L. Torun et al. / Tetrahedron 61 (2005) 8345–8350
8349
provide a quantitative yield of 12 as a pale green oil. IR
(neat): 1770 (C]O) cmK1
4.1.8. tert-Butyl 2-[(oxymethyl-15-crown-5)methyl]-
benzoate (18). By the procedure recorded above for
preparation of 17, hydroxymethyl-15-crown-5 (16)
(0.50 g, 2.00 mmol, dried at 80 8C under high vacuum for
24 h) was reacted with ester 14 to give 18 (0.71 g, 81%) as a
colorless oil. IR (neat): 1706 (C]O), 1134 (C–O) cmK1. 1H
NMR (CDCl3): d 1.58 (s, 9H), 3.60–3.88 (m, 21H), 4.91 (s,
2H), 7.20–7.90 (m, 4H). Anal. Calcd for C23H36O8: C,
62.71; H, 8.23. Found: C, 62.92; H, 7.96.
.
4.1.4. tert-Butyl 2-methylbenzoate (13).13 Pyridine
(8.9 mL, 110 mmol) and t-BuOH (10.4 mL, 110 mmol)
were added to a flask containing acid chloride 12 (5.67 g,
36.7 mmol). Upon stirring the solution overnight at room
temperature, a white precipitate formed. After addition of
CH2Cl2, the resulting solution was washed with water and
5% aq HCl. The organic layer was dried over Na2SO4 and
the solvent was evaporated in vacuo. The residue was
passed through a short column of alumina with petroleum
ether as eluent to give 6.02 g (85%) of ester 13 as a colorless
oil. IR (neat): 1718 (C]O) cmK1. 1H NMR (CDCl3): d 1.59
(s, 9H), 2.57 (s, 3H), 7.18–7.24 (m, 2H), 7.33 (d of d, 1H),
7.83 (d of d, 1H).
4.1.9. 2-[Oxymethyl-15-crown-5)methyl]benzoic acid (3).
By the procedure given above for the preparation of 2, ester
18 (0.71 g, 1.60 mmol) was hydrolyzed to provide 3 (0.53 g,
86%) as a pale yellow oil. IR (neat): 2870 (COOH), 1713
(C]O), 1119 (C–O) cmK1. 1H NMR (CDCl3): d 3.55–3.95
(m, 21H), 4.93 (s, 2H), 6.70 (br s, 1H), 7.35 (t, 1H), 7.55 (t,
1H) 7.65 (t, 1H), 8.05 (d, 1H). 13C NMR (CDCl3): d 70.08,
70.36, 70.53, 70.69, 71.03, 71.09, 71.25, 76.57, 77.00,
77.42, 78.55, 126.88, 127.02, 127.37, 127.69, 131.00,
131.15, 132.75, 141.06, 170.93. Anal. Calcd for
C19H28O8: C, 59.39; H, 7.34. Found: C, 59.44; H, 7.26.
4.1.5. tert-Butyl 2-(bromomethyl)benzoate (14).14 To a
solution of ester 13 (1.68 g, 8.76 mmol) in CCl4 (20 mL)
was added NBS (1.81 g, 10.52 mmol) and benzoyl peroxide
(0.20 g). The solution was irradiated for 2 h with a 500 watt
tungsten lamp, allowed to cool to room temperature and
washed with water. The organic layer was dried over
MgSO4 and evaporated in vacuo to provide a viscous oil.
Chromatography on silica gel with CCl4 as eluent gave 14
(1.46 g, 61%) as a colorless, viscous oil. 1H NMR (CDCl3):
d 1.62 (s, 9H), 4.93 (s, 2H), 7.29–7.48 (m, 3H), 7.87 (d of d,
1H).
4.1.10. tert-Butyl 2-[(oxymethyl-18-crown-6)methyl]-
benzoate (19). A solution of hydroxymethyl-18-crown-6
(7) (0.89 g, 2.96 mmol, dried at 80 8C under high vacuum
for 24 h) in THF (10 mL) was added to a flask containing
NaH (0.14 g, 3.55 mmol, 60% dispersion in mineral oil).
After the mixture was stirred for 5 min, a solution of ester 14
(0.80 g, 2.95 mmol) in THF (10 mL) was added. The
mixture was stirred for 5 h at room temperature and
the solvent was evaporated in vacuo. To the residue,
CH2Cl2 and water were added. The organic layer was dried
over MgSO4, concentrated, and chromatographed on silica
gel with CH2Cl2/MeOH (10:1) as eluent to give 19 (1.26 g,
89%) as a viscous, colorless oil. IR (neat): 1710 (C]O),
1126 (C–O) cmK1. 1H NMR (CDCl3): d 1.59 (s, 9H), 3.61–
3.86 (m, 25H), 4.91 (s, 2H), 7.30 (d of t, 1H), 7.48 (d of t),
7.65 (d of t), 7.86 (d of d, 1H). Anal. Calcd for C25H40O9: C,
61.97; H, 8.32. Found: C, 62.20; H, 8.16.
