N- and C-Acylation in β-Enamino Ketones: Structural Effects on Regiocontrol

Abstract

The acylation reaction of secondary (R¹ = H) β-enamino ketones [RCOCH=CHNR¹R², where R = CF₃, CCl₃, Ph, 4-FC₆H₄, 4-NO₂C₆H₄, thien-2-yl; R¹ = H, Me; R² = Me, Bn, Ph, 4-NO₂C₆H₄] with trifluoroacetic anhydride or ethyl oxalyl chloride in pyridine led regiospecifically to a series of 14 N-acylated enaminones in good yields (72-88%). On the other hand, when tertiary enaminones (R¹, R² = Me) were used, the acylation reaction led to a series of 12 C-acylated enaminones in good to excellent yields (75-92%).

ketones - enones - acylation - regioselectivity - substituent effects

References and Notes

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22

Typical Procedure for Synthesis of N-Acyl and α-C-Acyl Enaminones
A solution of β-enamino ketones (2 mmol), anhyd CH₂Cl₂ (6 mL), and pyridine (1.7 ml, 2 mmol) was added dropwise to a stirred solution of ethyl oxalyl chloride (0.22 mL, 2 mmol) or TFAA (0.28 mL, 2 mmol) in CH₂Cl₂ (8 mL) at 0 °C under nitrogen atmosphere. After warming to r.t. the solution was stirred at the temperature and time showed in Table [1] . The organic layer was then washed with a solution of H₂O-HCl (10:1; 1 × 20 mL) and with distilled H₂O (3 × 20 mL). Finally, the organic layer was dried over Na₂SO₄ and evaporated under vacuum to afford the N-acyl or α-C-acyl enaminones. When necessary, the products were recrystallized from hexane.
N -Benzyl- N -(4,4,4-trifluoro-3-oxobut-1-enyl)oxalamic Acid Ethyl Ester (Entry 1) Oil. ¹H NMR (200 MHz, CDCl₃): δ = 1.39 (br, 3 H, OCCH₃), 4.48 (br, 2 H, OCH₂), 4.96 (s, 2 H, CH₂Ph), 6.01 (d, 1 H, J = 14 Hz, H2), 7.21-7.36 (m, 5 H, Ph), 8.15 (br, 1 H, H3). ¹³C NMR (100 MHz, CDCl₃): δ = 13.7 (OCCH₃), 47.1 (CH₂Ph), 63.7 (OCH₂), 102.0 (C2), 116.0 (q, ¹ J _C-F = 290 Hz, CF₃), 126.6, 128.3, 129.1, 133.1 (Ph), 145.0 (C3), 160.2 (C4), 161.8 (C5), 179.1 (q, ² J _C-F = 36 Hz, C1). MS: m/z (%) = 329 (10) [M⁺], 260 (9) [M - CF₃], 228 (85) [M - C(O)CO₂Et], 91 (100) [CH₂Ph], 69 (5) [CF₃]. Anal. Calcd for C₁₅H₁₄F₃NO₄: C, 54.72; H, 4.29; N, 4.25. Found: C, 54.86; H, 4.53, N, 4.49.
N -Benzyl-2,2,2-trifluoro- N -(4,4,4-trifluoro-3-oxobut-1-enyl)acetamide (Entry 2) Oil. ¹H NMR (200 MHz, CDCl₃): δ = 5.05 (s, 2 H, CH₂Ph), 6.09 (d, 1 H, J = 14 Hz, H2), 7.18-7.38 (m, 5 H, Ph), 8.32 (d, 1 H, J = 14 Hz, H3). ¹³C NMR (100 MHz, CDCl₃): δ = 48.8 (CH₂Ph), 103.9 (C2), 115.6 (q, ¹ J _C-F = 288 Hz, CF₃), 115.9 (q, ¹ J _C-F = 290 Hz, CF₃), 126.3, 128.5, 129.3, 132.7 (Ph), 143.5 (C3), 157.2 (q, ¹ J _C-F = 38 Hz, C4), 179.0 (q, ¹ J _C-F = 36 Hz, C1). MS: m/z (%) = 325 (28) [M], 256 (29) [M - CF₃], 228 (76) [M - C(O)CF₃], 91 (100) [CH₂Ph], 69 (53) [CF₃]. Anal. Calcd for C₁₃H₉F₆NO₂: C, 48.01; H, 2.79; N, 4.31. Found: C, 48.20; H, 2.98, N, 4.58.
