols utilizing tert-butyldimethylsilyl chloride
as the monosilylating agent. The procedure was successfully ap-
plied to the monoprotection of several other aliphatic and aromatic
diols. Additionally, 9-aminodiamantan-4-carboxylic acid, which
has significant potential in medicinal and material sciences, was
prepared through Ritter reaction of 4,9-dihydroxydiamantane in tri-
fluoroacetic acid.
5
17
3
16
5
6
9
10
11
17
1
13
12
4
8
7
3
19
20
15
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10
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15
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7
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2
1
13
10
X
14
14
5
12
8
14
21
3
4
9
18
13
Y
Y
1, X = Y = H
4, X = Y = OH
2, X = H
3, X = Y = H
5, X = OH
6, X = Y = OH
Key words: amino acids, diols, monoprotection, nanostructures, si-
lyl protecting groups
7, X = H, Y = SH
Figure 1 Diamantane (1), triamantane (2), and [121]tetramantane
(3) with numbering of carbon atoms and their derivatives
Diamondoids comprise condensed adamantane moieties
with different steric allocations (Figure 1). While diaman-
tane (1), triamantane (2), and [121]tetramantane (3) are
synthetically available through elaborate multistep proce-
dures, the only convenient source of higher diamondoids
is their isolation from crude oil.2 Diamondoids are the
most thermodynamically stable hydrocarbons, and find-
ing effective methods for their selective functionaliza-
tions is an essential condition for their transformation to
valuable building blocks for a large variety of applications
ranging from pharmacology3 to nanotechnology.4 The
discovery of a negative electron affinity (NEA) of
[121]tetramantan-6-thiol (7, Figure 1) deposited on noble
metal surfaces disclosed the potential of diamondoids for
nanoelectronics.5 Monofunctionalized diamondoids are
attractive substrates for the preparation of self-assembled
monolayers (SAMs).6 A recent near-edge X-Ray absorp-
tion fine structure (NEXAFS) study of diamondoid thiol
SAMs showed that the surface bonding energy depends
strongly on the position of the thiol group in the molecule7
and the strongest attachments were found for the apical
derivatives. For such applications along with many oth-
ers,8 the preparation of apically functionalized derivatives
of diamondoids is necessary.
However, while apical functionalizations of diamantane
can be achieved through nitroxylation followed by rear-
rangement,9 the functionalization selectivities decrease
for higher diamondoids considerably due to increasing
number of similarly reactive bridgehead C–H bonds.10
Photoacetylation provides good selectivities for mono-
substitution at the apical positions,11 but it is laborious and
not suitable for large scale.
Another approach to apical diamondoid derivatives is the
protection12 of the corresponding apical diols 4–6 (Figure
1) readily available through dihydroxylation followed by
thermodynamically controlled rearrangement;13 the chal-
lenge then lies in the incorporation of two different apical
substituents. The reaction with 2,2,2-trifluoroethanol for
the monoprotection of the diols gives monoethers, whose
isolation requires column chromatography. This hampers
application of this strategy for the large scale preparative
synthesis of diamondoid derivatives. We now report a
convenient chromatography-free procedure for the prepa-
ration of apical monohydroxy diamondoids utilizing silyl
reagents that are not only useful for the preparation of de-
rivatives of 1, but also applicable to the higher members
of the diamondoid family as well as to several other hy-
drocarbon diols.
SYNTHESIS 2014, 46, 0787–0798
Advanced online publication: 10.01.2014
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DOI: 10.1055/s-0033-1338583; Art ID: SS-2013-Z0777-OP
© Georg Thieme Verlag Stuttgart · New York

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X
thus turned our attention to using the tert-butyldimethyls-
ilyl (TBDMS) group that is known to be more resistant to
hydrolysis.15
OH
OH
O
XCl
The reaction of diol 4 with TBDMSCl in neat 1-methyl-
imidazole in the presence of molecular iodine16 gave the
corresponding monoprotected derivative almost exclu-
sively in a 9:1 ratio of 10/11 at virtually complete (>95%)
conversion of starting material. Such exceptional mono-
protection efficiency is due to the relatively low solubility
of 10 in the reaction media that prevents further silylation.
The substantial difference in the solubilities of 10 and 1117
allows isolation of 10 in 66% preparative yield by simple
crystallization of the mixture from n-hexane. This is only
a little lower than the 78% yield achieved with the separa-
tion of this reaction mixture through column chromatog-
raphy.
X = TMS:
Py, CH2Cl2, r.t., 6 h
O
OH
O
X = TBDMS:
1-methylimidazole
I2, r.t., 2.5 d
X
X
3:5
9:1
4
8, X = SiMe3
10, X = SiMe2t-Bu
9, X = SiMe3
11, X = SiMe2t-Bu
Scheme 1 Monoprotection of diamantan-4,9-diol (4) with TMSCl
and TBDMSCl (ratio of the products in italics) under full conversion
of starting material
Easily removable silicon protecting groups are widely
used in organic synthesis.14 As trimethylsilyl chloride
(TMSCl) is inexpensive, we first attempted the monopro-
tection of diamantane-4,9-diol (4) with TMSCl (Scheme
1). Only moderate monoprotection selectivity was found
with TMSCl as the ratio of the mono- (8) and disilylated
(9) products was only 3:5 even at partial (ca. 50%) con-
version of the starting material. While unreacted 4 may be
separated by filtration, column chromatography is re-
quired for the separation of 8 from 9. The TMS group in 8
is also found to be too sensitive for further transforma-
tions of the OH group even under mild conditions. We
The TBDMS group in 10 tolerates the standard OH to Br
exchange conditions allowing the quantitative preparation
of bromide 12 in the reaction of 10 with SOBr2. Reduction
with LiAlH4 and hydrolysis of thus formed 13 to diaman-
tan-4-ol (14) occurs in high yields (Scheme 2). An overall
63% yield of 14 was achieved from 4. Alcohol 14 is a key
precursor for practically valuable apical18 diamantane de-
rivatives, for example, thiols,19 dienes,20 carboxylic ac-
ids,21 phosphines,18 and fluorides.12b
OH
Br
H
HCl
LiAlH4
SOBr2
CHCl3
MeOH
THF, Δ
Py, CH2Cl2
99%
96%
99%
OTBDMS
OTBDMS
OTBDMS
OH
10
12
13
14
Scheme 2 Synthetic sequence leading to diamantan-4-ol (yields of isolated products)
OH
OTBDMS
OTBDMS
1. TBDMSCl
1-methylimidazole
I2, 55 °C, 1.5 h
2. aq NaHSO3
+
OH
OH
OTBDMS
6:1
5
15
16
OH
OTBDMS
OTBDMS
1. TBDMSCl
1-methylimidazole
I2, 70 °C, 0.5 h
2. aq NaHSO3
+
OH
OH
OTBDMS
18
8:1
6
17
Scheme 3 Monoprotection of triamantan-9,15-diol (5) and tetramantan-6,13-diol (6) with TBDMSCl (ratio of the products in italics)
Synthesis 2014, 46, 787–798
© Georg Thieme Verlag Stuttgart · New York

PAPER
Apically Substituted Diamondoids
789
OTBDMS
OTBDMS
OTBDMS
OH
HCl
LiAlH4
SOBr2
CHCl3
MeOH
THF, Δ
Py, CH2Cl2
99%
97%
96%
OH
Br
15
OH
19
20
21
Br
HCl
SOBr2
LiAlH4
CHCl3
MeOH
Py, CH2Cl2
THF, Δ
97%
96%
99%
OTBDMS
17
OTBDMS
OTBDMS
OH
22
23
24
Scheme 4 Synthetic sequence leading to apical monohydroxy derivatives of triamantane and [121]tetramantane (yields of isolated products)
The above unequal substitution was successfully applied methanol–chloroform (Scheme 5). Although the desired
(Scheme 3) to other readily available13 diamondoid deriv- hydroxysilyl derivatives 15 and 17 dominate in this depro-
atives such as triamantan-9,15-diol (5) and tetramantan- tection step, we were not able to achieve satisfactory se-
6,13-diol (6). In contrast to 4, the reactions of diols 5 and lectivities (Scheme 5) even at moderate conversion.
