Ether Inclusion Compounds

a resin with unusual inclusions in his Metamorphoses the Roman poet Ovid (43 B.C. - 17 A.D.) describes the adventure of Phaethon, the son of the sun god Helios. Helios agreed to his son s request that he be allowed to drive the sun chariot. Phaethon had no experience, the horses ran wild, the chariot touched the heavens and the earth and left a track of fire in its wake. Zeus put an end to the chaos by means of a thunderbolt which catapulted Phaethon out of the chariot and down to the underworld Hades. Phaethon s sisters, the Heliads, wept for their brother they were turned into dolls and their tears to amber. 

Amber is by no means a uniform substance, but a mixture of resins. Most of it was formed in the tertiary period, an era which began about 65 million years ago and ended about 2 million years ago. The resin exudated by the plants attracted insects which were trapped by the sticky mass. Thus the inclusion of these insects and plants gives palaeontologists the rare possibility of studying extinct life forms in their natural state. About a thousand types of insects have been discovered in amber, which is mainly found on beaches in East Prussia.  

Chromates and dichromates arc highly toxic and can be cancerogenic. Protective gloves should be worn Trichloromethane is also highly toxic. 

Ten large test tubes with stoppers, spatula, protective gloves, safety glasses. Chemicals 

Crown ether 18-crown-6, ethanol, trichloromethane, potassium permanganate, manganate and dichromate, sodium chromate and ammonium dichromate. 

---

Table 35 Structurally characterized U 02 crown ether inclusion compounds.

Podates AcycHc analogues of crown ethers /coronands and cryptands (podands, eg, (11) (30) are also capable of forming inclusion compounds (podates) with cations and uncharged organic molecules, the latter being endowed with a hydrogen bond fiinctionahty. Podates normally are less stable than coronates and cryptates but have favorable kinetics. 

When the reaction of two compounds results in a product that contains all the mass of the two compounds, the product is called an addition compound. There are several kinds. In the rest of this chapter, we will discuss addition compounds in which the molecules of the starting materials remain more or less intact and weak bonds hold two or more molecules together. We can divide them into four broad classes electron donor-acceptor complexes, complexes formed by crown ethers and similar compounds, inclusion compounds, and catenanes. 

Chiral Recognition. The use of chiral hosts to form diastereomeric inclusion compounds was mentioned above. But in some cases it is possible for a host to form an inclusion compound with one enantiomer of a racemic guest, but not the other. This is caUed chiral recognition. One enantiomer fits into the chiral host cavity, the other does not. More often, both diastereomers are formed, but one forms more rapidly than the other, so that if the guest is removed it is already partially resolved (this is a form of kinetic resolution, see category 6). An example is use of the chiral crown ether (53) partially to resolve the racemic amine salt (54). " When an aqueous solution of 54 was... 

Fig. 29. Stereoview of the 1 1 DTU diethyl ether clathrate (the inclusion compound of DTU with diethylamine is isomorphous)45)...

Phenolic ethers, 10 574 Phenolic foundry resins, 18 788-789 Phenolic friction materials, 18 787-788 Phenolic herbicides, 13 293 Phenolic host inclusion compounds, 14 172-174... 

One of the more important recent developments in organometallic aluminum chemistry has been the formation and isolation of low-coordinate compounds, and, in particular, cations. These were first prepared in reactions of various aluminum reagents with crown ethers to form the inclusion compounds known as liquid clathrates. 71,72 Most of the evidence supports the presence of ion pairs as the basis of the solvent inclusion effect. Indeed, the compound [AlMe2-18-crown-6]+[AlMe2Cl2] was isolated from one such system (the cation is shown in Figure 6(a)).73 This was the first time the Me2Al+ unit had been structurally characterized. 

When a mixture of finely powdered 1 1 inclusion compound of (-)-l and 4-methyl-cyclohexanone 2a (1.5 g) and (carbethoxymethyl)triphenylphosphorane 3 (2.59 g) was kept at 70 °C, the Wittig-Horner reaction was completed within 4 h. To the reaction mixture was added ether-petroleum (1 1), and the precipitated solid (triphe-nylphosphine oxide and excess 3) was removed by filtration. The crude product left after evaporation of die solvent of the filtrate was distilled in vacuo to give (-)-4-methyl-l-(carbethoxymediylene)cyclohexane 4 of 42.3% ee in 73% yield. 

In Section 2, it was revealed that (/ )-(l-naphthyl)glycyl-CR)-phenylglycine (2) forms inclusion compounds with ethers (tetrahydrofuran and diethyl ether). X-ray crystallographic study showed that the dipeptide has the ability to form a parallel ... 

DCA is the first bile acid whose inclusion ability was confirmed in the crystalline state. During the last century many research groups dealt with the inclusion compounds of DCA with various guest molecules, such as aliphatic, aromatic and alicyclic hydrocarbons, alcohols, ketones, fatty acids, esters, ethers, nitriles, peroxides and amines, and so on [2], In 1972, Craven and DeTitta first reported the exact crystal structure of DCA with acetic acid [3], Subsequent crystallographic studies made clear that most of DCA inclusion crystals have bilayer... 

---