N -Phenyl- N -(4,4,4-trifluoro-3-oxobut-1-enyl)oxalamic Acid Ethyl Ester (Entry 3) Oil. ¹H NMR (200 MHz, CDCl₃): δ = 1.02 (br, 3 H, OCCH₃), 4.06 (br, 2 H, OCH₂), 5.59 (d, 1 H, J = 14 Hz, H2), 7.30-7.56 (m, 5 H, Ph), 8.77 (d, 1 H, J = 14 Hz, H3). ¹³C NMR (100 MHz, CDCl₃): δ = 13.4 (OCCH₃), 62.6 (OCH₂), 103.9 (C2), 116.0 (q, ¹ J _C-F = 291 Hz, CF₃), 128.2, 130.3, 130.7, 134.6 (Ph), 144.5 (C3), 159.9 (C4), 160.4 (C5), 179.5 (q, ² J _C-F = 35 Hz, C1). MS: m/z (%) = 315 (6) [M⁺], 242 (8) [M - CO₂Et], 218 (29) [M - C(O)CF₃], 146 (100), 104 (49), 77 (81) [Ph], 69 (13) [CF₃]. Anal. Calcd for C₁₄H₁₂F₃NO₄: C, 53.34; H, 3.84; N, 4.44. Found: C, 53.35; H, 4.10; N, 4.70.
2,2,2-Trifluoro- N -phenyl- N -(4,4,4-trifluoro-3-oxobut-1-enyl)acetamide (Entry 4) Mp 30-32 °C. ¹H NMR (200 MHz, CDCl₃): δ = 5.44 (d, 1 H, J = 14 Hz, H2), 7.27-7.60 (m, 5 H, Ph), 8.79 (d, 1 H, J = 14 Hz, H3). ¹³C NMR (100 MHz, CDCl₃): δ = 105.6 (C2), 115.4 (q, ¹ J _C-F = 288 Hz, CF₃), 115.9 (q, ¹ J _C-F = 288 Hz, CF₃), 128.3, 130.2, 130.9, 133.8 (Ph), 145.8 (C3), 156.2 (q, ¹ J _C-F = 38 Hz, C4), 179.5 (q, ¹ J _C-F = 36 Hz, C1). MS: m/z (%) = 311 (39) [M⁺], 242 (85) [M - CF₃], 214 (47) [M - C(O)CF₃], 172 (42), 145 (44), 117 (37), 77 (100) [Ph], 69 (43) [CF₃]. Anal. Calcd for C₁₂H₇F₆NO₂: C, 46.32; H, 2.27; N, 4.50. Found: C, 46.44; H, 2.36; N, 4.67.
N -(4-Nitrophenyl)- N -(4,4,4-trifluoro-3-oxobut-1-enyl)oxalamic Acid Ethyl Ester (Entry 5) Mp 93-95 °C. ¹H NMR (200 MHz, CDCl₃): δ = 1.19 (t, 3 H, OCCH₃), 4.19 (q, 2 H, OCH₂), 5.56 (d, 1 H, J = 14 Hz, H2), 7.53-8.44 (m, 4 H, C₆H₄), 8.71 (br, 1 H, H3). ¹³C NMR (100 MHz, CDCl₃): δ = 13.5 (OCCH₃), 63.4 (OCH₂), 104.1 (C2), 115.8 (q, ¹ J _C-F = 290 Hz, CF₃), 125.6, 129.5, 144.1, 148.7 (C₆H₄), 140.3 (C3), 159.2 (C4), 159.2 (C5), 179.1 (q, ² J _C-F = 36 Hz, C1). MS: m/z (%) = 360 (3) [M⁺], 291 (17) [M - CF₃], 287 (12) [M - CO₂Et], 263 (50) [M - C(O)CF₃], 191 (100), 145 (49), 116 (51), 76 (51), 69 (40) [CF₃]. Anal. Calcd for C₁₄H₁₁F₃N₂O₆: C, 46.68; H, 3.08; N, 7.78. Found: C, 46.66; H, 3.28; N, 7.87.
2,2,2-Trifluoro- N -(4-nitrophenyl)- N -(4,4,4-trifluoro-3-oxobut-1-enyl)acetamide (Entry 6) Mp 112-114 °C. ¹H NMR (200 MHz, CDCl₃): δ = 5.44 (d, 1 H, J = 14 Hz, H2), 7.54-8.49 (m, 4 H, C₆H₄), 8.75 (d, 1 H, J = 14 Hz, H2). ¹³C NMR (100 MHz, CDCl₃): δ = 105.9 (C2), 115.2 (q, ¹ J _C-F = 288 Hz, CF₃), 115.7 (q, ¹ J _C-F = 290 Hz, CF₃), 125.8, 130.0, 144.8, 149.1 (C₆H₄), 139.2 (C3), 155.5 (q, ¹ J _C-F = 39 Hz, C4), 180.7 (q, ¹ J _C-F = 35 Hz, C1). MS: m/z (%) = 356 (13) [M⁺], 287 (72) [M - CF₃], 259 (47) [M - C(O)CF₃], 217 (100), 116 (38), 69 (62) [CF₃]. Anal. Calcd for C₁₂H₆F₆N₂O₄: C, 40.47; H, 1.70; N, 7.86. Found: C, 40.64; H, 1.98; N, 8.02.