6 with TBDMSCl require heating (55 °C, and 70 °C, re-
spectively). The ratios of the corresponding mono- to di-
substituted products decrease insignificantly relative to 4
To maximize the yields of the desired monoprotected de-
rivatives, the hydrolytic step may be repeated at lower
conversion rates, each time utilizing recovered bis-TBD-
(Scheme 3). At almost complete conversion of starting
MSO-protected diamondoid as the starting material. Al-
material, these ratios were 6:1 and 8:1 for the silylation of
ternatively, at longer reaction times the hydrolysis of 16
and 18 quantitatively gives the respective diols 5 and 6
that could be reused for the monoprotection step.
5 and 6, respectively. The monosubstituted derivatives 15
and 17 were obtained after recrystallization in 53% and
62% yield, respectively.
The above procedure is useful for the monoprotection of
various diols (Table 1), in particular 1,4-dihydroxydia-
mantane (25), 4,9-dihydroxymethyldiamantane (26), 1,4-
Subsequent bromination gave 19 and 22, whose reduction
to 20 and 23 followed by hydrolysis leads to the respective
apical monohydroxy derivatives 21 and 24 in high prepar-
ative yields (Scheme 4).
dihydroxymethylcubane
(27),
1,4-dihydroxybicyc-
lo[2.2.2]nonane (28), linear alkane diols 29, 30, and for a
In order to recover significant amounts of bis-TBDMSO- number of aromatic hydroxy derivatives 31–33. In most
protected diamondoids 16 and 18 formed during the si- cases the monoprotected derivatives were isolated in good
lylation, we probed their partial hydrolysis with acidic preparative yields. However, the efficiency of the mono-
HCl
OTBDMS
OTBDMS
OTBDMS
OH
CHCl3
MeOH
1.5 h
+
+
OTBDMS
OTBDMS
OH
OTBDMS
OH
16
15, 49%
16, 30%
5, 21%
OTBDMS
HCl
OTBDMS
OH
CHCl3
MeOH
6 h
+
+
OTBDMS
OH
OTBDMS
OH
18
17, 72%
18, 4%
6, 23%
Scheme 5 Deprotection of bis-silylated diamondoid diols (yields are preparative)
© Georg Thieme Verlag Stuttgart · New York
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790
P. Kahl et al.
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protection generally is slightly lower than for 4 due to sible. Previous attempts to apply this reaction to 4
higher solubility of the monoprotected alcohols 34–42.
required monoprotection with 2,2,2-trifluoroethanol.12a
The choice of this model reaction is determined by the po-
tential of diamondoid amino derivatives in peptide syn-
thesis,22 medicinal chemistry,3 and materials sciences.23
Being intrigued by the unique behavior of diol 4 in the
monoprotection with silyl reagents, we envisaged that the
direct monosubstitution of the OH group with an acetami-
do moiety under Ritter reaction conditions would be fea-
Table 1 Yields of Isolated Products and Conversion of Starting Material (%) for the Reactions of Diols with TBDMSCla
Entry
Starting diol
Conversion
Product 1
Product 2
OH
OTBDMS
OTBDMS
1
99
HO
TBDMSO
HO
25
34, 85
43, 0
OTBDMS
OH
OTBDMS
2
66
HO
HO
TBDMSO
26
35, 40
44, 51
OTBDMS
OH
OTBDMS
3
98
HO
HO
TBDMSO
27
36, 20
45, 43
OH
OTBDMS
OTBDMS
4
5
6
92
61
86
HO
TBDMSO
HO
28
37, 52
46, 11
OTBDMS
OTBDMS
OTBDMS
OH
OH
OH
29
30
38, 27
39, 22
47, 54
OH
OH
OTBDMS
OTBDMS
OTBDMS
OH
48, 51
OH
OTBDMS
OTBDMS
7b
99
OH
OH
OTBDMS
49, 26
31
40, 45
Synthesis 2014, 46, 787–798
© Georg Thieme Verlag Stuttgart · New York

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Apically Substituted Diamondoids
791
Table 1 Yields of Isolated Products and Conversion of Starting Material (%) for the Reactions of Diols with TBDMSCla (continued)
Entry
Starting diol
Conversion
Product 1
Product 2
OTBDMS
OTBDMS
OH
8b
99
OH
OTBDMS
OH
32
41, 61
50, 20
OH
OH
OTBDMS
OH
OTBDMS
OTBDMS
9b
80
33
51, 32
42, 68
a TBDMSCl in 1.3 molar excess, r.t., reaction time: 1 d.
b Without the addition of iodine.
The Ritter reaction of 4 performed in TFA–ClCH2CN24 Koch–Haaf carboxylation to 57 (Scheme 6) and chloro-
followed by basic workup gave monoalcohol 52 in 49% acetamide cleavage25 gave amino acid 58 in overall 33%
preparative yield (Table 2, entry 1). We rationalize the yield. Neither step requires additional purification of the
moderate yield of the Ritter reaction by the formation of a reaction products. This is a good alternative to the 7% to-
number of side products 53–56. Longer reaction times tal yield six step synthesis of 58 from 4 suggested earli-
only slightly increase the yield of 52 but give substantially er.12a
larger amounts of disubstituted derivative 54 (entry 2).
In summary, we have shown that monoprotection of 4
The number of by-products can be reduced at higher reac-
with TBDMSCl is effective due to the low solubility of
tion temperatures (entries 3–5); however, this also reduces
the monosubstituted product that prevents further si-
the efficiency of monoacetamidation. Even with 1 equiv-
lylation. The monoprotection efficiency for triamantane
alent of ClCH2CN large amounts of dichloroacetamide 54
and tetramantane diols is only slightly lower and provides
access to apical monoalcohols with excellent yields. Prod-
formed (entry 5).
uct isolation through simple crystallization avoids chro-
Table 2 Ritter Reaction of 4 with Preparative Yields (%)a
O
O
O
O
O
HN
HN
O
CF3
O
CF3
HN
OH
Cl
Cl
Cl
Entry
N (equiv) Temp (°C) Time (h)
4
Cl
O
CF3
HN
O
CF3
OH
O
O
O
52
53
54
55
56
1
2
3
4
5
11
11
11
2
r.t.
r.t.
60
60
60
21
22
9
34
34
16
21
17
49
3
≤1
≥6
34
35
35
3
11
51
40
30
21
–
3
≤1
–
≤1
–
5.5
9
–
–
1b
5
12
–
–
a Reaction conditions: 4 (500 mg, 2.3 mmol), TFA (4.5 mL, 58.8 mmol, 25.9 equiv), 20% NaOH solution; N = ClCH2CN.
b Added in portions.
© Georg Thieme Verlag Stuttgart · New York
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S
O
O
1. H2SO4
1.
2.
H2N
NH2
1. TFA
ClCH2CN
r.t., 21 h
2. NaOH
OH
NH2
HN
OH
H
HN
HCO2
AcOH, EtOH
Δ, 4 h
NaOH
Cl
Cl
r.t., 2 h
2. H2O
49%
96%
70%
OH
O
OH
O
OH
4
52
57
58
Scheme 6 The preparation of 9-aminodiamantan-4-carboxylic acid (58) from diol 4
13C NMR (100 MHz, CDCl3): δ = 70.36 (C), 45.25 (CH2), 38.90
(CH), 2.93 (CH3).
matographic steps, making this method amenable to large
scale.
MS: m/z (%) = 364 (11), 349 (100), 309 (1), 275 (98), 219 (1), 201
(1), 179 (3), 167 (16), 151 (4), 129 (3), 105 (4), 91 (8), 73 (34), 55
(1).
The monoacetamidation of the diols under Ritter reaction
conditions in TFA is also effective and allows the reduc-
tion of the preparative steps towards 9-aminodiamantan-
4-carboxylic acid from readily available diol 4. Our new
method provides many key diamondoid derivatives that
have high potential in nanotechnology, medicinal, and
peptide chemistry.
HRMS: m/z calcd for C20H36O2Si2: 364.2254; found: 364.2237.
