The invention concerns synthesized amido-amine-based cationic gemini surfactants with flexible and rigid spacers and different hydrophobic. These gemini surfactants were prepared by modified procedure through amidation of long chain carboxylic acids using 3-(dimethylamino)-1-propylamine followed by treatment with halohydrocarbons and showed excellent thermal stability and surface properties useful for various oilfield applications such as enhanced oil recovery.

Disclosed is a method for preparing compound S-1 (S-1) comprising resolving compound rac-2 (rac-2) with a compound of Formula 3 wherein R.sup.1, R.sup.4, m and n are as defined in the disclosure.

##STR00001##

Disclosed is a method for preparing compound S-1 (S-1) comprising resolving compound rac-2 (rac-2) with a compound of Formula 3 wherein R.sup.1, R.sup.4, m and n are as defined in the disclosure.

##STR00001##

The present invention provides a method for preparing a pregabalin intermediate 3-carbamoymethyl-5-methylhexanoic acid without solvent. The method comprises the following steps: a) cooling an ammonia water system to a certain temperature; b) adding 3-isobutylglutaric anhydride dropwise to the system, then keeping temperature, and reacting; c) after completing the reaction, adding an acid to the system to adjust pH; d) after adjusting pH, cooling, then keeping temperature, crystallizing, then suction filtering and drying; and e) adding a solvent to the dried substance, slurrying, and suction filtering and drying to obtain the final product. The method provided in the present invention for preparing 3-carbamoymethyl-5-methylhexanoic acid is high-yield, green, environmentally-friendly, simple and convenient, and of less pollution.

The present invention provides a method for preparing a pregabalin intermediate 3-carbamoymethyl-5-methylhexanoic acid without solvent. The method comprises the following steps: a) cooling an ammonia water system to a certain temperature; b) adding 3-isobutylglutaric anhydride dropwise to the system, then keeping temperature, and reacting; c) after completing the reaction, adding an acid to the system to adjust pH; d) after adjusting pH, cooling, then keeping temperature, crystallizing, then suction filtering and drying; and e) adding a solvent to the dried substance, slurrying, and suction filtering and drying to obtain the final product. The method provided in the present invention for preparing 3-carbamoymethyl-5-methylhexanoic acid is high-yield, green, environmentally-friendly, simple and convenient, and of less pollution.

The present invention provides a method for preparing a pregabalin intermediate 3-carbamoymethyl-5-methylhexanoic acid without solvent. The method comprises the following steps: a) cooling an ammonia water system to a certain temperature; b) adding 3-isobutylglutaric anhydride dropwise to the system, then keeping temperature, and reacting; c) after completing the reaction, adding an acid to the system to adjust pH; d) after adjusting pH, cooling, then keeping temperature, crystallizing, then suction filtering and drying; and e) adding a solvent to the dried substance, slurrying, and suction filtering and drying to obtain the final product. The method provided in the present invention for preparing 3-carbamoymethyl-5-methylhexanoic acid is high-yield, green, environmentally-friendly, simple and convenient, and of less pollution.

N,N-(di)alkylaminoalkyl(meth)acrylamide or N,N-(di)alkylaminoalkyl (meth)acrylate and/or a quaternary ammonium salt thereof are prepared with a low content of a compound of formula (IV)

##STR00001##

wherein R.sub.5 in each case is a linear, branched or cyclic alkyl radical, an aryl radical which may also be substituted by one or more alkyl groups, the linear, cyclic or branched alkyl radical may have a length of 1-12 carbon atoms and is, for example, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, hexyl, heptyl, octyl, isooctyl, nonyl, decyl, undecyl, dodecyl.

N,N-(di)alkylaminoalkyl(meth)acrylamide or N,N-(di)alkylaminoalkyl (meth)acrylate and/or a quaternary ammonium salt thereof are prepared with a low content of a compound of formula (IV)

##STR00001##

wherein R.sub.5 in each case is a linear, branched or cyclic alkyl radical, an aryl radical which may also be substituted by one or more alkyl groups, the linear, cyclic or branched alkyl radical may have a length of 1-12 carbon atoms and is, for example, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, hexyl, heptyl, octyl, isooctyl, nonyl, decyl, undecyl, dodecyl.

N,N-(di)alkylaminoalkyl(meth)acrylamide or N,N-(di)alkylaminoalkyl (meth)acrylate and/or a quaternary ammonium salt thereof are prepared with a low content of a compound of formula (IV)

##STR00001##

wherein R.sub.5 in each case is a linear, branched or cyclic alkyl radical, an aryl radical which may also be substituted by one or more alkyl groups, the linear, cyclic or branched alkyl radical may have a length of 1-12 carbon atoms and is, for example, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, hexyl, heptyl, octyl, isooctyl, nonyl, decyl, undecyl, dodecyl.

The present invention provides a process for preparing 2-methyl-N-(2′-methylbutyl)butanamide of the following formula (1): the process comprising: subjecting an α-arylethyl-2-methylbutylamine compound of the following general formula (2): wherein Ar represents a substituted or unsubstituted aryl group having 6 to 20 carbon atoms, to N-2-methylbutyrylation to form an N-α-arylethyl-2-methyl-N-(2′-methylbutyl)butanamide compound of the following general formula (3): wherein Ar is as defined above, and removing the α-arylethyl group of the resulting compound (3) to form 2-methyl-N-(2′-methylbutyl)butanamide (1).

##STR00001##