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Substituent Effect on the Formation of Arylindanes by Dimerization of Ferulic Acid and its Related Compounds.

ABSTRACT: Homodimerization and crossed-dimerization reactions for ferulic acid and related compounds in an acidic ethanol solution were investigated via a formal [3 + 2] cycloaddition reaction. Arylindanes, as the major products, were produced from some of the acids with hydroxy group and/or methoxy groups at the para and meta positions of the phenyl ring. The formation of arylindane required the following consecutive reactions: (I) protonation of the first produced ester to afford to a benzylic cation, (II) which reacts with another ester to afford a new benzylic cation, and (III) followed by cyclization to produce the dimer. It is suggested that the para-substituent promoted both step I and step II and the meta-substituent accelerated step III. To rationalize the selectivity of homodimerization, the stability of the benzyl cations and the specific electron distribution on the molecular surface of each ester is discussed based on the results of the molecular orbital calculations.

SUBMITTER: Nomura E

PROVIDER: S-EPMC6645056 | biostudies-literature | 2018 Oct

REPOSITORIES: biostudies-literature

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Substituent Effect on the Formation of Arylindanes by Dimerization of Ferulic Acid and its Related Compounds.

Nomura Eisaku E Noda Takumi T Gomi Daiki D Mori Hajime H

ACS omega 20181008 10

Homodimerization and crossed-dimerization reactions for ferulic acid and related compounds in an acidic ethanol solution were investigated via a formal [3 + 2] cycloaddition reaction. Arylindanes, as the major products, were produced from some of the acids with hydroxy group and/or methoxy groups at the para and meta positions of the phenyl ring. The formation of arylindane required the following consecutive reactions: (I) protonation of the first produced ester to afford to a benzylic cation, ( ...[more]

PMID: 31458001

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Project description:Ruthenium complexes bearing protic diimine ligands are cytotoxic to certain cancer cells upon irradiation with blue light. Previously reported complexes of the type [(N,N)2Ru(6,6'-dhbp)]Cl2 with 6,6'-dhbp = 6,6'-dihydroxybipyridine and N,N = 2,2'-bipyridine (bipy) (1A), 1,10-phenanthroline (phen) (2A), and 2,3-dihydro-[1,4]dioxino[2,3-f][1,10]phenanthroline (dop) (3A) show EC50 values as low as 4 μM (for 3A) vs breast cancer cells upon blue light irradiation ( Inorg. Chem. 2017, 56, 7519). Herein, subscript A denotes the acidic form of the complex bearing OH groups, and B denotes the basic form bearing O- groups. This photocytotoxicity was originally attributed to photodissociation, but recent results suggest that singlet oxygen formation is a more plausible cause of photocytotoxicity. In particular, bulky methoxy substituents enhance photodissociation but these complexes are nontoxic ( Dalton Trans 2018, 47, 15685). Cellular studies are presented herein that show the formation of reactive oxygen species (ROS) and apoptosis indicators upon treatment of cells with complex 3A and blue light. Singlet oxygen sensor green (SOSG) shows the formation of 1O2 in cell culture for cells treated with 3A and blue light. At physiological pH, complexes 1A-3A are deprotonated to form 1B-3B in situ. Quantum yields for 1O2 (ϕΔ) are 0.87 and 0.48 for 2B and 3B, respectively, and these are an order of magnitude higher than the quantum yields for 2A and 3A. The values for ϕΔ show an increase with 6,6'-dhbp derived substituents as follows: OMe < OH < O-. TD-DFT studies show that the presence of a low lying triplet metal-centered (3MC) state favors photodissociation and disfavors 1O2 formation for 2A and 3A (OH groups). However, upon deprotonation (O- groups), the 3MLCT state is accessible and can readily lead to 1O2 formation, but the dissociative 3MC state is energetically inaccessible. The changes to the energy of the 3MLCT state upon deprotonation have been confirmed by steady state luminescence experiments on 1A-3A and their basic analogs, 1B-3B. This energy landscape favors 1O2 formation for 2B and 3B and leads to enhanced toxicity for these complexes under physiological conditions. The ability to convert readily from OH to O- groups allowed us to investigate an electronic change that is not accompanied by steric changes in this fundamental study.

Dataset Information

Substituent Effect on the Formation of Arylindanes by Dimerization of Ferulic Acid and its Related Compounds.

Publications

Substituent Effect on the Formation of Arylindanes by Dimerization of Ferulic Acid and its Related Compounds.

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