Silylation of Symmetrical Diamondoid Diols 4–6 with TBDM-
SCl; General Procedure
I2 (6.09 g, 24.00 mmol) was added to an ice-cooled suspension of
the respective diamondoid diol (4.00 mmol) and TBDMSCl (0.784
g, 5.20 mmol for 4 or 1.81 g, 12.00 mmol for 5 and 6) in 1-methyl-
imidazole (11 mL) while stirring. Upon addition, the bath was re-
moved and the reaction mixture was stirred at r.t. for 54 h for 4, at
55 °C for 1.5 h for 5, and at 70 °C for 0.5 h for 6. Upon completion
of the reaction, the mixture was slowly poured into a vigorously
stirred mixture of aq 15% NaHSO3 (150 mL) with CHCl3 (100 mL),
stirred for 10–20 min until the I2 color faded and the suspension
turned yellow. The CHCl3 layer was separated and the aqueous
phase was extracted with CHCl3 (3 × 15 mL). The combined organ-
ic extracts were washed with 5% aq HCl (2 × 25 mL), H2O (25 mL),
brine (25 mL), and dried (Na2SO4). The residue left after solvent re-
moval was crystallized from n-hexane to yield the respective pure
monosilyl-substituted derivatives 10, 15, and 17.
NMR spectra were recorded on Bruker Avance II spectrometers 200
MHz, 400 MHz, 600 MHz (1H); internal standard: TMS, and tri-
methylsilylpropanoic acid (TSP) for 58. GC/MS data were obtained
on the HP5890 GC instrument with an HP5971A or HP5972 mass-
selective detector at 70 eV with electron ionization (EI). High-reso-
lution mass spectra were recorded on a Finnigan MAT 95 instru-
ment with EI or Thermo Scientific LTQ FT Ultrahybrid mass
spectrometer with ESI using methanol solutions of the respective
compounds. 1H and 13C NMR spectra, X-ray data of 52, 57 and 58
as well as analytical data for compounds 34–51 are available in the
Supporting Information.
Silylation of Diamantan-4,9-diol (4) with TMSCl
Disilyl-substituted derivatives, slightly contaminated with the
monoprotected alcohols, could be obtained by evaporation of the
mother liquids.17
A suspension of diol 4 (1.00 g, 4.54 mmol) in a solution of TMSCl
(986 mg, 1.15 mL, 9.08 mmol) and pyridine (754 mg, 0.77 mL, 9.53
mmol) in CH2Cl2 (45 mL) was stirred at r.t. for 6 h. The diol was
filtered off, the precipitate was washed with CH2Cl2 (2 × 5 mL), and
air-dried to give unchanged 4 (462 mg). The mother liquors were
evaporated in vacuo and the residue was extracted with n-pentane
(4 × 40 mL) via decantation from the pyridinium salt. The combined
extracts were concentrated in vacuo and separated on a silica gel
column with 2.5% Et2O in n-pentane to give 8 and separately with
50% of Et2O in n-pentane to afford 9.
9-(tert-Butyldimethylsiloxy)diamantan-4-ol (10)
Yield: 0.884 g (66%); colorless solid; mp 171 °C.
1H NMR (400 MHz, CDCl3): δ = 1.94–1.82 (m, 6 H), 1.79–1.67 (m,
12 H), 1.40 (br s, 1 H), 0.84 (s, 9 H), 0.06 (s, 6 H).
13C NMR (100 MHz, CDCl3): δ = 69.50 (C), 67.24 (C), 45.23
(CH2), 44.66 (CH2), 38.80 (CH), 25.77 (CH3), 17.90 (C), –1.73
(CH3).
9-(Trimethylsiloxy)diamantan-4-ol (8)
Yield: 218 mg (30%); colorless solid; mp 163–164 °C.
1H NMR (400 MHz, CDCl3): δ = 1.93–1.86 (m, 6 H), 1.78 (d,
J = 2.8 Hz, 6 H), 1.72 (d, J = 2.9 Hz, 6 H), 1.33 (br s, 1 H), 0.12 (s,
9 H).
MS: m/z (%) = 334 (0.3), 319 (1), 277 (100), 261 (1), 221 (1), 203
(82), 185 (3), 138 (7), 107 (5), 91 (6), 75 (14), 55 (3).
HRMS: m/z calcd for C20H34O2Si: 334.2328; found: 334.2314.
15-(tert-Butyldimethylsiloxy)triamantan-9-ol (15)
Yield: 0.817 g (53%); colorless solid; mp 172 °C.
13C NMR (100 MHz, CDCl3): δ = 70.23 (C), 67.21 (C), 45.15
(CH2), 44.61 (CH2), 38.79 (CH), 38.72 (CH), 2.89 (CH3).
1H NMR (400 MHz, CDCl3): δ = 1.95–1.85 (m, 4 H), 1.76–1.68 (m,
6 H), 1.68–1.57 (m, 6 H), 1.39–1.30 (m, 7 H), 0.84 (s, 9 H), 0.06 (s,
6 H).
MS: m/z (%) = 292 (8), 277 (100), 261 (5), 220 (3), 203 (92), 187
(7), 165 (1), 139 (5), 107 (7), 91 (8), 75 (19), 67 (4), 55(4).
13C NMR (100 MHz, CDCl3): δ = 70.34 (C), 67.99 (C), 52.78
(CH2), 52.21 (CH2), 45.98 (CH2), 45.31 (CH2), 44.47 (CH), 39.71
(CH), 39.61 (CH), 38.65 (C), 36.48 (CH2), 33.77 (CH), 33.70 (CH),
25.79 (CH3), 17.91 (C), –1.69 (CH3).
HRMS: m/z calcd for C17H28O2Si: 292.1859; found: 292.1860.
4,9-Bis(trimethylsiloxy)diamantane (9)
Yield: 462 mg (52%); colorless solid; mp 155–156 °C.
1H NMR (400 MHz, CDCl3): δ = 1.87 (s, 6 H), 1.76 (s, 12 H), 0.12
(s, 18 H).
Synthesis 2014, 46, 787–798
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Apically Substituted Diamondoids
793
MS: m/z (%) = 386 (0.2), 371 (1), 329 (100), 313 (1), 255 (63), 237
(2), 197 (1), 181 (5), 164 (8), 156 (4), 145 (4), 131 (3), 105 (6), 91
(7), 75 (14).
[4-(tert-Butyldimethylsiloxymethyl)cuban-1-yl]methanol (36)
Yield: 55 mg (20%); colorless oil.
1H NMR (400 MHz, CDCl3): δ = 3.80–3.68 (m, 10 H), 1.36 (s, 1 H),
0.88 (s, 9 H), 0.04 (s, 6 H).
HRMS: m/z calcd for C24H38O2Si: 386.2641; found: 386.2618.
13C NMR (100 MHz, CDCl3): δ = 63.91 (CH2), 63.89 (CH2), 59.49
(C), 59.20 (C), 43.88 (CH), 43.59 (CH), 25.93 (CH3), 18.45 (C),
–5.15 (CH3).
13-(tert-Butyldimethylsiloxy)[121]tetramantan-6-ol (17)
Yield: 1.089 g (62%); colorless solid; mp 192 °C.
1H NMR (400 MHz, CDCl3): δ = 1.86 (br s, 2 H), 1.82 (br s, 2 H),
1.76–1.60 (m, 10 H), 1.41 (br s, 1 H), 1.37 (br s, 4 H), 1.35–1.30 (m,
8 H), 0.84 (s, 9 H), 0.06 (s, 6 H).
13C NMR (100 MHz, CDCl3): δ = 70.73 (C), 68.37 (C), 52.15
(CH2), 51.46 (CH2), 45.82 (CH2), 45.40 (CH), 45.29 (CH), 45.12
(CH2), 44.41 (CH2), 44.31 (CH2), 40.44 (CH), 40.35 (CH), 35.13
(CH), 35.02 (CH), 33.62 (C), 33.51 (C), 25.79 (CH3), 17.90 (C),
–1.68 (CH3).
