201596-36-3Relevant articles and documents
Ring-closing metathesis reaction-based synthesis of new classes of polyether macrocyclic systems
Naveen,Babu, Srinivasarao Arulananda
, p. 7758 - 7781 (2015/09/08)
Ring closing metathesis (RCM) reactions of suitable substrates having terminal olefins, which are assembled from various linkers and hydroxy benzaldehydes and syntheses of a wide range of 16-30 membered, new crown ether-type polyether, aza-polyether, bis aza-polyether macrocycles and dilactone moiety embedded polyether macrocycles (macrolides) are reported. After the ring-closure reaction, installation of different functional groups and functional group modification on the periphery of the synthesized polyether/crown ether macrocycles obtained in the RCM reactions are accomplished using the epoxidation, oxidation and catalytic hydrogenation-based synthetic transformations. Along this line, the syntheses of a variety of polyether macrocycles possessing epoxide or α-hydroxy ketone or 1,2-diol functionalities at the periphery have been shown. Furthermore, the synthesized α-hydroxy ketone functionality installed polyether macrocycles were subjected to the allylation and Reformatsky type reactions to obtain homoallyl alcohol moiety-based and lactone ring-appended polyether macrocycles.
Crown Ethers as New Catalysts in the Highly Regioselective Halogenative Cleavage of Epoxides with Elemental Halogen
Sharghi, Hashem,Massah, Ahmad Reza,Eshghi, Hossein,Niknam, Khodabakhsh
, p. 1455 - 1461 (2007/10/03)
The regioselective ring opening halogenation of some epoxides using elemental iodine and bromine in the presence of a series of new synthetic macrocycle diamides and also dibenzo-18-crown -6, 18-crown-6, and aza-18-crown-6 has been studied. The epoxides were subject to cleavage by elemental halogen (I2 and Br2) in the presence of these catalysts under mild reaction conditions in various aprotic solvents. In this study, reagents and conditions have been discovered with which the individual halohydrins can be synthesized in high yield and with more than 95% regioselectivity. The results can be discussed in terms of a four-step mechanism: (1) formation of a charge-transfer complex between catalyst and halogen, (2) release of halogen nucleophile from the complex, (3) reaction of the active nucleophile at the less sterically-hindered site in the epoxide, and (4) regeneration of catalyst. The major advantages of this method are high regioselectivity, simple regeneration of catalyst and its reuse through several cycles without a decrease in activity, and ease of workup of the reaction.