3-Dimethylaminomethylene-5,5,5-trifluoro-2,4-dioxo-pentanoic Acid Ethyl Ester (Entry 7) Oil. ¹H NMR (200 MHz, CDCl₃): δ = 1.37 (t, 3 H, OCCH₃), 2.98 (s, 3 H, NMe₂), 3.47 (s, 3 H, NMe₂), 4.35 (q, 2 H, OCH₂), 7.82 (s, 1 H, H4). ¹³C NMR (100 MHz, CDCl₃): δ = 13.6 (OCCH₃), 43.5 (NMe₂), 48.7 (NMe₂), 61.9 (OCH₂), 102.4 (C3), 116.7 (q, ¹ J _C-F = 291 Hz, CF₃), 160.8 (q, ⁴ J _C-F = 3 Hz, C4), 164.1 (C1), 177.6 (q, ² J _C-F = 34 Hz, C3′), 182.3 (C2). MS: m/z (%) = 267 (2) [M⁺], 194 (100) [M - CO₂Et], 144 (78), 69 (10) [CF₃]. Anal. Calcd for C₁₀H₁₂F₃NO₄: C, 44.95; H, 4.53; N, 5.24. Found: C, 45.28; H, 4.85; N, 5.48.
3-Dimethylaminomethylene-1,1,1,5,5,5-hexafluoro-pentane-2,4-dione (Entry 8) Mp 54-56 °C. ¹H NMR (200 MHz, CDCl₃): δ = 2.81 (s, 3 H, NMe₂), 3.45 (s, 3 H, NMe₂), 7.74 (s, 1 H, H4). ¹³C NMR (100 MHz, CDCl₃): δ = 43.1 (NMe₂), 48.9 (NMe₂), 100.3 (C3), 116.2 (q, ¹ J _C-F = 291 Hz, 2 CF₃), 159.4 (C4), 179.5 (q, ² J _C-F = 34 Hz, C2, C3′). MS: m/z (%) = 263 (19) [M⁺], 194 (86) [M - CF₃], 144 (100), 69 (31) [CF₃]. Anal. Calcd for C₈H₇F₆NO₂: C, 36.52; H, 2.68; N, 5.32. Found: C, 36.80; H, 3.01; N, 5.62.
N -Phenyl- N -(4,4,4-trichloro-3-oxobut-1-enyl)oxalamic Acid Ethyl Ester (Entry 9) Mp 82-84 °C. ¹H NMR (200 MHz, CDCl₃): δ = 1.04 (t, 3 H, OCCH₃), 4.07 (q, 2 H, OCH₂), 5.92 (d, 1 H, J = 14 Hz, H2), 7.32-7.55 (m, 5 H, Ph), 8.76 (d, 1 H, J = 14 Hz, H3). ¹³C NMR (100 MHz, CDCl₃): δ = 13.4 (OCCH₃), 62.5 (OCH₂), 96.0 (CCl₃), 103.1 (C2), 128.2, 130.2, 130.5, 135.0 (Ph), 144.1 (C3), 160.1 (C4), 160.3 (C5), 180.0 (C1). MS: m/z (%) = 246 (51) [M⁺ - CCl₃], 218 (6) [M - C(O)CCl₃], 146 (100), 117 (55) [CCl₃], 104 (66), 77 (77) [Ph]. Anal. Calcd for C₁₄H₁₂Cl₃NO₄: C, 46.12; H, 3.32; N, 3.84. Found: C, 46.11; H, 3.67; N, 4.09.