MS: m/z (%) = 259 (0.2), 247 (1), 221 (0.3), 203 (2), 189 (2), 165
(2), 145 (3), 129 (28), 115 (20), 105 (6), 91 (16), 75 (100), 73 (66),
59 (5).
ESI-HRMS: m/z [M + Na]+ calcd for C16H26O2Si + Na: 301.1600;
found: 301.1602.
1,4-Bis(tert-butyldimethylsiloxymethyl)cubane (45)
Yield: 165 mg (43%); colorless oil.
1H NMR (400 MHz, CDCl3): δ = 3.72 (s, 4 H), 3.69 (s, 6 H), 0.89
(s, 18 H), 0.05 (s, 12 H).
13C NMR (100 MHz, CDCl3): δ = 64.05 (CH2), 59.35 (C), 43.85
(CH), 25.95 (CH3), 18.45 (C), –5.14 (CH3).
MS: m/z (%) = 423 (1), 381 (70), 365 (2), 307 (100), 291 (5), 209
(1), 191 (12), 182 (9), 155 (7), 145 (6), 129 (5), 117 (4), 105 (6), 91
(7), 75 (14), 57 (3).
HRMS: m/z calcd for C28H42O2Si: 438.2954; found: 438.2928.
MS: m/z (%) = 261 (3), 247 (7), 203 (10), 189 (3), 173 (3), 147 (29),
129 (27), 115 (11), 89 (16), 75 (31), 73 (100), 59 (5).
Silylation of Diols 25–33 with TBDMSCl; General Procedure
A range of diols 25–33 (1.0 mmol) were silylated with TBDMSCl
following the same general procedure as that given above for the
silylation of symmetrical diamondoid diols 4–6 with TBDMSCl
(Table 1). The products are listed below.
HRMS: m/z calcd for C22H40O2Si2: 392.2567; found: 392.2547.
4-(tert-Butyldimethylsiloxy)bicyclo[2.2.2]octan-1-ol (37)
Yield: 123 mg (52%); colorless solid; mp 126–127 °C.
1H NMR (400 MHz, CDCl3): δ = 1.83–1.69 (m, 12 H), 1.40 (br s, 1
H), 0.81 (s, 9 H), 0.03 (s, 6 H).
13C NMR (100 MHz, CDCl3): δ = 70.48 (C), 68.16 (C), 34.89
(CH2), 34.73 (CH2), 25.68 (CH3), 17.85 (C), –2.04 (CH3).
4-(tert-Butyldimethylsiloxy)diamantan-1-ol (34)
Yield: 281 mg (85%); colorless solid; mp 121–122 °C.
1H NMR (400 MHz, CDCl3): δ = 2.17 (d, J = 11.8 Hz, 2 H), 2.09–
2.02 (m, 1 H), 1.91 (br s, 2 H), 1.82–1.76 (m, 3 H), 1.70–1.59 (m, 8
H), 1.45 (d, J = 11.8 Hz, 2 H), 1.38 (br s, 1 H), 0.84 (s, 9 H), 0.07
(s, 6 H).
13C NMR (100 MHz, CDCl3): δ = 69.54 (C), 69.43 (C), 45.90 (CH),
45.42 (CH2), 40.62 (CH2), 40.62 (CH2), 38.89 (CH), 38.75 (CH),
36.41 (CH2), 30.14 (CH), 25.79 (CH3), 17.91 (C), –1.76 (CH3).
MS: m/z (%) = 256 (2), 241 (1), 199 (100), 181 (1), 171 (1), 157 (2),
141 (2), 127 (11), 107 (4), 91 (3), 79 (12), 75 (60), 73 (15), 67 (3),
59 (3).
HRMS: m/z calcd for C14H28O2Si: 256.1859; found: 256.1857.
MS: m/z (%) = 334 (0.3), 319 (1), 301 (1), 277 (100), 259 (3), 203
(47), 185 (26), 165 (2), 143 (3), 129 (3), 117 (2), 105 (4), 91 (4), 75
(13), 55 (2).
1,4-Bis(tert-butyldimethylsiloxy)bicyclo[2.2.2]octane (46)
Yield: 37 mg (11%); colorless solid; mp 47–48 °C.
1H NMR (400 MHz, CDCl3): δ = 1.74 (s, 12 H), 0.81 (s, 18 H), 0.02
(s, 12 H).
HRMS: m/z calcd for C20H34O2Si: 334.2328; found: 334.2313.
13C NMR (100 MHz, CDCl3): δ = 70.36 (C), 35.16 (CH2), 25.72
(CH3), 17.87 (C), –2.02 (CH3).
[9-(tert-Butyldimethylsiloxymethyl)diamantan-4-yl]methanol
(35)
Yield: 95 mg (40%); colorless solid; mp 125–126 °C.
MS: m/z (%) = 355 (2), 313 (100), 239 (20), 181 (2), 147 (25), 128
(40), 107 (3), 85 (3), 75 (32), 73 (71), 59 (6).
1H NMR (400 MHz, CDCl3): δ = 3.26 (s, 2 H), 3.18 (s, 2 H), 1.74
(br s, 6 H), 1.49 (dd, J = 7.6, 2.1 Hz, 12 H), 1.34 (br s, 1 H), 0.89 (s,
9 H), 0.01 (s, 6 H).
HRMS: m/z calcd for C20H42O2Si2: 370.2723; found: 370.2672.
13C NMR (100 MHz, CDCl3): δ = 73.27 (CH2), 72.88 (CH2), 39.58
(CH2), 39.35 (CH2), 37.32 (CH), 37.22 (CH), 32.61 (C), 32.50 (C),
25.96 (CH3), 18.37 (C), –5.44 (CH3).
10-(tert-Butyldimethylsiloxy)decan-1-ol (38)
Yield: 47 mg (27%); colorless oil.
1H NMR (400 MHz, CDCl3): δ = 3.73–3.53 (m, 4 H), 1.65–1.43 (m,
MS: m/z (%) = 347 (1), 305 (100), 274 (1), 231 (20), 213 (9), 199
(1), 187 (2), 171 (1), 157 (3), 137 (7), 131 (5), 119 (3), 105 (5), 91
(6), 75 (10), 57 (2).
5 H), 1.42–1.21 (m, 12 H), 0.88 (s, 9 H), 0.03 (s, 6 H).
13C NMR (100 MHz, CDCl3): δ = 63.47 (CH2), 63.15 (CH2), 32.99
(CH2), 32.92 (CH2), 29.68 (CH2), 29.55 (CH2), 26.11 (CH3), 25.91
(CH2), 25.86 (CH2), 18.51 (C), –5.13 (CH3).
HRMS: m/z calcd for C22H38O2Si: 362.2641; found: 362.2600.
MS: m/z (%) = 231 (4), 213 (2), 185 (1), 157 (2), 143 (1), 129 (2),
115 (6), 105 (34), 97 (50), 93 (16), 83 (100), 75 (73), 73 (21), 69
(55), 57 (19), 55 (51).
ESI-HRMS: m/z [M + Na]+ calcd for C16H36O2Si + Na: 311.2382
4,9-Bis(tert-butyldimethylsiloxymethyl)diamantane (44)
Yield: 160 mg (51%); colorless solid; mp 113–114 °C.
1H NMR (400 MHz, CDCl3): δ = 3.18 (s, 4 H), 1.71 (s, 6 H), 1.47
(s, 12 H), 0.89 (s, 18 H), 0.02 (s, 12 H).
13C NMR (100 MHz, CDCl3): δ = 73.00 (CH2), 39.69 (CH2), 37.45
found: 311.2380.
(CH), 32.66 (C), 25.99 (CH3), 18.40 (C), –5.42 (CH3).
1,10-Bis(tert-Butyldimethylsiloxy)decane (47)
Yield: 133 mg (54%); colorless oil.
MS: m/z (%) = 461 (2), 419 (100), 345 (17), 287 (2), 213 (10), 185
(1), 181 (21), 157 (4), 143 (4), 131 (5), 117 (4), 105 (6), 91 (7), 73
(18), 59 (5).
1H NMR (400 MHz, CDCl3): δ = 3.59 (t, J = 6.6 Hz, 4 H), 1.50
(quint, J = 6.6 Hz, 4 H), 1.35–1.22 (m, 12 H), 0.89 (s, 18 H), 0.04
(s, 12 H).
