1584 Bull. Chem. Soc. Jpn. Vol. 80, No. 8 (2007)
Bis(arylthienyl)diphosphinidenecyclobutenes
1
2
(E,E)-1,2-Diphenyl-3,4-bis[(2,4,6-tri-t-butylphenyl)phosphin-
idene]cyclobutene (1P). To a solution of 12P (333 mg, 0.61
mmol)10 in THF (10 mL) was added t-butyllithium in pentane
(1.59 M, 1.2 mL, 1.9 mmol) at ꢂ98 ꢃC. The resulting solution was
stirred at ꢂ98 ꢃC for 10 min, and 1,2-dibromoethane (0.027 mL,
0.31 mmol) was added. The reaction mixture was allowed to warm
to room temperature and stirred for 6 h. Removal of the solvent
followed by column chromatography (SiO2/hexane to hexane:
EtOAc 50:1) afforded 210 mg (91%) of (E,E)-1P.4
175.3 (dd, JPC ¼ 18:0 Hz, JPC ¼ 9:2 Hz, P=C); 31P{1H} NMR
(162 MHz, CDCl3) ꢃ 171.4; UV–vis (CH2Cl2) 248 (log " 4.58),
315 (4.35), 359 (sh, 4.53), 397 (4.68), and 478 nm (4.34); IR
(KBr) 2960, 2904, 2868, 1593, 1479, 1454, 1394, 1362, 1238,
1215, 879, 840, 802, and 696 cmꢂ1. Found: C, 72.16; H, 7.47;
S, 13.80%. Calcd for C56H68P2S4: C, 72.22; H, 7.36; S, 13.77%.
3-(Biphenyl-4-yl)-2-bromo-1-(2,4,6-tri-t-butylphenyl)-3-(tri-
methylsiloxy)-1-phosphapropene (12PP). To a solution of (di-
bromomethylene)(2,4,6-tri-t-butylphenyl)phosphine (1.35 g, 3.02
mmol) in THF (30 mL) was added butyllithium in hexane (1.60
M, 2.06 mL, 3.30 mmol) at ꢂ98 ꢃC. The resulting solution was
stirred at ꢂ98 ꢃC for 10 min, and a solution of 4-biphenylcarbalde-
hyde (627 mg, 3.44 mmol) in THF (6 mL) was added. Then the
resulting mixture was allowed to warm to room temperature,
stirred for 30 min, and chlorotrimethylsilane (0.46 mL, 3.6 mmol)
was added. After stirring for an additional 30 min, an appropriate
amount of hexane was added, and the mixture was washed succes-
sively with water and brine and dried over MgSO4. The solvent
was removed in vacuo. Chromatographic treatment of the residue
(SiO2/hexane:EtOAc 100:1) afforded 1.55 g (82% yield) of 12PP:
Pale yellow powder, mp 139–141 ꢃC; Rf 0.52 (hexane:EtOAc =
20:1); 1H NMR (400 MHz, CDCl3) ꢃ 0.21 (9H, s, SiMe3), 1.33
(9H, s, p-t-Bu), 1.43 (9H, s, o-t-Bu), 1.51 (9H, s, o0-t-Bu), 5.76
3-(2,20-Bithienyl-5-yl)-2-bromo-1-(2,4,6-tri-t-butylphenyl)-3-
(trimethylsiloxy)-1-phosphapropene (12TT).
