1444
N. McGregor, C. Pardin, and W. G. Skene
thionyl chloride (950 mL, 13.2 mmol) drop wise. After 20 min of
stirring and warming to room temperature, 16 (2.50 g,
6.00 mmol) was added and the reaction mixture was stirred for
1.5 h. The solution was then cooled to 08C and tert-butyl amine
(1.75 mL, 16.5 mmol) was added followed by triethylamine
(2.30 mL, 16.5 mmol). The mixture was stirred for 6 h and it
was then quenched with water (200 mL). The product was
extracted into dichloromethane and dried with Na2SO4. The
solvent was removed under reduced pressure to yield the title
compound as a solid (1.15 g, 58 %). dH (400 MHz, CDCl3)
8.6 (d, 1H, J 8.8), 8.41–8.36 (m, 2H), 7.98 (d, 1H, J 7.6),
7.78 (t, 1H, J 4), 7.64 (t, 1H, J 8), 6.91 (s, 1H), 1.58 (s, 9H).
dC (400 MHz, CDCl3) 153.8, 140.5, 134.7, 130.5, 129.5, 129.9,
129.8, 128.5, 124.3, 121.3, 81.9, 28.7. MS (ESI) Calc. for
C15H15NO4SCl [M ꢁ H]ꢁ: 340.0. Found: 340.0.
The crude product 4 was crystallized from the aqueous layer
by acidification and cooling to 48C. The resulting crystals were
collected by vacuum filtration and washed with ice-cold water.
The product was dried overnight in a desiccator to give the
product as a light purple solid (257 mg, 69 %). dH (400 MHz,
CD3OD) 8.11 (s, 1H), 7.80 (d, 1H, J 8), 7.45 (d, 1H, J 8),
7.35–7.20 (m, 5H), 6.00 (d, 1H, J 8), 4.54 (s, 2H). HR-MS (ESI)
Calc. for C17H16BNO6S [M þ H]þ: 374.0864. Found: 374.0882.
5-(Benzylideneamino)naphthalene-1-sulfonamide (7)
To 2-methylpropan-2-ol (10 mL) was added 13 (100 mg,
0.45 mmol). The mixture was stirred to dissolve and then
benzaldehyde (0.059 mL, 0.58 mmol) was added. The reaction
was stirred under nitrogen at room temperature overnight.
A yellow precipitate formed that was collected by vacuum
filtration and then washed with ice-cold ethanol to yield the
title product (49 mg, 35 %). dH (400 MHz, CD3OD) 8.76 (s, 1H),
8.60 (d, 1H, J 8), 8.37 (d, 1H, J 8), 8.20 (d, 1H, J 6.4), 8.10
(s, 2H), 7.70–7.60 (m, 7H), 7.39 (d, 1H, J 6). HR-MS (ESI) Calc.
for C17H16BNO6S [M þ H]þ: 311.0849. Found: 311.0854.
5-Aminonaphthalene-1-sulfonamide (13)
In dichloromethane (100 mL) was dissolved 17 (600 mg,
1.59 mmol) to which was then added trifluoroacetic acid
(15 mL, 0.19 mol). The reaction mixture was left to stir over-
night at room temperature. Both the acid and solvent were
removed under reduced pressure. The resulting solid was
recrystallized from ethyl acetate by adding dichloromethane to
afford the product as a white solid (351 mg, 99 %). dH (400 MHz,
D2O/CD3CN) 8.24–8.19 (m, 2H), 7.99 (d, 1H, J 4.4), 7.54–7.49
(m, 2H), 6.99 (d, 1H, J 4 Hz).
5-(Benzylamino)naphthalene-1-sulfonamide (8)
To a 70/30 volume mixture of toluene/ethanol (20 mL) was
added 7 (49 mg, 0.16 mmol). To this was added NaBH4 (50 mg,
0.76 mmol) and the reaction was left to stir at room temperature
for 4 h. The reaction mixture was then partitioned between water
(50 mL) and ethyl acetate (50 mL). The aqueous layer was
washed with ethyl acetate (3 ꢄ 15 mL). The combined organic
layer was then washed with brine (2 ꢄ 10 mL), dried with
magnesium sulfate, filtered, and the solvent then evaporated.
Purification over a silica column using hexanes/ethyl acetate
yielded a yellow solid (28 mg, 58 %). dH (400 MHz, CD3OD)
8.56 (d, 1H, J 8), 8.09 (d, 1H, J 6.8), 7.55–7.20 (m, 10H),
6.48 (d, 1H, J 8), 4.53 (d, 2H, J 4). HR-MS (ESI) Calc. for
C17H16BNO6S [M þ H]þ: 313.1005. Found: 313.1011.
