A novel chemoselective cleavage of (tert-butyl)(dimethyl)silyl (TBS) ethers catalyzed by Ce(SO4)2·4 H2O

Article abstract of DOI:10.1002/hlca.201300354

(tert-Butyl)(dimethyl)silyl (^tBuMe₂Si; TBS) phenyl/alkyl ethers were efficiently cleaved to the corresponding parent hydroxy compounds in good yields using catalytic amounts of Ce(SO₄) ₂·4 H₂O by microwave-assisted or conventional heating in MeOH. Intramolecular and competitive experiments demonstrated the chemoselective deprotection of TBS ethers in the presence of triisopropylsilyl (ⁱPr₃Si; TIPS) and (tert-butyl)(diphenyl)silyl ( ^tBuPh₂Si; TBDPS) ethers. Copyright

Full text of DOI:10.1002/hlca.201300354

Helvetica Chimica Acta – Vol. 97 (2014)
965
A Novel Chemoselective Cleavage of (tert-Butyl)(dimethyl)silyl (TBS)
Ethers Catalyzed by Ce(SO4)2 · 4 H2O
by Davir Gonza´lez-Caldero´n*a), Carlos A. Gonza´lez-Gonza´leza), Aydee´ Fuentes-Benꢀteza),
Erick Cuevas-Ya´n˜ezb), David Corona-Becerrilb), and Carlos Gonza´lez-Romero*a)
a
´
´
) Departamento de Quꢀmica Organica, Facultad de Quꢀmica, Universidad Autonoma del Estado de
´
´
´
Mexico, Paseo Colon/Paseo Tollocan s/n, Toluca, Estado de Mexico, 50120, Mexico
(phone: þ 52-722-2175109 ext 113; fax: þ 52-722-2173890; e-mail: qfb_dgonzalez@yahoo.com.mx;
cgonzalezr@uaemex.mx)
b
´
) Centro Conjunto de Investigacion en Quꢀmica Sustentable UAEM-UNAM, Toluca-Atlacomulco Km.
´
14.5, San Cayetano, Toluca, Estado de Mexico, 50200, Mexico
(tert-Butyl)(dimethyl)silyl (tBuMe2Si; TBS) phenyl/alkyl ethers were efficiently cleaved to the
corresponding parent hydroxy compounds in good yields using catalytic amounts of Ce(SO4)2 · 4 H2O by
microwave-assisted or conventional heating in MeOH. Intramolecular and competitive experiments
demonstrated the chemoselective deprotection of TBS ethers in the presence of triisopropylsilyl (iPr3Si;
TIPS) and (tert-butyl)(diphenyl)silyl (tBuPh2Si; TBDPS) ethers.
Introduction. – Silyl ethers are among the most frequently used to protect OH
groups, because they are easily and efficiently installed and are stable to a variety of
reagents and reaction conditions [1]. In this context, the (tert-butyl)(dimethyl)silyl
(tBuMe2Si; TBS), triisopropylsilyl (iPr3Si; TIPS), and (tert-butyl)(diphenyl)silyl
(tBuPh2Si; TBDPS) moieties are among the most important protecting groups and
are often used in multistep organic syntheses [2]. Ce-based inorganic reagents for
desilylation have been reported, e.g., silica gel-supported ceric ammonium nitrate
(CAN-SiO2; stoichiometric amounts) [3], CAN/MeOH (1.2 equiv.) [4], CeCl3 · 7 H2O/
MeCN (2.0 equiv.) [5], and Ce(OTf)4/MeCN [6]. Unfortunately, none of these reagents
lead to selectivity for TBS, TIPS, or TBDPS ethers; moreover, stoichiometric amounts
of reagents are particularly disadvantageous for large-scale reactions.
Results and Discussion. – Within our current research, we observed that bis-TBS
ether 1a was cleaved within minutes upon microwave heating in MeOH containing
Ce(SO4)2 · 4 H2O. As a consequence, we decided to investigate the Ce(SO4)2 · 4 H2O-
catalyzed cleavage of silyl ether 1a in more detail.
Optimization studies for this cleavage process were carried out on 1a. Complete
removal of the silyl group elimination occurred within 20 min upon microwave heating
at 1308 in MeOH containing 20 mol-% Ce(SO4)2 · 4 H2O. At room temperature, silyl
group loss was slow, but it occurred at an acceptable rate at 608 (conventional heating)
and was complete within 12 h.
The optimized conditions, under microwave and conventional heating conditions
(12 h), were then used to study the deprotection of a series of silylated alcohols and/or
ꢁ 2014 Verlag Helvetica Chimica Acta AG, Zꢂrich

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Helvetica Chimica Acta – Vol. 97 (2014)
phenols (Table 1). Both TBS ethers of alcohols (Entries 1 – 3 and 5) and phenols
(Entries 7 and 10) were very efficiently cleaved in high yields, while TIPS aryl ethers
were cleaved only in trace amounts or not at all (Entries 8 and 11). TBDPS Alkyl and
aryl ethers were essentially inert.
The data in Table 1 clearly indicate that selective cleavage of TBS alkyl ethers
should be possible. Indeed, the results presented in Table 2 reveal that TBS groups of
alkyl ethers are cleanly and efficiently removed in the presence of TIPS phenyl
(Entries 1 and 2), or TBDPS phenyl (3 and 4) or alkyl (Entries 5 and 6) ethers within
the same molecule. In addition, we have also carried out a series of intermolecular
competition experiments (Table 3) which led to the conclusion that TBS aryl ethers are
very selectively cleaved in the presence of TIPS or TBDPS aryl ethers.
Conclusions. – We reported that catalytic amounts Ce(SO4)2 · 4 H2O in MeOH
selectively cleaves TBS phenyl or alkyl ethers in the presence of TIPS, or TBDPS
phenyl or aryl ethers. In addition to the selectivity, this methodology is noteworthy
because Ce(SO4)2 · 4 H2O is mild, easy to handle, and of relatively low toxicity.
