Facile Preparation of Substituted Allenic Esters via the Ortho Ester Claisen Rearrangement

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• The spectral and analytical data for the allenic esters 1b, 1c, and 3b-5b are given below: Methyl 3-Ethyl-3,4-pentadienoate (1b) as a colorless liquid: Rf 0.49 (EtO Ac-hexanes, 1:20); 1H NMR (CDCl3) δ 4.76 (d, J = 2.5 Hz, 1 H), 4.74 (d, J = 3.7 Hz, 1 H), 3.68 (s, 3 H), 3.00 (t, J = 2.3 Hz, 2 H), 2.00 (q. J = 7.1–7.4 Hz, 2 H), 1.01 (t, J = 7.3–7.4 Hz, 3 H); 13C NMR (CDCl3) δ 207.24, 172.28, 99.48, 77.16, 52.36, 39.11, 25.24, 12.47; IR (neat) 2969, 1961, 1743, 1436, 1338, 1243, 1198, 1162, 1015, 852 cm−1. Anal. Calcd for C8H12O2: C, 68.54; H, 8.63. Found: C, 68.77; H, 8.51. Ethyl 3-Ethyl-3,4-pentadienoate (1c) as a colorless liquid: Rf 0.38 (EtO Ac-hexanes, 1:20); 1H NMR (CDCl3) δ 4.73 (d, J = 2.5 Hz, 1 H), 4.71 (d, J = 3.7 Hz, 1 H), 4.11 (q, J = 7.1 Hz, 2 H), 2.95 (t, J = 2.4 Hz, 2 H), 2.02–1.97 (m, 2 H), 1.22 (t, J = 7.1 Hz, 3 H), 0.99 (t, J = 7.4 Hz, 3 H); 13C NMR (CDCl3) δ 207.19, 171.74. 99.55, 77.06, 61.12, 39.22, 25.22, 14.73, 1243; IR (neat) 2971, 2938, 1961, 1736, 1462, 1367, 1324, 1259, 1159, 1031, 851 cm−1. Anal. Calcd for C9H14O2: C. 70.10; H, 9.15. Found: C, 69.82; H, 8.80. Methyl 5-Phenyl-3,4-pentadienoate (3b) as a pale yellow liquid: Rf 0.35 (EtOAc-hexanes, 1:20); 1H NMR (CDCl3) δ 7.33–7.22 (m, 5 H), 6.24 (d, J = 6.4 Hz, 1 H), 5.71 (t, 1 H), 3.74 (s, 3 H), 3.21–3.17 (dd, J = 2.7, 7.2 Hz, 2 H); 13C NMR (CDCl3) δ 206.89, 172.23, 129.20, 128.20, 127.73, 127.49, 96.24, 88.69, 52.60, 34.84; IR (neat) 3030, 2953, 1961, 1729, 1497, 1459, 1434, 1339, 1258, 1195, 1168, 1026, 698 cm−1. Anal. Calcd for C12H12O2: C, 76.57; H, 6.43. Found: C, 76.86; H, 6.25. Methyl 6-Phenyl-3,4-hexadienoate (4b) as a pale yellow liquid: Rf 0.38 (EtOAc-hexanes, 1:20); 1H NMR (CDCl3) δ 7.41–7.24 (m, 5 H), 5.47–5.38 (m, 2 H), 3.68 (s, 3 H), 3.41 (d, J = 7.1 Hz, 2 H), 3.02 (d, J = 6.7 Hz, 2 H); 13C NMR (CDCl3) δ 206.87, 172.21, 128.91, 128.82, 127.30, 126.57, 101.85, 89.71, 52.47, 35.11, 34.84; IR (neat) 3025, 2967, 1962, 1729, 1475, 1338, 1327, 1257, 1119, 1011, 697 cm−1. Anal. Calcd for C13H14O2: C, 77.20; H, 6.98. Found: C, 76.95; H, 7.30. Methyl 5-Phenyl-3,4-hexadienoate (5b) as a pale yellow liquid: Rf 0.39 (EtOAc-hexanes, 1:20); 1H NMR (CDCl3) δ 7.45–7.23 (m, 5 H), 5.61 (t, 1 H), 3.73 (s, 3 H), 3.16 (d, J = 7.2 Hz, 2 H), 2.13 (d, J = 2.8 Hz, 3 H); 13C NMR (CDCl3) δ 206.94, 172.53, 128.93, 128.89, 127.43, 126.41, 102.03, 86.67, 52.53, 35.12, 17.45; IR (neat) 3035, 2973, 1967, 1723, 1488, 1452, 1345, 1271, 1185, 1158, 1022, 712 cm−1. Anal. Calcd for C13H14O2: C, 77.20; H, 6.98. Found: C, 76.91; H, 7.23
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