79376-82-2

Upstream product

• 3043-52-5 1,2,3,3,4,5-hexamethyl-6-methylene-cyclohexa-1,4-diene 
• 594-19-4 tert.-butyl lithium 

Downstream Products

• 3043-52-5 1,2,3,3,4,5-hexamethyl-6-methylene-cyclohexa-1,4-diene 
• 917-54-4 methyllithium 
• 56909-25-2 2,3,4,5,6-pentamethylneopentylbenzene 
• 75948-84-4 1,1,2,3,5,6-hexamethyl-4-neopentyl-2,4-cyclohexadiene 
• 75948-80-0 1,1,2,3,5,6-hexamethyl-4-neopentyl-2,5-cyclohexadiene 
• 75948-85-5 C₁₇H₂₉⁽²⁾H 
• 75948-81-1 C₁₇H₂₉⁽²⁾H 

Relevant academic research and scientific papers

First Determination of the Structure of an Ion-Paired Species in Nonpolar Media: 1H, 13C, and 7Li NMR Spectra of Peralkylcyclohexadienyllithium Compounds

Peralkylcyclohexadienyllithium compounds (2a,b), formed by addition of alkyllithiums to triene 1, are shown to exist as ion-paired aggregates containing conjugated anions bent out of the plane at the saturated ring carbon.Both 13C and 7Li NMR spectra show 2a,b to form two distinctly different ion-paired species - tight peripherally solvated ion-pair aggregates in the presence of mainly tertiary amines and loose separated ion-pair dimers favored with THF, glymes, and HMTP.The latter exhibit two 7Li(+) peaks, one due to Li sandwiched between two anions in a triple ion and the other situated external to it.In the case of 2b with THF both ion-pair species are dimers, and the equlibrium (A(-)Li(+))2*(THF)2 + THF (A2Li)(-) + Li(THF)3(+) is characterized with ΔH = -4 kcal and ΔS = -16 eu.The exchange of ions between ion pairs of 2b with THF is generally slow on the NMR time scale.However, above 0 deg C the lithium exchange rate between the solvated site in the loose ion-pair dimer and the lithium in the tighter ion-pair dimer lies on the NMR time scale.The mean lifetime of lithium in the triple ion is always > 10 s.The slow ion-exchange rates are ascribed to the crowded substitution around 2a,b.

Formation of Peralkylcyclohexadienyllithium Compounds

1,1,2,3,5,6-Hexamethyl-4-methylene-2,5-cyclohexadiene (1) reacts with alkyllithium compounds, RLi (R= n-Bu, sec-Bu, and t-Bu), at 2O deg C in hydrocarbon solution or in the presence of ethers or tertiary amines, which act as ligands, to give stable, soluble 1,1,2,3,5,6-hexamethyl-4-alkylcyclohexadienyllithium compounds, 3a-c.On heating, the latter aromatize to pentamethylalkylbenzenes, 4a-c, with extrusion of methyllithium, while on hydrolysis of 3a-c isomeric substituted cyclohexadienes are obtained.The effects have been investigated of varying RLi structure, ligand, and temperature on the rates of addition and aromatization reactions.Ligand metalation by RLi is a significant side reaction.Addition is faster with ligands known to reduce the association of alkyllithium compounds.Aromatization is faster in the presence of THF which favors formation of loose ion pairs and is slower with heavy substitution on the ring.It is proposed that large substituents (neopentyl) destabilize the transition states for aromatization due to steric interactions.