Shine et al.
and the data agreed well with those of Herges and Hoock.6
From integration of the unoverlapped methyl-group signals
at 1.82 and 1.81 ppm and from averaging of 13C peak heights,
the two isomers were found to be present in a ratio of 55:45,
but we are unable to name the dominant isomer. 18, 1H NMR,
CDCl3, δ (J): 5.75 (7.3, 3.3), qd, and 5.71 (7.3, 3.5), qd, 1H;
4.99 (3.5), a multiplet of nine peaks representing two unre-
solved overlapping qd, 1H; 1.82 (7.5), d, and 1.81 (7.0), d, 3H;
1.67 (6.5), d, and 1.66 (6.5), d, 3H. 13C NMR, methyl groups
only, δ: 14.5, 13.4. Other 13C data were as reported.6
sure to give a residue to which was added 10 mL of cold MeCN.
Undissolved Th was removed by filtration. To the filtrate was
added 10 mL of 1% NaHCO3 solution, and the aqueous solution
was extracted with 50 mL of ether. The ether layer was
separated, dried over Na2SO4, and concentrated under reduced
pressure to give an oil. The oil was loaded onto a silica gel
column with a small amount of CHCl3. Elution with hexane
containing 1-5% ethyl acetate gave 9 mg (0.005 mmol, 0.26%)
of 11c as an oil, 17 mg (0.110 mmol, 5.5%) of 12c as an oil,
and 23 mg (0.117 mmol, 5.8%) of 13c, mp 31-32 °C. Products
11c and 12c were identified by comparison of their GC and
NMR data with those of the prepared authentic compounds;
12c was also identified with mass spectrometry (MS). Product
13c was identified with NMR and MS. Authentic 13c was not
Conversion of 18 into 11a and 12a via 2,3,4-Hexatriene.
A mixture of dithiolanes 18 was prepared from 4.0 g (9.47
mmol) of 19 and 3.0 g (16 mmol) of K2CS3 as described. The
reaction gave 2.3 g of crude 18, which was subjected to
desulfurization with 2.0 g of Raney nickel in 10 mL of DMF.
The product of desulfurization, 2,3,4-hexatriene,6 was not
isolated but along with some DMF was distilled off under
vacuum into a receiver containing 5 mL of CDCl3, 4.0 g of
alumina, and 0.1 mL of HBF4. That mixture was stirred for 1
h, and a sample was withdrawn for NMR spectroscopy. The
NMR spectrum showed signals characteristic of 11a and 12a
but shifted downfield by the presence of so much DMF in the
solution. The observed spectra agreed well with those of a
mixture of authentic 11a and 12a in d7-DMF. The observed
NMR spectra were as follows: 11a, 1H NMR, δ (J): 2.72 (7.2),
q, 4H; 0.99 (7.3), t, 6H. 13C NMR, δ: 200.2, 29.3 (CH2), 6.8
1
prepared. 13c, H NMR, CDCl3, δ (J): 5.63 (6.5), d, 1H; 4.63
(8.0, 6.0, 2.0), tdt, 1H; 2.10 (7.0, 2.0), td, 2H; 1.91, s, 3H; 1.59-
1.45, m, 2H; 1.43-1.28, m, 6H; 0.86 (7.5), t, 3H; 0.84 (7.3), t,
3H. 13C NMR, δ : 168.8 (CdO), 83.3 and 79.2 (yne), 41.6 (CH),
38.4 (CH2), 30.7 (CH2), 23.3 (CH3), 21.9 (CH2), 18.9 (CH2), 18.3
(CH2), 13.6 (CH3), 13.5 (CH3). MS: 196 (M + 1; 100), 114 (M
- 81; 13), 57 (M - 138; 9), 43 (M - 152; 39).
Reaction of 7d with Alumina under CHCl3. Formation
of 11c and 12c. Because adducts 7 and 8 are insoluble in
CHCl3, the alumina was added to a stirred suspension of 500
mg (0.67 mmol) of 7d in 150 mL of CHCl3. Workup and column
chromatography gave 27 mg (0.158 mmol, 16%) of 11c and 21
mg (0.136 mmol, 20%) of 12c. The products were identified
with GC and NMR.
1
(CH3). 12a, H NMR, δ (J): 4.38 (6.5, 1.8), qt, 1H; 2.13 (7.5,
2.0), qd, 2H; 1.30 (6.5), d, 3H; 1.05 (7.5), t, 3H. 13C NMR, δ:
84.2 and 82.8 (yne), 57.4 (CH), 25.0 (CH2), 14.0 (CH3), 12.3
(CH3). Authentic compounds had the following NMR spectra:
Reaction of 7c with Alumina under MeCN. Formation
of 11b, 12b, and 13b. Reaction was carried out as described
for 7d, with 800 mg (1.12 mmol) of 7c. Prior to separation of
products with column chromatography, the crude residue was
analyzed with GC, which gave 0.065 mmol (6%) of 4-octyne,
0.12 mmol (11%) of 11b, 0.098 mmol (9%) of 12b, 0.17 mmol
(15%) of 13b, 1.87 mmol (84%) of Th, and 0.068 mmol (3%) of
ThO. 11b (0.046 mmol, 4%), 12b (0.059 mmol, 5%), and 13b
(0.096 mmol, 9%), mp 41-42 °C, were isolated with column
chromatography and were characterized with NMR spectros-
copy. The NMR spectra of 11b and 12b agreed well with those
1
11a, H NMR, d7-DMF, δ (J): 2.76 (7.2), q, 4H; 0.99 (7.3), t,
1
6H. 13C NMR, δ: 200.5, 29.5, 7.0. 12a, H NMR, d7-DMF, δ
(J): 5.30 (5.5), d, 1H (OH); 4.40, m, 1H; 2.18 (7.5, 1.6), qd, 2H;
1.30 (7.0), d, 3H; 1.06 (7.5), t, 3H. 13C NMR, δ: 84.4, 83.8, 57.6,
25.4, 14.3, 12.4.