HRMS: m/z calcd for C28H52O2Si2: 476.3506; found: 476.3476.
© Georg Thieme Verlag Stuttgart · New York
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P. Kahl et al.
PAPER
13C NMR (100 MHz, CDCl3): δ = 63.48 (CH2), 33.05 (CH2), 29.75
(CH2), 29.60 (CH2), 26.14 (CH3), 25.96 (CH2), 18.53 (CH), –5.10
(CH3).
MS: m/z (%) = 274 (23), 217 (100), 201 (5), 187 (2), 161 (8), 143
(3), 115 (5), 108 (3), 77 (2), 57 (2).
HRMS: m/z calcd for C16H22O2Si: 274.1389; found: 274.1382.
MS: m/z (%) = 345 (4), 329 (2), 219 (3), 189 (26), 163 (14), 147
(60), 97 (45), 83 (100), 75 (51), 69 (47), 55 (28).
ESI-HRMS: m/z [M + Na]+ calcd for C22H50O2Si2 + Na: 425.3247
found: 425.3250.
2,7-Bis(tert-butyldimethylsiloxy)naphthalene (50)
Yield: 77 mg (20%); colorless solid; mp 54–55 °C.
1H NMR (400 MHz, CDCl3): δ = 7.63 (d, J = 8.8 Hz, 2 H), 7.04 (d,
J = 2.2 Hz, 2 H), 6.92 (dd, J = 8.8, 2.3 Hz, 2 H), 1.02 (s, 18 H), 0.25
(s, 12 H).
13C NMR (100 MHz, CDCl3): δ = 153.85 (C), 136.01 (C), 128.99
(CH), 125.07 (C), 119.81 (CH), 113.86 (CH), 25.72 (CH3), 18.24
(C), –4.33 (CH3).
8-(tert-Butyldimethylsiloxy)octan-1-ol (39)
Yield: 49 mg (22%); colorless oil.
1H NMR (400 MHz, CDCl3): δ = 3.59 (dt, J = 10.7, 6.6 Hz, 4 H),
1.74 (br s, 1 H), 1.60–1.42 (m, 4 H), 1.38–1.25 (m, 8 H), 0.87 (s, 9
H), 0.03 (s, 6 H).
13C NMR (100 MHz, CDCl3): δ = 63.26 (CH2), 62.89 (CH2), 32.78
(CH2), 32.70 (CH2), 29.36 (CH2), 29.35 (CH2), 25.93 (CH3), 25.68
(CH2), 25.65 (CH2), 18.32 (C), –5.32 (CH3).
MS: m/z (%) = 388 (19), 373 (2), 331 (100), 275 (15), 231 (5), 217
(4), 185 (6), 137 (32), 73 (31), 57 (8).
HRMS: m/z calcd for C22H36O2Si2: 388.2254; found: 388.2254.
2′-(tert-Butyldimethylsiloxy)[1,1′-binaphthalen]-2-ol (42)
MS: m/z (%) = 203 (1), 185 (1), 157 (2), 129 (1), 115 (3), 111 (8),
105 (23), 101 (5), 93 (10), 89 (4), 75 (57), 73 (15), 69 (100), 55 (40).
ESI-HRMS: m/z [M + Na]+ calcd for C14H32O2Si + Na: 283.2069
found: 283.2070.
Yield: 218 mg (68%); colorless wax.
1H NMR (400 MHz, CDCl3): δ = 7.97–7.81 (m, 4 H), 7.42–7.18 (m,
7 H), 7.12–7.06 (m, 1 H), 5.05 (s, 1 H), 0.53 (s, 9 H), 0.01 (s, 3 H),
–0.20 (s, 3 H).
13C NMR (100 MHz, CDCl3): δ = 152.31 (C), 151.42 (C), 134.20
(C), 133.83 (C), 130.59 (CH), 129.75 (C), 129.72 (CH), 129.17 (C),
128.13 (CH), 127.96 (CH), 127.08 (CH), 126.21 (CH), 125.29
(CH), 125.27 (CH), 124.28 (CH), 123.12 (CH), 121.26 (CH),
118.32 (C), 117.56 (CH), 115.52 (C), 25.00 (CH3), 17.59 (C), –4.39
(CH3), –4.61 (CH3).
1,8-Bis(tert-butyldimethylsiloxy)octane (48)
Yield: 164 mg (51%); colorless oil.
1H NMR (400 MHz, CDCl3): δ = 3.59 (t, J = 6.6 Hz, 4 H), 1.56–
1.45 (m, 4 H), 1.35–1.25 (m, 8 H), 0.89 (s, 18 H), 0.04 (s, 12 H).
13C NMR (100 MHz, CDCl3): δ = 63.32 (CH2), 32.87 (CH2), 29.43
(CH2), 25.98 (CH3), 25.75 (CH2), 18.37 (C), –5.27 (CH3).
MS: m/z (%) = 400 (14), 385 (1), 343 (100), 327 (5), 309 (3), 269
(5), 239 (6), 171 (2), 164 (1), 75 (27), 73 (6), 57 (1).
MS: m/z (%) = 317 (1), 219 (1), 189 (14), 163 (7), 147 (40), 130
(10), 111 (16), 101 (3), 89 (4), 75 (32), 69 (100), 55 (27).
HRMS: m/z calcd for C26H28O2Si: 400.1859; found: 400.1859.
ESI-HRMS: m/z [M + Na]+ calcd for C20H46O2Si2 + Na: 397.2934
found: 397.2935.
2,2′-Bis(tert-butyldimethylsiloxy)-1,1′-binaphthalene (51)
Yield: 132 mg (32%); colorless solid; mp 61–62 °C.
4-(tert-Butyldimethylsiloxy)phenol (40)
Yield: 100 mg (45%); colorless solid; mp 57–59 °C.
1H NMR (400 MHz, CDCl3): δ = 7.87–7.81 (m, 4 H), 7.34–7.19 (m,
8 H), 0.51 (s, 18 H), 0.05 (s, 6 H), –0.14 (s, 6 H).
1H NMR (400 MHz, CDCl3): δ = 6.74–6.66 (m, 4 H), 4.99 (br s, 1
H), 0.97 (s, 9 H), 0.16 (s, 6 H).
13C NMR (100 MHz, CDCl3): δ = 149.78 (C), 149.30 (C), 120.78
(CH), 115.93 (CH), 25.68 (CH3), 18.15 (C), –4.54 (CH3).
13C NMR (100 MHz, CDCl3): δ = 151.12 (C), 134.60 (C), 129.27
(C), 128.70 (CH), 127.68 (CH), 125.96 (CH), 125.88 (CH), 123.28
(CH), 122.13 (C), 120.56 (CH), 25.08 (CH3), 17.63 (C), –4.23
(CH3), –4.48 (CH3).
MS: m/z (%) = 224 (20), 167 (100), 151 (2), 137 (2), 123 (1), 107
(2), 93 (1), 84 (1), 75 (6), 61 (2).
MS: m/z (%) = 514 (5), 457 (10), 369 (1), 343 (4), 309 (2), 265 (1),
239 (1), 148 (1), 115 (17), 73 (100), 59 (3).
HRMS: m/z calcd for C12H20O2Si: 224.1233; found: 224.1235.
HRMS: m/z calcd for C32H42O2Si2: 514.2723; found: 514.2723.
1,4-Bis(tert-Butyldimethylsiloxy)benzene (49)
Bromination of TBDMSO-Protected Diamondoid Alcohols 10,
15, and 17; General Procedure
Yield: 87 mg (26%); colorless solid; mp 48–49 °C.
1H NMR (400 MHz, CDCl3): δ = 6.70 (s, 4 H), 0.98 (s, 18 H), 0.17
(s, 12 H).
13C NMR (100 MHz, CDCl3): δ = 149.74 (C), 120.52 (CH), 25.70
(CH3), 18.16 (C), –4.51 (CH3).
