N. Nakajima et al. / Tetrahedron 58 (2002) 3561±3577
3575
5.23 (2H, s, H2C), 3.79 (3H, s, H3C); 13C NMR (CDCl3)
159.9, 158.0 (t, J28.4 Hz, C(1)), 130.0, 126.9, 117.5 (tq,
J33.8, 287.8 Hz, C(4)), 113.9, 108.2 (tq, J38.9,
267.1 Hz, C(3)), 108.0 (tt, J32.2, 259.7 Hz, C(2)), 69.6,
55.0; 19F NMR (CDCl3) 281.2, 2118.2, 2126.9; IR (neat,
cm21) 2842 (w), 1682 (m), 1617 (m), 1559 (w), 1541 (w),
1518 (m), 1354 (m), 1323 (m), 1306 (m), 1221 (s), 1177 (s),
1125 (s), 1075 (m), 1036 (m), 967 (m), 934, (m), 826 (m),
749 (m); EI-MS (70 eV) 333 (M1, 32), 332 (42), 331 (31),
316 (46), 271 (25), 257 (72), 256 (100), 255 (72), 242 (76),
241 (100), 227 (44), 211 (21), 169 (92), 136 (67), 135 (85),
122 (100), 121 (100), 91 (74), 68 (58), 67 (85), 56 (33); EI-
HRMS calcd for C12H10F7NO2 (M1), 333.0599; found,
333.0574.
194 (11), 166 (15), 152 (32), 151 (100), 150 (29), 149 (19),
135 (37), 108 (20), 107 (58), 106 (20), 67 (25), 56 (21); EI-
HRMS calcd for C11H12F5NO3 (M1), 313.0737; found,
313.0742.
5.4.14. 3,4-Dimethoxybenzyl 2-chloro-2,2-di¯uoroaceti-
midate (42C). Imidate formation according to the general
procedure using 3,4-dimethoxybenzyl alcohol (168 mg,
1 mmol),
2-chloro-2,2-di¯uoroacetamide
(427 mg,
3.3 mmol), DMSO (1.07 mL, 15 mmol), (COCl)2 (260 mL,
3.0 mmol), Et3N (1.38 mL, 10 mmol) and DBU (150 mL,
1.0 mmol) afforded a colorless oil, which was puri®ed by
silica gel column chromatography (hexane/EtOAc, 3/1) and
following Kugelrohr distillation to give 238 mg (85%) of
the 2-chloro-2,2-di¯uoroacetimidate as a colorless oil: Rf
1
0.45 (hexane/EtOAc, 3/1); bp 1408C/1.8 mmHg; H NMR
5.4.12. 3,4-Dimethoxybenzyl 2,2,2-tri¯uoroacetimidate
(42A). Imidate formation according to the general pro-
cedure using 3,4-dimethoxybenzyl alcohol (841 mg,
5 mmol), 2,2,2-tri¯uoroacetamide (1.8 g, 16 mmol),
DMSO (3.41 mL, 48 mmol), (COCl)2 (1.31 mL,
15 mmol), Et3N (5.35 mL, 38 mmol) and DBU (1.5 mL,
10 mmol) afforded a colorless oil, which was puri®ed by
silica gel column chromatography (hexane/EtOAc, 3/1)
and following Kugelrohr distillation to give 1.07 g (81%)
of the 2,2,2-tri¯uoroacetimidate as a colorless solid: Rf 0.39
(hexane/EtOAc, 3/1); mp 73±748C; bp 120±1258C/
(CDCl3) 8.12 (1H, s, NH), 6.81 (3H, m, HC(Ar)), 5.15 (2H,
s, H2C), 3.77 (3H, s, Me) 3.76 (3H, s, Me); 13C NMR
(CDCl3) 159.5 (t, J32.9 Hz, C(1)), 149.0, 148.7, 127.3,
120.8, 117.6 (t, J293.2 Hz, C(2)), 111.3, 110.8, 69.3,
55.5; 19F NMR (CDCl3) 261.7; IR (neat, cm21) 3305 (w),
3006 (w), 2959 (w), 2840 (w), 1742 (m), 1680 (s), 1595 (m),
1520 (s), 1466 (m), 1422 (m), 1331 (m), 1269 (s), 1242 (m),
1161 (s), 1142 (s), 1080 (s), 1028 (s), 976 (s), 853 (m), 806
(m), 766 (w), 689 (w), 613 (w), 556 (w); EI-MS (70 eV) 281
(31), 280 (18), 279 (M1, 92), 278 (15), 269 (63), 264 (27),
244 (14), 194 (30), 166 (41), 152 (100), 151 (100), 150 (65),
135 (100), 121 (36), 108 (80), 107 (100), 106 (98), 105 (70),
90 (65), 71 (87), 69 (87), 67 (100), 51 (36); EI-HRMS calcd
for C11H12ClF2NO3 (M1), 279.0474; found, 279.0480.
1
0.3 mmHg; H NMR (CDCl3) 8.25 (1H, s, NH), 6.84 (3H,
m, HC(Ar)), 5.19 (2H, s, H2C), 3.83 (3H, s, Me), 3.82 (3H, s,
Me); 13C NMR (CDCl3) 157.5 (q, J38.0 Hz, C(1)), 149.1,
148.8, 127.1, 121.0, 115.4 (q, J280.0 Hz, C(2)), 111.4,
110.8, 69.1, 55.5; 19F NMR (CDCl3) 274.7; IR (neat,
cm21) 3305 (w), 2961 (w), 2840 (w), 1744 (w), 1686 (s),
1595 (m), 1520 (s), 1466 (m), 1422 (m), 1354 (m), 1269 (s),
1242 (s), 1202 (s), 1161 (s), 1080 (s), 1028 (s), 849 (m), 808
(m), 768 (w), 642 (w), 556 (w); EI-MS (70 eV) 264 (10),
263 (M1, 65), 262 (36), 261 (10), 248 (22), 232 (10), 193
(13), 192 (51), 165 (46), 152 (100), 151 (100), 135 (62), 107
(100), 106 (63), 73 (60), 69 (54), 67 (69), 51 (25); EI-HRMS
calcd for C11H12F3NO3 (M1), 263.0769; found, 263.0768.
