Relevant articles and documents
Steric Hindrance Underestimated: It is a Long, Long Way to Tri- tert-alkylamines
Banert, Klaus Heck, Manuel Ihle, Andreas Kronawitt, Julia Pester, Tom Shoker, Tharallah
Ten different processes (Methods A-J) were tested to prepare tertiary amines bearing bulky alkyl groups. In particular, SN1 alkylation of secondary amines with the help of 1-adamantyl triflate (Method D) and reaction of N-chlorodialkylamines with organometallic reagents (Method H), but also attack of the latter reagents at iminium salts, which were generated in situ by N-alkylation of imines (Method J), led to trialkylamines with unprecedented steric congestion. These products showed a restriction of the rotation about the C-N bond. Consequently, equilibration of rotamers was slow on the NMR time scale resulting in distinguishable sets of NMR data at room temperature. Furthermore, tertiary amines with bulky alkyl substituents underwent Hofmann-like elimination when heating in toluene to form an olefin and a secondary amine. Since the tendency to take part in this decay reaction correlated with the degree of steric hindrance around the nitrogen atom, Hofmann elimination at ambient temperature, which made the isolation of the tertiary amine difficult, was observed in special cases.
THE INFLUENCE OF INTERLAYER WATER ON CLAY CATALYSTS. INTERLAMELLAR CONVERSION OF 2-METHYLPROPENE
Ballantine, James A. Jones, William Purnell, J. Howard Tennakoon, Dayananda T. B. Thomas, John M.
Evidence is provided for two alternative pathways for the reactions undergone by 2-methylpropene between the layers of a sheet silicate catalyst (Al3+-exchanged montmorillonite).This clay, when it initially contains ca. 12percent interlayer water, catalyses the addition of either water or methanol to 2-methylpropene to yield, respectively, t-butanol or 2-methoxy-2-methyl propane (methyl tertiary butyl ether, MTBE), whereas the same clay following deliberate dehydration acts as an effective catalyst for the oligomerisation of 2-methylpropene.Similar results are obtained with an Al3+-exchanged synthetic hectorite.
