Facial Selectivities of Diels-Alder Dienophiles
J . Org. Chem., Vol. 61, No. 9, 1996 3165
Diels-Ald er Rea ction of 1d w ith 1,3-Bu ta d ien e. Two
diastereomers were separated by flash column chromatogra-
phy (ethyl acetate:n-hexane 1:10).
En d o-a d d u ct (9a ): mp > 300 °C (colorless prisms, recrys-
tallized from n-hexane). Anal. Calcd for C23H16O3: C, 81.16;
H, 4.74. Found: C, 81.03; H, 4.61.
An ti-a d d u ct (5d ): mp 272.0-273.0 °C (colorless prisms,
recrystallized from ethyl acetate/n-hexane). Anal. Calcd for
C22H12O3F4: C, 66.01; H, 3.02. Found: C, 65.71; H, 2.74.
Syn -a d d u ct (6d ): mp 242.0-242.5 °C (colorless prisms,
recrystallized from ethyl acetate/n-hexane). Anal. Calcd for
C22H12O3F4: C, 66.01; H, 3.02. Found: C, 65.80; H, 2.96.
Diels-Ald er Rea ction of 1e w ith 1,3-Bu ta d ien e. Two
diastereomers were separated by flash column chromatogra-
phy (ethyl acetate:n-hexane 1:10).
Exo-a d d u ct (10a ): mp 241.0-242.5 °C (colorless rods,
recrystallized from ethyl acetate/n-hexane). Anal. Calcd for
C23H16O3: C, 81.16; H, 4.74. Found: C, 80.95; H, 4.62.
Diels-Ald er Rea ction of 1b w ith Cyclop en ta d ien e.
Four diastereomers were separated by HPLC (10% ethyl
acetate/n-hexane), and then preparative TLC (dichloromethane:
n-hexane 2:3).
An ti-en d o-a d d u ct (9b): mp 265.0-266.0 °C (colorless
plates, recrystallized from ethyl acetate/n-hexane). Anal.
Calcd for C24H18O4: C, 77.82; H, 4.90. Found: C, 77.95; H,
4.73.
An ti-a d d u ct (5e): mp 290.0 °C (colorless needles, recrystal-
lized from ethyl acetate/n-hexane). Anal. Calcd for C24H14
-
O3F6: C, 62.08; H, 3.04. Found: C, 61.98; H, 2.98.
An ti-exo-a d d u ct (10b ): mp 179.5-180.5 °C (colorless
prisms, recrystallized from ethyl acetate/n-hexane). Anal.
Calcd for C24H18O4: C, 77.82; H, 4.90. Found: C, 77.76; H,
4.94.
Syn -en d o-a d d u ct (11b): mp 244.5-245.5 °C (colorless
prisms, recrystallized from ethyl acetate/n-hexane). Anal.
Syn -a d d u ct (6e): mp 224.0-224.5 °C (colorless prisms,
recrystallized from ethyl acetate/n-hexane). Anal. Calcd for
C24H14O3F6: C, 62.08; H, 3.04. Found: C, 62.32; H, 2.83.
Diels-Ald er Rea ction of 1a w ith 2,3-Dim eth yl-1,3-
bu ta d ien e. A solution of 1a (28 mg, 0.10 mmol) in 3 mL of
dichloromethane was treated with 2,3-dimethyl-1,3-butadiene
(34 mg, 0.41 mmol, 4.1 equiv). The mixture was stirred at 23
°C for 15 h, and then 2,3-dimethyl-1,3-butadiene and dichlo-
romethane were removed at reduced pressure. The residue
was flash-chromatographed (dichloromethane) to give 36 mg
(100%) of 7a : mp 256.5 °C (colorless prisms, recrystallized
from ethyl acetate/n-hexane). Anal. Calcd for C24H20O3: C,
80.88; H, 5.66. Found: C, 80.75; H, 5.67.
Calcd for C24
4.82.
