624
B. H. Bhide, A. J. Kalaria and B. M. Panchal
Vol. 39
hydrochloric acid (6 N, 100 mL) and extracted with ether (2 × 50
Anal. Calcd. for C H O : C, 69.89; H, 6.84. Found: C,
12 14 3
mL). The organic layer was washed with cold water (100 mL) and
69.98; H, 6.73.
saturated NaHCO solution (50 mL). The solution was then dried
3
General Procedure for the Conversion of Isobenzofuran-1-ones
(2a-f) to1H,4H-3,3-Dimethyl-2-benzopyran-1-ones (3a-f) and
(3g).
over anhydrous .Na SO , and the solvent was evaporated to give
2
4
phthalides (2a-f). The phthalides (2a-f) were purified by column
chromatography over silica gel using 50% petroleum ether-benzene
as an eluent. The liquid products were further purified by distillation.
Method A.
Phthalides (2a-f) (1.7 mmoles) were mixed with cold conc.
(±)-3-Ethyl-3-methylisobenzofuran-1-one (2a).
H SO (2mL) and after shaking well the mixture was warmed on
2
4
This compound was obtained as colorless liquid, 2g (44.4%),
a boiling water bath for 1 hr and kept at room temperature for 24
hrs. The reaction mixture was decomposed by adding cold water
(50mL) and extracted with ether (2 × 25mL). The organic layer
was washed with saturated sodium bicarbonate solution(50mL)
and cold water (50mL), dried over anhydrous sodium sulfate and
evaporated to give a product (3a-f) in 35-40% yield.
-1
1
bp 125 °C 15mm/Hg; ir (neat):1763cm (γ-lactone); H nmr : δ
0.76(t, 3H, CH CH at C , J = 6.6Hz), 1.65 (s, 3H, CH at C ),
2
3
3
3
3
1.9 (q, 2H, CH CH at C J = 6.6Hz), 7.3-7.9 (m, 3H, C ,C ,C -
2
3
3,
4
5
6
H), 7.9(d, 1H, C -H, J = 7.8 Hz).
7
Anal. Calcd. for C H O : C, 74.98; H, 6.86. Found: C,
11 12
2
75.75; H, 6.98.
Method B.
(±)-5-Chloro-3-ethyl-3-methyl-isobenzofuran-1-one (2b).
Phthalides (2a-e) (1.7 mmoles) were treated with anhydrous
This compound was obtained as white needles, 2.4g (45%), mp
AlCl (300mg) in dry methylene chloride (25mL) at reflux tem-
-1
1
3
85°; ir (KBr): 1760 cm (γ-lactone); H nmr : δ 0.77 (t, 3H,
CH CH at C J = 6.5Hz), 1.63 (s, 3H, CH at C ), 1.9 (q, 2H,
perature for 1-2 hrs (monitored by TLC). Methylene chloride was
evaporated and the residue decomposed with HCl (6N) and
extracted with ether (2 × 25mL). The organic layer was washed
with saturated sodium bicarbonate solution(50mL) and cold
water (50mL), dried over anhydrous sodium sulfate and evapo-
2
3
3,
3
3
CH CH at C J = 6.5Hz ), 7.3-7.5 (m, 2H, C , C -H), 7.9 (d, 1H,
2
3
3,
4
6
C -H, J = 7.8Hz).
7
Anal. Calcd. for C H ClO : C, 62.72; H, 5.26. Found: C,
11 11
2
62.56; H, 5.53.
rated to give crude (3a-e). Reaction of 2f with AlCl gave 3f and
3
(±)-3-Ethyl-3,5-dimethyl-isobenzofuran-1-one (2c).
demethylated product 3-methyl mellein (3g). They were purified
by column chromatography over silica gel using 50% pet.ether-
benzene as an eluent to give 3a-f and 3g in (45-50%) yield,
identical with those obtained from method A.
This compound was obtained as white needles, 2.2g (44.6%),
-1
1
mp 62°; ir (KBr):1743 cm (γ-lactone); H-nmr : δ 0.76 (t, 3H,
CH CH at C J = 6.6Hz), 1.63 (s, 3H,CH at CH ), 1.9 (q, 2H,
2
3
3,
3
3
CH CH at CH J = 6.6 Hz ), 2.4 (s, 3H, CH at C ), 7.1-7.3 (m,
2H, C4,C6-H), 7.8 (d, 1H, C7-H, J = 7.8Hz).
2
3
3,
3
5
1H,4H-3,3-Dimethyl-2-benzopyran-1-one (3a).
This compound was obtained as colorless liquid, 0.14g (48%),
Anal. Calcd. for C
H O : C, 75.76; H, 7.41. Found: C,
12 14 2
o
bp 145° 15mm/Hg; lit[9].,bp 153-154 11mm/Hg; ir(KBr): 1710
75.58; H, 7.56.
-1
1
cm (δ-lactone); H nmr : δ 1.45(s, 6H, 2 CH at C ), 3.02 (s,
3
3
(±)-3-Ethyl-3,4,6-trimethyl-isobenzofuran-1-one (2d).