Representative Procedure for the Reductive
Amination of 1–4
In absolute ethanol (20 mL) was dissolved 11 (159 mg, 1 mmol)
to which was added 2-formylphenylboronic acid (232 mg,
1.55 mmol). The reaction mixture was refluxed for 6 h under N2.
The solvent was then removed under reduced pressure and the
resulting Schiff base was dissolved in anhydrous methanol
(10 mL). Sodium borohydride (151 mg, 4 mmol) was then added
and the reaction mixture was stirred at room temperature for 4 h.
The reaction was quenched with water (80 mL) and the aqueous
fraction was washed with dichloromethane (3 ꢄ 25 mL). The
product 1 was obtained as a white powder (211 mg, 36 %) after
purifying the organic layer on silica flash column chromatog-
raphy using dichloromethane/methanol eluent. dH (400 MHz,
CD3OD) 7.56 (t, 2H, J 8.8), 7.43 (d, 1H, J 7.6), 7.34 (t, 1H, J 8.2),
7.27–7.22 (m, 3H), 7.10 (t, 1H, J 8.0), 6.81 (d, 1H, J 7.0), 6.49 (d,
1H, J 7.4), 4.49 (s, 2H). HR-MS (ESI) Calcd. for C17H17BNO3
[M þ H]þ: 294.1296. Found 294.1298.
N-Benzylidenedecan-1-amine (10)
To benzaldehyde (510 mL, 5 mmol) was added n-decylamine
(1.01 mL, 5.05 mmol). The mixture was heated to 808C under
nitrogen atmosphere in the presence of molecular sieves for
15 min. The reaction mixture was then allowed to cool to room
temperature and the product was obtained as a light yellow oil
(1.21 g, 99 %). dH (400 MHz, CDCl3) 8.30 (s, 1H), 7.74 (m, 2H),
7.43 (m, 3H), 4.14 (q, 1H), 3.62 (t, 2H), 1.72 (t, 2H), 1.35–1.25
(m, 16H).
The crude product 2 was crystallized from the aqueous layer
by acidification and cooling to 48C. The resulting crystals were
collected by vacuum filtration and washed with ice-cold water.
The product was dried overnight in a desiccator to give the
product as a light purple solid (273 mg, 76 %). dH (400 MHz,
CD3OD þ Et3N) 8.22 (t, 2H, J 8.7), 8.16 (d, 1H, J 7.2),
7.44–7.42 (m, 2H), 7.31 (q, 2H, J 7.3), 7.23 (t, 1H, J 7.8), 6.67
(d, 1H, J 7.1), 4.53 (s, 2H). HR-MS (ESI) Calc. for C15H16BNO3
[M þ H]þ: 294.1296. Found: 294.1298.
Di-tert-butyl 3,30-(2-Amino-9H-fluorene-9,9-diyl)
dipropanoate (20)
In dimethyl sulfoxide (5 mL) was dissolved 18 (362 mg,
2 mmol). Tetrabutylammonium bromide (19 mg, 0.06 mmol)
was added followed by 50 % aqueous sodium hydroxide
(800 mL, 15.5 mmol). After 20 min of stirring, the solution of
18 turned red and to this was added drop wise tert-butyl acrylate
(1.17 mL, 8 mmol). The reaction mixture was stirred at room
temperature for 5 h. Water (50 mL) was then added to quench the
reaction and the product was extracted with ethyl acetate
(3 ꢄ 20 mL). The combined organic layers were then washed
with brine (20 mL) and dried with MgSO4. The solvent was then
removed under reduced pressure and the crude product was
purified by silica flash column chromatography using hexanes/
ethyl acetate eluent to yield 20 (630 mg, 72 %). dH (400 MHz,
The crude product 3 was obtained by extracting with ethyl
acetate (3 ꢄ 25 mL) followed by drying with Na2SO4. The
product was recrystallized from ethyl acetate upon adding
diethyl ether to yield a yellow solid (168 mg, 47 %).
dH (400 MHz, CD3OD) 8.40 (d, 1H, J 8.5), 8.23 (d, 1H, J 7.3),
7.99 (d, 1H, J 8.6), 7.52 (t, 1H, J 8.0), 7.46 (d, 1H, J 7.7),
7.35 (t, 2H, J 8.1), 7.25–7.23 (m, 2H), 6.61 (d, 1H, J 7.8), 4.53
(s, 2H). HR-MS (ESI) Calc. for C15H16BNO3 [M þ H]þ:
294.1296. Found: 294.1298.