The preparation of 3-substituted-1,5-dibromopentanes as precursors to heteracyclohexanes

Abstract

SummaryThe methodology to prepare 3-substituted 1,5-dibromopentanes I and their immediate precursors, which include 3-substituted 1,5-pentanediols VII or 4-substituted tetrahydropyrans VIII, is surveyed. Such dibromides I are important intermediates in the preparation of liquid crystalline derivatives containing 6-membered heterocyclic rings. Four dibromides 1a–1d containing simple alkyl and more complex fragments at the 3-position were prepared. 3-Propyl- and 3-pentyl-pentane-1,5-diol (2a,b) were prepared starting from either glutaconate or malonate diesters, while tetrahydropyrans 3c and 3d were obtained from tetrahydro-4H-pyran-4-one. The advantages and disadvantages of each route are discussed. Dibromides 1c and 1d were used to prepare sulfonium zwitterions 11c and 11d.

Thermal and Photophysical Properties of Highly Quadrupolar Liquid‐Crystalline Derivatives of the [closo‐B12H12]2− Anion

“…The preparation of derivatives 2B[ n ]‐ p was accomplished by starting with either mercaptan [ closo ‐B 12 H 11 ‐1‐SH] 2− ( 4 a ) or its protected forms 4 b and 4 c (Scheme ). Thus, the alkylative cyclization reaction of 4 a ‐[Na], 4 b ‐[Et 4 N], or 4 c ‐[Me 4 N] with dibromide 5 in the presence of an appropriate base, [R 4 N]OH, gave the 4‐pentylthianium derivatives 6 ‐[Et 4 N] or 6 ‐[Me 4 N] in 75–80 % yield, based on 4 a , or about 50 % based on 4 b and 4 c (Scheme ). Subsequent treatment of 6 ‐[R 4 N] with 4‐MeOC 6 H 4 I(OAc) 2 in 70 % aqueous TFA gave a mixture of bis‐zwitterions 7‐ m and 7‐ p (Ar=4‐anisyl).…”

“…Disodium salt 4 a ‐[Na] (3.00 g, 13.64 mmol) was dissolved in CH 3 CN (80 mL). Dibromide 5 (4.10 g, 13.65 mmol) and [Me 4 N][OH] ⋅ 5 H 2 O (4.71 g, 26.0 mmol) were added and the reaction mixture was stirred overnight at 80 °C. The mixture was cooled, the solvent was evaporated, and the residue was suspended in water and filtered.…”

Polar Liquid Crystals Derived from Sulfonium Zwitterions of the [closo‐1‐CB11H12]– Anion

“…The desired 12‐phenyliodonium derivatives 5[ n ] were easily separated from small amounts of the 7‐iodonium isomers by chromatography . Subsequent reaction of 5[ n ] with Me 2 NCHS gave the protected mercaptans 6[ n ] , which were cycloalkylated with appropriate dibromides 7 under basic and hydrolytic conditions to give 1[ n ] . Thus, the sulfonium zwitterions 1[ n ] were obtained in four steps from the parent anion B with an overall yield of ca.…”

“…Initially, the method of Jelinek et al was used: the parent anion B was thiolated and, without isolation, the resulting mercaptan 11[0] was cycloalkylated with 1,5‐dibromopentane to give sulfonium derivative 2[0]d in 41 % overall yield (Scheme ). To obtain a higher purity of the mercaptan, the modification of Mirkin et al was employed, and the cycloalkylation with dibromide 7a gave the desired zwitterion 2[5]a in 10 % yield. Unfortunately the process was irreproducible.…”

Tributylhexadecylphosphonium Bromide, a Novel Nuclear Factor of Activated T Cells Signaling Inhibitor, Blocks Interleukin-2 Induction Associated with Inhibition of p70 Ribosomal Protein S6 Kinase Phosphorylation

“…1A. The use of THPB as a phase-transfer catalyst has been reported, [15][16][17] but to our knowledge there is no report on the relationship between THPB and NFAT. THPB inhibited NFAT-dependent reporter activity stimulated by PMA/ionomycin with an IC 50 value of 31 nM (Fig.…”