2694 J . Org. Chem., Vol. 67, No. 8, 2002
Notes
Sch em e 4
(1 mL). The resulting mixture was stirred at the same temper-
ature for 1 h, and then sodium borohydride (0.112 g, 3.0 mmol)
was added to the mixture at 0 °C, which was stirred at room
temperature for 1 h. The reaction mixture was quenched with
saturated ammonium chloride, and the aqueous layer was
extracted with diethyl ether (25 mL × 3). The organic layers
were combined, washed with brine, and dried over magnesium
sulfate. After filtration, the solvents were removed under
reduced pressure to provide the crude product, which was
purified through flash chromatography (n-hexanes-EtOAc (10:
1)) on silica gel.
ter t-Bu tyl 3-[N-(4-Meth oxyph en yl)am in o]-2-ter t-bu tylth io-
4,4,4-tr iflu or obu ta n oa te (syn -11a ). This compound was ob-
tained as colorless crystals (0.142 g, 70%): mp 58-60 °C; IR
(neat) 3424, 1728 cm-1; 1H NMR (CDCl3) δ 6.79 (d, J ) 9.1 Hz,
2H), 6.70 (d, J ) 9.1 Hz, 2H), 4.4-4.2 (m, 1H), 3.85-3.75 (m,
1H), 3.75 (s, 3H), 3.53 (d, J ) 6.8 Hz, 1H), 1.42 (s, 9H), 1.38 (s,
9H); 19F NMR (CDCl3) δ 88.3 (d, J ) 6 Hz, CF3); MS m/z 407
(11) [M]+, 204 (100), 148 (29), 92 (43), 57 (55). Anal. Calcd for
1.49 (s, 9H), 1.34 (s, 9H); 19F NMR (CDCl3) δ 88.3 (d, J ) 6 Hz,
CF3); MS m/z 407 (3) [M]+, 204 (100), 148 (17), 92 (34), 57 (43).
Anal. Calcd for C19H28F3NO3S: C, 56.00; H, 6.93; N, 3.44.
Found: C, 55.66; H, 7.13; N, 3.81.
ter t-Bu tyl 3-[N-(4-Ch lor oph en yl)am in o]-2-(ter t-bu tylth io)-
4,4,4-tr iflu or obu ta n oa te (a n ti-11b). Flash chromatography
(n-hexanes-EtOAc (20:1)) on silica gel gave a pale yellowish oil
1
(0.154 g, 75%): IR (neat) 3420, 1726 cm-1; H NMR (CDCl3) δ
7.14 (d, J ) 8.8 Hz, 2H), 6.62 (d, J ) 8.8 Hz, 2H), 5.53 (d, J )
9.2 Hz, 1H), 4.3-4.0 (m, 1H), 3.57 (d, J ) 3.6 Hz, 1H), 1.49 (s,
9H), 1.35 (s, 9H); 19F NMR (CDCl3) δ 88.0 (d, J ) 7 Hz, CF3);
MS m/z 413 (3) [M + 2]+, 411 (11) [M]+, 282 (14), 208 (60), 148
(54), 92 (98), 57 (100). Anal. Calcd for C18H25ClF3NO2S: C, 52.49;
H, 6.12; N, 3.40. Found: C, 52.24; H, 6.42; N, 3.19.
ter t-Bu tyl 3-[N-(4-Ch lor op h en yl)a m in o]-2-(ter t-bu tylsu l-
fon yl)-4,4,4-tr iflu or obu ta n oa te (a n ti-12b). To a solution of
m-chloroperbenzoic acid (0.215 g, 1.25 mmol) in dry CH2Cl2 (3
mL) at 0 °C was added anti-11b (0.206 g, 0.5 mmol) dissolved
in CH2Cl2 (2 mL). The resulting mixture was stirred at the same
temperature for 3 h and was quenched by the addition of
saturated sodium hydrogencarbonate. The aqueous layer was
extracted with diethyl ether (25 mL × 3). The organic layers
were combined, washed with brine, and dried over magnesium
sulfate. After filtration, the solvents were removed under
reduced pressure to provide a solid which was purified by
recrystallization from CHCl3 to give single crystals of 12b (0.201
g, 90%): mp 164-166 °C dec; IR (neat) 3408, 1734 cm-1; 1H NMR
(CDCl3) δ 7.15 (d, J ) 8.8 Hz, 2H), 6.68 (d, J ) 8.8 Hz, 2H), 5.85
(d, J ) 8.8 Hz, 1H), 4.8-4.5 (m, 1H), 4.31 (d, J ) 2.4 Hz, 1H),
1.55 (s, 9H), 1.47 (s, 9H); 19F NMR (CDCl3) δ 87.7 (d, J ) 6 Hz,
CF3). Anal. Calcd for C18H25ClF3NO2S: C, 48.70; H, 5.68; N, 3.16.
