Notes
J . Org. Chem., Vol. 61, No. 10, 1996 3569
the resulting precipitate was removed by filtration. The filtrate
was concentrated and the residue column chromatographed on
silica gel (eluent: hexane/CH2Cl2, 1/1, then neat CH2Cl2) to give
the title thiolester (907 mg, 58%) as a colorless oil and unreacted
10 (390 mg, 30%). 9: 1H-NMR δ 1.57 (s, 6 H), 2.28 (s, 3 H),
3.75 (s, 2 H), 6.87 (dt, J ) 1.8, 7.4 Hz, 1 H), 7.30 (dt, J ) 1.3, 7.5
Hz, 1H), 7.36 (dd, J ) 1.9, 8.0 Hz, 1 H), 8.00 (dd, J ) 1.3, 7.8
Hz, 1 H); 13C-NMR δ 27.8, 30.5, 38.7, 40.2, 94.6, 127.9, 128.2,
128.7, 143.7, 146.6, 195.5; IR (CDCl3, cm-1) 1688. Anal. Calcd
for C12H15IOS: C, 43.13; H, 4.52. Found: C, 43.27; H, 4.61.
2-(2-Iod op h en yl)-2-m eth ylp r op a n eth iol (10). To a solu-
tion of 9 (710 mg, 2.13 mmol) in Et2O (20 mL) cooled to -78 °C
under N2 was added dropwise DIBALH (5.3 mL, 1 M in CH2-
Cl2). After the addition was complete, the reaction mixture was
slowly warmed to 0 °C over 0.5 h and then quenched with dilute
aqueous HCl (3 M, 10 mL). The organic layer was separated,
washed with water and brine, and dried (Na2SO4). Removal of
solvent followed by column chromatography on silica gel (elu-
ent: hexane/CH2Cl2, 9/1) gave 10 (587 mg, 94%) as a colorless
oil: 1H-NMR δ 0.95 (t, J ) 8.8 Hz, 1 H), 1.59 (s, 6 H), 3.27 (d, J
) 8.8 Hz, 2 H), 6.87 (dt, J ) 1.8, 7.4 Hz, 1 H), 7.32 (dt, J ) 1.3,
7.5 Hz, 1 H), 7.40 (dd, J ) 1.8, 8.0 Hz, 1 H), 8.01 (dd, J ) 1.3,
7.8 Hz, 1 H); 13C-NMR δ 27.7, 34.5, 41.6, 94.4, 128.0, 128.2,
129.6, 143.6, 146.3. Anal. Calcd for C10H13IS: C, 41.11; H, 4.48.
Found: C, 41.22; H, 4.46.
P r ep a r a tion of Th iolester s 11-14, 17 a n d 23. Gen er a l
P r oced u r e via Acyl Ch lor id es. A solution of the appropriate
carboxylic acid (1.0 mmol) in benzene (10 mL) was treated at
room temperature with oxalyl chloride (0.87 mL, 10 mmol) and
a small drop of DMF. After 0.5 h, the solvent and excess reagent
were removed in vacuo and the crude acid chloride was taken
up with CH2Cl2 (15 mL). DMAP (159 mg, 1.3 mmol) was then
added followed by the appropriate thiol (4 or 10). The resulting
mixture was stirred at room temperature until the reaction was
complete (0.5 to 16 h). Hexane (15 mL) was then added, and
the precipitates were removed by filtration. The filtrate was
concentrated to dryness and the product purified by column
chromatography on silica gel.
S-2-(2-Iod op h en yl)eth yl 2-(Allyloxy)th ioben zoa te (11).
11 was prepared from 2-allyloxybenzoic acid (178 mg, 1.0 mmol)
and thiol 4 according to the general procedure. Column chro-
matography on silica gel (eluent: CH2Cl2/hexane, 1/2) gave 11
(400 mg, 94%) as a colorless oil: 1H-NMR δ 3.06 -3.29 (m, 4
H), 4.67 (dt, J ) 5.1, 1.5 Hz, 2 H), 5.31 (dquart, J ) 10.5, 1.4
Hz, 1 H), 5.49 (dquart, J ) 17.3, 1.5 Hz, 1 H), 6.04 -6.16 (m, 1
H), 6.89-7.03 (m, 3 H), 7.27 -7.41 (m, 3 H), 7.78 -7.83 (m, 2
H); 13C-NMR δ 29.5, 40.4, 69.9, 100.4, 113.4, 118.0, 120.6, 127.3,
128.3, 128.4, 129.7, 130.1, 132.6, 133.4, 139.5, 142.9, 156.8, 190.7;
IR (CDCl3, cm-1) 1672. Anal. Calcd for C18H17IO2S: C, 50.95;
H, 4.04. Found: C, 50.97; H, 4.00.
S-2-(2-Iod op h en yl)-2-m eth ylp r op yl 2-(Allyloxy)th ioben -
zoa te (12). 12 was prepared from 2-(allyloxy)benzoic acid (178
mg, 1.0 mmol) and thiol 10 according to the general procedure.
