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B. J. Brennan et al. / Tetrahedron Letters 55 (2014) 1062–1064
chloroform and filtered, and the filtrate was dried under reduced pressure. The
crude solid was chromatographed on a silica column using chloroform eluent
containing 3% ethanol. Fractions containing the desired product were
combined and dried under reduced pressure to yield a white solid (1.106 g,
65%). 1H NMR (400 MHz, CDCl3, d): 7.73 (d, J = 7.4 Hz, 2H, Ar-H), 7.70 (d,
J = 7.4 Hz, 2H, Ar-H), 3.89 (t, J = 5.9 Hz, 6H, O-CH2), 2.91 (t, J = 5.9 Hz, 6H, N-
CH2), 1.32 (s, 12H, CH3). 13C (100 MHz, CDCl3, d): 145.6, 133.6, 133.4, 83.3, 57.8,
51.2, 24.8. HRMS (API, QTOF) m/z calcd for C18H29BNO5Si [M+H]+, 378.1903;
Found, 378.1909.
synthetic conduits for attachment of phenylsilatrane species. Sta-
bility of the silatrane moiety to palladium catalysts and silica-gel
chromatography provided simple routes to boronic ester- and al-
kyne-functionalized silatrane building blocks. Strategies and
routes to a variety of complex molecules, functional surfaces, and
materials are currently being examined for applications of these
silatrane species. With surface-functionalized metal oxides being
increasingly applied in a variety of applications, silatranes will
undoubtedly be utilized as reagents for these transformations.
15. 4-((Trimethylsilyl)ethynyl)phenyl silatrane. To a dry round bottom flask were
added 23 mg copper(I) iodide (1.2 ꢀ 10ꢁ4 mol), 72 mg triphenylphosphine
(2.7 ꢀ 10ꢁ4 mol), 1.00 g 4-bromophenyl silatrane (3.0 ꢀ 10ꢁ3 mol), 5 mL
triethylamine, and 15 mL DMF. The solution was purged with nitrogen, and
55 mg (6.0 ꢀ 10ꢁ5 mol) of tris(dibenzylideneacetone) dipalladium (Pd2(dba)3)
was added along with 1.0 mL (7.1 ꢀ 10ꢁ3 mol) trimethylsilylacetylene. A reflux
condenser was attached, and the system was purged with nitrogen and heated
at 80 °C for 23 h. The reaction was cooled and transferred to a separatory
funnel with 60 mL of dichloromethane. The solution was washed with water,
and the solvent was distilled under reduced pressure to yield a brown solid.
The solid was redissolved in dichloromethane, and filtered through CeliteÒ, and
the solvent was distilled under reduced pressure. The crude material was
chromatographed on a silica gel column using dichloromethane eluent and
fractions were collected. Fractions containing the desired product were
combined and dried under reduced pressure to yield a pale yellow solid
(463 mg, 44%). 1H NMR (400 MHz, CDCl3, d): 7.66 (d, J = 8.2 Hz, 2H, Ar-H), 7.36
(d, J = 8.2 Hz, 2H, Ar-H), 3.89 (t, J = 5.9 Hz, 6H, O-CH2), 2.91 (t, J = 5.9 Hz, 6H, N-
CH2), 0.23 (s, 9H, Si-CH3). 13C (100 MHz, CDCl3, d): 143.1, 133.9, 130.7, 122.1,
106.5, 92.8, 57.7, 51.1, 0.11. HRMS (API, QTOF) m/z calcd for C17H26NO3Si2
[M+H]+, 348.1446; Found, 348.1448.
Acknowledgments
We would like to thank the Yale West Campus Analytical Core
staff for help with instrumentation. This work was funded grants
from the U.S. Department of Energy (DE-FG02-07ER15909 and
DE-FG02-03ER15393), and a generous grant from Tom Steyer and
Kathryn Taylor.
Supplementary data
Supplementary data (synthesis and characterization of the de-
scribed molecules) associated with this article can be found, in
16. 4-Ethynylphenyl silatrane. To a mixture of 3 mL dichloromethane and 3 mL
methanol in
a
dry round bottom flask were added 50 mg 4-
((trimethylsilyl)ethynyl)phenyl silatrane (1.4 ꢀ 10ꢁ4 mol) and 22 mg of
powdered anhydrous potassium carbonate (1.6 ꢀ 10ꢁ4 mol). The mixture
was sonicated briefly, stirred under nitrogen atmosphere for 13 h, and then
References and notes
quenched with 10
l
L of glacial acetic acid (1.75 ꢀ 10ꢁ4 mol). The solution was
placed into a separatory funnel and washed twice with water, and the organic
layer was dried under reduced pressure to yield a pale yellow solid (34 mg,
88%). 1H NMR (400 MHz, CDCl3, d): 7.69 (d, J = 8.2 Hz, 2H, Ar-H), 7.39 (d,
J = 8.2 Hz, 2H, Ar-H), 3.89 (t, J = 5.9 Hz, 6H, O-CH2), 3.00 (s, 1H, CH), 2.90 (t,
J = 5.9 Hz, 6H, N-CH2). 13C (100 MHz, CDCl3, d): 143.8, 134.1, 130.8, 120.8, 84.9,
76.2, 57.6, 51.0. HRMS (API, QTOF) m/z calcd for C14H18NO3Si [M+H]+,
276.1050; Found, 276.1048.