4.1.6. tert-Butyl 2-[(oxymethyl-12-crown-4)methyl]-
benzoate (17). A solution of hydroxymethyl-12-crown-4
(15) (0.41 g, 2.00 mmol, dried at 90 8C under high vacuum
for 24 h) in THF (10 mL) was added to a flask containing
NaH (0.09 g, 2.2 mmol, 60% dispersion in mineral oil).
After stirring the mixture for 10 min, a solution of ester 14
(0.54 g, 2.00 mmol) in THF (10 mL) was added. The
mixture was stirred for 5 h at room temperature and the
solvent was evaporated in vacuo. To the residue were added
CH2Cl2 and water. The organic layer was dried over
MgSO4, concentrated, and chromatographed on deactivated
alumina with EtOAc as eluent to yield 17 (0.55 g, 68%) as a
colorless oil. IR (neat): 1705 (C]O), 1134 (C–O) cmK1. 1H
NMR (CDCl3): d 1.58 (s, 9H), 3.50–4.00 (m, 17H), 4.91
(s, 2H), 7.25–7.90 (m, 4H). Anal. Calcd for C21H32O7: C,
63.60; H, 8.14. Found: C, 63.42; H, 7.83.
4.1.11. 2-[Oxymethyl-18-crown-6)methyl]benzoic acid
(4). By the procedure given above for the preparation of
2, ester 19 (0.71 g, 1.60 mmol) was hydrolyzed to provide 4
(0.53 g, 86%) as a pale yellow oil. IR (neat): 2850 (OH);
1712 (C]O), 1125 (C–O) cmK1 1H NMR (CDCl3): d
.
3.65–3.74 (m, 22H), 3.83–3.86 (m, 3H), 7.35 (d of t, 1H),
7.53 (d of t, 1H), 7.64 (d of d, 1H), 8.02 (d of t, 1H) 10.90 (br
s, 1H). 13C NMR (CDCl3): d 69.59, 70.41, 70.54, 70.66,
70.75, 71.35, 71.40, 76.57, 77.00, 77.42, 78.13, 127.00,
127.64, 128.12, 131.06, 132.46, 140.57, 170.71. Anal. Calcd
for C21H32O9: C, 58.87, H, 7.53. Found: C, 58.92; H, 7.48.
4.1.7. 2-[Oxymethyl-12-crown-4)methyl]benzoic acid (2).
To ester 17 (0.55 g, 1.40 mmol) was added 6 N HCl (5 mL)
and the mixture was stirred at room temperature under
nitrogen for 3 h. The acidic solution was made basic
(pHw12) with 20% aq NaOH. The basic solution was
extracted with CH2Cl2 (3!10 mL) and acidified to pH 1
with 6 N HCl. The acidic solution was extracted with
CH2Cl2 (3!25 mL). The combined organic layers were
dried over MgSO4 and evaporated in vacuo to give 2
(0.45 g, 96%) as a pale yellow oil. IR (neat): 2864 (COOH),
1
4.2. H NMR investigations of lariat ether carboxylic
acids and their alkali metal carboxylates
1715 (C]O), 1136 (C–O) cmK1
.
1H NMR (CDCl3): d
Lariat ether sodium, potassium, rubidium, and cesium
carboxylates were produced by stirring 2–4 with an excess
of the alkali metal carbonate in CDCl3 at room temperature
followed by filtration with the filtrate passing directly into
the NMR tube. The lithium lariat ether carboxylates were
prepared by reaction of solutions of 2–4 in THF with
1 equiv of n-BuLi in THF at K78 8C. The THF was
3.40–3.95 (m, 17H), 4.92 (s, 2H), 6.70 (br s, 1H), 7.35
(t, 1H), 7.55 (m, 2H), 7.99 (d, 1H). 13C NMR (CDCl3): d
70.07, 70.18, 70.51, 70.93, 70.93, 71.49, 71.56, 76.57,
77.00, 77.42, 78.48, 127.20, 127.63, 127.75, 130.15, 131.36,
132.93, 140.80, 171.44. Anal. Calcd for C17H24O7: C,
59.96; H: 7.11. Found: C, 59.95; H, 7.23.