Thiophenes as Traps for Benzyne
SCHEME 3
was passed through a 15 g silica gel column with hexane
as the eluent to give 300 mg (27%) of the product 2c as a
1
colorless oil: H NMR 8.22(m,1H), 7.75(m,1H), 7.32(m,3H),
6
1
2
2
1
7
.96(m,6H), 2.48(s,3H); 13C NMR 137.9, 136.2, 133.8, 133.4,
28.9, 128.2, 127.9, 126.6, 126.4, 126.2, 125.5, 124.7, 19.6; MS
52(6), 251(20), 250(100), 249(17), 235(25), 234(31), 217(14),
15(12), 202(16), 171(7), 141(18), 139(12), 129(10), 128(14),
17(11), 115(19); IR 3060, 1585, 1475, 1440, 1375, 1010, 810,
20. Anal. Calcd for C17H14S: C, 81.6; H, 5.6. Found: C, 81.5;
H, 5.7.
1
-m eth yl-3-n a p h th yl p h en yl su lfid e (2d ) was prepared
as described below for 2f from 1.0 g (4.5 mmol) of 3-bromo-1-
methylnaphthalene,41 0.78 g (6.4 mmol) of crude sodium
thiophenoxide, 20 mg of o-phenylenebis[diphenylphosphino]-
nickel(II) bromide,42 and 2 mL of ethylene glycol to give after
1
workup 0.78 g (49%) of 2d : bp 186-190°C/0.4 mmHg; H NMR
7
.91(dd, 1H, J ) 7.5 Hz, J ) 2.0 Hz), 7.70(dd, 1H, J ) 7.5 Hz,
J ) 2.0 Hz), 7.69(s, 1H), 7.46(m, 2H), 7.34(s, 1H), 7.2-7.4(m,
5
1
3
3
H), 2.60(s, 3H, CH ); C NMR 136.1, 135.6, 134.0, 132.3,
reactivity of aryl anions in Diels-Alder reactions with
benzyne,32 may be a more reactive diene component in
131.7, 130.7(×2), 129.3, 129.2(×2), 128.6, 128.1, 126.9, 126.3,
+
1
26.1, 124.1, 19.2; MS 250(M , 100), 249(14), 235(13), 234-
the [4+2]-cycloaddition. The rearrangement of 10 to 11
would be driven by the increased stability of R-thienyl
anions33 and finds analogy in the reactions of other
(
(
18), 217(13), 215(5), 202(11), 171(16), 141(15), 139(22), 129-
3), 117(8), 115(16). Anal. Calcd for C17 14S: C, 81.6; H, 5.7.
H
Found: C, 81.5; H, 5.9.
2
5
benzyne-sulfur betaines. The intermediacy of ylide 11
1-Meth yl-2-th iop h en yln a p h th a len e (2f). A solution of 2
g (11 mmol) of 1-methyl-2-nitronaphthahlene43 in 100 mL of
95% ethanol was hydrogenated in a Parr apparatus with 0.2
g of 5% Pd(C) at room temperature and 25 psi. Removal of
the catalyst and solvent gave a solid residue, which was
crystallized from petroleum ether (bp 35-60°C) to afford 1.6
permits mechanistic rationalizations of the formation of
8
,34
and o-(2-thienyl)biphenyl (3)8
2
-phenylthiophenes (12)
in the reactions of benzynes with thiophene. Both mech-
anisms involve a Stevens35 or similar36 rearrangement,
the former directly on ylide 11 and the latter on betaine
44
g (93%) of 1-methyl-2-naphthylamine: mp 51°C (lit. 50-51
1
3 produced by the addition of a second molecule of
1
°
C); H NMR 7.84(d, 1H, J ) 8.6 Hz), 7.68(d, 1H, J ) 8.1 Hz),
benzyne to 11.
7.53(d, 1H, J ) 8.7 Hz), 7.43(m, 1H), 7.23(m, 1H), 6.90(d, 1H,
13
J ) 8.7 Hz), 2.35(s, 3H, CH
3
); C NMR 141.1, 133.6, 128.5,
1
(
28.4, 127.0, 126.1, 122.4, 121.9, 118.3, 112.7, 11.5; MS 157-
Exp er im en ta l Section
+
M , 100), 156(82), 129(20), 128(27), 127(16).
Gen er a l Meth od s. Analytical instrumentation and meth-
ods as well as standard conditions for the reactions of the
thiophenes with DPIC are described in detail in an earlier
A solution of 1.57 g (10 mmol) of 1-methyl-2-naphthylamine
in 2 mL of acetonitrile was added over 10 min to a magnetically
stirred mixture of 2.68 g (12 mmol) of CuBr, 1.76 g of isoamyl
nitrite, and 40 mL of freshly distilled acetonitrile. The mixture
was stirred for 30 min and poured into 200 mL of 20% HCl,
which was extracted with 2 × 100 mL of ether. The combined
ether extracts were washed with 2 × 100 mL of 20% HCl, dried
9
paper in this series.
