[111-92-2] · C8H19N · Dibutylamine · (MW 129.28)
Physical Data: mp -62 °C; bp 159 °C; d 0.767 g cm-3; n
Solubility: very sparingly sol H2O; sol most organic solvents.
Preparative Methods: from butyl bromide and ammonia;5b separation of the mono-, di-, and tributylamines is required.
Form Supplied in: liquid; commercially available.
Purification: can be dried over and distilled from fresh potassium hydroxide immediately before use.
Handling, Storage, and Precautions: is a flammable, colorless liquid. Harmful by inhalation and by eye and skin contact.
Dibutylamine can be used for the purification of diterpene carboxylic acids,6 long-chain fatty acids,7 and benzoic acids.8 The free carboxylic acids can be regenerated by treatment of the amine salts in ethanol with Acetic Acid. Other secondary amines (e.g. diisopentylamine,6 diisobutylamine6b) can also be used.
Dibutylamine can also be used in different elimination reactions as a hindered strong base. When 1,1,1-trichloro-2-methyl-2-propanol is treated with 4 equiv of Thionyl Chloride, a catalytic amount of dibutylamine at reflux then affords pure 3,3,3-trichloro-2-methyl-1-propene in good yield by water elimination, similar to t-Butylamine, Triethylamine, aniline, and dimethylaniline (eq 1).1 In the presence of other amines, such as octylamine, Piperidine, Pyridine or tetramethylammonium chloride, isomerized product is also formed.
The base-catalyzed detosylation rate of 1-(p-toluenesulfonyl)-2-propyl p-toluenesulfonate depends on the polarity of the solvent used (eq 2).2 In acetonitrile and 50% aqueous dioxane the strongest catalytic base is dibutylamine, followed by hexylamine and triethylamine. In solvents with a medium dielectrict constant (e.g. chloroform, chlorobenzene), the above the order is reversed.2
For the amine-catalyzed nucleophilic isomerization of ethyl cis-2-cyano-3-(2-methoxyphenyl)acrylate to the trans derivative (eq 3)3 in benzene the order of reactivity of the amines is dibutylamine > dipropylamine > diisobutylamine > tributylamine > diisopropylamine > triethylamine > pyridine > 2,6-Lutidine. This isomerization can also be influenced by solvent3 and other oxygen9 and carbon nucleophiles.9
Base-induced rearrangement of epoxides with lithium alkylamides can yield allylic alcohols, isomerized derivatives, ketones, or, by direct nucleophilic substitution, amine alcohols. Cyclohexene oxide (1) gives 2-cyclohexen-1-ol (2) near quantitatively with lithium dibutylamide4 (prepared in situ from a 15% solution of n-Butyllithium in hexane and an ethereal solution of dibutylamine) or lithium dipropylamide, while other lithium amides afford low to moderate yields of the allylic alcohol (2), very little ketone (3) and 3-cyclohexen-1-ol (5), and extensive amounts of the amino alcohol adduct (4) (eq 4).
2-Unsubstituted 3-nitro-2H-chromenes can be prepared in fair to excellent yields either by the reaction of 2-hydroxybenzaldehydes and Nitroethylene in boiling chloroform, or by the reaction of 2-hydroxybenzaldehydes, 2-nitroethanol, and 2 equiv of phthalic anhydride in boiling toluene in the presence of 0.2-0.5 equiv of dibutylamine (eq 5).5 Other amines, like Diisopropylethylamine and 1,4-Diazabicyclo[2.2.2]octane, lead to a rapid polymerization of nitroethylene. Ammonium chlorides10 like dibutylammonium, diisopropylammonium, diethylammonium, dioctylammonium, piperidinium, and morpholinium chlorides in boiling isopentyl acetate lead to lower yields or more difficult purification.
CHINOIN, Budapest, Hungary