Acetylene → Ethyl Penta-2,4-dienoate

Participants

Reaction Steps

(2E,4E)-5-(2-Bromo-cyclopent-1-enyl)3-methyl-penta-2,4-dienoic acid ethyl ester (1.43 g) was dissolved in 5 ml of benzene. At ambient temperature was added successively: 293 mg of Pd(Ph3P)4, 95 mg of CuI, 147 mg of (Ph)3P, and 8 ml of piperidine. To this mixture was added via dropping funnel within 1 hour 2-ethynyl-1,3,3-trimethyl-1-cyclohexene (745 mg) dissolved in 5 ml of benzene. After 4.5 hours, additional acetylene (350 mg) was added and stirring continued for 30 minutes. The mixture was then poured into crushed ice/HCI, extracted with EtOEt, washed twice with water, dried over Na2SO4, and evaporated to dryness. Medium pressure chromatography (SiO2, hexane/AcOEt=98/2) yielded 1.478 g of (2E, 4E)-3-Methyl-5-(2,6,6-trimethyl-cyclohex-1-enylethynyl)-cyclopent-1-enyl]-penta-2,4-dienoic acid ethyl ester as a yellow oil.

Provenance & Evidence