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Data for 1 (C8HBr2F5), F
w = 351.91;
monoclinic crystal system; space group P21/n (an alternate setting of P21/c [No. 14]), a = 4.2574(6), b = 37.836(5), c = 5.8166(8) Å; β = 96.478(2)˚; V = 931.0(2) ų; Z = 4; ρ
calcd = 2.511
g
cm-³; 2θ
max = 52.68˚; µ = 8.744 mm-¹; T = -80 ˚C;
total data collected = 7332; R
1 = 0.0688 [1617
observed reflections with F
o
² ÷ 2σ(F
o
²)]; wR
2 = 0.1884
for 136 variables and 1900 unique reflections with F
o
² ÷ -3σ(F
o
²);
residual electron density = 1.576 and -1.452
e Å-³. CCDC 725485.
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Data for 11 (C16H15F5Si), F
w = 330.37;
monoclinic crystal system; space group P21/c (No. 14), a = 8.3640(5), b = 18.3726(11), c = 10.9822(7) Å; β = 104.5167(9)˚; V = 1633.74(17) ų; Z = 4; ρ
calcd = 1.343
g cm-³; 2θ
max = 52.76˚; µ = 0.186 mm-¹;
T = -80 ˚C;
total data collected = 12874; R
1 = 0.0381 [2844
observed reflections with F
o
² ÷ 2σ(F
o
²)]; wR
2 = 0.1125
for 201 variables and 3346 unique reflections with F
o
² ÷ -3σ(F
o
²);
residual electron density = 0.210 and -0.241
e Å-³. CCDC 725483.
<A NAME="RS04609ST-26">26</A>
Data for 27b (C23H21F5Si), F
w = 420.49;
triclinic crystal system; space group P1 (No.
2), a = 7.5471(8), b = 16.2227(18), c = 18.215(2) Å; α = 83.2514(15), β = 81.0827(16), γ = 84.9478(16)˚; V = 2182.3(4) ų; Z = 4; ρ
calcd = 1.280
g cm-³; 2θ
max = 52.00˚; µ = 0.155 mm-¹; T =
-80 ˚C;
total data collected = 14651; R
1 = 0.0460 [6050 observed
reflections with F
o
² ÷ 2σ(F
o
²)]; wR
2 = 0.1342
for 523 variables and 8490 unique reflections with F
o
² ÷
-3σ(F
o
²);
residual electron density = 0.329 and -0.165
e Å-³. CCDC 725482.
<A NAME="RS04609ST-27">27</A>
Intermolecular distances are based
on the separation of planes generated from all non-hydrogen atoms
of neighboring molecules using Mercury 1.3.
<A NAME="RS04609ST-28">28</A>
Data for 5×decafluorotolan (4:1,
C86H20F30), F
w = 1623.02; triclinic
crystal system; space group P1 (No. 2), a = 7.2628(8), b = 13.1573(14), c = 18.0306(19) Å; α = 80.3101(17), β = 82.1018(17), γ = 81.9049(18)˚; V = 1670.0(3) ų; Z = 1; ρ
calcd = 1.614
g cm-³; 2θ
max = 52.80˚; µ = 0.152 mm-¹; T = -80 ˚C;
total data collected = 13414; R
1 = 0.0460 [4226
observed reflections with F
o
² ÷ 2σ(F
o
²)]; wR
2 = 0.1494
for 523 variables and 6819 unique reflections with F
o
² ÷ -3σ(F
o
²);
residual electron density = 0.397 and -0.189
e Å-³. CCDC 725484.
<A NAME="RS04609ST-29">29</A>
The synthesis of 5, 10, 12, 17, and 24 has
been communicated, see ref. 7.
<A NAME="RS04609ST-30">30</A>
TLC analysis often indicated that
reactions were complete soon after addition of base (ca. 30 min),
although warming of the reaction solution in the TLC capillary could
influence this analysis.
<A NAME="RS04609ST-31">31</A>
Luu T.
McDonald R.
Tykwinski RR.
Org.
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<A NAME="RS04609ST-32">32</A>
General procedure
for FBW rearrangements29Unless otherwise noted in the individual
procedures, in a flame-dried flask, a solution of the dibromoolefin
(2.00 mmol) in anhydrous hexanes (30 mL, freshly distilled from CaH2)
was cooled to -78 ˚C under a positive
pressure of N2. n-BuLi (2.5 M in hexanes, 1.05 equiv) was slowly
added dropwise over a period of ca. 5 min. The reaction was allowed
to warm to r.t. over ˜1 h, stirred for 3 h,30 and then quenched
through the addition of aqueous NH4Cl (50 mL). Et2O (50 mL) was
added, and the organic layer was separated, washed with distilled
H2O (3 25 mL), dried over MgSO4, filtered, and the solvent removed
in vacuo. Column chromatography (silica gel) gave the desired product.