´
Financial support from UAEMex (Project No. 2441) and CONACyT (postgraduate scholarship) is
gratefully acknowledged. The authors would like to thank the referee and Joseph M. Muchowski (visiting
professor, UNAM) for their valuable comments and suggestions; M. N. Zavala-Segovia, L. Triana-Cruz
´
(CCIQS UAEMex-UNAM), and E. Dꢀaz-Torres (UNAM) for the technical support. Special thanks to
SIGNA S. A. de C. V. for its valuable assistance.

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Table 1. Deprotection of Silyl Ethers Using 20 mol-% Ce(SO4)2 · 4 H2O by Microwave (MW) or
Conventional Heating
Entry
Silyl ether
Alcohola)
Yield [%]b)c)
MWd)
De)
96
88
95
NR
91
trace
94
trace
NR
90
NR
NR
1
2
3
4
5
6
7
8
9
1a
2a
3a
3b
4a
4b
5a
5b
5c
6a
6b
6c
1
2
3
3
4
4
5
5
5
6
6
6
94
90
93
NR
96
NR
94
NR
NR
93
trace
NR
10
11
12
a) Confirmed by comparison of the, 1H- and 13C-NMR, and MS data with those of the authentic sample.
b) Yields refer to chromatographically isolated pure compounds. c) In some cases, no reaction (NR)
occurred, or product yields were very low, and ca. 90 – 98% of starting material was recovered. d) At 1308,
20 min. e) At 608, 12 h.
Table 2. Intramolecular Chemoselective Deprotection of TBS Alkyl Ethers in the Presence of a) TIPS or
TBDPS Phenyl Ethers (Entries 1 – 4) and b) TBDPS Alkyl Ethers (Entries 5 and 6)
Entry
Substrate
Producta)
Yield [%]b)
Dc)
MWd)
1
2
3
4
5
6
7a
8a
7c
8c
9a
7b
8b
7d
8d
9
95
96
94
93
95
93
93
96
92
97
92
96
10a
10
a) Confirmed by comparison of the 1H- and 13C-NMR, and MS data with those of the authentic sample.
b) Yields refer to chromatographically isolated pure compounds. c) At 608, 12 h. d) At 1308, 20 min.

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Table 3. Chemoselective Deprotection of TBS Phenyl Ethers in the Presence of TIPS and TBDPS Phenyl
Ethers Evaluated by Competition Experiments
Substrates
Productsa) (Yield [%])b)
Dc)
MWd)
11a þ 12b
12a þ 11b
11 (90) þ 12b (97)
12 (87) þ 11b (95)
11 (92) þ 12b (94)
12 (90) þ 11b (96)
a) Confirmed by comparison of the 1H- and 13C-NMR, and MS data with those of the authentic sample.
b) Yields refer to chromatographically isolated pure compounds. c) At 608, 12 h. d) At 1308, 20 min.
Experimental Part
General. The starting materials were purchased from Aldrich Chemical Co. and were used without
further purification. The microwave-assisted reactions were performed using a focused microwave unit
Anton-Paar Synthos 300; constant factor of the microwave, 1.214. The temp. was monitored with an IR
temp. sensor. In all experiments, the microwave temp. was held constant. Reactions were carried out in 5-
ml glass vessels with a magnetic stir bar, which were sealed with a cap septum. The specific reaction time
corresponds to the total irradiation time. After completion of the reaction, the mixture was cooled to 258
via air-jet cooling. TLC: Silica-gel plates (SiO2; 0.20-mm thickness); visualization with UV light at
254 nm or by staining with a base soln. of CoCl2/H2SO4 ac. (2 g/100 ml H2SO4 10%), followed by heating.
Flash column chromatography (FC): SiO2 60 (230 – 400 mesh). M.p.: FischerꢀJohns Scientific melting-
point apparatus; uncorrected. 1H- and 13C-NMR spectra: Bruker Avance 300 MHz, and a Varian
500 MHz; d in ppm rel. to Me4Si as internal standard, J in Hz. MS: Shimadzu GCMS-QP2010 Plus; in m/
z (rel. %).
Microwave Irradiation. A 10-ml reaction vessel was charged with a magnetic stir bar, 0.4 mmol of
TBS ether, and 20 mol-% Ce(SO4)2 · 4 H2O in 2 ml of MeOH. A septum cap was affixed, and the vessel
was placed in the microwave cavity of an Anton-Paar microwave equipment. The stirred mixture was
irradiated at 1308 for 20 min. After cooling to r.t., TLC indicated the disappearance of starting material.
The solid Ce(SO4)2 was filtered off, and the solvent was removed under reduced pressure. FC afforded
the pure alcohol. All products were spectrally identical with authentic alcohols.
Conventional Heating. A 10-ml round-bottom flask was equipped with a magnetic stir bar and a
reflux condenser. Then, TBS ether (0.4 mmol) and 20 mol-% Ce(SO4)2 · 4 H2O were added in MeOH
(2.0 ml). The mixture was stirred at 608 for 12 h. After cooling to r.t., TLC indicated the disappearance of
starting material. The solid Ce(SO4)2 was filtered off, and the solvent was removed under reduced
pressure. FC afforded the pure alcohol. All products were spectrally identical with authentic alcohols.