Detection and Assay of Hydrogen. Formation of H2 in
reactions of adducts with alumina under CHCl3 was detected
with GC, using a stainless steel column, 9 ft × 1/8 in, packed
with 5 Å molecular sieves, isothermally at 35 °C, and with a
thermal conductivity detector. Assay of H2 was made by
measuring the increase in pressure caused by H2 formation
in a sealed vessel, using a silicon pressure sensor, electrometer-
617, MPX2050 series. The sensor was attached to the reaction
vessel via the vessel’s septum and was calibrated before use
at six pressures between 1 and 6 psi. Qualitative detection of
H2 was obtained with 7c and 7d. Reaction of each adduct (1.4
mmol) with 10 g of alumina under 40 mL of CHCl3 was allowed
to run for 2 h in a 50 mL flask sealed with a septum. Samples
of 100 µL were drawn from the headspace and were found to
contain H2, O2, and N2, identified with their retention times
of 0.5, 1.5, and 5.0 min, respectively. Control experiments
showed that without the addition of an adduct, the headspace
registered only O2 and N2 in the GC. Quantitative measure-
ments were made with the pressure sensor. The amount
(mmol) of H2 expected to be formed in a reaction was equated
to the amount of diketone that had been formed and measured
in separate experiments. The anticipated increase in head-
space pressure caused by that amount of H2 was then
calculated from the ideal gas equation and compared with the
increase measured with the sensor. Thus, from 7c (1.4 mmol),
0.12 mmol of 11b had been obtained. The anticipated equiva-
lent of H2 in increased pressure was 1.59 psi, whereas the
measured increase was 1.34 psi (84%). Analogous experiments
with 7d resulted in 91% of the anticipated amount of H2.
1
of the prepared authentic compounds. 13b, H NMR, CDCl3,
δ (J): 5.61, bs, 1H (NH); 4.65 (8.0, 5.5, 2.3) tdt, 1H; 2.15 (7.0,
2.0), td, 2H; 1.98, s, 3H; 1.65, m, 2H; 1.52 (7.2), sext, 2H; 0.98
(7.3), t, 3H; 0.97 (7.3), t, 3H. 13C NMR, δ: 168.8 (CdO), 83.5
and 79.1 (yne), 43.1 (CH), 29.3 (CH2), 23.3 (CH3), 22.1 (CH2),
20.6 (CH2), 13.4 (CH3), 9.9 (CH3). HRMS (CI) [M + H]+: calcd
for C10H18NO, 168.138839; found, 168.138838 (error 0.01 ppm).
Reaction of 7c with Alumina under CHCl3. Formation
of 11b and 12b. Reaction was carried out as with 7d, using
500 mg (0.70 mmol) of 7c, and gave by GC 0.14 mmol (20%) of
4-octyne, 0.17 mmol (24%) of 11b, 0.12 mmol (17%) of 12b,
1.04 mmol (74%) of Th, and 0.15 mmol (11%) of ThO. After
column chromatography, 11b (0.075 mmol, 11%) and 12b (0.10
mmol, 14%) were isolated and characterized with NMR
spectroscopy.
Reaction of 7b with Alumina under MeCN. Formation
of 11a, 12a, and 13a. Reaction was carried out as described
for 7d. GC analysis of the crude mixture of products gave
3-hexyne (1%), 11a (1%), 12a (1%), 13a (6%), Th (99%), and
ThO (0.5%). Only 13a, mp 39-40 °C, was isolated with column
chromatography. 13a, 1H NMR, CDCl3, δ (J): 5.66, bs, 1H;
4.76 (7.5, 6.8, 2.3), qdt, 1H; 2.18 (7.5, 2.0), qd, 2H; 1.97, s, 3H;
1.36 (7.0), d, 3H; 1.12 (7.5), t, 3H. 13C NMR, δ : 168.7 (CdO),
84.1 and 79.6 (yne), 37.4 (CH), 23.3 (CH3), 22.9 (CH3), 13.8
(CH3), 12.2 (CH2). HRMS (CI) [M + H]+: calcd for C8H14NO,
140.107539; found, 140.107508 (error 0.22 ppm).
Reaction of 7d with Alumina under MeCN. Formation
of 11c, 12c, and 13c. A solution of 1.5 g (2.01 mmol) of 7d in
50 mL of MeCN was placed in a 250 mL flask containing 40 g
of alumina. The mixture was stirred at room temperature for
6 h and was filtered through fritted glass. The alumina was
washed with 50 mL of ether. A further 400 mL of ether was
added to the filtrate, and the precipitate of unreacted 7d was
removed. The filtrate was concentrated under reduced pres-
Reaction of 7b with Alumina under CHCl3 and CDCl3.
GC analysis of products from reaction in CHCl3 gave 3-hexyne
(2%), 11a (29%), 12a (9%), Th (97%), and ThO (1%). The
identification of products was made with the use of authentic
compounds. Reaction was also carried out with 105 mg (0.152
mmol) of 7b and 1 g of alumina under 2.5 mL of CDCl3. The
3882 J. Org. Chem., Vol. 70, No. 10, 2005