3-Pentafluorophenyl-2-propynoic acid (2)
Using
the general procedure, 1 (0.500 g, 1.42 mmol) in hexanes (30 mL)
was reacted with n-BuLi (1.15 mL, 2.90 mmol, 2.5 M in hexanes) for
1 h and then warmed to r.t. MgBr2 (0.29 g, 1.6 mmol) was added in
one portion, and the inhomogeneous mixture was stirred for 15 min.
Dry CO2 gas was bubbled through the solution as it was allowed to
warm to r.t. and stirred overnight. Et2O (50 mL) and aqueous 10% HCl
(50 mL) were added and the organic phase was separated and washed
with distilled H2O, followed by 10% aqueous NaOH (3 30
mL). The aqueous phases were collected and acidified with aqueous
10% HCl (50 mL). Et2O (3 30 mL) was
added and the organic phases were separated, dried over MgSO4, treated
with activated charcoal, and filtered. Solvent removal gave 2 (0.182
g, 28%) as a colorless solid. Data were consistent with
those reported.11 Mp 96-98 ˚C (Lit.11 105-106 ˚C).
IR (neat): 3055 (s), 2987 (s), 2241 (s), 1694 (s), 1522 (s) cm-1; 1H NMR
(400 MHz, CDCl3): d = 10.19 (br); 19F (376 MHz, CDCl3): d = -132.9
to -133.0 (m, 2 F), -146.6 (tt, 3J = 21 Hz, 5J = 4
Hz, 1 F), -160.2 to -160.4 (m, 2 F); 13C{1H} NMR (125
MHz, CDCl3): d = 157.0, 148.4 (d mult, 1J = 258
Hz), 143.8 (d mult, 1J = 260 Hz), 137.8
(d mult, 1J = 260 Hz), 96.8 (app td, J = 17.4,
3.9 Hz), 90.1-90.0 (m), 72.4-72.2 (m); EIMS: m/z (%) = 192.0
(100) [M - CO2]+; HRMS: m/z [M - CO2]+ calcd
for C8HF5: 191.9998; found: 191.9974. Anal. Calcd for C9HF5O2: C,
45.76; H, 0.42. Found: C, 45.98; H, 0.67.
1,4-[Bis(pentafluorophenyl)]-1,3-butadiyne
(4)
Using the general procedure, 1 (0.700 g, 1.99
mmol) in hexanes (30 mL) was reacted with n-BuLi (1.7 mL, 4.1 mmol,
2.4 M in hexanes). Aqueous work up gave a faint-yellow oil that
was immediately dissolved in CH2Cl2 (ca. 5 mL) and added dropwise
over 30 min to a solution of Hay catalyst [CuCl (0.200
g, 2.04 mmol) and TMEDA (1.21 g, 10.4 mmol, 1.6 mL)] in
CH2Cl2 (50 mL). The reaction was stirred overnight, Et2O (50 mL)
and aqueous 10% HCl (50 mL) were added, and the organic
phase was separated, washed with distilled H2O (3 50
mL), dried over MgSO4, filtered, and the solvent removed in vacuo.
Column chromatography (pentane) gave 4 (0.146 g, 37%) as
a colorless solid. Spectral data for this compound were consistent
with those reported.12
1-Pentafluorophenyl-5-(tert-butyldimethylsilyl)-2,4-pentadiyn-1-one
(19)
To anhydrous CH2Cl2 (100 mL, freshly distilled
from CaH2) was added pentafluorophenyl benzoyl chloride (1.61 g,
11.4 mmol) and 18 (1.50 g, 6.35 mmol). The temperature of the solution
was lowered to 0 ˚C under a positive pressure
of N2, and AlCl3 (1.01 g, 7.63 mmol) was added portion-wise over 5
min. The reaction was stirred at 0 ˚C, monitored
by TLC until starting material was no longer observed (typically
ca. 3 h), and then carefully poured into aqueous 10% HCl
(50 mL) in ice (50 g); CAUTION: exothermic. Pentane (50 mL) was
added and the organic layer was separated, washed with distilled
H2O (3 50 mL), dried over MgSO4, treated with
activated charcoal, filtered, and the solvent removed in vacuo.
Column chromatography (CH2Cl2-pentane, 1:4) gave 19 (0.754
g, 2.11 mmol, 33%), as a clear pale-yellow oil. Rf = 0.35
(CH2Cl2-pentane, 1:4). IR (neat): 2955 (m), 2193 (s), 2099
(s), 1659 (s), 1522 (m) cm-1; 1H NMR (400 MHz,
CDCl3): d = 0.97 (s, 9 H), 0.19 (s, 6 H); 19F (376 MHz, CDCl3): d = -140.3
to -140.4 (m, 2 F), -146.8 (tt, 3J = 21 Hz, 5J = 6
Hz, 1 F), -160.3 to -160.5 (m, 2 F); 13C{19F} NMR
(100 MHz, CDCl3): d = 166.9, 145.6, 144.0, 137.8, 113.9,
100.5-100.4 (m), 86.1, 79.3, 72.6, 25.5 (q sept, J = 126,
6 Hz), 16.9-16.8 (m), -5.2 (q mult, 1J = 126
Hz); HRMS (EI): m/z [M+] calcd.
for C17H15F5OSi: 358.0812; found: 358.0809. Anal. Calcd for C17H15F5OSi:
C, 56.98; H, 4.19. Found: C, 57.35; H, 4.20.
