화학공학소재연구정보센터
Journal of Electroanalytical Chemistry, Vol.572, No.1, 1-14, 2004
Two new compounds from the electroreduction of hypostictic acid
The electrochemical reduction of hypostictic acid (1) (1,4-dihydroxy-10-methoxy-5,8,11-trimethyl-1H-benzo[e]furo-[3',4':3,4]be nzo[b][1,4]dioxepine-3,7-dione) on glassy carbon electrodes was studied for the first time in DMF by cyclic voltammetry, rotating disc and ring electrodes, and long-term controlled-potential electrolysis. Parameters involving data from cyclic voltammetry and the rotating disc electrode. such as E-p1 vs. log nu, E-p/2,E-1 - E-p1 vs. log nu, alpha(app) vs. log nu, and E-1/2 vs. log omega, have shown behavior that can be correlated to a stepwise dissociative electron transfer. The reduction mechanism of I proceeds through a disproportionation step followed by the absorption of a proton from 1 (self-protonation step), producing hypostictinolide (4) (4-hydroxy-10-methoxy-5,8,11-trimethyl-1H-benzo[e]furo[3',4':3,4]benzo[b ][1,4]dioxepine-3,7-dione). The overall reaction is 2 RHX + 2(e-) --> RH2 + RX- + X-. The two other new compounds formed by long-term controlled-potential electrolysis-compound 5 (2-hydroxy-4-methoxy-3,6-dimethyl-1H-benzoic acid-7-hydroxy-6-methyl-1-oxo-1,3-dihydro-isobenzofuran-5-yl-ester) and compound 9 (8-hydroxy-3-methoxy-1,4,9-trimethyl-11-oxo-11H-dibenzo[b,e][1,4]dioxepi ne-7-carbaldehyde) suggest that 4 is easily modified by chemical and/or electrochemical reactions. Compound 4 suffers electrochemical reduction in the same potential range as I and follows a mechanism involving the transfer of two heterogeneous electrons in order to produce 5. The overall reaction is RH2 + 2 RHX + 2(e-) --> RH4 + 2 RX-. Compound 4 appears to undergo also a chemical reaction whose product can follow an electrochemical mechanism similar to that from 1 to 4, thus producing 9. Compounds 4, 5, and 9 were elucidated by HRMS and 1D- and 2D-NMR methods. D-0 = 4.6 x 10(-6) cm(2) s(-1) and k(0) = 9.4 x 10(-3) cm s(-1) were found for the electrochemical reduction of 1. (C) 2004 Elsevier B.V. All rights reserved.