Found: C, 48.61; H, 6.05; N, 2.95.
Dep r otection of th e N-p-Meth oxyp h en yl Gr ou p of 11.
A solution of 11a (0.203 g, 0.5 mmol) in CH3CN (5 mL) was
treated at room temperature with cerium ammonium nitrate
(CAN) (0.822 g, 1.5 mmol) dissolved in H2O (1.7 mL), and the
reaction mixture was stirred for 3 h. The aqueous layer was
extracted with diethyl ether (25 mL × 3). The organic layers
were combined and washed with brine, and then anhydrous
hydrazine (0.062 g, 2 mmol) was added. The organic layers were
dried over magnesium sulfate, filtered, and concentrated under
reduced pressure to provide the crude product mixture, which
was purified through flash chromatography (n-hexanes-EtOAc
(5:1)) on silica gel.
C
19H28F3NO3S: C, 56.00; H, 6.93; N, 3.44. Found: C, 56.02; H,
6.93; N, 3.60.
ter t-Bu tyl 3-[N-(4-Ch lor oph en yl)am in o]-2-(ter t-bu tylth io)-
4,4,4-tr iflu or obu ta n oa te (syn -11b). This compound was ob-
tained as colorless crystals (0.146 g, 71%): mp 100-101 °C; IR
(neat) 3408, 1722 cm-1; 1H NMR (CDCl3) δ 7.15 (d, J ) 8.8 Hz,
2H), 6.65 (d, J ) 8.8 Hz, 2H), 4.5-4.2 (m, 1H), 4.05 (d, J ) 9.2
Hz, 1H), 3.53 (d, J ) 6.7 Hz, 1H), 1.43 (s, 9H), 1.38 (s, 9H); 19F
NMR (CDCl3) δ 88.2 (d, J ) 6 Hz, CF3); MS m/z 413 (2) [M]+,
411 (4) [M]+, 286 (6), 208 (57), 148 (66), 92 (91), 57 (100). Anal.
Calcd for C18H25F3NO2S: C, 52.49; H, 6.12; N, 3.40. Found: C,
52.57; H, 6.34; N, 3.30.
Red u ction of 10 to a n ti-11. To a solution of anhydrous
sodium borohydride (0.113 g, 3.0 mmol) in dry di(iethylene
glycol) dimethyl ether (1 mL), stirred for 30 min at 0 °C, was
added the â-imino ester 10a (0.203 g, 0.5 mmol) in THF (2 mL),
and the reaction mixture was stirred at room temperature for 3
h. After almost all the starting material was converted (moni-
tored by TLC), 10 mL of diethyl ether was added and the reaction
mixture was quenched with 10 mL of saturated ammonium
chloride. The aqueous layer was extracted with diethyl ether
(25 mL × 3). The combined organic extracts were washed with
brine, dried over magnesium sulfate, and concentrated under
reduced pressure to furnish the crude product. Purification was
carried out as indicated in each case.
ter t-Bu tyl 3-[N-(4-Meth oxyp h en yl)a m in o]-2-(ter t-bu tyl-
th io)-4,4,4-tr iflu or obu ta n oa te (a n ti-11a ). Flash chromatog-
raphy (n-hexanes-EtOAc (15:1)) on silica gel gave a pale
yellowish oil (0.147 g, 72%): IR (neat) 3428, 1728 cm-1; 1H NMR
(CDCl3) δ 6.78 (d, J ) 9.0 Hz, 2H), 6.66 (d, J ) 9.0 Hz, 2H), 5.11
(br, 1H), 4.2-4.0 (m, 1H), 3.75 (s, 3H), 3.57 (d, J ) 3.7 Hz, 1H),
ter t-Bu tyl 3-Am in o-2-(ter t-bu tylth io)-4,4,4-tr iflu or obu -
ta n oa te (syn -13a ). This compound was obtained as a colorless
oil (0.093 g, 62%): IR (neat) 3420, 3380, 1734 cm-1 1H NMR
;
(CDCl3) δ 3.8-3.5 (m, 1H), 3.28 (d, J ) 8.1 Hz, 1H), 1.70 (brs,
2H), 1.46 (s, 9H), 1.38 (s, 9H); 19F NMR (CDCl3) δ 86.9 (d, J )
6 Hz, CF3); MS m/z 302 (1) [M + 1]+, 230 (4), 148 (32), 92 (38),