General procedure for the synthesis of lauryl betaine from dodecanol and methyl 2-(dimethylamino)acetate:
1. Preparation of lauryl N,N-dimethylglycinate: in a 1 L three-necked flask fitted with a Dean-Stark separator, methyl 2-dimethylaminoacetate (189 g; 1.61 mol; 1.5 eq.), lauryl alcohol (200 g; 1.07 mol) and Novozym 435 (20 g) were added. Subsequently 80 ml of heptane was added as solvent. The reaction mixture was heated in an oil bath at 65 °C and the system pressure was adjusted to about 110 mm Hg to promote efficient separation of the heptane/methanol azeotrope. After 5 hours of reaction, 99.1% conversion of the product was confirmed by NMR analysis. Upon completion of the reaction, the reaction mixture was filtered to remove the enzyme catalyst, the enzyme catalyst was washed with heptane, and the filtrates were combined and concentrated to afford 289 g of lauryl N,N-dimethylamino glycinate in 99% yield.
Product Characterization:
1H NMR (500MHz, CDCl3) δ 4.13 (t, 2H); 3.16 (s, 2H); 2.35 (s, 6H); 1.64 (m, 2H); 1.26 (s, 18H); 0.88 (t, 3H).
HPLC analytical conditions: 150 × 4.6 mm Zorbax SB-C8 column, mobile phase initially 75:25 (v:v) methanol:water (containing 0.1% trifluoroacetic acid), gradient to 100% methanol in 1 min, hold for 9 min, ELSD detector, retention time (tR) of 5.2 min.
