Notes
J . Org. Chem., Vol. 64, No. 23, 1999 8739
cooling to room temperature. If necessary, 1H NMR analysis was
also useful to determine the extent of desired elimination and
decomposition promoted by the acid. The reaction duration
usually falls in the range of 8-36 h. If severe precipitation or
gummy residue occurs, the final yield would likely be low. After
cooling to room temperature, the mixture was first filtered
through a small bed of silica gel using 25% EtOAc in hexane as
the eluting solvent. The solvent was concentrated under reduced
pressure, and the residue was purified by flash silica gel column
chromatography27 (gradient solvent system, 0-25% EtOAc in
hexane) to provide the desired pyrones.
Ch a r a cter iza tion s of O-Meth yl Oxim es 10-18 a n d 30.
6-Isop r op yl-4-oxo-4H-1-ben zop yr a n -3-ca r boxa ld eh yd e 3-O-
m eth yl oxim e (10): Rf ) 0.46 (25% EtOAc in hexane); 1H NMR
(300 MHz, CDCl3) syn δ 1.29 (d, 6 H, J ) 6.9 Hz), 3.03 (septet,
1 H, J ) 6.9 Hz), 4.05 (s, 3 H), 7.40 (dd, 1 H, J ) 2.4, 8.7 Hz),
7.57 (dd, 1 H, J ) 1.8, 8.7 Hz), 7.82 (s, 1 H), 8.08 (d, 1 H, J ) 2.1
Hz), 9.36 (s, 1 H); anti δ 1.29 (d, 6 H, J ) 6.9 Hz), 3.03 (septet,
1 H, J ) 6.9 Hz), 3.94 (t, 3 H, J ) 0.9 Hz), 7.57 (dd, 1 H, J )
1.8, 8.7 Hz), 8.08 (d, 1 H, J ) 2.1 Hz), 8.38 (d, 1 H, J ) 0.9 Hz);
13C NMR (75 MHz, CDCl3) δ 23.9, 33.8, 62.1, 62.8, 117.0, 118.2,
122.8, 123.0, 123.8, 133.0, 133.2, 136.9, 141.4, 146.8, 152.8, 160.2,
175.7, (missing 11 signals because of overlap); IR (neat) cm-1
2962m, 1652s, 1619m; MS (EI) m/e (% relative intensity) 245
(7) M+, 215 (19), 216 (100). Anal. Calcd for C14H15NO3: C 68.56,
H 6.16, N 5.71. Found: C 68.70, H 6.28, N 5.64.
M+, 191 (16), 192 (100). Anal. Calcd for C11H8FNO3: C 59.73, H
3.65, N 6.33. Found: C 59.60, H 3.75, N 6.08.
6-Ch lor o-7-m et h yl-4-oxo-4H -1-b en zop yr a n -3-ca r b oxa l-
d eh yd e 3-O-m eth yl oxim e (15): Rf ) 0.44 (25% EtOAc in
hexane); mp 150-153 °C; 1H NMR (300 MHz, CDCl3) syn δ 2.49
(s, 3 H), 4.05 (s, 3 H), 7.35 (s, 1 H), 7.76 (s, 1 H), 8.36 (s, 1 H),
9.32 (s, 1 H); anti δ 2.49 (s, 3 H), 3.95 (s, 3 H), 7.36 (s, 1 H), 8.15
(s, 1 H), 8.25 (s, 1 H), 8.36 (s, 1 H); 13C NMR (75 MHz, CDCl3)
δ 21.0, 62.3, 63.1, 115.5, 117.3, 120.3, 123.1, 123.2, 125.8, 126.0,
132.6, 132.7, 136.5, 141.0, 143.6, 143.9, 152.9, 154.1, 154.6, 160.3,
174.4 (missing three signals because of overlap); IR (neat) cm-1
3070w, 1649s, 1620m; MS (EI) m/e (% relative intensity) 251
(5) M+, 222 (34), 221 (19), 220 (100). Anal. Calcd for C12H10
-
ClNO3: C 57.27, H 4.01, N 5.57. Found: C 57.43, H 4.14, N 5.55.
