1230 J . Org. Chem., Vol. 64, No. 4, 1999
Newcomb et al.
(3H, m), 1.71 (1H, m), 2.14 (2H, q, J ) 7.2 Hz), 2.44 (1H, m),
6.08 (1H, t, J ) 7.5 Hz), 7.16-7.41 (10H, m) 11.5-11.9 (1H,
bs). 13C NMR (CDCl3): δ 16.8, 27.4, 29.5, 33.0, 39.2, 126.8,
126.9, 127.2, 128.0, 128.1, 129.3, 129.8, 140.1, 142.0, 142.7,
183.2. MS: m/z (rel intens), 91 (45.8), 115 (68.3), 165 (20.3),
167 (25.5), 178 (22.5), 193 (100.0), 294 (30.4). ΗRMS: calcd
for C20H22O2, 294.1619; found, 294.1618.
opening due to a systematic error in the latter values.
The new values for reactions of PhSeH with primary
alkyl radicals suggest that previous radical rate constants
at ambient temperature determined by competition
against PhSeH trapping should be reduced by about 35%.
7,7-Dip h en yl-2-m eth yl-6-h ep ten oic a cid 2-th ioxo-2H-
p yr id in -1-yl ester (3b) was prepared from 1.0 g (3.4 mmol)
of the above acid by the general method. Column chromatog-
raphy (hexanes:EtOAc; 6:4) on silica gel gave 1.1 g of PTOC
Exp er im en ta l Section
Gen er a l Meth od s. Commercially available reagents were
purchased from Aldrich Chemical Co. unless otherwise noted.
All moisture-sensitive reactions were performed in a flame-
dried glassware under an atmosphere of nitrogen. Tetrahy-
drofuran (THF) and ether were freshly distilled from sodium
benzophenone ketyl under nitrogen immediately before use.
Methylene chloride was distilled under a nitrogen atmosphere
from phosphorus pentoxide. Benzene was distilled over calcium
hydride under nitrogen. Dimethyl formamide (DMF) was
distilled from calcium hydride. N-Hydroxypyridine-2-thione
sodium salt was prepared as described previously.34
1
ester 3b (2.73 mmol, 80%). H NMR (CDCl3): δ 1.38 (3Η, d, J
) 6.9 Hz), 1.50-1.66 (3H, m), 1.91 (1H, m), 2.17 (2H, q, J )
7.2 Hz), 2.82 (1H, m), 6.09 (1H, t, J ) 7.2 Hz), 6.60 (1H, dt, J
) 1.8, 6.9 Hz), 7.16-7.41 (11H, m), 7.46 (1H, dt, J ) 1.5, 6.9
Hz), 7.69 (1H, dt, J ) 1.8, 9.0 Hz). 13C NMR (CDCl3): δ 16.8,
27.3, 29.4, 32.8, 37.4, 112.4, 126.8, 126.9, 127.2, 128.0, 128.2,
129.0, 129.8, 133.3, 137.5, 137.6, 140.0, 142.2, 142.5, 171.9,
175.9.
7,7-Dip h en yl-2,2-d im eth yl-6-h ep ten oic a cid was pre-
pared by the reaction of 5-bromo-1,1-diphenyl-1-pentene with
the enolate prepared by reaction of isobutyric acid and LDA.
To a flame-dried flask under nitrogen equipped with a stir bar
was added 2.16 g (21.3 mmol, 2.2 equiv) of freshly distilled
diisopropylamine and 20 mL of anhydrous THF. The solution
was cooled to 0 °C, and 21.3 mmol of n-BuLi (8.54 mL of a 2.5
M solution in hexanes) was added via syringe. The resulting
solution was stirred at 0 °C for 0.5 h and then cooled to -78
°C. A solution of 0.854 g (9.7 mmol) of isobutyric acid in 5 mL
of THF was slowly added to the reaction flask by cannula.
After allowing the reaction to warm to 20 °C for 0.5 h followed
by the addition of DMPU (5 mL), the reaction mixture was
cooled to -50 °C. A solution of 2.9 g (9.7 mmol) of 5-bromo-
1,1-diphenyl-1-pentene in 5 mL of THF was added to the flask
by cannula. The reaction was allowed to warm to room
temperature and to stand overnight. The mixture was dis-
solved in water (50 mL), and the resulting mixture was
extracted with ether (3 × 5 mL) to remove organic impurities.
The basic aqueous solution was acidified (HCl) and extracted
with ether (3 × 25 mL). The combined organic phase was dried
over MgSO4 and concentrated. The crude product was purified
by recrystallization from hexanes:ethanol to yield 2.0 g (6.5
mmol, 67%) of the desired acid as colorless crystals. Mp: 109-
109.5 °C. 1H NMR (CDCl3): δ 1.19 (6Η, s), 1.40-1.48 (2H, m),
1.53-1.56 (2H, m), 2.11 (2H, q, J ) 7.0 Hz), 6.06 (1H, t, J )
7.5 Hz), 7.14-7.38 (10H, m), 11.6-11.9 (1H, bs). 13C NMR
(CDCl3): δ 24.9, 25.3, 30.1, 40.0, 42.1, 126.8, 126.9, 127.2,
128.0, 128.1, 129.5, 129.9, 140.1, 141.8, 142.7, 184.6. MS: m/z
(rel intens), 91 (36.8), 115 (63.7), 178 (24.6), 180 (33.5), 193
(100.0), 206 (23.5), 308 (24.5). ΗRMS: calcd for C21H24O2,
308.1776; found, 308.1780.
