Über hochverzweigte aliphatische Verbindungen, 4. Mitt.: Ergiebigere Synthesen des Triisopropylamins

Kuffner, Friedrich; Koechlin, Werner

doi:10.1007/bf00903145

Cited by 26 publications

(11 citation statements)

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“…First, we looked for an efficient method to prepare the model compound 9 by using established methods. Whereas Bruylants reaction via 2-(diisopropylamino)propionitrile is well-known , to effectively transform 20 into 16 , the analogous attempts with substrate 18 (Method A) were completely unsuccessful (Scheme ). Treatment of 18 with diisopropyl sulfate (Method B) also did not lead to 9 although a similar S N 2 alkylation of diisopropylamine was reported to produce 16 with an 18% yield .…”

Section: Results and Discussionmentioning

confidence: 99%

Steric Hindrance Underestimated: It is a Long, Long Way to Tri-tert-alkylamines

et al. 2018

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Ten different processes (Methods A-J) were tested to prepare tertiary amines bearing bulky alkyl groups. In particular, S1 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.

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Section: Results and Discussionmentioning

confidence: 99%

Steric Hindrance Underestimated: It is a Long, Long Way to Tri-tert-alkylamines

et al. 2018

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“…2. The p K a value of is only known in aqueous diglyme, where it is between 6.9 and 9.2, depending on the water content [47]. Even with the smaller of these values, using the reduction potential of Table 1 and the calculated heats of formation (∆ H f ( D • ), − 33 kJ/mol; ∆ H f ( DH ), − 111 kJ/mol) we arrive at an exergonicity of at least − 50 kJ/mol, which means that a reversibility of that deprotonation can be discounted.…”

Section: Resultsmentioning

confidence: 99%

“…TIPA was synthesized and purified according to a literature procedure [47]; DABCO and all the sensitizers were commercially obtained and purified by double sublimation. The purchased solvent acetonitrile- d 3 was carefully dried to a water content of less than 5 × 10 − 4 M in a specially designed apparatus [53].…”

Section: Methodsmentioning

confidence: 99%

Electron and hydrogen self-exchange of free radicals of sterically hindered tertiary aliphatic amines investigated by photo-CIDNP

Goez¹,

Frisch²,

Sartorius³

2013

Beilstein J. Org. Chem.

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SummaryThe photoreactions of diazabicyclo[2,2,2]octane (DABCO) and triisopropylamine (TIPA) with the sensitizers anthraquinone (AQ) and xanthone (XA) or benzophenone (BP) were investigated by time-resolved photo-CIDNP (photochemically induced dynamic nuclear polarization) experiments. By varying the radical-pair concentration, it was ensured that these measurements respond only to self-exchange reactions of the free amine-derived radicals (radical cations DH • + or α-amino alkyl radicals D •) with the parent amine DH; the acid–base equilibrium between DH • + and D • also plays no role. Although the sensitizer does not at all participate in the observed processes, it has a pronounced influence on the CIDNP kinetics because the reaction occurs through successive radical pairs. With AQ, the polarizations stem from the initially formed radical-ion pairs, and escaping DH • + then undergoes electron self-exchange with DH. In the reaction sensitized with XA (or BP), the polarizations arise in a secondary pair of neutral radicals that is rapidly produced by in-cage proton transfer, and the CIDNP kinetics are due to hydrogen self-exchange between escaping D • and DH. For TIPA, the activation parameters of both self-exchange reactions were determined. Outer-sphere reorganization energies obtained with the Marcus theory gave very good agreement between experimental and calculated values of ∆G ‡ 298.

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“…tert -Octylamine was obtained from TCI (Japan). The Grignard-reagents 2- exo -norbornylMgBr, EtMgBr, neopentylMgBr, cyclopentylMgBr, and t -BuMgBr were prepared from the corresponding alkyl bromide and magnesium turnings following a general literature procedure and used immediately after preparation. , Compounds 8 , 9 , 11 , 12 , 13 , 17 , 25a , , 26b , 27e , 27g , 28c , 29c-d , di- tert -butylamine, 1,1,3,3-tetramethylisoindoline, 1,1,3,3-tetraethyl-isoindoline, di- tert -amyl-amine, , tert -butyl- tert -octylamine, di-1-adamantylamine, 3,3,5,5-tetramethylmorpholin-2-one, tert -butylcyclohexylamine, 2-ethyl-1,1,3,3-tetraethylisoindoline ( 30c ), 2-isopropyl-1,1,3,3-tetraethylisoindoline ( 30d ), and N - tert -butyl- N -tritylamine ( 34 ) were prepared according to reported procedures. The NMR data of amine 40c were confirmed by the literature …”

Section: Methodsmentioning

confidence: 99%

Synthesis of Trialkylamines with Extreme Steric Hindrance and Their Decay by a Hofmann-like Elimination Reaction

et al. 2020

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A number of amines with three bulky alkyl groups at the nitrogen, which surpass the steric crowding of triisopropylamine considerably, were prepared by using different synthetic methods. It turned out that treatment of N-chlorodialkylamines with organometallic compounds, for example, Grignard reagents, in the presence of a major excess of tetramethylenediamine offered the most effective access to the target compounds. The limits of this method were also tested. The trialkylamines underwent a dealkylation reaction, depending on the degree of steric stress, even at ambient temperature. Because olefins were formed in this transformation, it showed some similarity with the Hofmann elimination. However, the thermal decay of sterically overcrowded tertiary amines was not promoted by bases. Instead, this reaction was strongly accelerated by protic conditions and even by trace amounts of water. Reaction mechanisms, which were analyzed with the help of quantum chemical calculations, are suggested to explain the experimental results.

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Über hochverzweigte aliphatische Verbindungen, 4. Mitt.: Ergiebigere Synthesen des Triisopropylamins

Cited by 26 publications

References 0 publications

Steric Hindrance Underestimated: It is a Long, Long Way to Tri-tert-alkylamines

Steric Hindrance Underestimated: It is a Long, Long Way to Tri-tert-alkylamines

Electron and hydrogen self-exchange of free radicals of sterically hindered tertiary aliphatic amines investigated by photo-CIDNP

Synthesis of Trialkylamines with Extreme Steric Hindrance and Their Decay by a Hofmann-like Elimination Reaction

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