6,8-Dim e t h yl-4-oxo-4H -1-b e n zop yr a n -3-c a r b oxa ld e -
h yd e 3-O-m eth yl oxim e (16): Rf ) 0.41 (25% EtOAc in hexane);
mp 103-106 °C; 1H NMR (300 MHz, CDCl3) syn δ 2.37 (s, 3 H),
2.40 (s, 3 H), 4.02 (s, 3 H), 7.29 (s, 1 H), 7.76 (s, 1 H), 8.38 (s, 1
H), 9.34 (s, 1 H); anti δ 2.37 (s, 3 H), 2.40 (s, 3 H), 3.92 (s, 3 H),
7.29 (s, 1 H) 7.79 (s, 1 H), 8.25 (s, 1 H), 8.38 (s, 1 H); 13C NMR
(75 MHz, CDCl3) δ 15.4, 15.5, 21.0, 62.2, 62.9, 115.2, 116.8, 123.0,
123.2, 123.7, 123.8, 127.6, 135.2, 135.3, 136.4, 136.6, 137.1, 141.6,
152.6, 153.2, 153.2, 160.0, 175.8 (missing three signals because
of overlap); IR (neat) cm-1 3064w, 2971w, 1650s, 1620m; MS
(EI) m/e (% relative intensity) 231 (7) M+, 201 (17), 200 (100).
Anal. Calcd for C13H13NO3: C 67.52, H 5.67, N 6.06. Found: C
67.50, H 5.78, N 5.95.
4-Oxo-4H-1-ben zop yr a n -3-ca r boxa ld eh yd e 3-O-m eth yl
oxim e (11): Rf ) 0.36 (25% EtOAc in hexane); mp 75-77 °C;
1H NMR (300 MHz, CDCl3) syn δ 4.05 (s, 3 H), 7.40-7.49 (m, 2
H), 7.67-7.72 (m, 1 H) 7.80 (s, 1 H),8.24 (m, 1 H), 9.37 (s, 1 H);
anti δ 3.95 (s, 3 H), 7.40-7.49 (m, 2 H), 7.67-7.72 (m, 1 H),
8.24 (m, 1 H), 8.29 (s, 1 H), 8.41 (s, 1 H); 13C NMR (75 MHz,
CDCl3) δ 62.1, 62.9, 115.5, 117.2, 118.3, 124.0, 125.7, 126.0,
126.2, 134.0, 134.2, 136.7, 141.09, 141.13, 152.9, 155.7, 156.2,
160.2, 160.3, 175.4, (missing two signals because overlap); IR
(neat) cm-1 2941w, 1661s, 1622m; MS (EI) m/e (% relative
intensity) 203 (7) M+, 173 (16), 172 (100). Anal. Calcd for C11H9-
NO3: C 65.02, H 4.46, N 6.89. Found: C 65.11, H 4.60, N 6.86.
6-Ch lor o-4-oxo-4H-1-ben zop yr a n -3-ca r boxa ld eh yd e 3-O-
m eth yl oxim e (12): Rf ) 0.43 (25% EtOAc in hexane); mp 97-
100 °C; 1H NMR (300 MHz, CDCl3) syn δ 4.05 (s, 3 H), 7.44 (dd,
1 H, J ) 2.1, 9.0 Hz), 7.64 (dd, 1 H, J ) 2.4, 9.9 Hz), 7.77 (s, 1
H), 8.20 (d, 1 H, J ) 2.4 Hz), 9.37 (s, 1 H); anti δ 3.95 (s, 3 H),
7.44 (dd, 1 H, J ) 2.1, 9.0 Hz), 7.63 (dd, 1 H, J ) 2.4, 9.0 Hz),
8.20 (d, 1 H, J ) 2.4 Hz), 8.26 (s, 1 H), 8.41 (s, 1 H); 13C NMR
(75 MHz, CDCl3) δ 62.2, 63.0, 115.5, 117.4, 120.0, 120.1, 124.9,
125.4, 125.7, 131.8, 134.3, 134.5, 136.3, 136.2, 140.7, 152.9, 154.0,
154.5, 160.2, 160.3, 174.2 (missing one signal because overlap);
IR (neat) cm-1 2937w, 1651s, 1616m; MS (EI) m/e (% relative
intensity) 237 (6) M+, 208 (32), 207 (100). Anal. Calcd for C11H8-
ClNO3: C 55.60, H 3.39, N 5.89. Found: C 55.31, H 3.60, N 5.83.
