Pivalic acid → 4-Methoxycarbonylmethyl-4-(3'-methoxyphenyl)-1-methyl-3-methylene-2-piperidone

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The allylic alcohol 27 of Example 9 (1.22 g, 4.96 mmol), trimethyl orthoacetate (5.52 g, 46 mmol), and pivalic acid (25 mg, 0.50 mmol) were placed in diglyme (25 mL) and refluxed at 155°-160° C. (internal) with fractionation to remove CH3OH. after 18 h the solvents were evaporated and the residue distilled [bp 175°-185° C. (0.15 mm)] to return 1.21 g (80%) of methyl ester 28. Upon standing the ester crystallized: mp 85°-86° C.; NMR δ7.30 (m, 1H), 6.86 (m, 4H), 6.65 (s, 1H), 5.57 (s, 1H), 3.76 (s, 3H), 3.47 (s 3H), 3.17 (m, 3H), 2.87 (s, 4H), 2.53 (m, 2H); IR 1733, 1653, 1595 cm-1 ; mass spectrum m/e (rel intensity) 303 (38), 230 (100). Anal. Calcd for C17H21NO4 : C, 67.3; H, 7.0; N, 4.6. Found: C, 67.2; H, 7.0; N, 4.6.

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