2-tert-Butyl-1,1,3,3-tetramethylguanidine

2-*tert*-Butyl-1,1,3,3-tetramethylguanidine
Names
	IUPAC name 2-tert-butyl-1,1,3,3,-tetramethylguanidine
	Other names BTMG, Barton's base
Identifiers
CAS Number	29166-72-1;
3D model (JSmol)	Interactive image;
ChemSpider	2808676;
ECHA InfoCard	100.157.697
PubChem CID	3571581;
CompTox Dashboard (EPA)	DTXSID10393758 ;
	InChI InChI=1S/C9H21N3/c1-9(2,3)10-8(11(4)5)12(6)7/h1-7H3 Key: YQHJFPFNGVDEDT-UHFFFAOYSA-N;
	SMILES CC(C)(C)N=C(N(C)C)N(C)C;
Properties
Chemical formula	C9H21N3
Molar mass	171.288 g·mol−1
Hazards
GHS pictograms
GHS Signal word	Danger
GHS hazard statements	H302, H314
GHS precautionary statements	P260, P264, P270, P280, P301+312, P301+330+331, P303+361+353, P304+340, P305+351+338, P310, P321, P330, P363, P405, P501
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
	Infobox references

2-tert-Butyl-1,1,3,3-tetramethylguanidine is an organic base, also known as Barton's base. It is named after Nobel Prize-winning British chemist Derek Barton. Barton and his assistants prepared a series of guanidines with steric hindrance in 1982; in this case five alkyl groups: four methyl groups and one tert-butyl group.[1][2] These bases were some of the strongest known at the time. In 50% water/ethanol, the acidity constant (pK_a) of Barton's base is 14.[1] In acetonitrile its pK_a is 24.31.

Synthesis

The base is prepared by the reaction of tert-butylamine with a Vilsmeier salt. The latter is the reaction product of phosgene with N,N,N′,N′-tetramethylurea.

Applications

Barton's base can be used in many organic reactions, including in alkylations and in the formation of aziridines. It is often a milder alternative to traditional, strong inorganic bases.

References

Barton, Derek H. R.; Elliott, John D.; Géro, Stephen D. (1982). "Synthesis and properties of a series of sterically hindered guanidine bases". J. Chem. Soc., Perkin Trans. 1 (0): 2085–2090. doi:10.1039/P19820002085.
Reason and imagination : reflections on research in organic chemistry : selected papers of Derek H.R. Barton. World Scientific/Imperial College Press. ISBN 9810213611.

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[:0-1] Barton, Derek H. R.; Elliott, John D.; Géro, Stephen D. (1982). "Synthesis and properties of a series of sterically hindered guanidine bases". J. Chem. Soc., Perkin Trans. 1 (0): 2085–2090. doi:10.1039/P19820002085.

[2] Reason and imagination : reflections on research in organic chemistry : selected papers of Derek H.R. Barton. World Scientific/Imperial College Press. ISBN 9810213611.