Copper-containing DNA–Silica Mineral Complexes for the Asymmetric Diels–Alder Reaction

Abstract

Materials Deoxynucleic Acid from salmon testes (st-DNA) was purchased from Aldrich and used as received. N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride (TMAPS) and tetraethyl orthosilicate (TEOS) were purchased from TCI and used as received. All other chemicals and solvents were purchased from Sigma-Aldrich Chemicals Co., Wako Pure Chemical Ind. Ltd., TCI, and Nacalai Chemical Co. Water was deionized (specific resistance of > 18.0 MW cm at 25 °C) by a Milli-Q system (Millipore Corp.). Aza-chalcone 1a was synthesized as reported procedure. 1 Cyclopentadiene was prepared by cracking dicyclopentadiene. Substrate 4 for intramolecular Friedel-Crafts alkylations was synthesized as previously reported. 4 Methods For the synthesis of substrates and the preparative-scale reactions, NMR spectra were obtained on a JEOL JNM ECA-600 spectrometer operating at 600 MHz for 1 H NMR and in CDCl 3 unless otherwise noted. Flash Column chromatography was performed employing WakoGel

α,β‐Unsaturated 2‐Acyl‐Imidazoles in Asymmetric Biohybrid Catalysis

“…The method proved highly effective with selectivities reaching up to 94 % ee in the Diels‐Alder cycloaddition between α,β‐unsaturated 2‐acyl pyridine 11 and cyclopentadiene. Following these results, the authors also developed DNAsilica minerals made from cationic Mg(II) ions, N ‐trimethoxysilylpropyl‐ N , N , N ‐trimethylammonium chloride (TMAPS), tetraethoxysilane (TEOS) and a Cu/ligand complex …”

“…Following these results, the authors also developed DNAsilica minerals made from cationic Mg(II) ions, N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride (TMAPS), tetraethoxysilane (TEOS) and a Cu/ligand complex. [62] Considering the crucial importance of heterogeneous catalysis for industrial applications, our group has also em- barked on the development of an eco-friendly and recyclable biohybrid catalyst. Our approach, which relied on the use of commercially available cellulose-supported (CS) DNA in conjunction with a Cu(II)/L3 complex, led to high levels of selectivity in both the Friedel-Crafts alkylation and the Michael addition on α,β-unsaturated 2-acyl imidazole 8 (Figure 19).…”

Chalcones, a Privileged Scaffold: Highly Versatile Molecules in [4+2] Cycloadditions

“…+ to deliver quantitative yields and 99% ee with the same substrates. [113] Oxa-dienes 64 are typically formed with o-alkenylarene aldehydes 63 and a metal-halogen salt. These compounds [a] The reaction was performed between chalcone 31 and cyclopentadiene (34) 1 : 5. behave as electron-deficient dienes in reactions with electronrich dienophiles.…”

“…Moreover, the catalyst was recovered 10 times, observing a maximum decrease in the ee to 85%, with conversion >97% [112] . Years later, DNA‐Cu(II) was supported on Si(OEt) 4 with Si(OEt) 3 ‐C 3 H 6 ‐N(Me) 3 + to deliver quantitative yields and 99% ee with the same substrates [113] …”