Several synthetic pathways to cyclohex-5-ene-1R, 2S, 3R, 4Rtetrol (conduritol C) and cyclohex-5-ene-1S, 2R, 3R, 4R-t e t r o l (conduritol F) are compared; each is analyzed for effectiveness of waste minimization. The latest synthesis, reported in this manuscript, combines enzymatic transformations with electrochemical methods. The concept of "effective mass yield" (EMY) is defined and illustrated.

No abstract

By using direct and indirect electrochemical methods, rate constants (ko) for cyclopropane ring opening of radical anions derived from the one-electron reduction of trans-1-benzoyl-2-phenylcyclopropane, trans-1-benzoyl-2-vinylcyclopropane, 2-methylenecyclopropyl phenyl ketone, spiro[anthracene-9,1'-cyclopropan-10-one], 3-cyclopropylcyclohex-2-en-1-one, and 3-(1-methylcyclopropyl)cyclohex-2-en-1-one were determined. Qualitatively, rate constants for ring opening of these (and other cyclopropyl- and cyclobutyl-containing radical anions) can be rationalized on the basis of the thermodynamic stability of the radical anion, the ability of substituents on the cyclopropyl group to stabilize the radical portion of the distonic radical anion, and the stability of the enolate portion of the distonic radical anion. On the basis of this notion, a thermochemical cycle for estimating deltaG(o) for ring opening was presented. For simple cyclopropyl-containing ketyl anions, a reasonable correlation between log(ko) and deltaG(o) was found, and stepwise dissociative electron transfer theory was applied to rationalize the results. Activation energies calculated with density functional theory (UB3LYP/6-31+G*) correlate reasonably well with measured log(ko). The derived log(ko) and deltaG(o) and log(ko) vs E(a) plots provide the basis for a "calibration curve" to predict rate constants for ring opening of radical anions derived from carbonyl compounds, in general.

Results pertaining to the direct and indirect electrochemistry of 5,7-di-tert-butylspiro[2.5]octa-4,7-dien-6-one (1a), 1-methyl-5,7-di-tert-butylspiro[2.5]octa-4,7-dien-6-one (1b), and 1,1,-dimethyl-5,7-di-tert-butylspiro[2.5]octa-4,7-dien-6-one (1c) are reported. Product analyses reveal that reduction of all these substrates leads to cyclopropane ring-opened products; ring opening occurs with modest selectivity leading to the more substituted (stable) distonic radical anion. The direct electrochemistry of these compounds is characterized by rate limiting electron transfer (with α ≈ 0.5), suggesting that while ring opening is extremely rapid, the radical anions do have a discrete lifetime (i.e., electron transfer and ring opening are not concerted). Utilizing homogeneous redox catalysis, rate constants for electron transfer between 1a, 1b, and 1c and a series of aromatic radical anions were measured; reduction potentials and reorganization energies were derived from these rate constants by using Marcus theory.

No abstract