1H and 13C NMR spectra of CDCl3 solutions were obtained
at 300 or 500 MHz and 75 or 125 MHz, respectively. Gas
chromatography analyses were performed using flame ioniza-
tion detectors on 15 m × 0.54 mm bonded phase SE-30 and
Carbowax columns. GC-mass spectrometry was accomplished
with a Hewlett-Packard Model 5791 mass selective detector
interfaced to a Hewlett-Packard Model 5890 series II gas
chromatograph; a 30 m × 0.25 mm capillary bonded phase
Carbowax column was employed. High-resolution mass spec-
tral analyses were performed by the Central Instrumentation
Facility at Wayne State University. Melting points are uncor-
rected. Radial chromatography was performed on plates coated
with 2 mm of TLC grade silica gel with gypsum binder and
fluorescent indicator.
Gen er a l P r oced u r e for P r ep a r a tion of P TOC Ester s
3a -c. To a solution of the appropriate acid (1.0 equiv) in dry
benzene at 0 °C under nitrogen was added dropwise oxalyl
chloride (2.5 equiv) via syringe followed by two drops of DMF.
The reaction mixture was stirred for 4-5 h at room temper-
ature until gas evolution ceased. The excess oxalyl chloride
and benzene were removed under reduced pressure. The
resulting acid chloride was dissolved in dry benzene and
transferred by cannula into a light-shielded flask in an ice bath
containing a suspension of N-hydroxypyridine-2-thione sodium
salt (1.1 equiv) and a catalytic amount of DMAP (5 mol %) in
dry benzene. The mixture was allowed to warm to room
temperature with stirring and was maintained at room tem-
perature for 3 h. The mixture was diluted with ether and
washed with a saturated NaHCO3 solution and a saturated
NaCl solution. The organic layer was dried over MgSO4 and
concentrated to give the crude PTOC ester which was purified
by column chromatography on silica gel or by recrystallization.
7,7-Dip h en yl-6-h ep ten oic a cid 2-th ioxo-2H-p yr id in -1-
yl ester (3a ) was prepared as previously described.18
7,7-Dip h en yl-2-m eth yl-6-h ep ten oic a cid was obtained by
hydrolysis of ethyl 7,7-diphenyl-2-methyl-2-(ethoxycarbonyl)-
6-heptenoate25 followed by thermal decarboxylation of the
malonic acid. A solution of the diester25 (3.0 g, 7.63 mmol) and
KOH (0.86 g, 19.1 mmol, 2.5 equiv) in 60 mL of 95% ethanol
was heated at reflux for 5 h. The mixture was cooled to room
temperature and concentrated at reduced pressure. The
residue was dissolved in water (30 mL), and the mixture was
extracted with ether (5 mL) to remove organic impurities. The
basic aqueous layer was acidified to pH 2-3 with a 1 M HCl
solution, and the resulting solution was extracted with ether
(3 × 20 mL). The organic layer was washed with a saturated
solution of brine, dried over MgSO4, and concentrated to give
the crude product. A flask containing 2.6 g of diacid was
equipped with a bubbler and heated at 170 °C in an oil bath
until the evolution of CO2 ceased (ca. 3 h). The desired product
was purified by column chromatography on silica gel (hexanes:
EtOAc; 1:1) to yield 2.0 g (6.80 mmol, 89%) of a pale yellow
oil. 1H NMR (CDCl3): δ 1.18 (3H, d, J ) 7.2 Hz), 1.45-1.54
7,7-Dip h en yl-2,2-d im eth yl-6-h ep ten oic a cid 2-th ioxo-
2H-p yr id in -1-yl ester (3c) was prepared from 0.4 g (1.3
mmol) of the above acid by the general method. The crude
residue was purified by recrystallization from hexanes:ether
to give 0.45 g (1.08 mmol, 83%) of PTOC ester 3c as bright
yellow crystals. 1H NMR (CDCl3): δ 1.42 (6Η, s), 1.53-1.60
(2H, m), 1.74 (2H, m), 2.16 (2H, q, J ) 7.5 Hz), 6.09 (1H, t, J
) 7.5 Hz), 6.59 (1H, dt, J ) 1.5, 6.5 Hz), 7.15-7.40 (12H, m),
7.67 (1H, d, J ) 9.0 Hz). 13C NMR (CDCl3): δ 25.0, 25.2, 29.9,
39.9, 42.4, 112.5, 126.8, 126.9, 127.2, 128.0, 128.2, 129.1, 129.8,
133.3, 137.5, 137.6, 140.0, 142.2, 142.5, 171.9, 175.9.
1,1-Dip h en yl-1-h exen e (6a ) was prepared as previously
described.18
1,1-Dip h en yl-1-h ep ten e (6b). To a light-protected solution
of 100 mg (0.25 mmol) of PTOC ester 3b in 10 mL of dry,
degassed THF under nitrogen with a stir bar was added 393
mg (10 equiv, 265 µL, 2.5 mmol) of PhSeH via syringe. The
shield was removed, and the reaction mixture was irradiated
at room temperature with a 150 W tungsten-filament lamp
at a distance of 0.5 m for 2 h. The solvent was removed at
reduced pressure. Column chromatography of the crude prod-
ucts on silica gel (2% EtOAc in hexanes, Rf ) 0.8) gave 37 mg
1
(0.15 mmol, 60%) of desired product 6b as a colorless oil. H
(34) Esker, J . L.; Newcomb, M. J . Org. Chem. 1993, 58, 4933-4940.
NMR (CDCl3): δ 0.89 (3H, t, J ) 7.1 Hz), 1.29 (4H, m), 1.47