To a solution
of (dibromomethylene)(2,4,6-tri-t-butylphenyl)phosphine (3.00 g,
6.49 mmol) in THF (100 mL) was added butyllithium in hexane
(1.59 M, 4.10 mL, 6.49 mmol) at ꢂ98 ꢃC. The resulting solution
was stirred at ꢂ98 ꢃC for 10 min, and 2,20-bithiophene-5-carbalde-
hyde (1.26 g, 6.49 mmol) was added. The resulting mixture was
then allowed to warm to room temperature, stirred for 30 min,
and chlorotrimethylsilane (0.82 mL, 6.49 mmol) was added. After
stirring for an additional 30 min, the solvent was removed in
vacuo. Chromatographic treatment of the residue (SiO2/hexane
to hexane:EtOAc 50:1) afforded 3.31 g (80% yield) of 12TT: Pale
yellow powder, mp 148–149 ꢃC; Rf 0.40 (hexane:EtOAc 20:1);
1H NMR (400 MHz, CDCl3) ꢃ 0.25 (9H, s, SiMe3), 1.35 (9H, s, p-
t-Bu), 1.49 (9H, s, o-t-Bu), 1.52 (9H, s, o0-t-Bu), 5.91 (1H, d,
3JPH ¼ 12:2 Hz, P=C–CH), 6.93 (1H, m, thienyl), 7.00–7.10
(2H, m, thienyl), 7.16 (1H, m, thienyl), 7.20 (1H, m, thienyl),
3
(1H, d, JPH ¼ 12:9 Hz, P=C–CH), and 7.33–7.66 (11H, m,
arom.); 13C{1H} NMR (100 MHz, CDCl3) ꢃ 0.79 (s, SiMe3), 31.9
4
4
(s, p-CMe3), 33.1 (d, JPC ¼ 6:1 Hz, o-CMe3), 33.3 (d, JPC
¼
ꢀ
ꢀ
7.42 (1H, s, m-Mes ), and 7.44 (1H, s, m0-Mes ); 13C{1H} NMR
7:4 Hz, o0-CMe3), 35.5 (s, p-CMe3), 38.4 (s, o-CMe3), 38.5 (s,
o0-CMe3), 80.4 (d, 2JPC ¼ 36:9 Hz, COSi), 122.6 (s, arom.), 126.9
(s, arom.), 127.6 (s, arom.), 127.7 (s, arom.), 129.2 (s, arom.),
(100 MHz, CDCl3) ꢃ 0.6 (s, SiMe3), 31.7 (s, p-CMe3), 33.1 (d,
4JPC ¼ 6:7 Hz, o-CMe3), 33.2 (d, JPC ¼ 7:0 Hz, o0-CMe3), 35.4
4
(s, p-CMe3), 38.3 (s, o-CMe3), 38.4 (s, o0-CMe3), 77.1 (d, 2JPC
40:9 Hz, COSi), 122.6 (s, m-Mes ), 123.4 (s, thienyl), 123.8 (s,
¼
137.4 (d, JPC ¼ 54:1 Hz, ipso-Mes ), 140.7 (s, arom.), 141.3
1
ꢀ
ꢀ
thienyl), 124.5 (s, thienyl), 125.3 (s, thienyl), 128.1 (s, thienyl),
ꢀ ꢀ
(s, arom.), 141.4 (s, arom.), 151.2 (s, p-Mes ), 153.7 (s, o-Mes ),
154.0 (s, o0-Mes ), and 168.2 (d, JPC ¼ 65:3 Hz, P=C);
31P{1H} NMR (162 MHz, CDCl3) ꢃ 253.1; UV (CH2Cl2) 251
(log " 4.44) and 274 nm (4.44); IR (KBr) 2958, 2904, 2868,
1703, 1595, 1479, 1398, 1362, 1252, 1209, 1076, 877, 843, 760,
737, and 696 cmꢂ1. Found: m=z 645.2288. Calcd for C35H48-
79BrNaOPSi: Mþ + Na, 645.2288.
ꢀ
1
1
ꢀ
136.9 (d, JPC ¼ 54:1 Hz, ipso-Mes ), 137.0 (thienyl), 138.2
3
(thienyl), 146.4 (d, JPC ¼ 12:4 Hz, thienyl), 151.3 (s, p-arom.),
2
2
153.6 (d, JPC ¼ 2:2 Hz, o-arom.), 153.9 (d, JPC ¼ 2:1 Hz, o0-
arom.), and 166.3 (d, JPC ¼ 64:0 Hz, P=C); 31P{1H} NMR
1
(162 MHz, CDCl3) ꢃ 257.7; UV–vis (CH2Cl2) 247 (log " 4.31),
276 (4.05), 320 (4.27), and 383 nm (sh, 3.39); IR (KBr) 2962,
2871, 1593, 1473, 1398, 1363, 1252, 1070, 877, 843, 795, and
688 cmꢂ1. Found: m=z 657.1414. Calcd for C31H4479BrNaOPS2Si:
Mþ + Na, 657.1416.
(E,E)-1,2-Di(biphenyl-4-yl)-3,4-bis[(2,4,6-tri-t-butylphenyl)-
phosphinidene]cyclobutene (1PP). To a solution of 12PP (500
mg, 0.80 mmol) in THF (3 mL) was added t-butyllithium in pen-
tane (1.42 M, 1.70 mL, 2.41 mmol) at ꢂ98 ꢃC. The resulting solu-
tion was stirred at ꢂ98 ꢃC for 30 min and 0.40 mmol of 1,2-dibro-
moethane was added. The reaction mixture was stirred for 1 h and
refluxed for 1 h. Appropriate amount of hexane was added and the
mixture was washed successively with water and brine, dried over
MgSO4, and the solvent was removed under reduced pressure.
