Sodium Hydroxide → HCID 9964160, compound

Participants

Reaction Conditions

Reaction Steps

A cold solution (−5 to 8° C.) of sodium borohydride (0.6 g) in 2N-sodiumhydroxide (1.5 mL) was added dropwise very slowly to a stirred solution of 2,6-dimethyl-4-oxo-heptanoic acid (3) (1.0 g) in methanol (20 mL) and stirring was continued overnight. Methanol was evaporated and more water (3-4 mL) was added to the residue and the mixture was once again cooled to −5 to 0° C. and then acidified with cold dilute hydrochloric acid and then extracted with ether (3×50 mL). The combined extracts were washed with brine, dried (Na2SO4) and then concentrated to give a crude liquid which was loaded on silica gel column and the column was eluted with an increasing amount of hexane/ethyl acetate (100:0 to 95:5). The fractions were monitored on TLC plate and then the desired fractions were combined and solvent was removed under vacuum to afford 4-isobutyl-2-methyl-4-butanolide (trans:cis=68:32 on NMR basis) of formula (1) in 76% yield as a colourless oil with coconut flavour; Rf=0.80 (10% ethylacetate in hexane); IR (film) λmax 2962, 1772, 1558, 1457, 1362, 1173, 1135, 1004, 1024, 926 cm−1; 1H NMR δ4.63-4.55 (dqd, 0.32H, cis-5-CH), 4.46-4.38 (dtd, 0.68H, trans-5-CH), 2.73-2.62 (m, 1H, 3-CH), 2.55-2.47 (m, 1H, 7-CH), 2.09-2.04 and 1.84-1.78 (2 m, 2H, 4-CH2), 1.67-1.61 and 1.50-1.41 (2 m, 2H, 6-CH2), 1.36-1.26 and 1.27-1.25 (2d, 3H, 10-CH3), 0.96-0.95 and 0.94-0.93 (2d, 6H, 8-CH3 & 9-CH3) (FIG. 3); 13C NMR δ179.42 (d, C-2), 76.55 (d, C-5), 44.43 (d, C-3), 37.69 (s, C-4), 35.69 (d, C-7), 33.77 (s, C-6), 21.92 (d, C-10), 15.65, 14.89 (2s, C-8 and C-9) (FIG. 4); GC of compound 1 appeared at tr=30.24 and tr=30.44 also confirms the presence of isomers (FIG. 5); EIMS m/z 156 [M]+ (1.3), 99 (100%), 84 (5.4), 71 (28.5), 56 (14.7), 42 (12.8) (FIG. 6).

Provenance & Evidence