(3aR,4S,5R,6aS)-3,3a,4,5,6,6a-Hexahydro-5-hydroxy-4-(hydroxymethyl)-2H-cyclopenta[b]furan-2-
one (1). White solid. M.p. 115 – 1178. 1H-NMR (300 MHz, CDCl3): 0.9 (s, OH); 1.22 (s, OH); 1.9 – 2.2 (m,
1 H); 2.41 (td, J ¼ 6.6, 21.5, 1 H); 2.56 (d, J ¼ 2.4, 1 H); 2.62 (td, J ¼ 2.4, 5.0, 2 H); 2.67 (d, J ¼ 2.1, 1 H);
2.80 (dd, J ¼ 9.6, 18.0, 2 H); 3.63 (dd, J ¼ 7.2, 10.5, 1 H); 3.73 (dd, J ¼ 5.7, 10.5, 1 H); 3.85 (d, J ¼ 6.6, 1 H);
4.19 (q, J ¼ 6.3, 1 H); 4.94 (td, J ¼ 2.7, 7.0, 1 H). 13C-NMR (75 MHz, CDCl3): 35.2 (CH2); 39.5 (CH); 40.7
(CH2); 55.1 (CH); 63.6 (CH2); 75.5 (CH); 83.4 (CH); 176.8 (C¼O). EI-MS: 173 ([M þ 1]þ), 154 (12),
137 (15), 126 (30), 95 (18), 82 (40), 67 (23), 54 (100), 41 (30), 28 (19), 4 (15).
(3aR,4S,5R,6aS)-5-{[(tert-Butyl)(dimethyl)silyl]oxy}-4-({[(tert-butyl)(dimethyl)silyl]oxy}methyl)-
3,3a,4,5,6,6a-hexahydro-2H-cyclopenta[b]furan-2-one (1a). White solid. M.p. 60 – 638. 1H-NMR

Helvetica Chimica Acta – Vol. 97 (2014)
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(500 MHz, CDCl3): 0.045 – 0.036 (m, 12 H); 0.86 (s, 9 H); 0.88 (s, 9 H); 1.99 – 1.95 (m, 2 H); 2.25 – 2.2 (m,
1 H); 2.53 (dd, J ¼ 18.0, 3.0, 1 H); 2.68 – 2.63 (m, 2 H); 2.77 (dd, J ¼ 18.0, 10.5, 1 H); 3.47 (dd, J ¼ 10.5, 5.5,
1 H); 3.54 (dd, J ¼ 10.5, 5.5, 1 H); 4.15 (q, J ¼ 5.0, 2 H); 4.92 (dt, J ¼ 7.0, 2.5, 1 H). 13C-NMR (125 MHz,
CDCl3): ꢀ 5.5 (4 MeSi); 18.2 (2 C); 25.8 (6 Me); 35.5 (CH2); 39.1 (CH); 41.0 (CH2); 56.9 (CH2); 62.5
(CH); 74.5 (CH); 84.1 (CH); 177.2 (C¼O).
1
2-(1H-Indol-3-yl)ethanol (2). Beige solid. M.p. 56 – 598. H-NMR (500 MHz, CDCl3): 1.9 (s, OH);
3.0 (t, J ¼ 6.5, 2 H); 3.86 (t, J ¼ 6.5, 2 H); 6.9 (s, 1 H); 7.11 (t, J ¼ 7.5, 1 H); 7.19 (t, J ¼ 7.5, 1 H); 7.30 (d, J ¼
7.5, 1 H); 7.59 (d, J ¼ 7.5, 1 H); 8.16 (s, NH). 13C-NMR (125 MHz, CDCl3): 28.7 (CH2); 62.5 (CH2); 111.3
(CH); 112.1 (C); 118.8 (CH); 119.4 (CH); 122.1 (CH); 122.6 (CH); 127.4 (C); 136.4 (C). EI-MS: 161
(Mþ), 159 (12), 133 (25), 117 (12), 102 (6), 85 (100), 77 (7).
3-(2-{[(tert-Butyl)(dimethyl)silyl]oxy}ethyl)-1H-indole (2a). Amber oil. 1H-NMR (500 MHz,
CDCl3): 0.0 (s, 6 H); 0.8 (s, 9 H); 2.9 (t, J ¼ 7.5, 2 H); 3.8 (t, J ¼ 7.5, 2 H); 6.95 – 6.94 (m, 1 H); 7.09 –
7.07 (m, 1 H); 7.142 – 7.140 (m, 1 H); 7.28 – 7.26 (m, 1 H); 7.57 – 7.56 (m, 1 H); 7.85 (s, NH). 13C-NMR
(125 MHz, CDCl3): 0.0 (2 MeSi); 23.6 (C); 31.2 (3 Me); 34.2 (CH2); 69.1 (CH2); 116.3 (CH); 118.3 (C);
124.1 (CH); 124.4 (CH); 127.1 (CH); 127.3 (CH); 132.9 (C); 141.3 (C). EI-MS: 275 (Mþ), 260 (42), 218
(61), 200 (12), 144 (100), 130 (8).
3-Phenoxypropane-1,2-diol (3). White solid. M.p. 50 – 538. 1H-NMR (500 MHz, CDCl3): 3.28 (s,
2 H); 3.70 – 3.64 (m, 2 H); 3.78 – 3.76 (m, 1 H); 3.97 – 3.96 (m, 2 H); 4.08 – 4.06 (m, 1 H); 6.88 – 6.86 (m,
2 H); 6.96 – 6.92 (m, 1 H); 7.26 – 7.23 (m, 2 H). 13C-NMR (125 MHz, CDCl3): 63.7 (CH2); 68.9 (CH2);
70.5 (CH); 114.5 (2 CH); 121.2 (CH); 129.5 (2 CH); 158.4 (C). EI-MS: 168 (Mþ), 150 (50), 136 (22), 119
(30), 94 (100), 77 (28), 66 (35).
2,2,3,3,8,8,9,9-Octamethyl-5-(phenoxymethyl)-4,7-dioxa-3,8-disiladecane (3a). Colorless liquid.
1H-NMR (300 MHz, CDCl3): 0.17 – 0.058 (m, 12 H); 0.9 (s, 18 H); 3.71 (d, J ¼ 6.0, 2 H); 3.91 – 3.90
(m, 1 H); 4.16 – 4.09 (m, 2 H); 6.97 – 6.94 (m, 3 H); 7.34 – 7.29 (m, 2 H). 13C-NMR (75 MHz, CDCl3):
ꢀ 4.62 (2 MeSi); ꢀ 4.54 (2 MeSi); 18.3 (2 C); 25.9 (6 Me); 65.0 (CH2); 69.9 (CH2); 72.1 (CH); 114.4
(2 CH); 120.5 (CH); 129.3 (2 CH); 159.0 (C). EI-MS: 397 (Mþ), 303 (70), 277 (10), 249 (12), 207 (11),
171 (52), 133 (75), 89 (12), 73 (16).
