LITHIUM TETRAMETHYLPIPERIDIDE Chemical Properties

solubility 

sol most organic solvents including THF, Et2O, hexane.

form 

solid

Safety Information

Hazard Codes 

F,C

Risk Statements 

63-14/15-34-62

Safety Statements 

16-26-36/37/39-43-45

RIDADR 

UN 3131 8(4.3) / PGII

WGK Germany 

3

LITHIUM TETRAMETHYLPIPERIDIDE Usage And Synthesis

Physical properties

Lithium 2,2,6,6-Tetramethylpiperidide exists in THF solution as a dimer-monomer equilibrium mixture; additives such as HMPA increase monomer concentration. X-ray structure determination shows that LiTMP crystallizes as a tetramer from hexane/pentane mixtures.

Uses

Lithium 2,2,6,6-tetramethylpiperidide is a strong base and can be used:

• For the synthesis of enamines from terminal epoxides through trans-α-lithiated epoxide as an intermediate.
• For ortholithiation of arenes such as 1,3-bis(trifluoromethyl)benzene, 4,4-dimethyl-2-phenyl-2-oxazoline, 1,4-bis(trifluoromethyl)benzene and 1,3-dimethoxybenzene.
• In combination with Lewis donor ligand, N,N,N′,N′-tetramethylethylenediamine (TMEDA) for deprotonative metalation of methoxy-substituted arenes.{21]

Application

Lithium 2,2,6,6-Tetramethylpiperidide (LTMP) is a strong, highly hindered, nonnucleophilic base (pKa = 37.3) capable of selective deprotonation of aromatics, heteroaromatics, and aliphatic C-H acidic sites in the presence of a variety of functional groups; also compatible with several electrophiles for in situ quenching of kinetically derived lithiated species.

Preparation

Preparative Method of Lithium 2,2,6,6-Tetramethylpiperidide: prepared in Et2O or THF solutions immediately before use by treatment of commercially available dry 2,2,6,6-Tetramethylpiperidine with n-Butyllithium (1:1). Tetramethylpiperidine is dried by heating a mixture of the base with CaH2 at reflux for 4 h in a preflamed flask, followed by distillation at atmospheric pressure (bp 152 °C). It should be stored in a septum sealed bottle.

storage

LiTMP solutions are pyrophoric, can cause severe burns, and should always be handled and transferred under an inert atmosphere. Solutions of LiTMP show a loss of activity (50% in THF; 60% in Et2O) after 12 h at 24 °C. Use in a fume hood.

LITHIUM TETRAMETHYLPIPERIDIDE(38227-87-1)Related Product Information

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