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Upstream product

• 124-09-4 1,6-Hexanediamine 
• 1571-08-0 methyl 4-formylbenzoate 

Downstream Products

• 264191-32-4 N,N'-bis(4-methoxycarbonylbenzyl)-1,6-hexanediamine 
• 264191-33-5 N,N'-bis(tert-butoxycarbonyl)-N,N'-bis(4-methoxycarbonylbenzyl)-1,6-hexanediamine 
• 264191-36-8 N,N'-bis(tert-butoxycarbonyl)-N,N'-bis(4-azidomethylbenzyl)-1,6-hexanediamine 
• 264191-34-6 N,N'-bis(tert-butoxycarbonyl)-N,N'-bis(4-hydroxymethylbenzyl)-1,6-hexanediamine 
• 264191-35-7 N,N'-bis(tert-butoxycarbonyl)-N,N'-bis(4-chloromethylbenzyl)-1,6-hexanediamine 
• 264191-37-9 N,N'-bis(4-azidomethylbenzyl)-1,6-hexanediamine 

Relevant academic research and scientific papers

Neutralization of a sec-ammonium group unusually stabilized by the "rotaxane Effect": Synthesis, structure, and dynamic nature of a "free" sec-amine/crown ether-type rotaxane

A fifteen-year riddle has been settled: neutralization, the most popular chemical event, of a crown ether/sec-ammonium salt-type rotaxane has been achieved and a completely nonionic crown ether/sec-amine-type rotaxane isolated. A [2]rotaxane was prepared as a typical substrate from a mixture of dibenzo[24]crown-8 ether (DB24C8) and sec-ammonium hexafluorophosphate (PF 6) with a terminal hydroxy group through end-capping with 3,5-dimethylbenzoic anhydride in the presence of tributylphosphane as a catalyst in 90 % yield. A couple of approaches to the neutralization of the ammonium rotaxane were investigated to isolate the free sec-amine-type rotaxane by decreasing the degree of thermodynamic and kinetic stabilities. One approach was the counteranion-exchange method in which the soft counterion PF 6- was replaced with the fluoride anion by mixing with tetrabutylammonium fluoride, thus decreasing the cationic character of the ammonium moiety. Subsequent simple washing with a base allowed us to isolate the free sec-amine-type rotaxane in a quantitative yield. The other approach was a synthesis based on a protection/deprotection protocol. The acylation of the sec-ammonium moiety with 2,2,2-trichloroethyl chloroformate gave an N-carbamated rotaxane that could be deprotected by treating with zinc in acetic acid to afford the corresponding free sec-amine-type rotaxane in a quantitative yield. The structure of the free sec-amine-type rotaxane was fully confirmed by spectral and analytical data. The generality of the counteranion-exchange method was also confirmed through the neutralization of a bisammonium-type [3]rotaxane. The mechanism was studied from the proposed potential-energy diagram of the rotaxanes with special emphasis on the role of the PF 6- counterion. Neutral and free: The neutralization of the ammonium group of crown ether/sec-ammonium salt-type rotaxanes is a simple, yet important issue, which had not been solved to date. Neutral rotaxanes had not been isolated because of their unusual stability; however, the successful synthesis of free amine-type rotaxanes has now been achieved. The key to canceling this strong stabilization is the construction of a multiple equilibrium system and the successful removal of the conjugate acid from the reaction system (see scheme). Copyright

Molecular Shuttles by the Protecting Group Approach

Two new [2]rotaxane-based molecular shuttles, in which a mechanically bound dibenzo[24]crown-8 (DB24C8) macroring shunts back and forth between two dialkylammonium recognition sites situated on a chemical dumbbell, have been constructed by a novel synthetic strategy that relies upon the use of the tert-butoxycarbonyl (Boc) protecting group. During the syntheses of both molecular shuttles, this protecting group masks a dialkylammonium recognition center which is liberated only after the [2]rotaxane constitution is established. In both cases, the molecular shuttles' other dialkylammonium center is essential for the rotaxane-forming reactions and it ensures that DB24C8 is interpenetrated by threadlike precursors, as a result of noncovalent bonding interactions, to produce [2]pseudorotaxanes which are stoppered subsequently through 1,3-dipolar cycloadditions between azides and bulky acetylenedicarboxylates. The new molecular shuttles have been examined by means of dynamic 1H NMR spectroscopy, which reveals that the movements of the DB24C8 macroring are very highly dependent both on solvent properties and on the nature of the spacer unit linking the two dialkylammonium centers. Thus, DB24C8 shunts facilely between the dialkylammonium centers when the shuttles are dissolved in solvents that readily donate their nonbonding electrons into noncovalent bonds, e.g., DMF, and when spacer units that do not offer much steric resistance to shuttling, e.g., hexamethylene, are used. On the other hand, shuttling is difficult in solvents that are less inclined to donate their electrons into noncovalent bonds, e.g., (CDCl2)2, and when relatively bulky benzenoid spacer units, e.g., p-xylylene, link the two dialkylammonium centers. It has been proposed that the DB24C8 might act as a "ferry" which carries a proton between dialkylammonium and dialkylamine moieties in a singly protonated [2]rotaxane by means of ion-dipole interactions.