One-pot synthesis of 6-(thien-2-yl)- and 6-(fur-2-yl)salicylates based on regioselective [3 + 3] cyclocondensations of 1,3-bis(trimethylsilyloxy)-1,3-butadienes

Abstract

6-(Thien-2-yl) and 6-(fur-2-yl)salicylates are prepared by TiCl(4)-mediated [3 + 3] cyclocondensations of 1,3-bis(trimethylsilyloxy)-1,3-butadienes with 3-(thien-2-yl)- and 3-(fur-2-yl)-3-silyloxy-2-en-1-ones, respectively. The regioselectivity of the cyclization depends on the substitution pattern of the 3-silyloxy-2-en-1-one.

Synthesis, structures, electrochemical and quantum chemical investigations of Ni(ii) and Cu(ii) complexes with a tetradentate Schiff base derived from 1-(2-thienyl)-1,3-butanedione

“…Compound 1 has also been synthetized by the LDA-mediated reaction of acetone with 2thiophenecarbonyl chloride in THF at -78 °C and isolated in 34% yield as a yellowish oil. 10 Although we prepared compound 1 as a white solid whose high purity was established by combustion analysis, its IR, 1 H and 13 C NMR spectral data (see Experimental) fully agree with the reported keto-enol structure (Z)-4-Hydroxy-4-(2-thienyl)-3-buten-2-one elucidated by 2D NMR method. 10 Only this isomer is found in solution and in the solid-state.…”

“…10 Although we prepared compound 1 as a white solid whose high purity was established by combustion analysis, its IR, 1 H and 13 C NMR spectral data (see Experimental) fully agree with the reported keto-enol structure (Z)-4-Hydroxy-4-(2-thienyl)-3-buten-2-one elucidated by 2D NMR method. 10 Only this isomer is found in solution and in the solid-state. Note that in the case of the NaH-mediated reaction, the isolated product is a 85/15 keto-enol/diketone tautomeric mixture.…”

“…5 Those easily synthetized and easily tunable dicarbonyl building blocks, presenting a keto-enol tautomerism, [6][7][8] are readily tailored to bring about donor, acceptor, polymerizable, or electroactive groups at the three carbon atoms constituting the propane-1,3-dione skeleton. [7][8][9][10][11][12][13][14] β-diketones containing a thiophene group are of particular interest because they can be used as starting materials for the construction of Schiff base derivatives and metal complexes tagged with electroactive thiophene moieties, thus allowing electrochemical polymerization to conveniently enable the direct preparation of an insoluble polymeric coating on the surface of the electrode. [15][16][17] In this context, we have recently disclosed the generation and characterization of a polythienyl-containing β-diketonate copper(II) compound and its deposition on an electrode, upon electropolymerization of the [Cu(II)-bis-{1-(2-thienyl)-3-(3-thienyl)propane-1,3-dionato}] complex using potentiodynamic method.…”

“…20 Those experiments clearly demonstrate that the electronics play an important role in the final outcome of the electropolymerization process. Therefore, pursuing along this line, we thought that such electropolymerization could be applied to first raw transition metal complexes with the symmetrically-substituted electron-rich Schiff bases 2 obtained by double condensation of ethylenediamine with the known 2-thenoylacetone 1, that mainly exists as its keto-enol tautomer (Z)-4-Hydroxy-4-(2-thienyl)-3-buten-2-one 10,11 (see formulas in Scheme 1).…”

Synthesis of Fluorinated Arenes and Hetarenes Based on One-Pot Cyclizations of 1,3-Bis(trimethylsilyloxy)-1,3-butadienes

“…42 The enones 23 are readily available by reaction of enol ethers 22 with trifluoroacetic anhydride (Scheme 10). 36c-e,43 The best yields of products 24 were obtained for reactions of substituted enones 23 (R 1 = Me, Et).…”