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BzN
HOOC
2-(N-(but-2-ynyl)benzamido)-2-methylhexa-3,4-dienoic acid (182). To a solution of amido-
acid 181 (100 mg, 0.408 mmol) in DMF (3 mL) was added NaH (23 mg, 0.90 mmol) at rt. The
reaction mixture turned bright yellow and after 2 min, 1-bromo-2-butyne (39 µL, 0.45 mmol)
was added. The reaction mixture was stirred at rt for 1 h and then poured into a diluted aq.
NaHCO3 solution. The aqueous layer was extracted once with EtOAc and the organic layer was
discarded. The aqueous layer was acidified to approximately pH = 2.0 by dropwise addition of
6M HCl (pH was followed using pHydrion strips) and then extracted with EtOAc (3 x 25 mL).
The organics were combined, washed with water, dried over MgSO4 and concentrated under
vacuum to afford 182 (103 mg, 85%) as a mixture of diastereomers in ~ 2 : 1 ratio.
1 H NMR (300 MHz, CDCl3): δ 9.61 (bs, 1H), 7.79-7.76 (m, 0.67H), 7.65-7.63 (m, 1.33H), 7.53-
36 (m, 3H), 5.74-5.68 (m, 1H), 5.54-5.34 (m, 1H), 4.03-4.00 (m, 2H), 1.85 (s, 3H), 1.75 (s, 3H),
1.75-1.68 (m, 3H); IR (thin film): ν 3062, 2990, 2629, 1967, 1714, 1641 cm -1 ; MS m/z (%) 297
(42), 282 (15), 252 (70), 200 (55), 105 (100); EI-HRMS calcd for C18H19NO3 m/z [M] +
297.1365, found 297.1363.
O
Bz
1-Benzoyl-5-ethylidene-2-methyl-4-vinyl-1,2,5,6-tetrahydropyridine-2-carboxylic acid
(177). Allenyne 182 (103 mg, 0.347 mmol) was placed in a 15 mL test tube and toluene (3 mL)
was added. The resulting solution was deoxygenated by bubbling Ar via a needle for 3 min.
OH
225
182
N
177
•
H