2,2,9,9-Tetramethyl-5-(phenoxymethyl)-3,3,8,8-tetraphenyl-4,7-dioxa-3,8-disiladecane (3b). Slightly
yellow oil. 1H-NMR (500 MHz, CDCl3): 1.09 – 1.02 (m, 18 H); 3.76 (d, J ¼ 2.4, 2 H); 3.98 – 3.96 (m, 1 H);
4.16 – 4.12 (m, 2 H); 6.75 – 6.73 (m, 2 H); 6.93 – 6.91 (m, 1 H); 7.25 – 7.21 (m, 6 H); 7.34 – 7.31 (m, 4 H);
7.42 – 7.40 (m, 4 H); 7.63 – 7.57 (m, 4 H); 7.70 – 7.67 (m, 4 H). 13C-NMR (125 MHz, CDCl3): 19.5 (2 C);
27.0 (12 Me); 64.9 (CH2); 68.6 (CH); 72.3 (CH2); 114.6 (CH); 120.6 (CH); 127 (7 CH); 129 (7 CH); 133.6
(5 CH); 134 (4 CH); 136 (4 C); 158.9 (C). EI-MS: 391 (20), 331 (8), 253 (12), 215 (100), 199 (30), 152
(20), 139 (20), 79 (42).
Menthol (¼ 5-Methyl-2-(1-methylethyl)cyclohexanol; 4). White solid. M.p. 41 – 448. 1H-NMR
(500 MHz, CDCl3): 0.62 – 0.61 (m, 1 H); 0.83 – 0.81 (m, 3 H); 0.92 – 0.92 (m, 6 H); 1.05 – 1.03 (m, 1 H);
1.42 (s, OH); 1.65 – 1.62 (m, 1 H); 1.98 – 1.97 (m, 1 H); 2.19 – 2.18 (m, 1 H); 3.41 – 3.39 (m, 1 H).
13C-NMR (125 MHz, CDCl3): 16.0 (Me); 21.0 (Me); 22.2 (Me); 23.1 (CH2); 25.7 (CH); 31.6 (CH); 34.5
(CH2); 45.0 (CH2); 50.1 (CH); 71.4 (CH). EI-MS: 156 (Mþ), 138 (100), 119 (20), 106 (55), 95 (30), 86
(10), 57 (40).
2-{[(tert-Butyl)dimethylsilyl]oxy}-4-methyl-1-(1-methylethyl)cyclohexane (4a). Colorless liquid.
1H-NMR (300 MHz, CDCl3): 0.098 (s, 6 H); 0.78 – 0.77 (m, 6 H); 0.92 (s, 9 H); 1.21 – 1.19 (m, 1 H);
1.42 – 1.38 (m, 1 H); 1.70 – 1.59 (m, 2 H); 1.92 – 1.89 (m, 1 H); 2.31 – 2.22 (m, 1 H); 3.49 – 3.39 (m, 1 H).
13C-NMR (75 MHz, CDCl3): ꢀ 4.8 (MeSi); ꢀ 3.7 (MeSi); 15.7 (C); 18.1 (Me); 21.3 (2 Me); 22.0 (CH2);
25.0 (CH); 25.0 (3 Me); 31.7 (CH); 34.6 (CH2); 45.5 (CH2); 50.3 (CH); 72.4 (CH). EI-MS: 270 (Mþ), 255
(30), 216 (65), 155 (10), 143 (81), 131 (42), 128 (100), 115 (8), 85 (53), 51 (20).
1,1’-{(tert-Butyl){[5-methyl-2-(1-methylethyl)cyclohexyl]oxy}silylene}bis(benzene) (4b). White sol-
1
id. M.p. 61 – 638. H-NMR (500 MHz, CDCl3): 0.51 – 0.49 (m, 3 H); 0.71 – 0.68 (m, 3 H); 0.79 – 0.76 (m,
3 H); 1.1 (s, 9 H); 1.27 – 1.24 (m, 1 H); 1.54 – 1.50 (m, 2 H); 1.73 – 1.69 (m, 1 H); 2.28 – 2.25 (m, 1 H);
3.42 – 3.40 (m, 1 H); 7.30 – 7.28 (m, 6 H); 7.59 – 7.55 (m, 4 H). 13C-NMR (125 MHz, CDCl3): 15.7 (Me);
19.7 (Me); 21.5 (Me); 22.4 (CH2); 25.2 (CH); 27.3 (3 Me); 31.7 (CH); 34.6 (CH2); 45.4 (CH2); 50.6 (CH);
73.9 (CH); 127 (6 CH); 129 (4 CH); 134.4 (2 C). EI-MS: 337 (30), 217 (20), 199 (80), 139 (100), 137
(28), 95 (21), 81 (57).

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N-(4-Hydroxyphenyl)acetamide (5). White solid. M.p. 169 – 1718. 1H-NMR (300 MHz, CDCl3/
DMSO): 1.99 (s, 3 H); 6.66 – 6.63 (m, 2 H); 7.28 – 7.23 (m, 2 H); 9.12 (s, NH). 13C-NMR (75 MHz, CDCl3/
DMSO): 23 (Me); 114 (2 CH); 120 (2 CH); 129.9 (C); 152.7 (C); 167.7 (C¼O). EI-MS: 151 (Mþ), 121
(4), 109 (100), 80 (10), 65 (2), 53 (4), 42 (5), 26 (5).