2,2,2-Trifluoro- N -phenyl- N -(4,4,4-trichloro-3-oxobut-1-enyl)acetamide (Entry 10) Mp 85-87 °C. ¹H NMR (200 MHz, CDCl₃): δ = 5.77 (d, 1 H, J = 14 Hz, H2), 7.30-7.59 (m, 5 H, Ph), 8.79 (d, 1 H, J = 14 Hz, H3). ¹³C NMR (100 MHz, CDCl₃): δ = 95.8 (CCl₃), 105.1 (C2), 115.4 (q, ¹ J _C-F = 287 Hz, CF₃), 128.3, 130.2, 130.8, 134.2 (Ph), 145.3 (C3), 156.0 (q, ² J _C-F = 38 Hz, C4), 179.7 (C1). MS: m/z (%) = 359 (1) [M⁺], 242 (100) [M - CCl₃], 214 (4) [M - C(O)CCl₃], 172 (23), 145 (21) [C(O)CCl₃], 117 (19) [CCl₃], 77 (53) [Ph], 69 (12) [CF₃]. Anal. Calcd for C₁₂H₇Cl₃F₃NO₂: C, 39.98; H, 1.96; N, 3.88. Found: C, 40.04; H, 2.12; N, 3.99.
5,5,5-Trichloro-3-dimethylaminomethylene-2,4-dioxo-pentanoic Acid Ethyl Ester (Entry 11) Mp 93-95 °C. ¹H NMR (200 MHz, CDCl₃): δ = 1.38 (t, 3 H, OCCH₃), 3.05 (s, 3 H, NMe₂), 3.46 (s, 3 H, NMe₂), 4.35 (q, 2 H, OCH₂), 8.31 (s, 1 H, H4). ¹³C NMR (100 MHz, CDCl₃): δ = 13.6 (OCCH₃), 43.3 (NMe₂), 48.5 (NMe₂), 61.5 (OCH₂), 96.3 (C3), 98.0 (CCl₃), 161.7 (C4), 164.5 (C1), 179.5 (C2), 182.5 (C3′). MS: m/z (%) = 315 (1) [M⁺], 280 (3) [M - Cl], 242 (85) [M - CO₂Et], 214 (12) [M - C(O)CO₂Et], 198 (6) [M - CCl₃], 170 (97) [M - C(O)CCl₃], 92 (100). Anal. Calcd for C₁₀H₁₂Cl₃NO₄: C, 37.94; H, 3.82; N, 4.42. Found: C, 38.23; H, 4.16; N, 4.61.
1,1,1-Trichloro-3-dimethylaminomethylene-5,5,5-trifluoropentane-2,4-dione (Entry 12) Mp 94-96 °C. ¹H NMR (200 MHz, CDCl₃): δ = 2.87 (s, 3 H, NMe₂), 3.42 (s, 3 H, NMe₂), 7.93 (s, 1 H, H4). ¹³C NMR (100 MHz, CDCl₃): δ = 42.3 (NMe₂), 48.9 (NMe₂), 95.5 (CCl₃), 100.1 (C3), 116.5 (q, ¹ J _C-F = 291 Hz, CF₃), 157.9 (C4), 178.6 (q, ² J _C-F = 34 Hz, C2), 184.2 (C3′). MS: m/z (%) = 312 (4) [M + 2], 276 (7) [M - Cl], 242 (5) [M - CF₃], 194 (100) [M - CCl₃], 166 (6) [M - C(O)CCl₃], 144 (92), 116 (13), 69 (24) [CF₃]. Anal. Calcd for C₈H₇Cl₃F₃NO₂: C, 30.75; H, 2.26; N, 4.48. Found: C, 30.77; H, 2.48; N, 4.57.
N -(3-Oxo-3-phenylpropenyl)- N -phenyloxalamic Acid Ethyl Ester (Entry 13) Mp 56-58 °C. ¹H NMR (200 MHz, CDCl₃): δ = 1.00 (br, 3 H, OCCH₃), 4.02 (br, 2 H, OCH₂), 6.13 (d, 1 H, J = 14 Hz, H2), 7.34-7.73 (m, 10 H, 2 Ph), 8.62 (br, 1 H, H3). ¹³C NMR (100 MHz, CDCl₃): δ = 13.3 (OCCH₃), 62.1 (OCH₂), 109.6 (C2), 127.8, 128.3, 128.4, 129.9, 130.0, 132.5, 135.4, 137.6 (2 Ph), 140.3 (C3), 160.4 (C4), 160.5 (C5), 189.5 (C1). MS: m/z (%) = 323 (10) [M⁺], 322 (26), 250 (30) [M - CO₂Et), 222 (53) [M - C(O)CO₂Et], 218 (41) [M - C(O)Ph], 105 (94) [C(O)Ph], 77 (100) [Ph]. Anal. Calcd for C₁₉H₁₇NO₄: C, 70.58; H, 5.30; N, 4.33. Found: C, 70.76; H, 5.53; N, 4.13.