5-tert-Butyldimethylsilyl-2,4-butynoic
acid
1-(tert-Butyldimethylsilyl)butadiyne31 (1.30
g, 7.93 mmol) was added to anhydrous THF (75 mL) and the mixture
was cooled to -78 ˚C under a positive
pressure of N2. CH3Li (6.0 mL, 9.0 mmol, 1.5 M in Et2O) was added
and the mixture was stirred for 1 h. Dry CO2 gas was bubbled through
the solution as it was allowed to warm to r.t. and stirred overnight.
Et2O (50 mL) and aqueous 10% HCl were added and the organic
phase was separated, washed with distilled water (3 50
mL), dried over MgSO4, treated with activated charcoal, and filtered.
Solvent removal in vacuo gave 5-tert-butyldimethylsilyl-2,4-butynoic
acid (1.35 g, 82%) as a pale-yellow solid. Mp 52-53 ˚C.
IR (neat): 3400-2700 (br), 2955 (s), 2248 (m), 2206 (s),
2108 (s), 1691 (s) cm-1; 1H NMR (400 MHz, CDCl3): d = 10.28
(s), 0.96 (s, 9 H), -0.17 (s, 6 H); 13C NMR (100 MHz, CDCl3): d = 156.8,
95.5, 86.0, 73.7, 65.4, 26.0, 16.8, -5.2; MS (EI): m/z (%) = 208.1
(8) [M+], 151.0 (64) [M - t-Bu]+,
107.0 (100) [M - t-Bu - CO2]+; HRMS: m/z [M+] calcd.
for C11H16O2Si: 208.0920; found: 208.0922. Anal. Calcd for C11H16O2Si:
C, 63.46; H, 7.69. Found: C, 63.28; H, 7.96.
1-tert-Butyldimethylsilyl-5-dibromomethylene-7-pentafluorophenyl-1,3,6-heptatriyne
(26a)
SOCl2 (1.49 g, 0.9 mL, 12.5 mmol) was added
to 5-tert-butyldimethylsilyl-2,4-butynoic acid (0.520 g, 2.50 mmol) in
a flask protected from moisture with a drying tube containing CaCl2.
The mixture was stirred at r.t. overnight. The excess SOCl2 was
removed in vacuo to provide 25a, which was subjected to acylation
with acetylene 8 (0.580 g, 2.20 mmol) and AlCl3 (0.351 g, 2.64 mmol)
in CH2Cl2 (75 mL) as described for compound 19. The ketone product
was immediately dissolved in anhydrous CH2Cl2 (50 mL, freshly distilled
from CaH2) and carried on to the next step.CBr4 (0.476 g, 1.44 mmol)
and Ph3P (0.754 g, 2.88 mmol) were added to CH2Cl2 (50 mL) and allowed
to stir for 5 min at r.t. until the mixture turned bright orange.
This solution was cooled to 0 ˚C, the reserved
ketone was slowly added over a period of 20 min, and the reaction
was stirred overnight. The solvent was reduced to ca. 10 mL, pentane (100
mL) was added and the inhomogeneous mixture was filtered through
a plug of Celite and the solvent removed in vacuo. Column chromatography
(pentane) gave 26a (0.219 g, 0.407 mmol, 19%) as a pale-yellow
solid. Mp 104-105 ˚C. Rf = 0.66
(pentane). IR (neat): 2954 (m), 2197 (w), 2098 (m), 1502 (s) cm-1; 1H
NMR (400 MHz, CDCl3): d = 0.97 (s, 9 H), 0.18 (s, 6 H); 19F
(376 MHz, CDCl3): d =
-134.8 to -134.9
(m, 2 F), -150.7 (app t, J = 21
Hz, 1 F),
-161.6 to -161.7 (m, 2 F); 13C {1H} NMR
(100 MHz, CDCl3): d = 147.0 (d mult, 1J = 256
Hz), 142.6 (dtt, 1J = 259 Hz, J = 14
Hz, J = 5 Hz), 137.6 (d mult, 1J = 252
Hz), 114.4 (br), 112.4, 99.2 (app td, J = 18
Hz, J = 4 Hz), 96.3 (app q, J = 4
Hz), 94.8, 87.5, 81.4, 79.9 (app q, J = 4
Hz), 70.7, 26.0, 16.8, -5.0; HRMS (EI): m/z [M+] calcd.
for C20H1579Br81BrF5Si: 537.9210; found: 537.9213. Anal. Calcd for
C20H15Br2F5Si: C, 44.61; H, 2.79. Found: C, 45.01; H, 3.06.