1
N-(4-{[(tert-Butyl)(dimethyl)silyl]oxy}phenyl)acetamide (5a). White solid. M.p. 95 – 978. H-NMR
(300 MHz, CDCl3): 0.17 (s, 6 H); 0.96 (s, 9 H); 2.1 (s, 3 H); 6.78 – 6.75 (m, 2 H); 7.35 – 7.32 (m, 2 H); 7.6 (s,
NH). 13C-NMR (75 MHz, CDCl3): ꢀ 4.5 (2 Me); 18.1 (C); 24.2 (Me); 25.6 (3 Me); 120.2 (2 CH); 121.6
(2 CH); 131.5 (C); 152.3 (C); 168.4 (C¼O). EI-MS: 265 (Mþ), 250 (5), 208 (100), 192 (5), 180 (8), 166
(30), 149 (8), 134 (5), 116 (4), 106 (15), 73 (37), 43 (35).
N-(4-{[Tris(1-methylethyl)silyl]oxy}phenyl)acetamide (5b). White solid. M.p. 64 – 668. 1H-NMR
(300 MHz, CDCl3): 1.10 – 1.07 (m, 18 H); 1.28 – 1.21 (m, 3 H); 2.0 (s, 3 H); 6.80 (d, J ¼ 9.0, 2 H); 7.34 (d,
J ¼ 9.0, 2 H); 7.9 (s, NH). 13C-NMR (75 MHz, CDCl3): 12.5 (3 CH); 17.8 (6 Me); 24.1 (Me); 119.8
(2 CH); 121.5 (2 CH); 131.4 (C); 152.6 (C); 168.5 (C¼O). EI-MS: 307 (Mþ), 264 (82), 236 (60), 222 (18),
208 (80), 194 (45), 178 (12), 134 (12), 93 (12), 75 (22), 43 (100).
N-(4-{[(tert-Butyl)(diphenyl)silyl]oxy}phenyl)acetamide (5c). Slightly yellow oil. 1H-NMR
(500 MHz, CDCl3): 1.0 (s, 9 H); 2.0 (s, 3 H); 6.69 – 6.68 (m, 2 H); 7.19 – 7.17 (m, 2 H); 7.41 – 7.33 (m,
7 H); 7.73 – 7.69 (m, 3 H); 7.9 (s, NH). 13C-NMR (125 MHz, CDCl3): 19.4 (C); 24.2 (Me); 26.6 (3 Me);
115.8 (CH); 119.8 (CH); 121.5 (CH); 122.6 (CH); 127.4 (CH); 129.5 (4 CH); 129.7 (3 CH); 131.2 (C);
132.8 (CH); 134.9 (2 CH); 152.3 (C); 154.1 (C); 162.7 (C); 168.0 (C¼O). EI-MS: 389 (Mþ), 350 (100),
290 (40), 272 (38), 231 (25), 149 (20), 77 (8).
Hydroquinone (¼ Benzene-1,4-diol; 6). White solid. M.p. 1718. 1H-NMR (300 MHz, CDCl3): 6.6 (s,
4 H); 7.4 (s, 2 H). 13C-NMR (75 MHz, CDCl3): 115.8 (4 CH); 149.5 (2 C). EI-MS: 110 (Mþ), 81 (33), 63
(8), 53 (32), 39 (21).
1,4-Bis{[(tert-Butyl)(dimethyl)silyl]oxy}benzene (6a). White solid. M.p. 42 – 448. 1H-NMR
(300 MHz, CDCl3): 0.16 (s, 12 H); 0.97 (s, 8 H); 6.6 (s, 4 H). 13C-NMR (75 MHz, CDCl3): ꢀ 4.4
(4 Me); 18.1 (2 C); 25 (6 Me); 120.5 (4 CH); 149.7 (2 C). EI-MS: 138 (Mþ), 323 (5), 281 (100), 239 (10),
225 (15), 112 (12), 73 (75), 57 (12), 41 (12).
1,4-Bis{[tris(1-methylethyl)silyl]oxy}benzene (6b). White solid. M.p. 228. 1H-NMR (300 MHz,
CDCl3): 1.09 – 1.06 (m, 32 H); 1.25 – 1.17 (m, 6 H); 6.7 (s, 4 H). 13C-NMR (75 MHz, CDCl3): 12.5 (6 CH);
17.8 (12 Me); 120.3 (4 CH); 150 (2 C). EI-MS: 422 (Mþ), 379 (97), 351 (40), 337 (15), 323 (40), 309 (25),
195 (10), 112 (70), 105 (50), 87 (28), 73 (39), 59 (55), 43 (22).
1,4-Bis{[(1,1-dimethylethyl)diphenylsilyl]oxy}benzene (6c). White solid. M.p. 121 – 1238. 1H-NMR
(300 MHz, CDCl3): 1.0 (s, 18 H); 6.4 (s, 4 H); 7.30 – 7.40 (m, 12 H); 7.63 – 7.60 (m, 8 H). 13C-NMR
(75 MHz, CDCl3): 19.4 (2 C); 26.5 (6 Me); 120.0 (4 CH); 127.6 (CH); 129.6 (CH); 135.5 (CH); 149.5
(2 C). EI-MS: 586 (Mþ), 391 (10), 318 (3), 215 (100), 199 (83), 139 (57), 79 (75), 63 (28).
4-({[(1,1-Dimethylethyl)dimethylsilyl]oxy}methyl)-2-methoxy-1-{[tris(1-methylethyl)silyl]oxy}ben-
zene (7a). Yellow oil. 1H-NMR (300 MHz, CDCl3): 0.03 (s, 3 H); 0.08 (s, 3 H); 0.94 (s, 9 H); 1.10 (d, J ¼
7.2, 18 H); 1.3 – 1.2 (m, 3 H); 3.8 (s, 3 H); 4.67 (s, 2 H); 6.72 (dd, J ¼ 8.0, 1.5, 1 H); 6.82 (d, J ¼ 8.0, 1 H);
6.87 (d, J ¼ 1.5, 1 H). 13C-NMR (75 MHz, CDCl3): ꢀ 5.1 (MeSi); ꢀ 2.9 (MeSi); 12.9 (3 CH); 17.9
(6 Me); 18.4 (C); 25.7 (3 Me); 55.4 (MeO); 65.0 (CH2); 110.5 (CH); 118.3 (CH); 120.0 (CH); 134.6 (C);
144.4 (C); 150.7 (C).
