Henry N. C. Wong

Synthesis of Eupolauridine and Its Benzo-Annulated Derivative

Abstract The unique diazafluoranthene alkaloid eupolauridine (1) was synthesized by a three-step route utilizing as the initial step the thermal rearrangement of the oxime O-crotyl ether 12, which afforded onychine (2). Bracher pyridine synthesis procedure subsequently converted 2 into 1. On the other hand, Friedlander reaction was employed for the synthesis of 3, which is a benzo-annulated derivative of eupolauridine (1).

Dibenzo[a,e]cyclooctene: a nonplanar radical cation

Upon oxidation to the radical cation, the eight-membered ring in dibenzo[a,e]cyclooctene (2) seems to retain its tub-shaped geometry; in this regard, 2 resembles the parent cyclooctateraene 1.

Electrochemical reduction of sym-dibenzocyclooctatetraene, sym-dibenzo- 1,5-cyclooctadiene-3,7-diyne, and sym-dibenzo-1,3,5-cyclooctatrien-7-yne

A study of the electroreduction of sym-dibenzocyclooctatetraene (DBCOT), sym-dibenzo1,5-cyclooctadiene-3,7diyne (DBCOD) and sym-dibenzo-l,3,5-cyclooctatrien-7-yne (DBCOM) in DMF-TBAP solutions was carried out to investigate the effects of differences in the structure of the central eight-membered ring on the electrochemical behavior. The reversible half-wave potentials ( E , 1 2 9 , heterogeneous electron-transfer rate constants ( k s ) , transfer coefficients, and pseudo-firstorder rate constants of the following chemical reactions were determined by cyclic voltammetric-digital simulation techniques. The results are consistent with reduction of tub-shaped DBCOT to a planar radical anion and dianion and of planar or almost planar DBCOM and DBCOD to planar radical anions. Estimates of the energy of the conformational change were obtained by comparison of E 119 to calculated energies of the lowest unoccupied molecular orbital and from the k , values. The electrochemical behavior of cyclooctatetraene (COT) and related compounds and the electron spin resonance (ESR) of the associated radical anions have been the subjects of numerous investigations.2-8 The general picture which emerges is that reduction of the tub-shaped COT produces a planar or nearly planar radical anion (COT.-); the large change in molecular geometry leads to a high activation energy and hence slow electron-transfer rates. The second reduction step to the dianion involves only small changes in geometry and hence more rapid electron transfer. A more detailed explanation of the experimental results requires taking account of solvation changes, ion pairing effects, and following protonation reactions. Recently, Wong, Garratt, and Sondheimerg reported the synthesis of sym-dibenzo-l,5-cyclooctadiene-3,7-diyne (DBCOD) and sym-dibenzo1,3,5-cyclooctatrien-7-yne (DBCOM). The central eight-membered ring in these com-