2,2,2-Trifluoro- N -(3-oxo-3-phenylpropenyl)- N -phenyl-acetamide (Entry 14) Mp 110-112 °C. ¹H NMR (200 MHz, CDCl₃): δ = 5.99 (d, 1 H, J = 14 Hz, H2), 7.33-7.70 (m, 10 H, 2 Ph), 8.65 (d, 1 H, J = 14 Hz, H3). ¹³C NMR (100 MHz, CDCl₃): δ = 111.3 (C2), 115.6 (q, ¹ J _C-F = 288 Hz, CF₃), 128.0, 128.4, 128.5, 130.0, 130.4, 132.8, 134.8, 137.5 (2 Ph), 141.9 (C3), 155.8 (q, ² J _C-F = 38, C4), 189.3 (C1). MS: m/z (%) = 319 (52) [M⁺], 318 (100), 222 (8) [M - C(O)CF₃], 214 (23) [M - C(O)Ph], 105 (21) [C(O)Ph], 77 (50) [Ph], 69 (9) [CF₃]. Anal. Calcd for C₁₇H₁₂F₃NO₂: C, 63.95; H, 3.97; N, 4.39. Found: C, 63.74; H, 4.14; N, 4.58.
3-Benzoyl-4-dimethylamino-2-oxobut-3-enoic Acid Ethyl Ester (Entry 15) Oil. ¹H NMR (200 MHz, CDCl₃): δ = 1.09 (t, 3 H, OCCH₃), 2.81 (s, 3 H, NMe₂), 3.35 (s, 3 H, NMe₂), 3.89 (q, 2 H, OCH₂), 7.42-7.75 (m, 5 H, Ph), 7.87 (s, 1 H, H4). ¹³C NMR (100 MHz, CDCl₃): δ = 13.0 (OCCH₃), 42.1 (NMe₂), 47.4 (NMe₂), 60.7 (OCH₂), 106.9 (C3), 127.8, 128.4, 131.6, 139.4 (Ph), 159.0 (C4), 164.3 (C1), 182.9 (C2), 192.9 (C3′). MS: m/z (%) = 275 (4) [M⁺], 202 (36) [M - CO₂Et], 174 (2) [M - C(O)CO₂Et], 105 (100) [C(O)Ph], 77 (60) [Ph]. Anal. Calcd for C₁₅H₁₇NO₄: C, 65.44; H, 6.22; N, 5.09. Found: C, 65.45; H, 6.37; N, 5.18.
2-Dimethylaminomethylene-4,4,4-trifluoro-1-phenyl-butane-1,3-dione (Entry 16) Oil. ¹H NMR (200 MHz, CDCl₃): δ = 2.71 (s, 3 H, NMe₂), 3.31 (s, 3 H, NMe₂), 7.50-7.85 (m, 5 H, Ph), 7.76 (s, 1 H, H4). ¹³C NMR (100 MHz, CDCl₃): δ = 41.1 (NMe₂), 47.6 (NMe₂), 105.3 (C3), 117.1 (q, ¹ J _C-F = 291 Hz, CF₃), 128.3, 128.8, 132.7, 138.6 (Ph), 157.0 (C4), 176.6 (q, ² J _C-F = 33 Hz, C2), 194.0 (C3′). MS: m/z (%) = 271 (9) [M⁺], 202 (32) [M - CF₃], 174 (7) [M - C(O)CF₃], 105 (100) [C(O)Ph], 77 (63) [Ph], 69 (4) [CF₃]. Anal. Calcd for C₁₃H₁₂F₃NO₂: C, 57.57; H, 4.46; N, 5.16. Found: C, 57.69; H, 4.79; N, 5.27.
N -[3-(4-Fluorophenyl)-3-oxopropenyl]- N -phenyl-oxalamic Acid Ethyl Ester (Entry 17) Mp 87-89 °C. ¹H NMR (200 MHz, CDCl₃): δ = 1.01 (br, 3 H, OCCH₃), 4.03 (br, 2 H, OCH₂), 6.08 (d, 1 H, J = 14 Hz, H2), 7.07-7.76 (m, 4 H, C₆H₄), 7.34-7.55 (m, 5 H, Ph); 8.60 (br, 1 H, H3). ¹³C NMR (100 MHz, CDCl₃): δ = 13.5 (OCCH₃), 62.3 (OCH₂), 109.3 (C2), 115.5 (d, ² J _C-F = 22 Hz, C₆H₄), 128.5, 130.1, 130.2, 135.6 (Ph), 130.6 (d, ³ J _C-F = 9 Hz, C₆H₄), 134.2 (d, ⁴ J _C-F = 3 Hz, C₆H₄), 140.9 (C3), 160.5 (C4), 160.6 (C5), 165.4 (d, ¹ J _C-F = 254 Hz, C₆H₄), 188.1 (C1). MS: m/z (%) = 341 (6) [M⁺], 340 (27), 268 (49) [M - CO₂Et), 240 (49) [M - C(O)CO₂Et], 218 (55) [M - C(O)C₆H₄ (4-F)], 123 (100) [C(O)C₆H₄ (4-F)], 95 (49) [C₆H₄ (4-F)], 77 (30) [Ph]. Anal. Calcd for C₁₉H₁₆FNO₄: C, 66.86; H, 4.72; N, 4.10. Found: C, 66.46; H, 4.90; N, 4.12.
