[CH3:1][CH:2]([C:6](=[O:8])[CH3:7])[C:3](=[O:5])[CH3:4].[CH:9](=O)[C:10]1[CH:15]=[CH:14][CH:13]=[CH:12][CH:11]=1.B(OCCCC)(OCCCC)O[CH2:19][CH2:20][CH2:21]C.[CH2:33](N)[CH2:34][CH2:35][CH3:36]>C(OCC)(=O)C>[CH3:1][CH:2]([C:6](=[O:8])[CH:7]=[CH:36][C:35]1[CH:21]=[CH:20][CH:19]=[CH:33][CH:34]=1)[C:3](=[O:5])[CH:4]=[CH:9][C:10]1[CH:15]=[CH:14][CH:13]=[CH:12][CH:11]=1Boric anhydride (0.49 g, 7.0 mmol) was combined with 3-methyl-2,4-pentanedione (5, 1.14 g, 10.0 mmol) and stirred for 24 hr at room temperature under a nitrogen atmosphere. A solution of ethyl acetate (10 ml), benzaldehyde (1b, 2.05 ml, 20.2 mmol) and tributyl borate (11.0 ml, 40.5 mmol) was added and the mixture stirred for 15 min at room temperature. Butylamine (0.20 ml, 2.0 mmol) was added dropwise over 30 min and stirring was continued for 24 hr at room temperature. The resulting mixture was filtered to afford a solid. The crude solid was triturated with methanol to give 1.80 g (62%) of an orange solid: mp 154-157° C. [expected mp 154-157° C.]; 1H NMR: δ 2.17 (s, 3H), 7.12 (d, 2H, J=15.5 Hz), 7.38 (m, 6H), 7.58 (m, 4H), 7.74 (d, 2H, J=15.5 Hz); 13C NMR: δ 12.1, 106.2, 120.8, 182.1, 128.8, 129.9, 135.4, 141.3, 182.4. Anal. Calcd for C20H18O2: C, 82.73; H, 6.25. Found: C, 82.69; H, 6.36.
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