6,8-D ib r o m o -4-o x o -4H -1-b e n zo p y r a n -3-c a r b o x a ld e -
h yd e 3-O-m eth yl oxim e (17): Rf ) 0.53 (25% EtOAc in hexane);
mp 148-150 °C; 1H NMR (300 MHz, CDCl3) syn δ 4.07 (s, 3 H),
8.03 (d, 1 H, J ) 2.4 Hz), 8.30 (d, 1 H, J ) 2.4 Hz), 8.48 (s, 1 H),
9.46 (s, 1 H); anti δ 3.96 (s, 3 H), 8.03 (d, 1 H, J ) 2.4 Hz), 8.22
(s, 1 H), 8.30 (d, 1 H, J ) 2.4 Hz), 8.48 (s, 1 H); 13C NMR (75
MHz, CDCl3) δ 62.5, 63.3, 113.30, 113.33, 115.8, 117.9, 119.2,
119.3, 126.2, 126.3, 128.2, 128.5, 135.9, 140.0, 140.1, 140.3, 153.0,
160.3, 173.8 (missing three signals because of overlap); IR (neat)
cm-1 3070w, 2940w, 1659s, 1614w; MS (EI) m/e (% relative
intensity) 363 (5), 361 (11), 359 (5) M+, 332 (49), 331 (20), 330
(100). Anal. Calcd for C11H7Br2NO3: C 36.60, H 1.95, N 3.88.
Found: C 36.73, H 1.86, N 3.88.
6,8-D ic h lo r o -4-o x o -4H -1-b e n zo p y r a n -3-c a r b o x a ld e -
h yd e 3-O-m eth yl oxim e (18): Rf ) 0.56 (25% EtOAc in hexane);
mp 146-149 °C; 1H NMR (300 MHz, CDCl3) syn δ 4.05 (s, 3 H),
7.70 (d, 1 H, J ) 2.4 Hz), 8.06 (d, 1 H, J ) 2.4 Hz), 8.45 (s, 1 H),
9.42 (s, 1 H); anti δ 3.94 (s, 3 H), 7.71 (d, 1 H, J ) 2.4 Hz), 8.06
(d, 1 H, J ) 2.4 Hz), 8.19 (s, 1 H), 8.45 (s, 1 H); 13C NMR (75
MHz, CDCl3) δ 62.5, 63.2, 115.8, 117.9, 124.3, 124.8, 125.8, 125.9,
131.5, 131.6, 134.3, 134.5, 135.8, 140.3, 150.7, 152.9, 160.1, 173.8,
173.9 (missing three signals because of overlap); IR (neat) cm-1
3073w, 2946w, 1665s; MS (EI) m/e (% relative intensity) 271 (6)
M+, 242 (65), 240 (100). Anal. Calcd for C11H7Cl2NO3: C 48.56,
H 2.59, N 5.15. Found: C 48.35, H 2.66, N 5.02.
6-Meth oxy-4-oxo-4H-1-ben zopyr an -3-car boxaldeh yde 3-O-
m eth yl oxim e (13): Rf ) 0.33 (25% EtOAc in hexane); mp 119-
1-Oxo-1H-n a p h t h o[2,1-b]p yr a n -2-ca r b oxa ld eh yd e (29).
The aldehyde 29 was prepared according to literature procedures:
15b Rf ) 0.51 (5% Et2O in CH2Cl2); mp 188-190 °C; lit. mp 192-
1
121 °C; H NMR (300 MHz, CDCl3) syn δ 3.94 (d, 3 H, J ) 2.7
1
Hz), 4.04 (s, 3 H), 7.27 (dd, 1 H, J ) 3.0, 8.9 Hz), 7.41 (d, 1 H,
J ) 9.3 Hz), 7.60 (d, 1 H, J ) 3.0 Hz), 7.82 (s, 1 H), 9.35 (s, 1 H);
anti δ 3.90 (s, 3 H), 3.94 (d, 3 H, J ) 2.7 Hz), 7.27 (dd, 1 H, J )
3.0, 9.0 Hz), 7.42 (d, 1 H, J ) 9.0 Hz), 7.59 (d, 1 H, J ) 3.0 Hz),
8.31 (s, 1 H), 8.40 (s, 1 H); 13C NMR (75 MHz, CDCl3) δ 56.0,
62.1, 62.8, 105.1, 105.2, 105.3, 105.4, 114.8, 116.5, 119.7, 124.1,
124.7, 136.9. 137.0, 141.3, 141.4, 151.1, 152.7, 157.4, 159.9, 160.0,
175.3 (missing two signals because of overlap); IR (neat) cm-1
3085w, 2940w, 1651s, 1615m; MS (EI) m/e (% relative intensity)
233 (12) M+, 202 (100). Anal. Calcd for C12H11NO4: C 61.80, H
4.75, N 6.01. Found: C 62.00, H 4.87, N 6.11.