H18O4: C, 77.82; H, 4.90. Found: C, 77.65; H,
Syn -exo-addu ct (12b): mp 250.0-250.5 °C (colorless prisms,
recrystallized from ethyl acetate/n-hexane). Anal. Calcd for
C24H18O4: C, 77.82; H, 4.90. Found: C, 77.54; H, 4.85.
Diels-Ald er Rea ction of 1c w ith Cyclop en ta d ien e.
Four diastereomers were separated by HPLC (20% dichlo-
romethane/n-hexane).
Diels-Ald er Rea ction of 1b w ith 2,3-Dim eth yl-1,3-
bu ta d ien e. Two diastereomers were separated by preparative
TLC (dichloromethane:n-hexane 2:3).
An ti-en d o-a d d u ct (9c): mp 296.0-300.0 °C (colorless
prisms, recrystallized from ethyl acetate/n-hexane). Anal.
Calcd for C23H15NO5: C, 71.68; H, 3.92; N, 3.63. Found: C,
71.46; H, 3.85; N, 3.79.
An ti-exo-a d d u ct (10c): mp 210.0-211.0 °C (colorless
needles, recrystallized from ethyl acetate/n-hexane). Anal.
Calcd for C23H15NO5: C, 71.68; H, 3.92; N, 3.63. Found: C,
71.85; H, 3.82; N, 3.89.
An ti-a d d u ct (7b): mp 244.0-245.0 °C (colorless prisms,
recrystallized from ethyl acetate/n-hexane). Anal. Calcd for
C25H22O4: C,77.70; H, 5.74. Found: C, 77.47; H5.51.
Syn -a d d u ct (8b): mp 214.0-215.0 °C (colorless flakes,
recrystallized from n-hexane). HRMS (M+) Calcd for C25H22
-
O4: 386.1518, Found: 386.1526.
Syn -en d o-a d d u ct (11c): mp 279.5-281.5 °C (colorless rods,
recrystallized from ethyl acetate/n-hexane). Anal. Calcd for
C23H15NO5: C, 71.68; H, 3.92; N, 3.63. Found: C, 71.45; H,
3.79; N, 3.90.
Diels-Ald er Rea ction of 1c w ith 2,3-Dim eth yl-1,3-
bu ta d ien e. Two diastereomers were separated by preparative
TLC (dichloromethane:n-hexane 1:2).
An ti-a d d u ct (7c): mp 245.0-248.0 °C (colorless powder,
recrystallized from ethyl acetate/n-hexane). Anal. Calcd for
C24H19NO5: C, 71.81; H, 4.77; N, 3.49. Found: C, 71.65; H,
4.88; N, 3.76.
Syn -exo-addu ct (12c): mp 267.0-267.5 °C (colorless prisms,
recrystallized from ethyl acetate/n-hexane). Anal. Calcd for
C23H15NO5‚1/2H2O: C, 70.05; H, 4.09; N, 3.55. Found: C, 70.24;
H, 3.75; N, 3.90.
Syn -a d d u ct (8c): mp 243.0-245.0 °C (colorless prisms,
recrystallized from ethyl acetate/n-hexane). Anal. Calcd for
C24H19NO5: C, 71.81; H, 4.77; N, 3.49. Found: C, 71.68; H,
4.66; N, 3.74.
Diels-Ald er Rea ction of 1d w ith 2,3-Dim eth yl-1,3-
bu ta d ien e. Two diastereomers were separated by flash
column chromatography (ethyl acetate:n-hexane 1:20).
An ti-a d d u ct (7d ): mp 267.5-268.0 °C (colorless rods,
recrystallized from ethyl acetate/n-hexane). HRMS Calcd for
C24H16O3F4: 428.1036. Found: 428.1064.
Diels-Ald er Rea ction of 1d w ith Cyclop en ta d ien e.
Four diastereomers were separated by flash column chroma-
tography (ethyl acetate:n-hexane 1:10) and then HPLC (10%
chloroform/n-hexane for 9d and 10d , 2% ethyl acetate/n-
hexane for 11d and 12d ).