2,2,2-Trifluoro- N -[3-(4-fluorophenyl)-3-oxopropenyl]- N -phenylacetamide (Entry 18) Mp 99-101 °C. ¹H NMR (200 MHz, CDCl₃): δ = 5.96 (d, 1 H, J = 14 Hz, H2), 7.06-7.73 (m, 4 H, C₆H₄), 7.34-7.60 (m, 5 H, Ph), 8.65 (d, 1 H, J = 14 Hz, H3). ¹³C NMR (100 MHz, CDCl₃): δ = 110.8 (C2), 115.6 (q, ¹ J _C-F = 288 Hz, CF₃), 115.6 (d, ² J _C-F = 22 Hz, C₆H₄), 128.6, 130.1, 130.5, 134.8 (Ph), 130.7 (d, ³ J _C-F = 9 Hz, C₆H₄), 133.9 (d, ⁴ J _C-F = 3 Hz, C₆H₄), 142.1 (C3), 155.9 (q, ² J _C-F = 38 Hz, C4), 165.5 (d, ¹ J _C-F = 255 Hz, C₆H₄), 187.6 (C1). MS: m/z (%) = 337 (13) [M⁺], 336 (50), 268 (10) [M - CF₃], 240 (7) [M - C(O)CF₃], 123 (100) [C(O)C₆H₄ (4-F)], 95 (58) [C₆H₄ (4-F)], 77 (22) [Ph], 69 (5) [CF₃]. Anal. Calcd for C₁₇H₁₁F₄NO₂: C, 60.54; H, 3.29; N, 4.15. Found: C, 60.60; H, 3.90; N, 4.46.
4-Dimethylamino-3-(4-fluorobenzoyl)-2-oxobut-3-enoic Acid Ethyl Ester (Entry 19) Oil. ¹H NMR (200 MHz, CDCl₃): δ = 1.12 (t, 3 H, OCCH₃), 2.81 (s, 3 H, NMe₂), 3.36 (s, 3 H, NMe₂), 3.94 (q, 2 H, OCH₂), 7.10-7.78 (m, 4 H, C₆H₄), 7.86 (s, 1 H, H4). ¹³C NMR (100 MHz, CDCl₃): δ = 13.4 (OCCH₃), 42.5 (NMe₂), 47.8 (NMe₂), 61.3 (OCH₂), 107.5 (C3), 115.3 (d, ² J _C-F = 22 Hz, C₆H₄), 131.4 (d, ³ J _C-F = 9 Hz, C₆H₄), 136.3 (d, ⁴ J _C-F = 3 Hz, C₆H₄), 159.1 (C4), 164.4 (C1), 164.9 (d, ¹ J _C-F = 253, C₆H₄), 183.0 (C2), 191.8 (C3′). MS: m/z (%) = 293 (6) [M⁺], 220 (68) [M - CO₂Et], 192 (4) [M - C(O)CO₂Et], 123 (100) [C(O)C₆H₄ (4-F)], 95 (40) [C₆H₄ (4-F)]. Anal. Calcd for C₁₅H₁₆FNO₄: C, 61.43; H, 5.50; N, 4.78. Found: C, 61.58; H, 5.78; N, 4.94.