Ma ter ia ls. The following known reactants or authentic
samples were synthesized by the cited literature procedures,
or where modified procedures were used, the physical and
spectral properties (mp, NMR, MS) were identical to the
indicated literature values or were consistent with the as-
over MgSO , and concentrated to an oily reddish residue, which
4
was passed through column of 25 g of silica gel using hexane
as the eluent. The solvent was removed and the residue
vacuum distilled to give a fraction boiling at 119°C/0.25 mmHg;
2-bromo-1-methylnaphthalene 0.66 g (30%): 1H NMR 7.98 (d,
1H, J ) 8.7 Hz), 7.74 (d, 1H, J ) 7.3 Hz), 7.56 (d, 1H, J ) 8.8
3
7
signed structures: diphenyliodonium-2-carboxylate (DPIC),
3
8
1
(
-naphthyl phenyl sulfide (2a ), 2-naphthyl phenyl sulfide
3
9
40
2b), 2-methyl-1-naphthyl phenyl sulfide (2e). All other
known compounds were commercially available.
-Meth yl-1-n a p h th yl p h en yl su lfid e (2c) was prepared
4
Hz), 7.44-7.54 (m, 3H), 2.74 (s, 3H, CH ); 13C NMR 133.4,
3
by adding a solution of 1.00 g (4.5 mmol) of 1-bromo-4-
methylnaphthalene in 5 mL of dry DMSO to a refluxing
solution of 990 mg (9.0 mmol) of thiophenol and 490 mg (9.0
mmol) of commercial sodium methoxide in 5 mL of DMSO.
After heating at reflux for 35 h, the reaction mixture was
cooled, diluted with ether, washed with 10% NaOH and water,
and dried. Evaporation of the solvent left a thick oil, which
133.3, 132.4, 130.0, 128.5, 127.4, 126.7, 125.7, 124.3, 122.7,
+
18.7; MS 222(M
(39), 115(48).
, 30), 220(33), 142(11), 141(100), 140(20), 139-
A mixture of 1.0 g (4.5 mmol) of 2-bromo-1-methylnaphtha-
lene, 0.67 g (5.5 mmol) of crude sodium thiophenoxide prepared
from thiophenol and NaH, 20 mg of o-phenylenebis[diphenyl-
42
phosphino]nickel(II) bromide, and 2 mL of ethylene glycol
was placed in a 2 mm thick-wall glass tube (30 cm × 12 mm
i.d.), solidified in liquid nitrogen, sealed under vacuum (0.25
mmHg), and heated at 200 °C for 24 h. The tube was cooled
to room temperature and then in liquid nitrogen and opened,
(
32) Hart, H.; Du, C. J . F.; Mohebalian, J . J . Org. Chem. 1988, 53,
720-2723.
33) Streitwieser, A.; Scannon, P. J . J . Am. Chem. Soc. 1973, 95,
273-6276.
34) Pansegrau, P. D.; Rieker, W. F.; Meyers, A. I. J . Am. Chem.
Soc. 1988, 110, 7178-7184.
35) Trost, B. M.; Melvin, L. S., J r. Sulfur Ylids, Emerging Synthetic
Intermediates, Chapter 7. Rearrangements; Academic Press: New York,
2
6
(
and the contents were poured into a mixture of 10 mL of CH
Cl
and 60 mL of ether. The solution was washed with 4 × 50
mL of water, dried (MgSO ), and concentrated to afford 1.05
2
-
(
2
(
4
g of an oily residue, which was chromatographed on 25 g of
1
975; Vol. 31.
36) Porter, A. E. A.; Rzepa, H. S. J . Chem. Soc., Perkin Trans. 1
(
1
988, 809-812.
(41) Foster, B.; Gaillard, B.; Mathur, N.; Pincock, A. L.; Pincock, J .
A.; Sehmbey, C. Can. J . Chem. 1987, 65, 1599-607.
(42) Cristau, H. J .; Chabaud, B.; Chene, A.; Christol, H. Synthesis
1981, 892-893.
(43) Topsom, R. D.; Vaughn, J . J . Chem. Soc. 1957, 2843.
(44) Terauchi, H.; Kowata, K.; Minematsu, T.; Takemura, S. Chem.
Pharm. Bull 1977, 25, 556-562.
(
(
(
37) Fieser, L. F.; Haddadin, M. J . Org. Synth. 1966, 46, 107.
38) Bacon, R. G. R.; Hill, H. A. O. J . Chem. Soc. 1964, 1108-1112.
39) Weinstein, A. H.; Pierson, R. M. J . Org. Chem. 1958, 23, 554-
5
2
60.
(
40) Truce, W. E.; Hampton, D. C. J . Org. Chem. 1963, 28, 2276-
279.
J . Org. Chem, Vol. 68, No. 1, 2003 73