Lewis Acid-Catalyzed Friedel−Crafts Alkylation of Ferrocene with Allylchlorosilanes

Abstract

Friedel-Crafts alkylations of ferrocene, 1, with allylchlorosilanes in the presence of Lewis acid catalysts under mild conditions gave regiospecific [1-methyl-2-(alkylchlorosilyl)ethyl]ferrocenes in fair to good yields depending upon the substituents on silicon, along with small amounts of dialkylated products. The alkylation of ferrocene with 1.2 equiv of (2-methylallyl)dimethylchlorosilane, 2b, at 0 °C gave monoalkylated ferrocene 3b and an isomeric mixture of dialkylated products in 76% and 4% yields, respectively. The yield of the dialkylated ferrocene mixture increased to 21% when 2 equiv of alkylating agent 2b was used. The two components of the dialkylated product mixture were identified as 1,1′-dialkylated ferrocene 4b (17%), and 1,3-dialkylated ferrocene 4b′ (4%). A higher yield of the 1,1′-diadduct compared to the 1,3-diadduct indicates that the electron-donating alkylsilyl group does not greatly enhance a second alkylation on the same ring. The reactivities of allylchlorosilanes in the ferrocene alkylations decrease in the following order: allyldialkylchlorosilane > allyl(alkyl)dichlorosilane . allyldichlorosilane ≈ allyltrichlorosilane. The catalytic efficiencies of Lewis acids for the alkylations decrease in the following order: HfCl 4 > ZrCl 4 > AlCl 3 > AlBr 3 >TiCl 4 .

Ferrocene-Based Porous Organic Polymer (FPOP): Synthesis, Characterization and an Electrochemical Study

“…In the case of the spectrum obtained for FPOP (Strategy B), the peak at 88.68 ppm corresponds to the substituted carbon atom of the cyclopentadienyl ring, while the peaks related to two unsubstituted carbon atoms are convoluted and, therefore, cannot be distinguished, producing one broad signal at 69.61 ppm. These results are in accordance with the ones reported in the literature, in which the prevalence of 1,1 dialkylation over 1,3-dialkylation of ferrocene is described for Lewis-acid catalyzed Friedel-Crafts alkylation under similar conditions (HfCl 4 in CH 2 Cl 2 ) [27] and for poly(ferrocenylene alkylene)s synthesized by ferrocene addition-condensation polymerization with aldehydes under BF 3 •Et 2 O in 1,2-DCE [28]. The dominance of 1,1 -structure over 1,3-dialkylated and other polyalkylated ferrocenes are due to the protic acid catalyzed trans-alkylation (i.e., retro-Friedel-Crafts) reaction, which favors the formation of 1,1 -disubstituted ferrocene.…”

Hydrophobic Polymer-Supported Lewis Acid for Solid-Phase Synthesis

“…Year 2016 | Volume 4 | Issue 1 | Page [32][33][34][35][36][37][38][39][40][41][42][43][44][45][46] limitation. Result demonstrated the higher concentration of aluminium and mercury metal for 5% CLD which was attenuated for higher CLD polymer.…”

Applications of Zirconium(IV) Chloride in Organic Synthesis

“…15 In 2000, Jung and co-workers studied the Friedel-Crafts alkylation of ferrocene with allyl chlorosilanes in the presence of Lewis acid catalysts under mild conditions and found that zirconium(IV) chloride was efficient, albeit less so than hafnium(IV) chloride. 16 In 1997, Harrowven and Dainty reported the transformation of 6-methoxytetralins into 8-methoxytetralins through the action of zirconium(IV) chloride (Scheme 2). 17 Exposure of 4 to five equivalents of zirconium chloride led to 5 in 53% conversion after 20 hours and 83% conversion after two days (Scheme 2).…”