Cylic ether

Epoxides are cylic ethers which are highly reactive because of the strained bond angles of a three-membered ring. Because of the high reactivity of epoxides, they are the starting materials for so-called epoxy resins used for high-strength adhesives. 

Racemic modifications may be resolved. There are very few examples of this approach having been employed successfully. The racemic cylic ether (RS)-36, which contains two CH2OCH2CO2H arms attached to the 3 and 3 positions on the axially chiral binaphthyl units, has been resolved (48-50, 93, 94) to optical purity in both its enantiomers by liquid-liquid chromatography using a chiral stationary phase of either (R)- or (S)-valine adsorbed on diatomaceous eaitii. Very recently, the optical resolution of crown ethers (/ S)-37 and (/ 5)-38, incorporating the elements of planar chirality in the form of a rron -doubly bridged ethylene unit, has been achieved (95) by HPLC on (+)-poly(triphenyl-methyl methacrylate). 

Intramolecular metathesis of dienes leads to ring-closing metathesis (RCM), offering a useful synthetic route to cyclic compounds. The Ru and Mo catalysts are extremely useful for RCM of dienes as a synthetic method for cycloalkenes, cylic ethers and... 

Sufficient examples have been demonstrated for this reaction to move into the synthesis of complex molecules. For example, the Nicolaou group has recently demonstrated that such a process can be used for the rapid generation of complex poly-cylic ethers (Eq. 6.26(a)) [45]. 

Packed capillary columns with chirally selective stationary phases (e.g., flr acid glycoprotein), as well as wall-immobilized, CD-based stationary phases, have been successfully used in CE chromatographic separations. Also, macro-cylic crown ethers, forming sterically selective complexes with the guest molecule, have been used for the resolution of optically active amines. 

Sila-l,3-dithiacyclopentane readily inserts strained ethers and lactones, as well as chlorofluoroketones, to give 1 2 polymers. With (CF3)2CO, however, the cylic monomer 13 has been reported, though slight changes in reaction conditions give only polymer. In contrast, the six-membered dithiasilacyclohexane 14 only yields the monomer (equation 55)13. 

Cylic imino ethers such as 2,2 -bis(2-oxazoline) (BOZ) react with carboxylic acid chain ends without production of a leaving group ... 

---