2H, benzylic -CH ), 7.1-7.5(m, 3H, C ,C ,C -H), 7.8 (d, 1H, C -
2
5
6
7
8
H, J= 8 Hz).
Anal. Calcd. for C H O : C, 74.98; H, 6.86. Found: C,
75.20; H, 6.92.
This compound was obtained as colorless liquid, 2.6g (50%),
-1
1
bp 118° 15mm/Hg; ir (neat): 1763 cm (γ-lactone); H nmr : δ
0.80 (t, 3H, CH CH at C3, J = 6.6Hz), 1.59 (s, 3H, CH at C3),
11 12
2
2
3
3
2.0 (q, 2H, CH CH at C3, J = 6.6 Hz), 2.3 & 2.4 ( 2s, 6H, CH at
2
3
3
1H,4H-6-Chloro-3,3-dimethyl-2-benzopyran-1-one (3b).
C4 & C6), 7.2 (s, 1H, C -H), 7.8 (s, 1H, C - H).
5
7
This compound was obtained as white needles, 0.17g (47.6%),
Anal. Calcd. for C
H O : C, 76.44; H, 7.89. Found: C,
13 16 2
-1
1
mp 157°; ir (KBr): 1716 cm (δ-lactone); H-nmr : δ 1.45(s, 6H,
2 CH at C ), 2.9 (s, 2H, benzylic -CH ), 7.2-7.5 (m, 2H, C &
76.32; H, 7.65.
3
3
2
5
(±)-3-Ethyl-3,5,6-trimethyl-isobenzofuran-1-one (2e).
C -H), 7.8 (d, 1H, C -H, J = 7.9Hz).
7
8
Anal. Calcd. for C H ClO : C, 62.72; H, 5.26. Found: C,
62.85; H, 5.43.
This compound was obtained as white needles, 2.45g (48%),
11 11
2
-1
1
mp 83°; ir (KBr): 1756 cm (γ-lactone); H-nmr : δ 0.79 (t, 3H,
CH CH at C , J = 6.8Hz ), 1.5 (s, 3H,CH at C ), 2.1 (q, 2H,
2
3
3
3
3
1H,4H-3,3,6-Trimethyl-2-benzopyran-1-one (3c).
CH CH at C , J = 6.8Hz), 2.3 (s, 6H,CH at C & C ), 7.2 (s,
2
3
3
3
5
6
13
This compound was obtained as a white needle, 0.11g (37%),
1H,C -H), 7.7 (s, 1H, C -H); C-nmr : δ 8.2 (-CH -CH ), 20.24
4
7
2
3
-1
1
mp 55° ; ir (KBr): 1715 cm (δ-lactone); H-nmr : δ 1.45 (s, 6H,
& 21.13 (CH at C & C ), 26.17 (CH at C ), 33.26 (-CH -),
3
5
6
3
3
2
2 CH at C ), 2.3 (s, 3H, CH at C ), 2.89 (s, 2H, benzylic -CH ),
87.96 (C ), 122.19 (=C<), 124.45 (=C<), 126.17 (=C<), 138.32
3
3
3
3
2
3
13
6.9-7.2 (m, 2H, C C -H), 7.9 (d, 1H, C -H, J = 7.9Hz); C-nmr :
(=C<), 144.59 (=C<), 152.26 (=C<), 170.76 (C Carbonyl).
5,
7
8
1
δ 12.10 & 12.25 (2 CH at C ), 22.4(CH at C ), 32.0(C ),
Anal. Calcd. for C
H O : C, 76.44; H, 7.89. Found: C,
3
3
3
6
4
13 16 2
82.3(C ), 125.0 (=C<), 128.53 (=C<), 135.24(=C<), 135.37
76.35; H, 7.71.
3
(=C<), 136.40(=C<), 136.99 (=C<), 166.57 (C Carbonyl).
1
(±)-3-Ethyl-3-methyl-7-methoxy-isobenzofuran-1-one (2f).
Anal. Calcd. for C
H O : C, 75.76; H, 7.41. Found: C,
12 14 2
This compound was obtained as white needles, 2.1g (41%), mp
75.88; H, 7.51.
-1
1
58°; ir (KBr): 1770 cm (γ-lactone); H-nmr : δ 0.75 (t, 3H,
CH CH at C J = 6.8Hz), 1.6 (s,3H,CH at C ), 1.99 (q, 2H,
1H,4H-3,3,5,7-Tetramethyl-2-benzopyran -1-one (3d).
2
3
3,
3
3
CH CH at C J = 6.8Hz), 3.9 (s, 3H,OCH at C ), 6.8-7.5 (m,
This compound was obtained as white needles, 0.13g (40%),
mp 77°; ir (KBr): 1720 cm (δ-lactone); H-nmr: δ 1.44 (s, 6H,
2
3
3,
3
7
-1
1
3H, C C C -H).
4, 5,
6