1
3-Methoxy-4-{[tris(1-methylethyl)silyl]oxy}benzenemethanol (7b). Yellow oil. H-NMR (300 MHz,
CDCl3): 1.09 (d, J ¼ 7.2, 18 H); 1.32 – 1.18 (m, 3 H); 3.8 (s, 3 H); 4.58 (s, 2 H); 6.72 (dd, J ¼ 8.0, 1.8, 1 H);
6.82 (d, J ¼ 8.0, 1 H); 6.86 (d, J ¼ 1.8, 1 H). 13C-NMR (75 MHz, CDCl3): 12.9 (3 CH); 17.9 (6 Me); 55.4
(MeO); 65.4 (CH2); 111.3 (CH); 119.4 (CH); 120.2 (CH); 134.1 (C); 145.1 (C); 151.0 (C).
(tert-Butyl)[4-({[(tert-butyl)(dimethyl)silyl]oxy}methyl)-2-methoxyphenoxy]diphenylsilane (7c).
1
Yellow oil. H-NMR (300 MHz, CDCl3): ꢀ 0.31 (s, 3 H); ꢀ 0.14 (s, 3 H); 0.73 – 0.72 (m, 9 H); 0.95 –
0.97 (m, 9 H); 4.44 – 4.30 (m, 3 H); 5.28 (s, 2 H); 6.55 – 7.06 (m, 3 H); 7.20 – 7.35 (m, 6 H); 7.58 – 7.65
(m, 4 H). 13C-NMR (75 MHz, CDCl3): ꢀ 5.0 (MeSi); ꢀ 4.6 (MeSi); 10.2 (C); 19.4 (C); 26.5 (3 Me); 31.6
(3 Me); 55.1 (Me); 64.8 (CH2); 115.5 (2 CH); 119.5 (2 CH); 121.6 (CH); 126.9 (2 CH); 127.7 (2 CH);
129.8 (2 CH); 132.9 (CH); 134.8 (CH); 135.5 (2 C); 136.9 (C); 138.3 (C); 154.9 (C).
(4-{[(tert-Butyl)(diphenyl)silyl]oxy}-3-methoxyphenyl)methanol (7d). Yellow oil. 1H-NMR
(300 MHz, CDCl3): 1.12 – 1.01 (m, 9 H); 2.97 (s, OH); 3.55 (s, 3 H); 4.49 (s, 2 H); 6.9 – 6.5 (m, 3 H);

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7.5 – 7.2 ( m, 6 H); 7.7 (d, J ¼ 7.8, 4 H). 13C-NMR (75 MHz, CDCl3): 19.0 (C); 26.6 (3 Me); 55.4 (Me); 65.3
(CH2); 111.5 (CH); 119.3 (CH); 120.0 (CH); 127.3 (CH); 127.5 (CH); 127.7 (CH); 128.1 (CH); 129.3
(CH); 129.6 (CH); 129.7 (CH); 133.6 (CH); 134.1 (CH); 134.4 (CH); 138.8 (2 C); 135.3 (C); 144.6 (C);
150.6 (C).
1-({[(tert-Butyl)(dimethyl)silyl]oxy}methyl)-3-{[tris(1-methylethyl)silyl]oxy}benzene (8a). Yellow
oil. 1H-NMR (300 MHz, CDCl3): 0.19 (s, 6 H); 1.05 (s, 9 H); 1.20 (d, J ¼ 7.0, 18 H); 1.45 – 1.29 (m,
3 H); 4.79 (s, 2 H); 6.85 (dd, J ¼ 7.8, 2.1, 1 H); 7.04 – 6.98 (m, 2 H); 7.22 – 7.34 (m, 1 H). 13C-NMR
(75 MHz, CDCl3): ꢀ 5.3 (2 MeSi); 12.7 (3 CH); 17.9 (6 Me); 18.0 (C); 25.9 (3 Me); 64.7 (CH2); 117.5
(CH); 118.4 (CH); 118.5 (CH); 129.0 (CH); 143.0 (C); 156.1 (C).
3-{[Tris(1-methylethyl)silyl]oxy}benzenemethanol (8b). Yellow oil. 1H-NMR (300 MHz, CDCl3):
1.10 (d, J ¼ 7.2, 18 H); 1.33 – 1.18 (m, 3 H); 1.77 (s, OH); 4.61 (s, 2 H); 6.80 (d, J ¼ 8.0, 1 H); 6.90 (d, J ¼
8.0, 2 H); 7.19 (t, J ¼ 8.0, 1 H). 13C-NMR (75 MHz, CDCl3): 12.7 (3 CH); 17.9 (6 Me); 65.2 (CH2); 118.4
(CH); 119.0 (CH); 119.4 (CH); 129.5 (CH); 142.5 (C); 156.3 (C).
(tert-Butyl)[3-({[(tert-butyl)(dimethyl)silyl]oxy}methyl)phenoxy]diphenylsilane (8c). Yellow oil.
1H-NMR (300 MHz, CDCl3): 0.0 (s, 6 H); 0.87 (s, 9 H); 1.1 (s, 9 H); 4.57 (s, 2 H); 6.62 (dd, J ¼ 8.0, 2.0,
1 H); 6.80 (d, J ¼ 2.0, 1 H); 6.83 (s, 1 H); 7.03 (t, J ¼ 8.0, 1 H); 7.43 – 7.32 (m, 6 H); 7.72 (d, J ¼ 8.0, 4 H).
13C-NMR (75 MHz, CDCl3): ꢀ 5.3 (2 Me); 18.4 (C); 19.5 (C); 25.9 (3 Me); 26.6 (3 Me); 64.7 (CH2);
117.5 (CH); 118.2 (CH); 118.7 (CH); 127.7 (CH); 128.9 (2 CH); 129.8 (4 CH); 133.1 (2 C); 135.5 (4 CH);
142.9 (C); 155.6 (C).
