Synthesis of N‐pivot lariat ethers

This review covers the main strategies for the synthesis of N‐pivot lariat ethers as well as their specific syntheses.     

Synthesis of mixed‐donor azaoxathia macrocyclic tetraamides,acyclic polyether di/and tetraamides and their C‐pivot lariat derivatives

The macrocyclic tetraamides 11a‐e and 15‐hydroxy macrocyclic tetraamides 23a‐c were prepared in good yields by the nucleophilic reaction of the potassium salts of the bis‐phenoles 10a‐c with the appropriate dihalo compounds 5a‐d and 15. Moreover, the acyclic diamides 7, 9, 17‐21 and bis‐acyclic tetraamide 22 were obtained in high yields by the reaction of the appropriate dichloro compounds with different phenoxides and secondary amines. Acylation of 23a‐c with different acid chlorides gave the corresponding esters 24a‐c. Compounds 24a‐c reacted with different secondary amines to afford the corresponding novel lariat macrocycles 25a‐d in high yields.     

Synthesis of lipophilic lariat ethers with pendant N‐(X)sulfonyl carboxamide groups

Synthetic routes to sixteen lipophilic lariat ether N‐(X)sulfonyl carboxamides with X = trifluoromethyl, methyl, phenyl, and p‐nitrophenyl are described. For this new family of proton‐ionizable lariat ethers in which the acidity can be ‘tuned’ by X group variation, the ring size is systematically varied from 12‐crown‐4 to 14‐crown‐4 to 15‐crown‐5 to 18‐crown‐6.     

DFT study of the carbon‐ and nitrogen‐pivot lariat crown ethers and their complexes with alkali metal cations: Na+, K+

In this work, a quantum mechanical research of five lariat crown ethers(LCEs), 2‐methoxy‐15‐crown‐5( A ), N‐methoxy‐4‐aza‐15‐crown‐5( B ), N‐methoxy‐4‐aza‐18‐crown‐6( C ), N‐methoxyethyl‐4‐aza‐18‐crown‐6( D ), N,N′‐bis(2‐metho xyethyl)‐4,13‐diaza‐18‐crown‐6( E ), which are based on either 15‐crown‐5 or 18‐crown‐6 frameworks and contain various pendant arms extending from either carbon or nitrogen atoms on the crown frameworks, had been done using density functional theory with B3LYP/6‐31G* method to obtain the electronic and geometrical structures of the LCEs and their complexes with alkali metal ions: Na⁺ and K⁺. The nucleophilicity of LCEs had been investigated by the Fukui functions. For complexes, the match between the cation and cavity size, the status of interaction between alkali metal ions and donor atoms in the LCEs, and the sidearm effect of the LCEs had been analyzed through the other calculated parameters, such as, highest occupied molecular orbital energy, lowest unoccupied molecular orbital energy, and energy gaps. In addition, the enthalpies of complexation reaction had been studied by the calculated thermodynamic data (298 K). The calculated results are all in a good agreement with the experimental data for the complexes. © 2009 Wiley Periodicals, Inc. J Comput Chem 2009     

Synthesis and structure of tribenzo-19-crown-6 lariat ethers

Abstract

Multistep preparative routes to a series of three new, protonionizable lariat ethers, sym-(R)tribenzo-19-crown-6-oxyacetic acids with R = H, C₃H₇, and C₈H₁₇ have been developed. The crystal structure of the synthetic intermediate sym-(hydroxy)(propyl)-tribenzo-19-crown-6 has been determined. The compound crystallized in the monoclinic space group P2₁/c with a = 8.902(4) Å, b = 10.296(5) Å, c = 27.631(9) Å, β = 97.41° with a volume of 2511.4 ų. The calculated density is 1.268 mg/mm³ with Z = 4. The final R values are R = 7.99% and R_w = 5.17% using 1558 observed reflections [F>3.0 [sgrave](F)].     

Synthesis of lariat ethers with pendent amine,amide, O‐benzylhydroxamate,and urethane groups

Synthetic routes to twenty‐six new crown ether compounds with pendent amine, amide, O‐benzylhydrox‐amate, and urethane groups are reported. The new lariat ether compounds are based on sym‐dibenzo‐16‐crown‐5, sym‐dicyclohexano‐16‐crown‐5, and 14‐crown‐4 scaffolds.     

The effect of sidearm heteroatoms and a quaternary methyl group at the pivot position in lariat ethers

A methyl group geminal to the “pivot” carbon in hydroxy-methyl-derived lariat ethers dramatically enhances the binding afforded a complexed cation by the sidearm.     

Synthesis of methyl-substituted lariat ethers containing a 13-crown-4 ring

Convenient synthetic procedures for preparing two kinds of methyl-substituted lariat ethers containing a 13-crown-4 ring, 1 and 2 , are described. Compounds 1a-1c were obtained from the reaction of 2-bromomethyl-2-methyl-13-crown-4 ( 5 ) with the appropriate alkoxide. Compound 5 was prepared without the need for prior protection of the bromomethyl group. For the synthesis of compounds 2a-2c , which possess an electron-donating group on the central carbon of the trimethyl moiety of the 13-crown-4 ring, the substituents were introduced before cyclization.     

Synthesis, solid-state structures and metal ion complexation behavior of 2-picolyloxy lariat ethers

Three new 2-picolyloxy lariat ether compounds are prepared and solid-state structures are determined for two of them. Complexation behavior for a series of lariat ethers with pyridyl-containing side arms toward alkali metal cations and Ag⁺ is assessed by two-phase metal picrate extraction from aqueous solutions into chloroform and in homogeneous solutions by isothermal titration calorimetry in methanol.     

Synthesis of lariat ether carboxylic acids based on dibenzo‐16‐crown‐5

Synthetic routes to forty‐seven dibenzo‐16‐crown‐5 compounds with pendant carboxylic acid groups are reported. When taken together with previously described lariat ether carboxylic acids, these new compounds provide several series with systematic structural variations including changes in the identity and attachment site(s) of one or more lipophilic groups and the length of the spacer that connects the carboxylic acid group to the polyether framework.