Column chromatography on silica gel (eluent: CH2Cl2/hexane,
1/2) gave 12 (430 mg, 95%) as a colorless oil: 1H-NMR δ 1.64 (s,
6 H), 3.91 (s, 2 H), 4.58 (dt, J ) 5.0, 1.6 Hz, 2 H), 5.23 (ddt, J )
10.7, 1.5, 1.5 Hz, 1 H), 5.41 (ddt, J ) 17.3, 1.5, 1.8 Hz, 1 H),
5.98 (m, 1 H), 6.83 -6.97 (m, 3 H), 7.29 -7.42 (m, 3 H), 7.66
(dd, J ) 1.7, 7.7 Hz, 1 H), 8.01 (dd, J ) 1.4, 7.8 Hz, 1H): 13C-
NMR δ 28.0, 38.9, 40.5, 69.6, 94.8, 113.3, 117.6, 120.5, 127.8,
128.1, 128.9, 129.5, 132.5, 133.0, 143.7, 146.9, 156.3, 191.1.
Anal. Calcd for C20H21IO2S: C, 53.10; H, 4.68. Found: C, 53.13;
H, 4.71.
25.6, 27.1, 27.9, 28.0, 30.6, 32.3, 32.9, 33.8, 34.1, 36.7, 37.7, 38.0,
39.4, 40.5, 40.6, 41.3, 41.5, 46.2, 47.6, 47.8, 54.3, 94.8, 122.8,
127.7, 128.0, 128.9, 143.2, 143.7, 147.0, 170.7, 171.0, 206.2.
Anal. Calcd for C44H63IO5S: C, 63.60; H, 7.64. Found: C, 63.48;
H, 7.65.
S-2-(2-Iod op h en yl)-2-m eth ylp r op yl 2-Allylth ioben zoa te
(13). 13 was prepared from 2-allylbenzoic acid2c (97.5 mg, 0.6
mmol) and thiol 10 according to the general procedure. Column
chromatography on silica gel (eluent: CH2Cl2/hexane, 1/4) gave
13 (254 mg, 97%) as a colorless oil: 1H-NMR δ 1.65 (s, 6 H),
3.54 (d, J ) 6.5 Hz, 2 H), 3.91 (s, 2 H), 4.97-5.04 (m, 2 H), 5.87-
6.00 (m, 1 H), 6.86 (dt, J ) 1.7, 7.5 Hz, 1 H), 7.18-7.41 (m, 5
H), 7.62 (d, J ) 7.8 Hz, 1 H), 8.01 (dd, J ) 1.3, 7.8 Hz, 1 H);
13C-NMR δ 28.0, 37.4, 39.3, 40.53, 94.7, 115.9, 126.0, 127.9,
128.2, 128.3, 128.8, 130.5, 131.4, 136.8, 137.9, 138.0, 143.7, 146.6,
194.2; IR (CDCl3, cm-1) 1665. Anal. Calcd for C20H21IOS: C,
55.05; H, 4.85. Found: C, 55.30; H, 4.76.
S-2-(2-Iod op h en yl)eth yl [((E)-3-P h en ylp r op -2-en yl)oxy]-
th ioa ceta te (15): DCC/DMAP Meth od . A mixture of (cin-
namyloxy)acetic acid20 (135 mg, 0.70 mmol), DMAP (17 mg, 0.14
mmol), and DCC (173 mg, 0.84 mmol) in DCM (10 mL) was
stirred at room temperature for 5 min before thiol 4 (222 mg,
0.84 mmol) was added. After stirring at room temperature
overnight the reaction mixture was concentrated to dryness.
Column chromatography of the residue on silica gel (eluent:
CH2Cl2/hexane, 1/1) gave 15 (289 mg, 94%) as a colorless oil:
1H-NMR δ 2.98-3.18 (m, 4 H), 4.20 (s, 2 H), 4.29 (dd, J ) 6.2,
1.3 Hz, 2 H), 6.30 (dt, J ) 15.9, 6.2 Hz, 1 H), 6.86 (d, J ) 15.9
Hz, 1 H), 6.92 (m, 1 H), 7.24-7.43 (m, 7 H), 7.82 (d, J ) 7.7 Hz,
1 H); 13C-NMR δ 27.8, 40.3, 72.6, 74.6, 100.3, 124.5, 126.5, 127.9,
128.3, 128.5, 129.9, 133.7, 136.2, 139.5, 142.4, 199.8; IR (CDCl3,
cm-1) 1681. Anal. Calcd for C19H19IO2S: C, 52.06; H, 4.37.
Found: C, 51.88; H, 4.29.