194 °C; H NMR (300 MHz, CDCl3) δ 7.56 (d, 1 H, J ) 9.0 Hz),
7.65-7.71 (m, 1 H), 7.78-7.84 (m, 1 H), 7.95 (dd, 1 H, J ) 1.3,
8.1 Hz), 8.16 (d, 1 H, J ) 9.0 Hz), 8.56 (s, 1 H), 10.00 (dd, 1 H,
J ) 0.6, 8.6 Hz), 10.51 (s, 1 H); 13C NMR (75 MHz, CDCl3) δ
117.3, 118.9, 122.2, 126.9, 127.4, 128.4, 129.8, 130.3, 131.0, 136.6,
157.5, 158.1, 177.7, 189.3; IR (neat) cm-1 2853w, 1697m, 1651s;
MS (EI) m/e (% relative intensity) 224 (14) M+, 196 (100). Anal.
Calcd for C14H8O3: C 75.00, H 3.60. Found: C 75.19, H 3.71.
Chemical Abstracts Registry Number: 23469-50-3 (supplied by
author).
1-Oxo-1H-n a p h th o[2,1-b]p yr a n -2-ca r boxa ld eh yd e 3-O-
m eth yl oxim e (30). Rf ) 0.62 (5% Et2O in CH2Cl2); mp 102-
6-F lu or o-4-oxo-4H-1-ben zop yr a n -3-ca r boxa ld eh yd e 3-O-
m eth yl oxim e (14): Rf ) 0.38 (25% EtOAc in hexane); mp 144-
147 °C; 1H NMR (300 MHz, CDCl3) syn δ 4.05 (s, 3 H), 7.38-
7.53 (m, 2 H), 7.88 (dd, 1 H, J ) 2.4, 8.1 Hz), 7.78 (s, 1 H), 9.39
(s, 1 H); anti δ 3.95 (s, 3 H), 7.38-7.53 (m, 2 H), 7.88 (dd, 1 H,
J ) 2.7, 8.1 Hz), 8.27 (d, 1 H, J -) 0.6 Hz), 8.42 (d, 1 H, J ) 0.3
Hz); 13C NMR (75 MHz, CDCl3) δ 62.2, 63.0, 110.9 (d, J ) 24.2
Hz), 111.0 (d, J ) 23.6 Hz), 114.9, 116.7, 120.6, 122.4, 125.2,
136.4, 136.3, 140.8, 140.8, 153.0, 158.2, 160.4, 161.5 (d, J ) 247.7
Hz), 174.7 (missing four signals because of overlap); IR (neat)
cm-1 2940w, 1652s; MS (EI) m/e (% relative intensity) 221 (7)
1
105 °C; H NMR (300 MHz, CDCl3) δ syn 3.95 (s, 3 H), 7.08 (d,
1 H, J ) 9.0 Hz), 7.42-7.36 (m, 1 H), 7.56-7.50 (m, 1 H), 7.59
(d, 1 H, J ) 8.0 Hz), 7.71 (d, 1 H, J ) 8.9 Hz), 7.73 (s, 1 H), 9.00
(s, 1 H), 9.68 (d, 1 H, J ) 8.6 Hz); anti 3.88 (s, 3 H), 7.10 (d, 1
H, J ) 9.1 Hz), 7.42-7.36 (m, 1 H), 7.56-7.50 (m, 1 H), 7.59 (d,
1 H, J ) 8.0 Hz), 7.71 (d, 1 H, J ) 8.9 Hz), 8.10 (s, 1 H), 8.19 (s,
1 H), 9.73 (d, 1 H, J ) 8.6 Hz); 13C NMR (75 MHz, CDCl3) δ
62.0, 62.7, 117.1, 117.5, 119.5, 126.8, 128.3, 128.4, 129.3, 129.4,
130.3, 130.7, 135.7, 135.9, 136.8, 141.4, 150.4, 156.9, 157.5, 157.8,
176.6, 176.7 (missing eight signals because of overlap); IR (neat)