Guanidines are a type of organic compounds that have gained increasing importance in organic synthesis processes over time. The functional group that characterises them consists of a carbon atom bonded to three nitrogen atoms and is present in some biologically relevant molecules such as arginine (an essential amino acid) or creatine.
They are related to other nitrogen-containing functionalities such as amines, amidines, imines, or ureas, and are characterized by their strongly basic nature. Some of them have been referred to as “superbases” for being stronger bases than the hydroxide ion, the strongest base in aqueous solution.
Their interest lies not only in their strength as bases but also in their lack of nucleophilic character. Some amidine-type bases such as DBN (1,5-diazabicyclo-[4.3.0]non-5-ene) or DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) are widely used in synthesis, but they are not economical and easily rented. This problem is avoided by using amidines, which are strong non-nucleophilic bases, or by using sterically hindered guanidines.
Preparation and characteristics
Penta-alkylguanidines meet these requirements well: they are strong bases, non-nucleophilic, resistant to alkylation, and economically viable. Among them, the most well-known is 2-tert-Butyl-1,1,3,3-tetramethylguanidine, known as Barton’s base in honor of its discoverer, Nobel laureate Derek Barton, who synthesized a series of sterically hindered guanidines with his team, this being the easiest to prepare.
In general, these alkylated guanidines are prepared from their corresponding urea, which is converted into a Vilsmeier salt using acid chlorides like phosgene (highly toxic) or oxalyl chloride. This salt then reacts with an amine to provide the desired guanidine.
Barton’s base
The Barton’s base is a colorless, corrosive liquid with a strong characteristic odor. In a 1:1 water and ethanol solution, it exhibits a pKa of 14, and in acetonitrile it reaches 24.3, indicating it is a truly strong base.
Although its preparation involves the use of highly toxic reagents, as mentioned earlier, and the process can be somewhat complex, careful handling can yield purity levels above 97%.
This product is sensitive to air and moisture and should be stored cold (2°C-8°C) under nitrogen.
At DC Fine Chemicals, with over 15 years of experience in fine chemical raw materials, we manufacture Barton’s base in-house (2-tert-butyl-1,1,3,3-tetramethylguanidine CAS 50-01-1), ensuring a minimum purity of 97.5%.
Please contact us for further details regarding 2-tert-butyl-1,1,3,3-tetramethylguanidine CAS 50-01-1 or any other products featured in our catalogue. We are delighted to assist you with your company’s needs.
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Article written by Fran Campos, R&D Manager at DC Fine Chemicals
Bibliographic references:
- Derek H. R. Barton, John D. Elliott and Stephen D. Géro, Synthesis and properties of a series of sterically hindered guanidine bases. J. Chem. Soc., Perkin Trans. 1, 1982, 2085-2090.
- Mihara, M., Moroga, K., Iwasawa, T., Nakai, T., Ito, T., Ohno, T., & Mizuno, T. (2018). Selective Synthesis of Carbonates from Glycerol, CO2, and Alkyl Halides Using tert-Butyltetramethylguanidine. Synlett, 29(13), 1759-1764.