Thiacrown-ethers

In particular, the macrocyclic tetrathia-crown ethers L1364-L1366 have been built according to Equation (6.28) [94]. Yields of these substances obtained in the presence of CS2CO3 in DMF amount to 88, 72 and 76%, respectively, and exceed those achieved by the alternative synthetic route in the presence of Na by 5-10 

In a similar [94] way L1367 (yield 52%) [98] and L1368 (yield 89%) [99] were prepared in DMF through the caesium ion-assisted reaction of 2-mercaptoethyl sulphide with 3,6-dithiaoctane-l,8-diyl bis(methanesulphonate) and 1,11-dichloro-3,6,9-trithiaundecane with 3-thiapentane-l,5-dithiol, respectively (Eq. 6.29). 

The thiacrown ether LI 371 was thesised (A) by the high dilution technique and (B) by using the -assisted reaction between the corresponding ligsons in 8.4% and 62% yield, respectively (Eq. 6.31) [103]. 

A further example is the synthesis of the thiacrown ether LI 372, containing an isobutenyl unit in the periphery (Eq. 6.32) [104]. 

Analogomly, starting from l,3-dichloro-2-methylenepropane and LI373 the tetrathiacrown ether L1374 was assembled in 70 /o yield (Eq. 6.33) [104], 

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Homolytic addition of dithiols to alkynes as a new approach to construction of dithiacyclanes and thiacrown ethers 97IZV1256. 

Thiacrown ether and related systems also tend to involve octahedrally coordinated rhodium(III) [107]. 

Substituted thiacrown ethers pendent on vinyl polymers [1228]... 

L. V. Minevski and J. A. Gaboury. Thiacrown ether compound corrosion inhibitors for alkanolamine units. Patent EP 962551, 1999. 

Another interesting application of thiadiazole chemistry is the synthesis of thiacrown ether. To this end, the precursor thiadiazole is treated with K2CO3 in the presence of 1,11-dichloro-3,6,9-trioxaundecane to give l,ll-bis(5-hydroxybenzofuran-2-sulfanyl)-3,6,9-trioxaundecane, which can be transformed into thiacrown ether 110 by treatment with tetraethylene glycol bis-tosylate and bases <00T3933>. 

Thia-8-oxoguanosine, 2 823 Thiaboranes, 4 170, 204 preparation, 4 205 Thiacrown ether monomers, 23 707 Thiacrown ether polymer ligands, 23 702 Thiamine, 2 737-738, 25 781, 795-796. 

Styryl dyes CESDs 3a-e, 4a-e incorporating thiacrown ether moieties exhibit a strong preference for the formation of complexes with heavy metal salts (Hg2+, Pb2+, Cd2+, Ni2+ or Zn2+perchlorates) [17,18],... 

Sekido, E., Saito, K., Naganuma, Y., and Kumazaki, H. (1985) Liquid-liquid extraction of some class B metal ions with thiacrown ether 1,4,8,11 -tetrathiacyclotetradecane, A nal. Sci, 1(4), 363-368. 

For the hydrolysis of cyano acetate with lipase, a method to improve the enantioselectivity was developed. The addition of a thiacrown ether largely improved the enantioselectivity to E = >700 from E = 53 without any additives (Figure 14(a)). 

In biological studies, apart from alkali and alkaline earth cations, zinc sensing is very important, especially in neuroscience. Binding of zinc and other (often toxic) transition metal ions requires receptors of different structure and coordination properties. Polypyridines, dendritic pyridines, and thiacrown ethers are the receptors of choice. 

Thiacrown ethers 10S2 Dihalogenid 1 (CH2)4 Step 1 CHCI3, reflux 2—3h B 8 90-92 2003PS1295... 

Oxa-thiacrown Ethers Containing Aliphatic Rings in a Cyclic Structure 832... 

Oxa-thiacrown Ethers Containing Double Bonds in the Cyclic Structure 834... 

Oxa-thiacrown Ethers Containing Additional Binding Sites 845... 

Oxa-thiacrown Ethers Containing One Crown Unit and One Calixarene Unit 849... 

Oxa-thiacrown Ethers Containing Two Crown Units and One Calixarene Unit 850... 

Recently many oxa-thiacrown ethers have been reported in last decade. In this section, oxa-thiacrown ethers are... 

General synthetic methods of crown ethers containing O and S atoms in the aliphatic cyclic structures, named oxa-thiacrown ethers, have already reported by the Pedersen and Bradshaw groups. Recent studies on the aliphatic oxa-thiacrown ethers have shifted to the structural study of metal complexes and complexation properties. 

Oxa-thiacrown ethers, 7 and 8, having hydroxymethyl groups on the crown rings, were prepared <1996MC9> and immobilized on a silica matrix coated with a>-(triethyoxysilyl)undecanoic acid. 

Oxa-thiacrown ethers 11 and 12 possessing a thioacetal unit have been prepared by Llorca et al. <1997AXC816>, and Romanski and Marchand <2004PJC223>, respectively. The X-ray structure of 11 showed that the S and O atoms were located at side positions of the quadrilateral. 

Marchand et al. have reported the synthesis and X-ray structures of the cage-annulated oxa-thiacrown ethers 15 <2002JCX447>. Using these oxa-thiacrown ethers except for 15g and 15h, Williams et al. measured the electrospray ionization (ESI) mass spectrometry (MS) of the complexes with Hg2+, Pb2+, Cd2+, and Zn2+ cations <2002ANC4423>. All of the macrocycles in series bound the mercury ion very selectively and efficiently in the presence of many other metal ions. 

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