(Aryltelluro)formates as Precursors of Alkyl Radicals
J . Org. Chem., Vol. 61, No. 17, 1996 5759
222 (3), 207 (34), 92 (24), 77 (100). Anal. Calcd for C8H8O2-
Te: C, 36.43; H, 3.06. Found: C, 36.39; H, 3.10.
7.04 (3H, m), 7.95-7.80 (2H, m); 13C NMR δ 14.32, 23.00,
25.99, 28.98, 29.34, 29.43, 32.07, 67.98, 114.01, 128.90, 129.54,
140.01, 156.51; 125Te NMR δ 767.8; IR ν (CdO) (neat) 1716
cm-1; MS m/ z (relative intensity) 364 (M+, 1.8), 320 (0.50),
284 (2), 154 (8.0), 56 (100); HRMS calcd for C15H22O2Te
364.0689, found 364.0678.
Meth yl [(4-flu or op h en yl)tellu r o]for m a te (11) was pre-
pared according to the standard protocol (A) using bis(4-
fluorophenyl) ditelluride and methyl chloroformate. Ku¨gelrohr
distillation (50-60° /0.075 mmHg) afforded 11 as a yellow oil
(93%): 1H NMR δ 3.27 (3H, s), 6.56-6.62 (2H, m), 7.47-7.51
(2H, m); 13C NMR δ 53.75, 107.70, 116.92 (d, J ) 20.7 Hz),
142.34 (d, J ) 8.1 Hz), 156.82, 163.74 (d, J ) 247.7 Hz); 125Te
NMR δ 765.3; IR ν (CdO) (neat) 1711 cm-1; MS m/ z (relative
intensity) 283 (M+, 21.5), 225 (61), 239 (8), 130 (9), 95 (100);
HRMS calcd for C8H7O2TeF 282.9421, found 282.9426.
Meth yl [(4-m eth oxyp h en yl)tellu r o]for m a te (12) was
prepared according to the standard protocol (A) using bis(4-
methoxyphenyl) ditelluride and methyl chloroformate. Re-
crystallization from ethanol gave a light brown, low melting
solid (87%): 1H NMR δ 3.16 (3H, s), 3.27 (3H, s), 6.58 (2H, d,
J ) 9 Hz), 7.71 (2H, d, J ) 9 Hz); 13C NMR δ 53.55, 54.57,
103.23, 115.73, 142.28, 160.95; 125Te NMR δ 751.9; IR ν (CdO)
(neat) 1712 cm-1; MS m/ z (relative intensity) 296 (M+, 33.0),
237 (100), 222 (31), 167 (4), 122 (35). Anal. Calcd for C9H10O3-
Te: C, 36.80; H, 3.43. Found; C, 36.76; H, 3.38.
2-Meth yl-1-p r op yl (p h en yltellu r o)for m a te (14) was pre-
pared according to the standard protocol (A) using diphenyl
ditelluride and isobutyl chloroformate. Ku¨gelrohr distillation
(60-70°/0.08 mmHg) afforded 14 as a yellow oil (86%): 1H
NMR δ 0.60 (6H, d, J ) 6.9 Hz), 1.58 (1H, m), 3.82 (2H, d, J
) 6.6 Hz), 6.95-7.05 (3H, m), 7.78-7.81 (2H, m); 13C NMR δ
18.78, 28.05, 73.64, 113.97, 128.90, 129.53, 140.07, 156.45;
125Te NMR δ 768.9; IR ν (CdO) (neat) 1709 cm-1; MS m/ z
(relative intensity) 308 (M+, 3.6), 284 (0.2), 208 (12), 77 (48),
56 (100). Anal. Calcd for C11H14O2Te: C, 43.20; H, 4.61.
Found; C, 43.03; H, 4.70.
2-Meth ylp r op yl [(4-flu or op h en yl)tellu r o]for m a te (15)
was prepared according to the standard protocol (A) using bis-
(4-fluorophenyl) ditelluride and isobutyl chloroformate. Ku¨gel-
rohr distillation (60-70°/0.075 mmHg) afforded 15 as a yellow
oil (83%): 1H NMR δ 0.61 (6H, d, J ) 6.9 Hz), 1.59 (1H, m),
3.83 (2H, d, J ) 6.6 Hz), 6.58-6.64 (2H, m), 7.51-7.56 (2H,
m); 13C NMR δ 18.75, 28.05, 73.76, 107.99, 116.90 (d, J ) 21.2
Hz), 142.42 (d, J ) 7.6 Hz), 156.45, 163.71 (d, J ) 248.3 Hz);
125Te NMR δ 760.3; IR ν (CdO) (neat) 1711 cm-1; MS m/ z
(relative intensity) 325 (M+, 3.1), 225 (17), 130 (5), 95 (36), 56
(100); HRMS calcd for C11H13O2TeF 324.9891, found 324.9898.