To a suspension of a TBDMS-monoprotected diamondoid diol
(2.00 mmol) in CH2Cl2 (6 mL) with pyridine (384 mg, 0.39 mL,
4.40 mmol) was added a solution of SOBr2 (832 mg, 0.31 mL, 4.00
mmol) in CH2Cl2 (2 mL) dropwise upon cooling in an ice bath. The
bath was removed and the resulting mixture was stirred at r.t. for 38
h. Then, the mixture was slowly poured into vigorously stirred sus-
pension of H2O (50 mL) with CH2Cl2 (50 mL) and was stirred for
10 min until the emulsion turned colorless. The organic layer was
separated and the aqueous layer was extracted with CH2Cl2 (4 × 10
mL). The combined organic extracts were washed with 5% aq HCl
(2 × 10 mL), H2O (20 mL), brine (20 mL), and dried (Na2SO4). Sol-
vent removal produced the crude tert-butyldimethylsiloxydiamon-
doid bromide that was suitable for the following step without
additional purification. For the preparation of an analytically pure
substance, the crude bromide was filtered through a silica gel layer
(n-pentane).
MS: m/z (%) = 338 (40), 323 (2), 281 (100), 239 (3), 225 (9), 209
(1), 181 (1), 167 (1), 151 (1), 135 (3), 112 (7), 91 (4), 73 (30), 59 (3).
HRMS: m/z calcd for C18H34O2Si2: 338.2097; found: 338.2107.
7-(tert-Butyldimethylsiloxy)naphth-2-ol (41)
Yield: 166 mg (61%); colorless solid; mp 116–118 °C.
1H NMR (400 MHz, CDCl3): δ = 7.66 (dd, J = 8.7, 6.5 Hz, 2 H),
7.05 (d, J = 2.2 Hz, 1 H), 7.01 (d, J = 2.4 Hz, 1 H), 6.96 (dd, J = 6.1,
2.5 Hz, 1 H), 6.94 (dd, J = 6.2, 2.4 Hz, 1 H), 5.30 (br s, 1 H), 1.04
(s, 9 H), 0.26 (s, 6 H).
13C NMR (100 MHz, CDCl3): δ = 154.16 (C), 153.68 (C), 135.95
(C), 129.56 (CH), 129.18 (CH), 124.76 (C), 119.72 (CH), 115.53
(CH), 113.67 (CH), 108.48 (CH), 25.70 (CH3), 18.25 (C), –4.35
(CH3).
9-Bromo-4-(tert-butyldimethylsiloxy)diamantane (12)
Yield: 790 mg (99%); colorless solid; mp 134–135 °C.
Synthesis 2014, 46, 787–798
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PAPER
Apically Substituted Diamondoids
795
1H NMR (400 MHz, CDCl3): δ = 2.38–2.30 (m, 6 H), 1.96 (br s, 3
H), 1.86 (br s, 3 H), 1.74–1.66 (m, 6 H), 0.84 (s, 9 H), 0.06 (s, 6 H).
MS: m/z (%) = 318 (0.4), 303 (1), 261 (96), 221 (1), 187 (100), 159
(1), 145 (2), 131 (5), 117 (2), 105 (5), 91 (8), 75 (11), 57 (2).
13C NMR (100 MHz, CDCl3): δ = 69.18 (C), 64.58 (C), 48.64
(CH2), 45.17 (CH2), 40.40 (CH), 38.26 (CH), 25.76 (CH3), 17.89
(C), –1.73 (CH3).
HRMS: m/z calcd for C20H34OSi: 318.2379; found: 318.2385.
9-(tert-Butyldimethylsiloxy)triamantane (20)
Yield: 718 mg (97%); colorless solid; mp 82–83 °C.
MS: m/z (%) = 398/396 (0.3), 383/381 (1), 341/339 (100), 317 (2),
295 (1), 277 (7), 267/265 (70), 221 (2), 203 (6), 185 (9), 157 (2),
143 (6), 130 (25), 105 (10), 91 (21), 75 (32), 57 (5).
1H NMR (400 MHz, CDCl3): δ = 1.82 (br s, 3 H), 1.75–1.60 (m, 13
H), 1.58 (br s, 1 H), 1.36 (br s, 2 H), 1.33–1.27 (m, 4 H), 0.85 (s, 9
H), 0.07 (s, 6 H).
13C NMR (100 MHz, CDCl3): δ = 70.72 (C), 53.38 (CH2), 46.19
(CH2), 45.73 (CH), 45.12 (CH2), 40.61 (CH), 38.01 (CH2), 37.59
(CH2), 37.37 (CH), 35.82 (C), 34.99 (CH), 34.12 (CH), 27.08 (CH),
25.83 (CH3), 17.93 (C), –1.66 (CH3).
HRMS: m/z calcd for C20H33BrOSi: 396.1484; found: 396.1443.
15-Bromo-9-(tert-butyldimethylsiloxy)triamantane (19)
Yield: 889 mg (99%); colorless solid; mp 78–79 °C.
1H NMR (400 MHz, CDCl3): δ = 2.37–2.22 (m, 4 H), 1.96 (br s, 2
H), 1.91–1.83 (m, 4 H), 1.76–1.56 (m, 8 H), 1.44 (br s, 2 H), 1.36
(br s, 2 H), 0.84 (s, 9 H), 0.06 (s, 6 H).
MS: m/z (%) = 370 (0.3), 355 (1), 313 (71), 239 (100), 183 (1), 169
(1), 156 (9), 143 (5), 129 (3), 105 (4), 91 (8), 73 (8).
13C NMR (100 MHz, CDCl3): δ = 70.13 (C), 65.03 (C), 55.95
(CH2), 52.38 (CH2), 49.39 (CH2), 45.78 (CH2), 43.96 (CH), 41.18
(CH), 40.43 (C), 39.63 (CH), 36.39 (CH2), 33.42 (CH), 33.17 (CH),
25.77 (CH3), 17.91 (C), –1.70 (CH3).
HRMS: m/z calcd for C24H38OSi: 370.2692; found: 370.2666.
6-(tert-Butyldimethylsiloxy)[121]tetramantane (23)
Yield: 813 mg (96%); colorless solid; mp 143–144 °C.
1H NMR (400 MHz, CDCl3): δ = 1.89–1.80 (m, 3 H), 1.75–1.61 (m,
12 H), 1.44 (br s, 2 H), 1.33 (br s, 2 H), 1.32–1.27 (m, 6 H), 1.27–
1.24 (m, 2 H), 0.85 (s, 9 H), 0.07 (s, 6 H).
MS: m/z (%) = 435/433 (1), 393/391 (100), 369 (1), 347 (3), 239
(7), 319/317 (99), 313 (4), 273 (3), 255 (5), 238 (17), 221/223 (2),
181 (4), 156 (32), 143 (9), 129 (8), 105 (9), 91 (15), 73 (19), 57 (6).
13C NMR (100 MHz, CDCl3): δ = 70.90 (C), 52.39 (CH2), 46.62
(CH), 46.22 (CH), 45.99 (CH2), 45.56 (CH2), 44.84 (CH2), 44.26
(CH2), 40.58 (CH), 38.12 (CH), 37.83 (CH2), 36.34 (CH), 35.85
(CH), 33.71 (C), 31.16 (C), 27.84 (CH), 25.82 (CH3), 17.92 (C),
–1.67 (CH3).
HRMS: m/z calcd for C24H37BrOSi: 448.1797; found: 448.1795.
13-Bromo-6-(tert-butyldimethylsiloxy)[121]tetramantane (22)
Yield: 990 mg (99%); colorless solid; mp 158–159 °C.
1H NMR (400 MHz, CDCl3): δ = 2.38–2.24 (m, 4 H), 1.96 (s, 2 H),
1.83, (br s, 4 H), 1.78–1.62 (m, 6 H), 1.48 (br s, 2 H), 1.36–1.31 (m,
6 H), 1.31–1.27 (m, 2 H), 0.84 (s, 9 H), 0.06 (s, 6 H).
13C NMR (100 MHz, CDCl3): δ = 70.62 (C), 65.54 (C), 55.26
(CH2), 51.99 (CH2), 49.23 (CH2), 45.73 (CH2), 45.29 (CH), 44.77
(CH), 44.28 (CH2), 43.96 (CH2), 41.93 (CH), 40.23 (CH), 35.73
(C), 35.03 (CH), 34.49 (CH), 33.29 (C), 25.79 (CH3), 17.91 (C), –
1.68 (CH3).
