ChemInform Abstract: On the Acidolytic Cleavage of Arylglycerol β‐Aryl Ethers.

Abstract

ChemInform Abstract The acidolytic cleavage of the lignin model compound (Ia) and its analogue (Ib) is investigated under various conditions.

Revisiting the Mechanism ofβ-O-4 Bond Cleavage during Acidolysis of Lignin. Part 2: Detailed Reaction Mechanism of a Non-Phenolic C6-C2Type Model Compound

“…The elementary reaction steps in the β-O-4 bond cleavage of V G during acidolysis can reasonably be assumed on the basis of the contents of earlier papers, [2][3][4][5][6][7][8][9][10][11][12][13][14] and the steps are shown in Figure 2. The initial step is protonation of the α-hydroxyl group (step I) followed by the release of water affording a benzyl cation-type intermediate (BC in Figure 2, step II).…”

“…V G-βD 2 was produced from this deuterated Eth following the same method as that used for the V G synthesis from Eth. [13] The mol% yield was about 89% on the basis of the amount of Eth used for the synthesis. The structure and purity were confirmed by 1 The compound with α-methyl ether V G-αOMe was synthesized from V G. V G (400 mg) was dissolved in 50 ml of methanol containing 500 mg of sulfuric acid, and allowed to react for 5 h at 45 • C. This methanol solution was mixed with 50 ml of chloroform and 30 ml of water, and extracted.…”

“…Presumed elementary reaction steps of V G during the acidolysis on the basis of the contents of earlier papers. [2][3][4][5][6][7][8][9][10][11][12][13] 274 Downloaded by [Erciyes University] at 22:37 04 January 2015 ratio is 3.9 in this study, step III is probably the major route. Further discussion of the predominance of step III over step V is as follows.…”

“…[3] However, because the hypothesized mechanism does not appear to explain the dependence of the acidolysis rate on the type of acid applied, [13,14] we reexamined the mechanism involved and published a paper on the reaction route of a C 6 -C 2 dimeric non-phenolic β-O-4 type lignin model compound, 2-(2-methoxyphenoxy)-1-(3,4-dimethoxyphenyl)ethanol (veratrylglycol-β-guaiacyl ether, V G in Figure 1). [14] It has been proven kinetically that V G is primarily and irreversibly converted into an enol ether compound, 1-(2-methoxyphenoxy)-2-(3,4-dimethoxyphenyl)ethene (EE in Figure 1), and the successive β-O-4 bond cleavage affords 2-methoxyphenol (guaiacol, G in Figure 1) and a Hibbert's monomer, 3,4-dimethoxyphenyl acetaldehyde (HK in Figure 1).…”

“…The β-O-4 bond cleavage during the acidolysis of lignin has been discussed in several papers, [2][3][4][5][6][7][8][9][10][11][12][13] and the mechanism involved and the rate-determining step have been suggested. [3] However, because the hypothesized mechanism does not appear to explain the dependence of the acidolysis rate on the type of acid applied, [13,14] we reexamined the mechanism involved and published a paper on the reaction route of a C 6 -C 2 dimeric non-phenolic β-O-4 type lignin model compound, 2-(2-methoxyphenoxy)-1-(3,4-dimethoxyphenyl)ethanol (veratrylglycol-β-guaiacyl ether, V G in Figure 1).…”