ELECTROSYNTHESIS OF CYCLOPENTADIENE DERIVATIVES FROM ELECTROCHEMICALLY INDUCED CHAIN-REACTIONS

The electrochemical reduction at -30 degrees C of 2,6-dichlorobenzalde hyde 1a, benzaldehyde 1b, and terephthalaldehyde 2 (ArCHO) in tetrahyd rofuran with tetrabutylammonium perchlorate as the supporting electrol yte under an argon atmosphere and in the presence of a proton donor AH (2) [fluorene (FIH2) or indene (InH2)] gives the carbinols ArCHOH-AH, which result from the addition of fluorenyl or indenyl anion. Under th e influence of generated base AH(-), the carbinols are dehydrated at r oom temperature to give the corresponding ArCH = A, which react with A H(2) to generate ArCH(AH)(2). The overall process, requiring only a ca talytic amount of electricity, occurs through three consecutive chain reactions. In the propagation step the anion AH-is regenerated. The st ructure of (InH)(2)CH-C6H4-CH(InH)(2), which is obtained from 2 in the presence of InH2, has been resolved by single-crystal X-ray diffracto metry: the four indenyl moieties are in the gamma form.