2-Dimethylaminomethylene-4,4,4-trifluoro-1-(4-fluoro-phenyl)butane-1,3-dione (Entry 20) Mp 56-58 °C. ¹H NMR (200 MHz, CDCl₃): δ = 2.71 (s, 3 H, NMe₂), 3.32 (s, 3 H, NMe₂), 7.12-7.87 (m, 4 H, C₆H₄), 7.76 (s, 1 H, H4). ¹³C NMR (100 MHz, CDCl₃): δ = 41.3 (NMe₂), 47.9 (NMe₂), 105.4 (C3), 115.5 (d, ² J _C-F = 21 Hz, C₆H₄), 117.2 (q, ¹ J _C-F = 291 Hz, CF₃), 131.6 (d, ³ J _C-F = 9 Hz, C₆H₄), 135.2 (d, ⁴ J _C-F = 3 Hz, C₆H₄), 157.2 (C4), 165.4 (d, ¹ J _C-F = 254 Hz, C₆H₄), 176.6 (q, ² J _C-F = 33 Hz, C2), 192.5 (C3′). MS: m/z (%) = 289 (9) [M⁺], 220 (32) [M - CF₃], 192 (7) [M - C(O)CF₃], 123 (100) [C(O)C₆H₄ (4-F)], 95 (49) [C₆H₄ (4-F)], 69 (6) [CF₃]. Anal. Calcd for C₁₃H₁₁F₄NO₂: C, 53.99; H, 3.83; N, 4.84. Found: C, 54.07; H, 3.89; N, 4.83.
4-Dimethylamino-3-(4-nitrobenzoyl)-2-oxobut-3-enoic Acid Ethyl Ester (Entry 21) Oil. ¹H NMR (200 MHz, CDCl₃): δ = 1.16 (t, 3 H, OCCH₃), 2.87 (s, 3 H, NMe₂), 3.42 (s, 3 H, NMe₂), 4.00 (q, 2 H, OCH₂), 7.87 (s, 1 H, H4), 7.89-8.26 (m, 4 H, C₆H₄). ¹³C NMR (100 MHz, CDCl₃): δ = 13.4 (OCCH₃), 43.0 (NMe₂), 48.2 (NMe₂), 61.6 (OCH₂), 107.2 (C3), 123.4, 129.6, 144.9, 149.2 (C₆H₄), 160.3 (C4), 164.2 (C1), 182.8 (C2), 191.1 (C3′). MS: m/z (%) = 320 (7) [M⁺], 247 (100) [M - CO₂Et], 219 (4) [M - C(O)CO₂Et], 150 (69) [C(O)C₆H₄ (4-NO₂)], 104 (47). Anal. Calcd for C₁₅H₁₆N₂O₆: C, 56.25; H, 5.03; N, 8.75. Found: C, 56.50; H, 5.22; N, 8.63.
2-Dimethylaminomethylene-4,4,4-trifluoro-1-(4-nitro-phenyl)butane-1,3-dione (Entry 22) Mp 100-102 °C. ¹H NMR (200 MHz, CDCl₃): d = 2.76 (s, 3 H, NMe₂), 3.40 (s, 3 H, NMe₂), 7.81 (s, 1 H, H4), 7.94-8.28 (m, 4 H, C₆H₄). ¹³C NMR (100 MHz, CDCl₃): d = 42.5 (NMe₂), 48.4 (NMe₂), 105.2 (C3), 117.1 (q, ¹ J _C-F = 291 Hz, CF₃), 123.7, 129.7, 143.9, 149.8 (C₆H₄), 158.5 (q, ⁴ J _C-F = 3 Hz, C4), 177.2 (q, ² J _C-F = 33 Hz, C2), 192.0 (C3¢). MS: m/z (%) = 316 (17) [M⁺], 247 (75) [M - CF₃], 219 (13) [M - C(O)CF₃], 150 (100) [C(O)C₆H₄ (4-NO₂)], 104 (49), 76 (43), 69 (6) [CF₃]. Anal. Calcd for C₁₃H₁₁F₃N₂O₄: C, 49.38; H, 3.51; N, 8.86. Found: C, 49.39; H, 3.67; N, 8.95.
N -(3-Oxo-3-thiophen-2-yl-propenyl)- N -phenyloxalamic Acid Ethyl Ester (Entry 23) Mp 83-85 °C. ¹H NMR (200 MHz, CDCl₃): d = 1.02 (br, 3 H, OCCH₃), 4.05 (br, 2 H, OCH₂), 6.02 (d, 1 H, J = 14 Hz, H2), 7.05, 7.44, 7.60 (m, 3 H, thien-2-yl), 7.34-7.54 (m, 5 H, Ph), 8.64 (br, 1 H, H3). ¹³C NMR (100 MHz, CDCl₃): d = 13.4 (OCCH₃), 62.3 (OCH₂), 109.4 (C2), 128.5, 130.0, 130.1, 135.6 (Ph), 128.0, 131.3, 133.6, 145.0 (thien-2-yl), 139.8 (C3), 160.4 (C4), 160.6 (C5), 181.4 (C1). MS: m/z (%) = 329 (1) [M⁺], 328 (4), 256 (9) [M - CO₂Et], 228 (24) [M - C(O)CO₂Et], 212 (100), 111 (80) [C(O)thien-2-yl], 77 (31) [Ph]. Anal. Calcd for C₁₇H₁₅NO₄S: C, 61.99; H, 4.59; N, 4.25. Found: C, 61.63; H, 4.86; N, 4.28.