MS: m/z (%) = 422 (0.3), 407 (1), 365 (53), 291 (100), 271 (1), 197
(1), 182 (20), 155 (7), 141 (5), 129 (6), 117 (3), 105 (5), 91 (7), 73
(8), 67 (3), 57 (2).
HRMS: m/z calcd for C28H42OSi: 422.3005; found: 422.2972.
Hydrolysis of TBDMSO-Diamondoids 13, 20, and 23; General
Procedure
To a solution of TBDMSO-diamondoid (2.00 mmol) in CHCl3–
MeOH (3:2 vol, 45 mL) was added concd HCl (37%, 0.86 mL) and
the resulting homogeneous mixture was stirred at r.t. for 7 h. Then,
solid NaHCO3 (2 g) was added, the mixture stirred for an additional
hour, and the liquid phase was filtered. The crude product after sol-
vent removal was washed with n-pentane (2 × 25 mL) on the filter
to remove silicon-containing by-products. Drying the resulted resi-
due in vacuo yielded 402 mg (99%) of diamantan-4-ol26 (14), or 494
mg (96%) of triamantan-9-ol26b (21), or 600 mg (97%) of [121]tet-
ramantan-6-ol10 (24), whose spectral properties correspond to that
of standard samples.9,10
MS: m/z (%) = 485/487 (1), 445/443 (62), 421 (2), 399 (1), 381 (6),
371/369 (88), 365 (10), 307 (11), 291 (25), 271 (2), 233 (2), 207 (4),
182 (100), 155 (20), 145 (16), 129 (17), 117 (9), 105 (15), 91 (21),
75 (30), 57 (9).
HRMS: m/z calcd for C28H41BrOSi: 500.2110; found: 500.2073.
Reduction of Bromo-TBDMSO-Diamondoids 12, 19, and 22;
General Procedure
To a suspension of LiAlH4 (400 mg, 10.54 mmol) in anhydrous
THF (10 mL) was added a solution of bromo-TBDMSO-protected
diamondoid (2.00 mmol) in anhydrous THF (5 mL) dropwise at r.t.
The reaction mixture was stirred under reflux for 35 h and then care-
fully added to a vigorously stirred mixture of ice (80 g), ice-cold
water (50 mL), and n-pentane (50 mL). To facilitate the separation
of the n-pentane layer, the mixture was slightly acidified with concd
HCl (37%, 5 mL). The organic layer was separated and the aqueous
layer was extracted with n-pentane (4 × 25 mL). The combined n-
pentane extracts were washed with H2O (30 mL) and brine (30 mL),
and dried (Na2SO4). The crude product after solvent removal was
pure enough for the subsequent step. For the preparation of analyt-
ically pure substance, it was filtered through a silica gel layer (n-
pentane).
Hydrolysis of Bis-TBDMSO-Protected Diamondoids 16 and 18;
General Procedure
Bis(tert-butyldimethylsiloxy)diamondoid (2.00 mmol) was dis-
solved in CHCl3–MeOH (6:1 vol, 23 mL) at r.t. and concd HCl
(37%, 11 drops) was added to the solution. The homogeneous reac-
tion mixture was stirred at r.t. for 1.5 h (16) or 6 h (18). Solid
NaHCO3 was added to neutralize the acid. The mixture was stirred
for an additional hour, filtered, and evaporated. CH2Cl2 (30 mL)
was added to the residue and the main amount of insoluble diol was
filtered and washed on the filter with CH2Cl2 (6 × 3 mL). The moth-
er liquors were evaporated and the mixture of products was separat-
ed on a silica gel column to isolate the diprotected TBDMSO-
diamondoid (2% Et2O in n-pentane) and monoprotected TBDMSO-
diamondoid (30% Et2O in n-pentane). Compounds 16, 15, and 5
were obtained from 9,15-bis(tert-butyldimethylsiloxy)triamantane
(16).
4-(tert-Butyldimethylsiloxy)diamantane (13)
Yield: 609 mg (96%); colorless solid; mp 115–116 °C.
1H NMR (400 MHz, CDCl3): δ = 1.89 (br s, 3 H), 1.80–1.75 (m, 1
H), 1.75–1.63 (15 H), 0.86 (s, 9 H), 0.07 (s, 6 H).
13C NMR (100 MHz, CDCl3): δ = 69.95 (C), 46.38 (CH2), 40.03
(CH), 37.30 (CH2), 36.52 (CH), 25.84 (CH3), 25.71 (CH), 17.95
(C), –1.69 (CH3).
9,15-Bis(tert-butyldimethylsiloxy)triamantane (16)
Yield: 299 mg (30%); colorless solid; mp 81–82 °C.
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1H NMR (400 MHz, CDCl3): δ = 1.87 (br s, 4 H), 1.75–1.61 (m, 10
H), 1.58 (br s, 2 H), 1.34 (s, 4 H), 1.31 (br s, 2 H), 0.85 (s, 18 H),
0.07 (s, 12 H).
13C NMR (100 MHz, CDCl3): δ = 70.42 (C), 52.97 (CH2), 46.08
(CH2), 44.64 (CH), 39.78 (CH), 38.62 (C), 36.59 (CH2), 33.87
(CH), 25.80 (CH3), 17.93 (C), –1.68 (CH3).
4,9-Bis(2-chloroacetamido)diamantane (54)12a
Yield: 7 mg (1%).
4,9-Bis(2,2,2-trifluoroacetoxy)diamantane (55)
Yield: 30 mg (3%); colorless solid; mp 199 °C.
1H NMR (400 MHz, CDCl3): δ = 2.23 (s, 12 H), 2.14 (s, 6 H).
13C NMR (100 MHz, CDCl3): δ = 155.99 (q, J = 41.3 Hz, CF3),
114.27 (q, J = 287.1 Hz, C), 84.85 (C), 39.75 (CH), 38.41 (CH2).
MS: m/z (%) = 485 (2), 443 (62), 369 (100), 353 (1), 311 (1), 239
(2), 221 (8), 193 (27), 183 (2), 165 (2), 145 (5), 133 (5), 119 (15),
105 (8), 91 (9), 73 (47).
19F NMR (376 MHz, CDCl3): δ = –75.7.
HRMS: m/z calcd for C30H52O2Si2: 500.3506; found: 500.3472.
MS: m/z (%) = 298 (75), 203 (1), 184 (38), 169 (5), 157 (6), 143
(10), 129 (12), 117 (8), 104 (100), 93 (20), 91 (33), 85 (2), 79 (25),
69 (44).
15-(tert-Butyldimethylsiloxy)triamantan-9-ol (15)
Yield: 376 mg (49%).
HRMS: No recording of HRMS was possible due to decomposition
of the compound.
Triamantan-9,15-diol (5)10
Yield: 114 mg (21%).
4-(2,2,2-Trifluoroacetoxy)diamantan-9-ol (56)
Yield: 78 mg (11%); colorless solid; mp 140 °C.
1H NMR (400 MHz, CDCl3): δ = 2.21 (s, 6 H), 2.03 (s, 6 H), 1.76
(s, 6 H), 1.31 (s, 1 H).
13C NMR (100 MHz, CDCl3): δ = 156.00 (q, J = 41.3 Hz, C),
114.30 (q, J = 287.8 Hz, CF3), 85.57 (C), 66.86 (C), 44.28 (CH2),
40.05 (CH2), 38.65 (CH), 38.46 (CH).
From 6,13-Bis(tert-butyldimethylsiloxy)[121]tetramantane (18):
Unreacted 18 was isolated from the reaction mixture (silica gel, n-
pentane) and was hydrolyzed again under the same reaction condi-
tions. This method was repeated three times. Ultimately, all resi-
dues were combined and separated on silica gel as mentioned above
to afford 18, 17, and 6.
6,13-Bis(tert-Butyldimethylsiloxy)[121]tetramantane (18)
Yield: 43 mg (4%); colorless solid; mp 315–317 °C.
