Inclusion compounds from diols

Figure 8. A stereoscopic view of the packing in the inclusion compound of 1,1,6,6-tetraphenylhexa-2,4-dyne-1,6-diol, 2, with (a) chalcone and (b) 9-anthraldehyde. 9-Anthraldehyde gives cage-type and chalcone gives channel-type structures. [Reproduced with permission from F. Toda, Topics Curr. Chem. 140, 43 (1987).]...

When racemic diol 10 is crystallised from small solvents, an extraordinary type of inclusion compound is formed. These compounds, (10)4-(guest), have a unit cell in space group IA acd containing 32 molecules of the host diol and... 

An interesting inclusion compound derived from 2,6-dimethylbicyclo[3.3.1]nonane-exo-2,exo-6-diol, 2, was reported by the group led by Bishop and Dance. " The crystal structure of the alicyclic diol 2 can be ho. construed as packing of helices along the c-axis. The parallel canals that result from the helical tubules have an unobstmcted triangular cross-sectional area of roughly 20 which are H3C ... 

Occasionally, a chiral diol can serve as host for one optical isomer (e.g., an epoxide), allowing the other one to be distilled out. The guest optical isomer can then be recovered by stronger heating. A quaternary ammonium salt, derived from the amino acid leucine, has been used to resolve 1,1 - bi-2-naphthol (7.4) by formation of an inclusion compound.57... 

Other diol hosts are also useful for the separation of guest isomers. As before, usually the p-isomers, e.g. of 38-40, form inclusion compounds thus they can be isolated from a mixture. In fact, o- 40 a) and p-xylene 40 b) were easily separated by Ic. The X-ray crystal structure of the inclusion compoimd of 7 c with 40b s shown in Fig. S ). 

Amide host compounds are also useful for the isolation of alcohols. For example, when a solution of 24 (2.0 g) and 70% aqueous solution of 2-propyn-l-ol (0.73 g) in n-butanol was kept at room temperature for 1 h, a 1 2 inclusion compound of 24 and 2-propyn-l-ol was formed as colorless crystals (1.45 g), which upon heating at 150 °C gave pure 2-propyn-l-ol (0.27 g, 58%) By the same method, 1,4-butane-diol, 2-butene-1,4-diol, 2-butyne-l,4-diol, ethylene glycol, and diethylene glycol were isolated in 50-70 % yields from their aqueous solutions... 

Xiong et al. also demonstrated that the chiral 2D framework [Cu(PPhj)(A,A( -(2-pyridyl-(4-pyridyl methyl)-amine)),5] C10 (9), with triangular cavities, synthesized from achiral components, [Cu(MeCN)j(PPh3)J[C10 ] and N,N -(2-pyridyl-(4-pyridyl methyl)-amine) can enantioselectively include 2-butanol [76]. Spontaneous resolution produced crystalline inclusion compound 91.5(2-butanol), which was structurally characterized. They manually separated the enantiomorphic forms of 91.5(2-butanol) according to their CD spectra in solid state and evacuated at 100°C to collect enantiopure 2-butanol. Although this work provides an economical route to enantioselective separation of racemic small diols, the separation... 

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