Sta n d a r d P r otocol (B) for th e P r ep a r a tion of Tellu r o-
for m a tes fr om Alcoh ols. Cycloh exyl (P h en yltellu r o)-
for m a te (19). Sodium borohydride (261 mg, 6.9 mmol) was
added with stirring to a solution of diphenyl ditelluride (930
mg, 2.3 mmol) in THF (50 mL). The reaction vessel was
purged with nitrogen, and methanol (∼250 µL) was added
dropwise until the red solution turned colorless (30 min). In
a separate reaction vessel, 20% phosgene solution (15 mL, 29
mmol) was added via syringe to a solution of cyclohexanol (500
mg, 5.0 mmol) in THF (50 mL) under nitrogen. The solution
was stirred for a further 60 min and concentrated in vacuo to
approximately half the original volume. After purging with
nitrogen, the solution of the chloroformate was transferred via
cannula into the solution containing the sodium phenyltel-
luroate, and the resulting light yellow solution was stirred at
room temperature under nitrogen overnight. Water (10 mL)
was added, and the mixture was extracted with ether (3 × 50
mL). The combined ether extracts were dried (MgSO4), and
the solvent was removed in vacuo. The telluroformate 19 was
obtained as a yellow oil after flash chromatogaphy (hexane/
ethyl acetate 99:1) (1.35 g, 90%): 1H NMR δ 0.93-1.63 (10H,
m), 4.95 (1H, m), 6.93-7.02 (3H, m), 7.80-7.83 (2H, m); 13C
NMR δ 23.52, 25.32, 31.84, 77.09, 114.32, 128.82, 129.50,
139.95, 155.81; 125Te NMR δ 771.6; IR ν (CdO) (neat) 1709
cm-1; MS m/ z (relative intensity) 333 (M+, 0.5), 289 (0.7), 208
(7), 130 (1), 83 (100). Anal. Calcd for C13H16O2Te: C, 47.05,
H, 4.86. Found C, 46.93, H, 4.96.
Cycloh exyl [(4-flu or op h en yl)tellu r o]for m a te (20) was
prepared according to the standard protocol (B) using bis(4-
fluorophenyl) ditelluride and cyclohexanol. Flash chromatog-
raphy (hexane/ethyl acetate 99:1) afforded 20 as a yellow oil
(73%): 1H NMR δ 0.92-1.62 (10H, m), 4.94 (1H, m), 6.60 (2H,
m), 7.55 (2H, m); 13C NMR δ 23.52, 25.27, 31.84, 77.30, 108.27
(d, J ) 3.5 Hz), 116.88 (d, J ) 20.8 Hz), 142.33 (d, J ) 7.6
Hz), 155.84, 163.70 (d, J ) 247.7 Hz); 125Te NMR δ 769.9; IR
ν (CdO) (neat) 1709 cm-1; MS m/ z (relative intensity) 352 (M+,
0.3), 225 (11), 220 (3), 95 (25), 83 (100). Anal. Calcd for
C13H15O2TeF: C, 44.62; H, 4.32. Found: C, 44.65; H, 4.38.
3â-Ch olesta n yl (p h en yltellu r o)for m a te (22) was pre-
pared according to the standard protocol (B) using diphenyl
ditelluride and 3â-cholestanol. Recrystallization from ethanol
1
gave 22 as a white solid (70%): mp ) 126-127°; H NMR δ
0.35-1.98 (46H, m), 4.97 (1H, m), 6.96-7.02 (3H, m), 7.84-
7.87 (2H, m); 13C NMR δ 12.12, 12.30, 19.00, 21.43, 22.77,
23.03, 24.33, 24.50, 28.01, 28.40, 28.63, 28.68, 32.13, 34.54,
35.38, 35.56, 36.20, 36.64, 36.78, 39.91, 40.34, 42.83, 44.56,
54.17, 56.66, 78.34, 114.32, 128.86, 129.58, 139.90, 156.03; 125
-
Te NMR δ 770.2; IR ν (nujol) (CdO) 1710 cm-1; MS m/ z
(relative intensity) 578 (14.4), 409 (3), 371 (69), 245 (10), 95
(100), 81 (82). Anal. Calcd for C34H52O2Te: C, 65.83; H, 8.45.