S-2-P h en yleth yl 2-(Allyloxy)th ioben zoa te (17): Au th en -
tic Sa m p le. 17 was prepared from O-allylsalicylic acid (35.6
mg, 0.20 mmol) and 2-phenylethanethiol (35 mg, 0.25 mmol)
according to the general procedure except that Et3N (35 µL, 0.25
mmol) was used as the base. Column chromatography on silica
gel (eluent: CH2Cl2/hexane, 1/1) gave 17 (58 mg, 97%) as a
colorless oil: 1H-NMR δ 2.95-3.00 (m, 2 H), 3.25-3.30 (m, 2
H), 4.67 (dt, J ) 5.1, 1.6 Hz, 2 H), 5.31 (dq, J ) 10.6, 1.4 Hz, 1
H), 5.49 (dq, J ) 17.3, 1.6 Hz, 1 H), 6.03-6.16 (m, 1 H), 6.95-
7.03 (m, 2 H), 7.21-7.49 (m, 6 H), 7.79 (dd J ) 7.7, 1.7 Hz, 1 H);
13C-NMR δ 30.9, 35.7, 69.6, 113.3, 117.9, 120.5, 126.3, 127.4,
128.4, 128.6, 129.7, 132.5, 133.3, 140.3, 158.7, 190.8; IR (CDCl3,
cm-1) 1666. Anal. Calcd for C18H18O2S: C, 72.45; H, 6.08.
Found: C, 72.44; H, 6.18.
S-2-P h en yleth yl [((E)-3-P h en ylp r op -2-en yl)oxy]th ioa ce-
ta te (23): Au th en tic Sa m p le. 23 was prepared from (cin-
namyloxy)acetic acid (38.6 mg, 0.20 mmol) in exactly the same
way as for the preparation of 17. Column chromatography on
silica gel (eluent: CH2Cl2/hexane, 1/1, then neat CH2Cl2) gave
23 (58 mg, 93%) as a colorless oil: 1H-NMR δ 2.87-2.92 (m, 2
H), 3.14-3.20 (m, 2 H), 4.19 (s, 2 H), 4.28 (dd, J ) 6.2, 1.1 Hz,
2 H), 6.30 (dt, J ) 15.9, 6.2 Hz, 1 H), 6.65 (d, J ) 15.9 Hz, 1 H),
7.21-7.42 (m, 10 H); 13C-NMR δ 29.2, 35.9, 72.6, 74.6, 124.5,
126.47, 126.53, 127.9, 128.4, 128.5 (2 × C), 133.7, 136.2, 139.9,
199.8; IR (CDCl3, cm-1) 1681. Anal. Calcd for C19H20O2S: C,
73.04; H, 6.45. Found: C, 73.04; H, 6.56.
Rea ction of 11 w ith Bu 3Sn H a n d TMS3SiH: Gen er a l
P r oced u r es for th e Gen er a tion of Acyl Ra d ica ls fr om
Th ioester s. A solution 11 (20 mg, 0.047 mmol), Bu3SnH (18
mg, 1.3 equiv), and AIBN (1 mg, 10%) in degassed benzene (2.0
mL) was heated to reflux under Ar for 1 h. After the mixture
was cooled to room temperature, the solvent was removed in
Hed er a gen in Dia ceta te 2-(2-Iod op h en yl)-2-m eth ylp r o-
p a n eth iol Ester (14). 14 was prepared from hederagenin
diacetate (128 mg, 0.23 mmol) and thiol 10 (73 mg, 0.25 mmol)
according to the general procedure. Column chromatography
on silica gel (eluent: EtOAc/hexane, 1/3) gave 14 (138 mg, 72%)
as a crystalline solid and the starting acid (30 mg, 23%). 14:
mp 102 -103 °C (CH2Cl2); [R]D ) +24° (c 1.8, CHCl3); 1H-NMR
δ 0.71 (s, 3 H), 0.83 (s, 3 H), 0.88 (s, 3 H), 0.89 (s, 3 H), 0.97 (s,
3 H), 1.09 (s, 3 H), 1.54 (s, 3 H), 1.56 (s, 3 H), 0.80-2.05 (m, 22
H), 2.02 (s, 3 H), 2.06 (s, 3 H), 2.88 (dd, J ) 3.7, 13.2 Hz, 1 H),
3.62 (d, J ) 13.5 Hz, 1 H), 3.68 (d, J ) 13.5 Hz, 1 H), 3.69 (d, J
) 11.7 Hz, 1 H), 3.88 (d, J ) 11.6 Hz, 1 H), 4.78 (dd, J ) 5.2,
11.1 Hz, 1 H), 5.24 (t, J ) 3.3 Hz, 1 H), 6.84 (dt, J ) 1.8, 7.6 Hz,
1 H), 7.24-7.35 (m, 2 H), 7.98 (dd, J ) 1.3, 7.8 Hz, 1 H); 13C-
NMR δ 13.1, 15.9, 17.4, 17.9, 20.9, 21.2, 22.9, 23.4, 23.6 (2 × C),
1
vacuo. Examination of the crude reaction mixture by H-NMR
spectroscopy revealed complete consumption of 11 with the
formation of the cyclized product 16, the simple reduction
product 17, and dihydrobenzothiophene (24) in a ratio of 16:17:
24 ) 96:4:94. Replacement of Bu3SnH with TMS3SiH (15 mg,
1.3 equiv) under the same conditions gave 16 and 24 both
1
quantitatively as determined from the H-NMR spectrum of the
crude reaction mixture.
Rea ction of 12 w ith Bu 3Sn H. 12 (45 mg, 0.10 mmol) was
treated with Bu3SnH under the standard conditions to give a
(20) Oh, T.; Wrobel, Z.; Rubenstein, S. M. Tetrahedron Lett. 1991,
32, 4647.