Crown ethers of low symmetry. Spiro crown ethers and 16-crown-5 derivatives

Abstract

The product esters 1 (0.58 g) in ethanol (2.0 mL) were hydrolyzed by boiling for 2 h with 0.208 g (3.5 mmol) of KOH in 2 mL of ethanol and 0.5 mL of water. The mixture was cooled, diluted with water (10 mL), neutralized with ca. 8 N acetic acid, and extracted with CH2C12. The organic layer was washed several times with water, dried, and evaporated to give 0.47 g of the acid. Recrystallization from methanol provided 0.20 g (38% overall yield) of all-trans-retinoic acid, mp 179-180 °C (lit.M mp 179-181 °C). From the recrystallization yield, the total yield of two isomers of 1 was >50%.B. With Isolation of 3. Wittig olefination conditions were similar to the previous experiment. From 1.52 g (1.67 mequiv) of 3 in THF (15.0 mL), 0.22 g (1.00 mmol) of 5, and 1 mL (1.67 mequiv) of NaOEt was obtained 0.18 g (55%) of crude 1. Mass spectral analysis showed M+ at mje 328, and the fragmentation pattern agreed with that of the corresponding methyl ester.18

Synthesis and light gas separations in cross-linked gemini room temperature ionic liquid polymer membranes

“…1 These compounds were prepared via a method identical to that for 1a except that an ␣,-oligo(ethylene glycol) ditosylate (147 mmol) was added instead of 1,6-dibromohexane [36]. ␣,-Oligo(ethylene glycol) ditosylates were prepared via a widely used literature method [15,37] …”

The First Examples of a Crown Ether Intramolecularly Encapsulating Mono‐ and Diorganotin Dications: Synthesis and Structures of [PhSnCH2([16]crown‐5)][ClO4]2 and [HOSnCH2([16]crown‐5)][Y]2 (Y=ClO4, CF3SO3)

“…Such a less symmetrical arrangement of crown ethers has proved to enhance their cationbinding abilities. [76] The unit cells of compounds 4 and 5 contain two independent molecules, the geometric parameters of which are similar. The overall structures closely resemble that of compound 3 with the difference that the axially bonded phenyl substituent Notably…”

Synthesis of C‐pivot lariat ethers

“…Weber [62] and Hakushi et al . [63] reported the synthesis of lariat ethers with symmetrical double side arms attached through a carbon pivot. They prepared bis(hydroxymethyl) crown ethers 179 , 180 , 181 , 182 , 183 by reaction of monobenzalpentaerythritol [64] ( 175 ) with the appropriate oligoethylene glycol ditosylates 15 , 49 , 59 , 176 , and 177 in the presence of NaH, NaOH, or KOH as a base in dioxane or THF, to give the corresponding spirocrown ethers 178 followed by acid hydrolysis (HCl/EtOH) or hydrogenolysis on treatment with H 2 , Pd/C (Scheme ).…”

“…Reaction of crown ether diols 180 and 181 with the corresponding oligoethylene glycol monoethyl ether tosylate or oligoethylene glycol tetrahydropyranyl ether in the presence of NaH in THF afforded the corresponding crown ether derivatives with double symmetrical oxyethylene side arms of various chain length (cf. Table 16) [59, 62, 63, 65].…”