反应详情

To a suspension of sodium hydride (2.6 g) in diglyme (10 mL) triethylphosphonoacetate (24 g, 107 mmol) was added dropwise under nitrogen in an ice bath (ca. 0° C.). The mixture was stirred for 30 min. and then 3-methyl-2-butanone (XII, 4.3 g, 50 mmol) was added dropwise and the mixture stirred at ambient temperature for three hours. The mixture was cooled, diluted cautiously with a large excess amount of water, and extracted with ether. The ethereal extract was dried over anhydrous magnesium sulfate, filtered and evaporated in vacuo to yield ethyl 3,4-dimethyl-2-pentenoate (XI, 7.1 g, 91%): NMR (Jeol C 60 HL, CDCl3) δ1.08 [6H, d, J=7 Hz, (CH3)2CH], 1.30 (3H, t, J=7 Hz, CH3CH2O), 2.15 (3H, d, J=1.5 Hz, CH3C=), 4.15 (2H, q, J=7 Hz, CH 3 CH2O), 5.68 (1H, br.s, CH=C); IR (neat) 1705 (C=O), 1640 (C=C), 1385 and 1365 [(CH3)2C] cm-1 ; GLC (2% OV-17, Chrom W 80/100, 2 mm×200 cm, 60° C., N2 30 cc/m) retention time, 9 min.

1. additionwas added dropwise under nitrogen in an ice bath (ca. 0° C.)
2. stirringthe mixture stirred at ambient temperature for three hours
3. temperatureThe mixture was cooled
4. extractionextracted with ether
5. extractionThe ethereal extract
6. dry with materialwas dried over anhydrous magnesium sulfate
7. filtrationfiltered
8. customevaporated in vacuo