(3-{[(tert-Butyl)(diphenyl)silyl]oxy}phenyl)methanol (8d). Yellow oil. 1H-NMR (300 MHz,
CDCl3): 1.1 (s, 9 H); 1.58 (s, OH); 4.48 (s, 2 H); 6.62 (dd, J ¼ 8.0, 2.0, 1 H); 6.81 (t, J ¼ 7.5, 2 H); 7.02
(t, J ¼ 7.8, 1 H); 7.43 – 7.31 (m, 6 H); 7.70 (d, J ¼ 7.5, 4 H). 13C-NMR (75 MHz, CDCl3): 19.5 (C); 26.6
(3 Me); 65.1 (CH2); 118.3 (CH); 118.9 (CH); 119.6 (CH); 127.8 (CH); 129.3 (2 CH); 129.9 (4 CH); 132.9
(2 C); 135.5 (4 CH); 132.9 (2 C); 135.5 (4 CH); 142.3 (C); 155.8 (C).
(3aR,4S,5R,6aS)-5-{[(tert-Butyl)(diphenyl)silyl]oxy}-3,3a,4,5,6,6a-hexahydro-4-(hydroxymethyl)-
2H-cyclopenta[b]furan-2-one (9). White solid. M.p. 141 – 1448. 1H-NMR (300 MHz, CDCl3): 1.06 (s,
9 H); 1.61 (s, OH); 2.04 (q, J ¼ 5.0, 3 H); 2.55 (d, J ¼ 2.4, 1 H); 2.59 (d, J ¼ 2.4, 1 H); 2.70 – 2.64 (m, 1 H);
2.80 (dd, J ¼ 17.4, 10.0, 1 H); 3.38 (t, J ¼ 6.3, 2 H); 4.10 (q, J ¼ 5.1, 1 H); 7.41 – 7.39 (m, 7 H); 7.68 – 7.66 (m,
5 H). 13C-NMR (75 MHz, CDCl3): 19.0 (C); 26.9 (3 Me); 35.7 (CH2); 39.0 (CH2); 40.8 (CH); 56.8 (CH);
62.1 (CH2); 75.6 (CH); 84.2 (CH); 127.7 (2 CH); 129.9 (4 CH); 133.4 (2 CH); 135.9 (2 CH); 177.5
(C¼O).
(3aR,4S,5R,6aS)-4-({[(tert-Butyl)(dimethyl)silyl]oxy}methyl)-5-{[(tert-butyl)(diphenyl)silyl]oxy}-
1
3,3a,5,5,6,6a-hexahydro-2H-cyclopenta[b]furan-2-one (9a). Colorless oil. H-NMR (300 MHz, CDCl3):
0.01 (s, 6 H); 0.87 (s, 9 H); 1.12 (s, 9 H); 2.08 – 2.06 (m, 3 H); 2.75 – 2.41 (m, 2 H); 2.88 (dd, J ¼ 18.6, 11.0,
1 H); 3.33 (dd, J ¼ 10.0, 6.0, 1 H); 3.48 (dd, J ¼ 10.0, 6.0, 1 H); 4.15 (q, J ¼ 5.0, 1 H); 7.51 – 7.41 (m, 7 H);
7.72 (d, J ¼ 7.5, 4 H). 13C-NMR (75 MHz, CDCl3): ꢀ 5.6 (Me); ꢀ 5.6 (Me); 18.1 (C); 19.0 (C); 25.8
(3 Me); 26.9 (3 Me); 35.9 (CH2); 39.9 (CH2); 41.1 (CH); 57.2 (CH); 63.32 (CH2); 76.3 (CH); 84.7 (CH);
127.7 (2 CH); 129.7 (4 CH); 133.6 (2 C); 135.8 (4 CH); 177.4 (C¼O).
2-[(1R,5S)-5-{[(tert-Butyl)(diphenyl)silyl]oxy}cyclopent-2-en-1-yl]ethanol (10). Colorless oil.
1H-NMR (300 MHz, CDCl3): 1.1 (s, 9 H); 1.83 – 1.71 (m, 1 H); 2.06 – 1.93 (m, 2 H); 2.19 (dd, J ¼ 17.0,
7.5, 1 H); 2.29 – 2.26 (m, 1 H); 2.34 – 2.31 (m, 1 H); 2.63 – 2.59 (m, 1 H); 3.78 – 3.64 (m, 1 H); 4.54 (q, J ¼
7.2, 1 H); 5.59 – 5.56 (m, 1 H); 5.66 – 5.63 (m, 1 H); 7.43 – 7.35 (m, 6 H); 7.70 – 7.66 (m, 4 H). 13C-NMR
(75 MHz, CDCl3): 19.3 (C); 27.0 (3 Me); 31.7 (CH2); 39.8 (CH2); 45.6 (CH); 61.4 (CH2); 75.2 (CH); 127.6
(2 CH); 127.7 (2 CH); 128.4 (CH); 129.7 (CH); 129.7 (CH); 133.0 (CH); 133.7 (C); 134.2 (C); 135.7
(2 CH); 135.8 (2 CH).
(tert-Butyl){[(1S,2R)-2-(2-{[(tert-butyl)(dimethyl)silyl]oxy}ethyl)cyclopent-3-en-1-yl]oxy}diphenyl-
1
silane (10a). Thick yellow oil. H-NMR (300 MHz, CDCl3): 0.02 (s, 6 H); 0.85 (s, 9 H); 1.01 (s, 9 H);
1.61 – 1.51 (m, 1 H); 2.22 – 1.94 (m, 3 H); 2.57 – 2.47 (m, 1 H); 3.71 – 3.57 (m, 2 H); 4.44 (q, J ¼ 7.0, 1 H);
5.50 – 5.45 (m, 1 H); 5.67 – 5.62 (m, 1 H); 7.39 – 7.25 (m, 7 H); 7.65 – 7.58 (m, 5 H). 13C-NMR (75 MHz,
CDCl3): 5.1 (2 Me); 18.4 (C); 19.4 (C); 26.0 (3 Me); 27.0 (3 Me); 31.9 (CH2); 39.9 (CH2); 45.3 (CH); 62.2
(CH2); 75.3 (CH); 127.5 (2 CH); 127.6 (2 CH); 127.8 (CH); 129.5 (CH); 129.6 (CH); 133.8 (CH); 134.1
(2 C); 134.8 (CH); 135.6 (CH); 135.78 (CH); 135.84 (CH).