Chromatographic treatment of the residue (SiO2/hexane) afforded
(E,E)-1PP quantitatively: Orange powder, mp 234–236 ꢃC; Rf
0.14 (hexane:EtOAc 50:1); 1H NMR (400 MHz, CDCl3) ꢃ 1.34
(E,E)-1,2-Di(2,20-bithienyl-5-yl)-3,4-bis[(2,4,6-tri-t-butylphen-
yl)phosphinidene]cyclobutene (1TT). To a solution of 12TT
(2.00 g, 3.15 mmol) in THF (73 mL) was added t-butyllithium in
pentane (1.45 M, 4.30 mL, 6.29 mmol) at ꢂ78 ꢃC. The resulting
solution was stirred at ꢂ78 ꢃC for 15 min, and 1,2-dibromoethane
(0.14 mL, 1.6 mmol) was added. The reaction mixture was stirred
for 10 min, allowed to warm to room temperature, and stirred for
additional 1 h. Removal of the solvent followed by column chro-
matography (Al2O3/hexane) afforded 1.41 g (96% yield) of (E,E)-
1TT: Red powder, mp 265–266 ꢃC (decomp); Rf 0.14 (hexane:
EtOAc 50:1); 1H NMR (400 MHz, CDCl3) ꢃ 1.37 (18H, s, p-t-Bu),
1.59 (36H, s, o-t-Bu), 5.54 (2H, d, 3JHH ¼ 3:9 Hz, 3-thienyl), 6.58
3
(18H, s, p-t-Bu), 1.59 (36H, s, o-t-Bu), 6.64 (4H, d, JPH ¼ 8:4
3
Hz, arom.), 7.10 (4H, d, JHH ¼ 8:4 Hz, arom.), 7.32 (2H, t,
3JHH ¼ 7:3 Hz, arom.), 7.38–7.43 (8H, m, arom.), and 7.50 (4H,
d, JHH ¼ 7:2 Hz, arom.); 13C{1H} NMR (100 MHz, CDCl3) ꢃ
3
3
3
(2H, d, JHH ¼ 3:9 Hz, 4-thienyl), 6.96 (2H, dd, JHH ¼ 5:0 Hz,
32.2 (s, p-CMe3), 33.8 (s, o-CMe3), 35.6 (s, p-CMe3), 39.1 (s,
o-CMe3), 122.4 (s, arom.), 126.6 (s, arom.), 127.1 (s, arom.),
128.0 (s, arom.), 129.28 (s, arom.), 129.31 (s, arom.), 131.4 (s,
3JHH ¼ 3:7 Hz, 40-thienyl), 7.03 (2H, m, 30-thienyl), 7.19 (2H, dd,
3JHH ¼ 5:0 Hz, JHH ¼ 1:1 Hz, 50-thienyl), and 7.44 (4H, s, m-
4
Mes ); 13C{1H} NMR (100 MHz, CDCl3) ꢃ 32.0 (s, p-CMe3),
33.6 (s, o-CMe3), 35.5 (s, p-CMe3), 38.8 (s, o-CMe3), 122.5 (s, m-
arom.), 136.2 (d, JPC ¼ 27:5 Hz, ipso-Mes ), 140.6 (s, arom.),
ꢀ
1
ꢀ
2
ꢀ
140.7 (s, arom.), 150.8 (s, p-Mes ), 155.3 (pseudo t, ð JPC
þ
ꢀ
arom.), 124.3 (s, thienyl), 124.6 (s, thienyl), 125.3 (s, thienyl),
128.3 (s, thienyl), 131.6 (s, thienyl), 131.8 (s, thienyl), 137.2 (d,
3JPCÞ=2 ¼ 4:9 Hz, P=C–C), 155.4 (s, o-Mes ), and 176.7 (dd,
1JPC ¼ 17:2 Hz, JPC ¼ 9:9 Hz, P=C); 31P{1H} NMR (162 MHz,
2
2
ꢀ
3
1JPC ¼ 26:4 Hz, ipso-Mes ), 146.2 (pseudo t, ð JPC þ JPCÞ=2 ¼
CDCl3) ꢃ 170.3; UV–vis (CH2Cl2) 250 (log " 4.55), 343 (4.69),
and 420 nm (sh, 4.22); IR (KBr) 2960, 2362, 2337, 1479, 1396,
ꢀ
ꢀ
5:5 Hz, P=C–C), 151.0 (s, p-Mes ), 155.7 (s, o-Mes ), and