17. 3-Aminophenyl silatrane. To a dry round bottom flask was added 5.21 g 3-
aminophenyltrimethoxysilane (2.4 ꢀ 10ꢁ2 mol) dissolved in 10 mL toluene. To
the solution was added 3.65 g triethanolamine (2.4 ꢀ 10ꢁ4 mol) and a catalytic
amount of sodium hydroxide (2 mg). A reflux condenser was attached and the
mixture was heated to 110 °C while stirring under a nitrogen atmosphere.
After 2 h, the reaction was cooled and filtered to yield a crude solid. This was
boiled for 10 min in 30 mL of chloroform and cooled, and 10 mL hexanes were
added. The precipitate was filtered to yield a white solid (4.43 g, 68%). 1H NMR
(400 MHz, CDCl3, d): 7.15 (dt, J = 7.4 Hz, 1.2 Hz, 1H, Ar-H), 7.10–7.07 (m, 2H,
Ar-H), 6.60 (ddd, J = 7.8 Hz, 2.3 Hz, 1.2 Hz, 1H, Ar-H) 3.90 (t, J = 5.9 Hz, 6H, O-
CH2), 3.50 (br s, 2H, NH2), 2.91 (t, J = 5.9 Hz, 6H, N-CH2). 13C (100 MHz, CDCl3,
d): 145.2, 142.6, 128.3, 124.7, 121.2, 115.2, 57.8, 51.2. HRMS (API, QTOF) m/z
calcd for C12H19N2O3Si [M+H]+, 267.1159; Found, 267.1159.
18. 4-Aminophenyl silatrane. To a dry round bottom flask were added 2.15 g 4-
aminophenyltrimethoxysilane (1.00 ꢀ 10ꢁ2 mol) and 1.52 g triethanolamine
(1.02 ꢀ 10ꢁ2 mol). A reflux condenser was attached and the mixture was
heated to 115 °C while stirring under a nitrogen atmosphere. After 3 h, the
reaction was cooled and the methanol was removed under reduced pressure to
yield a crude solid. This was recrystallized twice from chloroform and filtered
to yield a white solid (1.68 g, 62%). 1H NMR (400 MHz, CDCl3, d): 7.53 (d,
J = 8.6 Hz, 2H, Ar-H), 6.63 (d, J = 8.6 Hz, 2H, Ar-H), 3.87 (t, J = 5.9 Hz, 6H, O-CH2),
3.53 (br s, 2H, NH2), 2.88 (t, J = 5.9 Hz, 6H, N-CH2). 13C (100 MHz, CDCl3, d):
146.1, 135.3, 130.3, 114.6, 57.9, 51.2. HRMS (API, QTOF) m/z calcd for
13. 4-Bromophenyl silatrane. To a dry round bottom flask were added 20 mL of
toluene, 4.65 g of 4-bromophenyltrimethoxysilane (1.68 ꢀ 10ꢁ2 mol), 2.51 g of
triethanolamine (1.68 ꢀ 10ꢁ2 mol), and
a catalytic amount of sodium
hydroxide (5 mg). A reflux condenser was attached and the mixture was
stirred under a nitrogen atmosphere at 100 °C. After 2 h, the reflux condenser
was removed and methanol byproduct was distilled under
a nitrogen
atmosphere. After 1 h, the reaction was cooled and the precipitate was
collected by filtration and washed with toluene and methanol to yield a white
solid (4.86 g, 88%). 1H NMR (400 MHz, CDCl3, d): 7.60 (d, J = 8.2 Hz, 2H, Ar-H),
7.38 (d, J = 8.2 Hz, 2H, Ar-H), 3.89 (t, J = 5.9 Hz, 6H, O-CH2), 2.92 (t, J = 5.9 Hz,
6H, N-CH2). 13C (100 MHz, CDCl3, d): 141.2, 136.0, 130.2, 122.3, 57.6, 51.1.
HRMS (API, QTOF) m/z calcd for C12H17BrNO3Si [M+H]+, 330.0156; Found,
330.0160.
C
12H19N2O3Si [M+H]+, 267.1159; Found, 267.1166.
14. 4-(4,4,5,5-Tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl silatrane. To
a dry
round bottom flask were added 1.50 g 4-bromophenyl silatrane
(4.5 ꢀ 10ꢁ3 mol), 1.27 g bis(pinacolato)diboron (5.0 ꢀ 10ꢁ3 mol), and 1.34 g
potassium acetate (1.4 ꢀ 10ꢁ2 mol). DMSO (40 mL) was purged with nitrogen,
150 mg (1.8 ꢀ 10ꢁ4 mol) of [1,10-bis-(diphenylphosphino)ferrocene]Pd(II)
chloride (Pd(DPPF)Cl2) was added, and the solution was added to the round
bottom flask. The mixture was purged with nitrogen and then heated at 80 °C.
After 6 h, the reaction was cooled and 120 mL of water was added. The
precipitate was filtered and washed with water. The solid was dissolved in