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DOI: 10.1055/s-2008-1078506
Elaboration of the Oxazepine Ring System via CuI/l-Proline-Catalyzed Intramolecular Aryl Amination
Publication History
Publication Date:
19 June 2008 (online)
Abstract
A two-step approach for assembling oxazepines is described, which started from 2-aminophenols and substituted 2-bromobenzyl bromides and used CuI/l-proline-catalyzed coupling reaction as the key step.
Key words
cross-coupling - aryl bromide - ethers - oxazepines
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References and Notes
These authors contributed equally to this paper.
8
Typical Procedure
for Etherification
To a flask containing 2-aminophenol
(21 mmol) and Na2CO3 (40 mmol) was added DMF
(20 mL), DMSO (20 mL), and H2O (2 mL). At 0 ˚C
a solution of 2-bromobenzyl bromide (10 mmol) in DMF (5 mL) was
added dropwise. After the mixture was stirred for about 4 h, it
was filtered. The filtrate was partitioned between EtOAc and H2O.
The organic phase was separated, and the aqueous layer was extracted
with EtOAc. The combined organic phase was washed with H2O and
brine, dried over Na2SO4, and concentrated.
The residual oil was loaded on a silica gel column and eluted with
1:10 EtOAc-PE to afford the etherification product.
Typical Procedure
for Coupling
A Schlenk tube was charged with the above
ether (0.5 mmol), CuI (0.05 mmol), l-proline
(0.1 mmol), and DABCO˙6H2O (5.0 mmol), evacuated,
and backfilled with Ar. Then, DMSO (4 mL) and H2O (1
mL) were added. The reaction mixture was heated at 90 ˚C
until the starting material disappeared (monitored by TLC). The
cooled mixture was partitioned between EtOAc and H2O.
The organic phase was separated, and the aqueous layer was extracted
with EtOAc. The combined organic phase was washed with brine, dried
over Na2SO4, and concentrated. The crude product
was purified by column chromatography on silica gel to provide the
coupling product.
Selected Data
for 6c
¹H NMR (300 MHz, CDCl3): δ = 7.78
(dd, J = 1.8,
8.1 Hz, 1 H), 7.69 (d, J = 2.1
Hz, 1 H), 7.05 (d, J = 8.4
Hz, 1 H), 6.99 (dd, J = 1.5,
7.8 Hz, 1 H), 6.74 (td, J = 1.8,
7.8 Hz, 1 H), 6.59 (td, J = 1.2,
8.1 Hz, 1 H), 6.46 (dd, J = 1.8,
8.1 Hz, 1 H), 4.31 (s, 2 H), 3.84 (s, 1 H), 1.48 (s, 9 H). ¹³C
NMR (100 MHz, CDCl3): δ = 165.0, 161.2,
114.3, 138.6, 130.8, 130.4, 129.6, 127.4, 124.4, 121.8, 120.3, 119.4,
118.7, 80.8, 47.1, 28.1. ESI-MS: m/z = 298.1 [M + H]+.
ESI-HRMS: m/z calcd for C18H20NO3 [M + H]+:
298.1438; found: 298.1432.
Selected Data
for 6f
¹H NMR (300 MHz, CDCl3): δ = 8.41
(d, J = 8.1
Hz, 1 H), 7.76 (d, J = 8.4
Hz, 1 H), 7.40-7.53 (m, 3 H), 7.31 (dd, J = 1.2,
7.8 Hz, 1 H), 7.18 (d, J = 8.1
Hz, 1 H), 6.82 (td, J = 1.2,
7.2 Hz, 1 H), 6.69 (td, J = 1.5,
7.8 Hz, 1 H), 6.51 (dd, J = 1.2,
7.8 Hz, 1 H), 4.52 (s, 2 H), 3.75 (s, 1 H). ¹³C
NMR (100 MHz, CDCl3): δ = 153.3, 144.6,
139.2, 134.2, 127.6, 127.1, 126.6, 126.2, 126.1, 125.8, 124.4, 123.6,
122.0, 121.8, 119.2, 118.8, 46.9. ESI-MS: m/z = 248.1 [M + H]+. ESI-HRMS: m/z calcd for C17H14NO [M + H]+:
248.1070; found: 248.1068.
Selected Data
for 6h
¹H NMR (300 MHz, CDCl3): δ = 7.05-7.18
(m, 3 H), 6.97-6.99 (m, 1 H), 7.00 (d, J = 8.1,
1 H), 6.39 (dd, J = 1.5,
8.1 Hz, 1 H), 6.27 (d, J = 1.2
Hz, 1 H), 4.35 (s, 2 H), 3.56 (s, 1 H), 2.08 (s, 3 H). ¹³C
NMR (100 MHz, CDCl3): δ = 158.5, 142.9,
138.2, 133.9, 131.7, 128.9, 128.0, 124.1, 121.7, 120.4, 119.9, 118.9,
46.8, 20.5. ESI-MS: m/z = 212.0 [M + H]+.
Selected Data
for 6m
¹H NMR (300 MHz, CDCl3): δ = 7.02
(dd, J = 4.2,
5.1 Hz, 1 H), 6.91 (d, J = 4.2
Hz, 1 H), 6.59-6.70 (m, 3 H), 6.53 (t, J = 7.8
Hz, 1 H), 4.45 (s, 2 H), 3.68 (s, 3 H), 1.99 (s, 3 H). ¹³C
NMR (100 MHz, CDCl3): δ = 158.9, 152.4,
145.0, 136.6, 133.1, 125.9, 125.3, 120.9, 119.7, 118.0, 113.2, 113.1,
55.6, 46.3, 17.7. ESI-MS: m/z = 242.0 [M + H]+.
ESI-HRMS: m/z calcd for C15H16NO2 [M + H]+:
242.1179; found: 242.1176.