Amines, inclusion complex

Fig. 9. An inclusion complex formed between a protonated primary amine and a chiral crown ether.

The milder metal hydnde reagents are also used in stereoselective reductions Inclusion complexes of amine-borane reagent with cyclodexnins reduce ketones to opucally active alcohols, sometimes in modest enantiomeric excess [59] (equation 48). Diisobutylaluminum hydride modified by zmc bromide-MMA. A -tetra-methylethylenediamme (TMEDA) reduces a,a-difluoro-[i-hydroxy ketones to give predominantly erythro-2,2-difluoro-l,3-diols [60] (equation 49). The three isomers are formed on reduction with aluminum isopropoxide... 

Primary and secondary amines and amides are first chlorinated at nitrogen by the chlorine released by the gradually decomposing calcium hypochlorite. Excess chlorine gas is then selectively reduced in the TLC layer by gaseous formaldehyde. The reactive chloramines produced in the chromatogram zones then oxidize iodide to iodine, which reacts with the starch to yield an intense blue iodine-starch inclusion complex. 

The wheel-and-axle design as source for host-guest compounds was originally proposed by Toda and Hart in 1981 for hosts containing hydroxyl functions 481 (see Ch. 3, Sect. 2.1 of Vol. 140). The l,l,6,6-tetraphenylhexa-2,4-diyne-l,6-diol (24) provides a representative compound. It forms 1 2 crystalline inclusion complexes with a large number of small guest molecules, including a variety of ketones, amines, amides and a sulfoxide 48). 

A variety of alkyl amines B, including 1-propylamine, ethylene diamine, 1,3-diaminopropane, and (7 )-l-amino-2-propanol have been used as reactants. The guest exchange kinetic results are reported in Table 13. The presence of more than one reacting [/3-CD-H-A] structure is observed with A = DOPA and penicillamine. The results have been rationalized in terms of specific interactions in the relevant inclusion complexes which determine their structure and relative stability. 

Capping of inclusion complex with adamantane amine... 

Chiral crown ethers based on IB-crown-6 I Fig. 4> can form inclusion complexes with ammonium ions and proionated primary amines. Immobilization of these chiral crown ethers on a chromatographic support provides a chiral stationary phase which can resolve most primary amino acids, amines and amino alcohols. However, the stereogenic center must be in fairly close proximity in the primary aininc lor successful chiral separalion. Significantly, ihe chiral crown ether phase is unique in that ii is one of the few liquid chromatographic chiral stationary phases that does not require the presence of an aromatic ring to achieve chiral separations. 

Although, at that time, the term supramolecular chemistry had not yet been coined, the practical potential for inclusion complexation for acetylene alcohol guests 1 and 2 was recognized back in 1968 [12], Spectroscopic studies showed that 1 and 2 formed molecular complexes with numerous hydrogen-bond donors and acceptors, i.e. ketones, aldehydes, esters, ethers, amides, amines nitriles, sulfoxides and sulfides. Additionally, 1 formed 1 1 complexes with several n-donors, such as derivatives of cyclohexene, phenylacetylene, benzene, toluene, etc. The complexation process investigated by IR spectrometry revealed the presence of OH absorption bands at lower frequencies than those for uncomplexed 1 and 2 [12], These data, followed by X-ray studies, confirmed that the formation of intermolecular hydrogen bonds is the driving force for the creation of complexes [13],... 

These hosts were used to study inclusion complexation with aromatic guests in aqueous solution.23 The differences in binding between the phenethylamines and the benzylamines are shown in Table 1. Host 13 and 14 bound aromatic guests better than host 15 and 16. It is possible that the ammonium groups of the benzyl amine hosts are directed into the cavity this reduces its hydrophobicity and results in a low binding constant. There was also a strong... 

Figure 3. Computer imaging of the inclusion complexes of d- A) and 1-(B) propranolol with B-cyclodextrin. The chemical structures are illustrated with van der Waals radii shown for only the secondary amine of propranolol and the 2- and 3- hydroxyl groups of the B-cyclodextrin.

Fig. 33 Crystal structures of the inclusion complexes involving the hexaprotonated form of the bistren derivative 19 and bromide (a), and azide ions (d) [70]. The six secondary amine groups are protonated. All hydrogen atoms have been omitted for clarity, (b, C, e, f) Triangles have been obtained by linking the nitrogen atoms of the ammonium groups of each tren subunit, (c, f) 0 is the torsion angle for each pair of triangles...

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