19F NMR (376 MHz, CDCl3): δ = –75.76.
1H NMR (400 MHz, CDCl3): δ = 1.82 (br s, 4 H), 1.75–1.59 (m, 10
H), 1.35 (br s, 4 H), 1.33 (br s, 4 H), 1.31 (d, J = 3.1 Hz, 4 H), 0.85
(s, 18 H), 0.07 (s, 12 H).
13C NMR (100 MHz, CDCl3): δ = 70.82 (C), 52.26 (CH2), 45.91
(CH2), 45.48 (CH), 44.54 (CH2), 40.54 (CH), 35.21 (CH), 33.57
(C), 25.83 (CH3), 17.94 (C), –1.65 (CH3).
MS: m/z (%) = 316 (1), 202 (100), 184 (23), 173 (2), 159 (9), 145
(6), 134 (5), 104 (56), 95 (14), 91 (16), 79 (13), 69 (16).
HRMS: No recording of HRMS was possible due to decomposition
of the compound.
Diamantan-4,9-diol (4)13
Yield: 170 mg (34%).
MS: m/z (%) = 495 (42), 421 (100), 290 (30), 219 (24), 207 (7), 183
9-(2-Chloroacetamido)diamantan-4-carboxylic Acid (57)
4-(2-Chloroacetamido)diamantan-9-ol (52; 100 mg, 0.338 mmol)
was dissolved in ice-cold 92% H2SO4 (9 mL) and 100% formic acid
(7.5 mL) was added dropwise over 3 h to the stirred solution, which
was then poured onto 30 g crushed ice, resulting in a white precipi-
tate. The aqueous suspension was extracted with CHCl3 (4 × 10
mL). The combined organic phases were washed with H2O (4 × 10
mL) until the pH value was neutral and dried (Na2SO4). Removal of
the solvent in vacuo afforded 57; yield: 105 mg (96%); colorless
solid; mp 278 °C (dec.).
1H NMR (400 MHz, CDCl3): δ = 11.21 (br s, 1 H), 6.25 (s, 1 H),
3.95 (s, 2 H), 2.04 (s, 6 H), 2.00–1.86 (m, 12 H).
13C NMR (100 MHz, CDCl3): δ = 183.11 (C), 164.97 (C), 50.93
(C), 42.89 (CH2), 41.08 (CH2), 38.49 (CH2), 37.37 (CH), 35.95
(CH).
(6), 145 (82), 105 (9), 73 (70), 57 (6).
HRMS: m/z calcd for C34H56O2Si2: 552.3819; found: 552.3820.
13-(tert-Butyldimethylsiloxy)[121]tetramantan-6-ol (17)
Yield: 631 mg (72%).
[121]Tetramantan-6,13-diol (6)10
Yield: 150 mg (23%).
4-(2-Chloroacetamido)diamantan-9-ol (52)
Diamantan-4,9-diol (4; 0.5 g, 2.3 mmol) was dissolved in TFA (4.5
mL, 58.4 mmol) at r.t. and 2-chloroacetonitrile (1.6 mL, 25.4 mmol)
was added. The solution was stirred for 21 h, then cooled in an ice
bath to 0 °C, and treated with aq 20% NaOH (10 mL) carefully. The
suspension was extracted with CHCl3 (5 × 25 mL). The combined
organic phases were washed with H2O (2 × 25 mL) until the pH val-
ue was neutral and dried (Na2SO4). Removal of the solvent in vacuo
afforded a colorless solid. Flash chromatography on silica gel
(CH2Cl2–MeOH, 95:5) afforded products shown in Table 2.
13C NMR DEPT-Q-ONLY (100 MHz, CDCl3): δ = 38.47 (C).
HRMS: m/z calcd for C17H22ClNO3: 323.1288; found: 323.1281.
9-Aminodiamantan-4-carboxylic Acid (58)
4-(2-Chloroacetamido)diamantan-9-ol (52)
Compound 57 (236 mg, 0.729 mmol) and thiourea (117 mg, 1.53
mmol) were refluxed in a mixture of EtOH (4 mL) and AcOH (3
mL) for 4 h. After cooling to r.t., the suspension was further cooled
in an ice bath. Aq 20% NaOH (15 mL) and then aq 32% HCl (5 mL)
were added until the pH value was neutral. The formed precipitate
was collected by filtration, washed with H2O (2 × 5 mL) and dried
in vacuo over P2O5 at 130 °C to afford 58; yield: 127 mg (70%);
colorless solid; mp 325 °C (dec.).
Yield: 326 mg (49%); colorless solid; mp 203 °C.
1H NMR (400 MHz, CDCl3): δ = 6.24 (br s, 1 H), 3.94 (s, 2 H),
2.09–2.03 (m, 6 H), 1.99 (s, 3 H), 1.91 (s, 3 H), 1.80–1.71 (m, 6 H),
1.38 (br s, 1 H).
13C NMR (100 MHz, CDCl3): δ = 164.87 (C), 67.06 (C), 50.94 (C),
44.71 (CH2), 42.90 (CH2), 40.65 (CH2), 38.70 (CH), 37.30 (CH).
MS: m/z (%) = 295 (14), 260 (3), 218 (2), 203 (100), 185 (3), 104
(8), 91 (5), 77 (4).
1H NMR (400 MHz, D2O + 1 drop 30% NaOD): δ = 1.83–1.71 (m,
12 H), 1.59–1.51 (m, 6 H).
HRMS: m/z calcd for C16H22ClNO2: 295.1339; found: 295.1336.
13C NMR (100 MHz, D2O + 1 drop 30% NaOD): δ = 188.23 (C),
45.19 (C), 44.56 (CH2), 40.17 (C), 39.55 (CH2), 37.74 (CH), 36.20
(CH).
9-(2-Chloroacetamido)-4-(trifluoroacetoxy)diamantane (53)12a
Yield: 29 mg (3%).
HRMS: m/z calcd for C15H21NO2: 247.1572; found: 247.1568.
Synthesis 2014, 46, 787–798
© Georg Thieme Verlag Stuttgart · New York

PAPER
Apically Substituted Diamondoids
797
Product 58 (100 mg) was recrystallized from aq 32% HCl (5 mL).
The formed crystals of the amino acid hydrochloride were collected
by filtration, washed with cold H2O (5 mL), and dried in vacuo over
P2O5 at 140 °C. The NMR spectrum was identical with the one re-
ported in the literature.12a
(9) Fokin, A. A.; Tkachenko, B. A.; Gunchenko, P. A.; Gusev,
D. V.; Schreiner, P. R. Chem. Eur. J. 2005, 11, 7091.
(10) Schreiner, P. R.; Fokina, N. A.; Tkachenko, B. A.;
Hausmann, H.; Serafin, M.; Dahl, J. E. P.; Liu, S. G.;
Carlson, R. M. K.; Fokin, A. A. J. Org. Chem. 2006, 71,
6709.
(11) Fokin, A. A.; Gunchenko, P. A.; Novikovsky, A. A.;
Shubina, T. E.; Chernyaev, B. V.; Dahl, J. E. P.; Carlson, R.
M. K.; Yurchenko, A. G.; Schreiner, P. R. Eur. J. Org.
Chem. 2009, 5153.
(12) (a) Schwertfeger, H.; Wuertele, C.; Serafin, M.; Hausmann,
H.; Carlson, R. M. K.; Dahl, J. E. P.; Schreiner, P. R. J. Org.
Chem. 2008, 73, 7789. (b) Schwertfeger, H.; Wuertele, C.;
Hausmann, H.; Dahl, J. E. P.; Carlson, R. M. K.; Fokin, A.
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(13) Fokina, N. A.; Tkachenko, B. A.; Merz, A.; Serafin, M.;
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Acknowledgment
This work was supported by the Deutsche Forschungsgemeinschaft
(Schr 597/23-1). We are thankful to L. Wanka for fruitful discus-
sions.
Supporting Information for this article is available online at
http://www.thieme-connect.com/ejournals/toc/synthesis.SnuIomprifgtooatrinSugpIoi
nnfomartit
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