5.4.15. 3,4-Dimethoxybenzyl 2,2,3,3,4,4,4-hepta¯uoro-
butyrimidate (42D). Imidate formation according to the
general procedure using 3,4-dimethoxybenzyl alcohol
(168 mg, 1 mmol), 2,2,3,3,4,4,4-hepta¯uorobutyramide
(704 mg, 3.3 mmol), DMSO (1.07 mL, 15 mmol), (COCl)2
(260 mL, 3.0 mmol), Et3N (1.38 mL, 10 mmol) and DBU
(300 mL, 2.0 mmol) afforded a colorless oil, which was
puri®ed by silica gel column chromatography (hexane/
EtOAc, 3/1) and following Kugelrohr distillation to give
255 mg (70%) of the 2,2,3,3,4,4,4-hepta¯uorobutyrimidate
as a colorless oil: Rf 0.39 (hexane/EtOAc, 3/1); bp 2108C/
5.4.13. 3,4-Dimethoxybenzyl 2,2,3,3,3-penta¯uoropro-
pionimidate (42B). Imidate formation according to the
general procedure using 3,4-dimethoxybenzyl alcohol
(168 mg, 1 mmol), 2,2,3,3,3-penta¯uoropropionamide
(538 mg, 3.3 mmol), DMSO (1.07 mL, 15 mmol), (COCl)2
(260 mL, 3.0 mmol), Et3N (1.38 mL, 10 mmol) and DBU
(300 mL, 2.0 mmol) afforded a colorless oil, which was
puri®ed by silica gel column chromatography (hexane/
EtOAc, 3/1) and following Kugelrohr distillation to give
255 mg (82%) of the 2,2,3,3,3-penta¯uoropropionimidate
as a colorless solid: Rf 0.39 (hexane/EtOAc, 3/1); mp 56±
1
1.5 mmHg; H NMR (CDCl3) 8.43 (1H, s, NH), 6.86 (3H,
m, HC(Ar)), 5.23 (2H, s, H2C), 3.84 (6H, s, Me); 13C NMR
(CDCl3); 157.7 (t, J28.8 Hz, C(1)), 149.2, 148.9, 127.2,
120.9, 117.3 (tq, J33.8, 286.7 Hz, C(4)), 111.3, 110.9,
108.0 (tqt, J33.9, 38.9, 266.8 Hz, C(3)), 107.8 (tt,
J32.2, 259.3 Hz, C(2)), 69.5, 55.5, 55.4; 19F NMR
(CDCl3) 281.1 (t, J9.1 Hz), 2118.3 (sextet, J9.0 Hz),
2127.0 (t, J9.1 Hz); IR (neat, cm21) 3355 (w), 3306 (w),
2961 (w), 2840 (w), 1742 (w), 1680 (s), 1595 (m), 1520 (s),
1466 (m), 1424 (m), 1399 (w), 1321 (m), 1269 (s), 1229 (s),
1163 (s), 1125 (s), 1076 (m), 1030 (m), 968 (m), 926 (m),
851 (m), 806 (m), 749 (m), 648 (w), 556 (w); EI-MS (70 eV)
364 (14), 363 (M1, 86), 362 (32), 361 (4), 348 (20), 300
(35), 285 (10), 270 (18), 269 (85), 238 (17), 225 (8), 194
(18), 193 (12), 166 (31), 152 (83), 151 (100), 135 (77), 107
(100), 106 (56), 67 (53), 56 (29); EI-HRMS calcd for
C13H12F7NO3 (M1), 363.0705; found, 363.0711.
1
578C; bp 1508C/1.8 mmHg; H NMR (CDCl3) 8.46 (1H, s,
NH), 6.83 (3H, m, HC(Ar)), 5.21 (2H, s, H2C), 3.80 (6H, s,
Me); 13C NMR (CDCl3) 157.7 (t, J28.6 Hz, C(1)), 149.1,
148.9, 127.2, 120.7, 117.7 (tq, J35.5, 286.6 Hz, C(3)),
111.1, 110.8, 106.1 (qt, J39.7, 257.7 Hz, C(2)), 69.4,
55.53, 55.46; 19F NMR (CDCl3) 283.0, 2120.4; IR (KBr)
3305 (s), 2963 (m), 2840 (m), 1692 (s), 1609 (m), 1595 (m),
1520 (s), 1472 (m), 1426 (m), 1387 (m), 1321 (s), 1275 (s),
1252 (s), 1240 (s), 1181 (s), 1161 (s), 1142 (s), 1082 (s),
1028 (s), 999 (m), 909 (m), 880 (m), 855 (m), 812 (m), 749
(m), 642 (m), 577 (w), 423 (w); EI-MS (70 eV) 314 (8), 313
(M1, 54), 312 (7), 311 (8), 298 (18), 27 (4), 263 (4), 248 (3),
5.5. General procedure for benzyl protection
A solution of benzyl imidate, alcohol and acid was stirred at