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1-(4-Hydroxyphenyl)propan-1-one (11). White solid. M.p. 147 – 1498. H-NMR (300 MHz, CDCl3/
DMSO): 1.07 (t, J ¼ 7.0, 3 H); 2.82 (q, J ¼ 7.0, 2 H); 6.77 (d, J ¼ 9.0, 2 H); 7.74 (d, J ¼ 9.0, 2 H). 13C-NMR
(75 MHz, CDCl3/DMSO): 7.5 (Me); 30.0 (CH2); 114.3 (2 CH); 127.5 (C); 129.2 (2 CH); 161.0 (C); 198.0
(C¼O). EI-MS: 150 (Mþ), 120 (2), 93 (20), 65 (10), 63 (3), 38 (2), 26 (2).
1-(4-{[tert-Butyl(dimethyl)silyl]oxy}phenyl)propan-1-one (11a). White solid. M.p. 208. 1H-NMR
(300 MHz, CDCl3): 0.2 (s, 6 H); 0.9 (s, 9 H); 1.19 (t, J ¼ 7.2, 3 H); 2.93 (q, J ¼ 7.3, 2 H); 6.86 (d, J ¼ 8.9,
2 H); 7.89 (d, J ¼ 8.9, 2 H). 13C-NMR (75 MHz, CDCl3): ꢀ 4.4 (2 MeSi); 8.4 (Me); 18.2 (C); 25.5 (3 Me);
31.3 (CH2); 119.8 (2 CH); 130.1 (2 CH); 130.5 (C); 160.0 (C); 199.5 (C¼O). EI-MS: 264 (Mþ), 235 (40),
207 (100), 179 (17), 151 (15), 135 (10), 121 (5), 105 (2), 89 (5), 73 (7), 57 (11).
1-(4-{[Tris(1-methylethyl)silyl]oxy}phenyl)propan-1-one (11b). Thick yellow liquid. 1H-NMR
(300 MHz, CDCl3): 1.12 – 1.05 (m, 18 H); 1.31 – 1.23 (m, 3 H); 2.98 – 2.91 (m, 2 H); 6.90 (d, J ¼ 9.0,
2 H); 7.90 – 7.87 (m, 2 H). 13C-NMR (75 MHz, CDCl3): 8.4 (Me); 13.0 (3 CH); 17.0 (6 Me); 31.3 (CH2);
119.6 (2 CH); 130.1 (2 CH); 130.3 (C); 160.4 (C); 199.5 (C¼O). EI-MS: 306 (Mþ), 263 (38), 235 (22),
207 (33), 151 (6), 135 (6), 121 (6), 89 (25), 57 (100), 43 (20).
Vanillin (¼4-Hydroxy-3-methoxybenzaldehyde; 12). Thick yellow solid. M.p. 80 – 828. 1H-NMR
(300 MHz, CDCl3): 3.93 (s, 3 H); 6.45 (s, OH); 7.02 (d, J ¼ 8.4, 1 H); 7.42 – 7.39 (m, 2 H); 9.8 (s, 1 H).
13C-NMR (75 MHz, CDCl3): 56.0 (Me); 108.8 (CH); 114.4 (CH); 127.4 (CH); 129.7 (C); 147.1 (C); 151.7
(C); 190.9 (C¼O). EI-MS: 152 (Mþ), 151 (100), 137 (5), 123 (20), 109 (22), 93 (4), 81 (40), 65 (12), 53
(22), 39 (12).
4-{[(tert-Butyl)(dimethyl)silyl]oxy}-3-methoxybenzaldehyde (12a). Brown liquid. 1H-NMR
(300 MHz, CDCl3): 0.1 (s, 6 H); 0.9 (s, 9 H); 3.8 (s, 3 H); 6.95 (d, J ¼ 8.0, 1 H); 7.39 – 7.35 (m, 2 H);
9.8 (s, H). 13C-NMR (75 MHz, CDCl3): ꢀ 4.5 (2 Me); 18.4 (C); 25 (3 Me); 55.4 (Me); 110.1 (CH); 120.6
(CH); 126.1 (CH); 130.9 (C); 151.3 (C); 151.6 (C); 190.9 (C¼O). EI-MS: 267 ([M þ 1]þ), 251 (3), 225
(10), 209 (85), 194 (100), 179 (6), 165 (5), 73 (4).
4-{[(tert-Butyl)(diphenyl)silyl]oxy}-3-methoxybenzaldehyde (12b). Yellow oil. 1H-NMR (300 MHz,
CDCl3): 1.0 (s, 9 H); 3.6 (s, 3 H); 7.39 – 7.35 (m, 9 H); 7.73 – 7.67 (m, 5 H); 9.7 (s, 1 H). 13C-NMR
(75 MHz, CDCl3): 19.0 (C); 26.5 (3 Me); 109 – 135 (13 CH); 151.1 (2 C); 151.3 (2 C); 191.0 (C¼O). EI-
MS: 391 ([M þ 1]þ), 333 (70), 318 (70), 261 (10), 217 (55), 199 (100), 152 (30), 139 (60), 79 (70), 63 (11).
REFERENCES
[1] T. W. Greene, P. G. M. Wuts, ꢃProtective Groups in Organic Synthesisꢄ, 3rd edn., John Wiley & Sons,
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`
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Zborniꢅkovaꢅ, P. Fiedler, I. Rosenberg, Org. Lett. 2011, 13, 4200.
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Received September 26, 2013