An ti-en d o-a d d u ct (9d ): mp > 300 °C. HRMS (M+) Calcd
for C23H12O3F4: 412.0723. Found: 412.0716.
An ti-exo-a d d u ct (10d ): mp 261.5-262.5 °C (colorless rods,
recrystallized from n-hexane). Anal. Calcd for C23H12O3F4:
C, 67.00; H, 2.93. Found: C, 66.92; H, 2.72.
Syn -a d d u ct (8d ): mp 230.5-231.0 °C (colorless prisms,
recrystallized from ethyl acetate/n-hexane). HRMS Calcd for
C24H16O3F4: 428.1036. Found: 428.1053.
Syn -en d o-a d d u ct (11d ): mp 281.5-283.0 °C (colorless rods,
recrystallized from n-hexane). Anal. Calcd for C23H12O3F4:
C, 67.00; H, 2.93. Found: C, 66.71; H, 2.71.
Syn -exo-a d d u ct (12d ): mp 254.5-255.0 °C (colorless rods,
recrystallized from n-hexane). Anal. Calcd for C23H12O3F4:
C, 67.00; H, 2.93. Found: C, 67.23; H, 2.94.
Diels-Ald er Rea ction of 1e w ith Cyclop en ta d ien e.
Four diastereomers were separated by HPLC (5% ethyl
acetate/n-hexane).
An ti-en d o-a d d u ct (9e): mp 239.5-240.5 °C (colorless rods,
recrystallized from ethyl acetate/n-hexane). Anal. Calcd for
C25H14O3F6: C, 63.03; H, 2.96. Found: C, 62.92; H, 2.85.
An ti-exo-a d d u ct (10e): mp 238.0-238.5 °C (colorless
needles, recrystallized from ethyl acetate/n-hexane). Anal.
Calcd for C25H14O3F6: C, 63.03; H, 2.96. Found: C, 62.83; H,
2.72.
Syn -en d o-a d d u ct (11e): mp > 300 °C (colorless prisms,
recrystallized from ethyl acetate/n-hexane). Anal. Calcd for
C25H14O3F6: C, 63.03; H, 2.96. Found: C, 62.75; H, 2.66.
Syn -exo-a d d u ct (12e): mp > 300 °C (colorless prisms,
recrystallized from ethyl acetate/n-hexane). Anal. Calcd for
C25H14O3F6: C, 63.03; H, 2.96. Found: C, 62.81; H, 2.74.
Diels-Ald er Rea ction of 1e w ith 2,3-Dim eth yl-1,3-
bu ta d ien e. Two diastereomers were separated by flash
column chromatography (ethyl acetate:n-hexane 2:25).
An ti-a d d u ct (7e): mp 278.5-279.5 °C (colorless prisms,
recrystallized from ethyl acetate/n-hexane). Anal. Calcd for
C26H18O3F6: C, 63.42; H, 3.68. Found: C, 63.25; H, 3.31.
Syn -a d d u ct (8e): mp 246.0-246.5 °C (colorless prisms,
recrystallized from ethyl acetate/n-hexane). Anal. Calcd for
C26H18O3F6: C, 63.42; H, 3.68. Found: C, 63.51; H, 3.59.
Diels-Ald er R ea ct ion of 1a w it h Cyclop en t a d ien e.
Freshly distilled cyclopentadiene (222 mg, 3.36 mmol, 34
equiv) was added to a solution of 1a (27 mg, 0.099 mmol) in 3
mL of dichloromethane. The mixture was stirred at 23 °C for
15 h, and then cyclopentadiene and dichloromethane was
removed under reduced pressure. The residue was flash-
chromatographed (n-hexane, followed by dichloromethane) to
give 21 mg (63%) of a mixture of the endo-adduct 9a and the
exo-adduct 10a , which was separated by flash column chro-
matography (ethyl acetate:n-hexane 1:20).