2,2,2-Trifluoro- N -(3-oxo-3-thiophen-2-ylpropenyl)- N -phenylacetamide (Entry 24) Mp 81-83 °C. ¹H NMR (200 MHz, CDCl₃): d = 5.87 (d, 1 H, J = 14 Hz, H2), 7.05, 7.40, 7.59 (m, 3 H, thien-2-yl), 7.33-7.59 (m, 5 H, Ph), 8.66 (d, 1 H, J = 14 Hz, H3). ¹³C NMR (100 MHz, CDCl₃): d = 111.1 (C2), 115.6 (q, ¹ J _C-F = 288 Hz, CF₃), 128.6, 130.0, 130.1, 131.6 (Ph), 128.1, 130.4, 134.0, 144.8 (thien-2-yl), 141.2 (C3), 155.9 (q, ² J _C-F = 38 Hz, C4), 181.2 (C1). MS: m/z (%) = 325 (2) [M⁺], 324 (13), 212 (100), 111 (41) [C(O)thien-2-yl], 83 (7) [thien-2-yl], 69 (16) [CF₃]. Anal. Calcd for C₁₅H₁₀F₃NO₂S: C, 55.38; H, 3.10; N, 4.31. Found: C, 55.41; H, 3.47; N, 4.70.
4-Dimethylamino-2-oxo-3-(thiophene-2-carbonyl)but-3-enoic Acid Ethyl Ester (Entry 25) Oil. ¹H NMR (200 MHz, CDCl₃): d = 1.14 (t, 3 H, OCCH₃), 2.87 (s, 3 H, NMe₂), 3.35 (s, 3 H, NMe₂), 3.99 (q, 2 H, OCH₂), 7.06, 7.45, 7.62 (m, 3 H, thien-2-yl), 7.84 (s, 1 H, H4). ¹³C NMR (100 MHz, CDCl₃): d = 13.5 (OCCH₃), 42.3 (NMe₂), 48.0 (NMe₂), 61.6 (OCH₂), 108.0 (C3), 127.6, 133.1, 133.6, 146.9 (thien-2-yl), 158.2 (C4), 164.3 (C1), 182.6 (C2), 184.9 (C3¢). MS: m/z (%) = 281 (7) [M⁺], 208 (65) [M - CO₂Et], 180 (4) [M - C(O)CO₂Et], 111 (100) [C(O)thien-2-yl], 83 (9) [thien-2-yl]. Anal. Calcd for C₁₃H₁₅NO₄S: C, 55.50; H, 5.37; N, 4.98. Found: C, 55.61; H, 5.65; N, 5.27.
2-Dimethylaminomethylene-4,4,4-trifluoro-1-thiophen-2-ylbutane-1,3-dione (Entry 26) Oil. ¹H NMR (200 MHz, CDCl₃): d = 2.80 (s, 3 H, NMe₂), 3.30 (s, 3 H, NMe₂), 7.12, 7.56, 7.69 (m, 3 H, thien-2-yl), 7.73 (s, 1 H, H4). ¹³C NMR (100 MHz, CDCl₃): d = 40.4 (NMe₂), 47.5 (NMe₂), 105.2 (C3), 117.0 (q, ¹ J _C-F = 291 Hz, CF₃), 127.9, 133.7, 134.3, 145.7 (thien-2-yl), 156.2 (C4), 175.8 (q, ² J _C-F = 33 Hz, C2), 185.7 (C3¢). MS: m/z (%) = 277 (5) [M⁺], 208 (7) [M - CF₃], 180 (1) [M - C(O)CF₃], 111 (100) [C(O)thien-2-yl], 83 (8) [thien-2-yl], 69 (6) [CF₃]. Anal. Calcd for C₁₁H₁₀F₃NO₂S: C, 47.65; H, 3.64; N, 5.05. Found: C, 47.67; H, 3.87; N, 5.26.

23

Crystallographic data for entries 10 and 22, reported in this paper, have been deposited with the Cambridge Crystallog-raphic Data Center (CCDC 654351 and CCDC 654350, respectively). Copies of the data can be obtained, free of charge, on application to CCDC 12 Union Road, Cambridge CB2 1EZ, UK [fax: [phone] or e-mail: [e-mail]].