Tris(dimethylamino)methane
Trismethane is the simplest representative of the trismethanes of the general formula 3CH in which three of the four of methane's hydrogen atoms are replaced by dimethylamino groups. Trismethane can be regarded as both an amine and an orthoamide.
Trismethane is a strong base and can be used as a formylation agent, as aminomethylenation reagent and as a source for the basic biscarbene of the formula 2C:.
Preparation
Trismethane is formed in the reaction of N,N,N′,N′-Tetramethylformamidinium chloride or bisacetonitrile with lithium dimethylamide or sodium dimethylamide with yields between 55 and 84%.From dimethylamine and trimethoxyborane sodium dimethylamide is formed in situ in the presence of sodium hydride which reacts with N,''N,N'',N-tetramethylformamidinium chloride in 84% yield to trismethane and with bisacetonitrile in 77% yield.
The reaction of the dimethylformamide dimethylacetal, HC2N2, with dimethylamine in the presence of the acidic catalyst 2,4,6-tri-tert-butylphenol produces trismethane.
Trismethane is formed in good yield in the reaction of DMF with tetrakis(dimethylamino)titanium(IV).
N,''N,N'',N,''N″,N''″-Hexamethylguanidinium chloride forms trismethane in 53% yield under the exposure of the reducing agent sodium bis(2-methoxyethoxy)aluminium hydride.
Sodium hydride and trimethyl borate reduce N,''N,N'',N,''N″,N''″-hexamethylguanidinium chloride in 80% yield to trismethane.
Properties
Trismethane is a clear, colorless or pale yellow liquid with a strong ammoniacal odor. The compound is freely miscible with many non-polar aprotic and water-free solvents. However, when heated trismethane reacts with protic solvents but also with weak CH-acidic substances, such as acetone or acetonitrile.Upon heating to 150–190 °C decomposition occurs with the formation of tetrakis(dimethylamino)ethene, a strong electron donor.
Applications
Trismethane dissociates into N,''N,N'',N-tetramethylformamidinium cations and dimethylamide anions, which abstract protons from CH- and NH-acidic compounds. The anions thus formed add to the formamidinium cations which in turn eliminate dimethylamine and react to form dimethylaminomethylene compounds or amidines by aminomethyleneation.Reaction to form a methyl α-cyano-β-dimethylaminoacrylate:
Reaction to form N,''N-dimethyl-N''-p-nitrophenylformamidine:
Aminomethylenation provides intermediates for the synthesis of heterocycles such as pyrimidines, pyrazoles, 1,4-dihydropyridines and indoles.
N,''N,N'',N-Tetramethylselenourea is accessible by the extended heating of trismethane with selenium in xylene, biscarbene is suggested as an intermediate.