4-Pentynoic acid

• as building block for the synthesis of library of eight sequence-defined model oligomers
• in one-pot synthesis of the complex polycyclic heterocycles benzo[4,5]imidazo[1,2-c]pyrrolo[1,2-a]quinazolinone derivatives
• in the synthesis of various allenenols lactones [5(E)-(2-allenylidene)-tetrahydro-2-furanones]
• in the synthesis of a cyctotoxic macrolide by ring-closing metathesis of a bis acetylene

5390-04-5

6089-09-4

General procedure for the synthesis of 4-pentynoic acid from 4-pentyn-1-ol: 4-pentyn-1-ol (1 mL, 10.7 mmol) was dissolved in acetone and the solution was cooled to 0 °C. Jones' reagent was slowly added dropwise under vigorous stirring until the reaction mixture remained orange in color. Subsequently, the reaction mixture was allowed to warm up to room temperature and Jones reagent was continued to be added dropwise to maintain the orange color. The reaction mixture was stirred at room temperature for 1 hour. Upon completion of the reaction, water was added and extracted several times with ether (Et2O). The organic phases were combined, washed with saturated brine and dried over anhydrous sodium sulfate (Na2SO4). The solvent was removed by concentration under reduced pressure to give the crude product. Purification by rapid chromatography on silica gel (eluent: hexane/ether=8:2) gave the colorless oily product 4-pentynoic acid in 82% yield.1H NMR (400MHz, CDCl3) δ: 2.61-2.59 (m, 2H), 2.52-2.48 (m, 2H), 1.98-1.95 (m, 1H) ppm.