Found: C, 65.91, H, 8.52.
3â-Ch olesta n yl [(4-flu or op h en yl)tellu r o]for m a te (23)
was prepared according to the standard protocol (B) using bis-
(4-fluorophenyl) ditelluride and 3â-cholestanol. Recrystalli-
zation from ethanol gave 23 as a white solid (75%): mp )
1
113.5-114.5°; H NMR δ 0.38-1.99 (46H, m), 4.97 (1H, m),
6.62 (2H, m), 7.59 (2H, m); 13C NMR δ 12.13, 12.30, 19.00,
21.44, 22.76, 23.03, 24.33, 24.50, 28.02, 28.40, 28.62, 28.68,
32.13, 34.56, 35.38, 35.56, 36.20, 36.64, 36.78, 39.91, 40.33,
42.84, 44.57, 54.18, 56.62, 56.66, 78.58, 108.30, 116.95 (d, J )
21.2 Hz), 142.24 (d, J ) 7.6 Hz), 155.98, 163.72 (d, J ) 247.2
Hz); 125Te NMR δ 768.7; IR ν (CdO) 1717 cm-1; MS m/ z
(relative intensity) 578 (0.35), 495 (6), 370 (36), 316 (14), 203
(10), 81 (100). Anal. Calcd for C34H51O2TeF: C, 63.97; H, 8.05.
Found: C, 63.93; H 8.29.
3â-Ch olester yl [(4-flu or op h en yl)tellu r o]for m a te (25)
was prepared according to the standard protocol (B) using
diphenyl ditelluride and cholesterol. Recrystallization from
ethanol afforded 25 as a white solid (80%): mp ) 127-128°;
1H NMR δ 0.64-2.48 (43H, m), 4.98 (1H, m), 5.25 (1H, m),
6.95-7.05 (3H, m), 7.82-7.86 (2H, m); 13C NMR δ 12.03, 19.04,
19.23, 21.26, 22.79, 23.05, 24.35, 24.56, 28.29, 28.40, 28.60,
32.03, 32.21, 36.19, 36.64, 37.07, 38.69, 39.91, 40.07, 42.53,
50.13, 56.49, 56.88, 74.25, 78.52, 114.29, 123.17, 128.88,
129.58, 139.41, 139.88, 155.91; 125Te NMR δ 771.9; IR ν (Nujol)
(CdO) 1717 cm-1; MS m/ z (relative intensity) (21 eV) 575 (1.7),
369 (100), 284, (4), 207 (17), 175 (14), 161 (34). Anal. Calcd
for C34H50O2Te: C, 66.04; H, 8.15. Found: C, 66.16; H 7.98.
Ben zyl (p h en yltellu r o)for m a te (27) was prepared ac-
cording to the standard protocol (B) using diphenyl ditelluride
and benzyl alcohol. Flash chromatography (hexane/ethyl
1
acetate 98:2) afforded 27 as an orange oil (60%); H NMR δ
4.96 (2H, s), 6.94-7.02 (8H, m), 7.73-7.75 (2H, m); 13C NMR
δ 69.23, 113.95, 128.51, 128.64, 128.71, 128.96, 129.56, 135.66,
140.01, 156.45; 125Te NMR δ 784.2; IR ν (neat) (CdO) 1709
cm-1; MS m/ z (relative intensity) 342 (M+, 0.94), 298 (3), 207
(16), 91 (100), 77 (61); HRMS calcd for C14H12O2Te 341.9907,
found 341.9922.
Sta n d a r d P r otocol (C) for th e P r ep a r a tion of (P h en -
ylselen o)for m a tes fr om Ch lor ofor m a tes. Meth yl (P h en -
ylselen o)for m a te (13). Sodium borohydride (148 mg, 3.9
mmol) was added with stirring to a solution of diphenyl
diselenide (400 mg, 1.3 mmol) in THF (30 mL). The reaction
vessel was purged with nitrogen, and methanol (∼250 µL) was
added dropwise until the yellow solution turned colorless (30
min). When the evolution of hydrogen had ceased (∼60 min),
methyl chloroformate (265 mg, 2.8 mmol) was added via
1-Octyl (p h en yltellu r o)for m a te (17) was prepared ac-
cording to the standard protocol (B) using diphenyl ditelluride
and 1-octanol. Flash chromatography (hexane/ethyl acetate
98:2) afforded 17 as a yellow oil (98%): 1H NMR δ 0.89 (3H, t,
J ) 7.2 Hz), 1.03-1.38 (12H,m), 4.03 (2H, t, J ) 6.9 Hz), 6.95-