Effects of Non‐planarity in the Radical Anions of Tribenzo[a,c,e]cyclooctenes

Abstract

Dedicated to Prof. Edgar Heilhronner on the occasion of his 70th birthday (4.11.91) Reduction of tribenzo[a,c,e]cyclooctene (2) and its 2,3-and 1,4-dimethyl derivatives (4 and 5 ) , as well as of l,l-dimethyl-l0,11-propane-2,2-diylidene-lH-benzo[5,6]cycloocta[ 1,2,3,4-deflfluorene (6) and its 5,6-didehydro derivative (7) was followed by cyclic voltammetry. The radical anions of these compounds and those of their derivatives (D)2, (D)5, and (D)6, deuterated at C(9) in 2 and 5 or in the corresponding position of 6, have been characterized with the use of ESR, ENDOR, and TRIPLE-resonance spectroscopy. The cyclic-voltammetic and proton-hyperfine data are consistent with the increasing deviations of the radical anions from planarity in the order 6:,

Planar Dehydro[8]annulenes and Their Ramifications: Substituted Tribenzo[a,c,e]cyclooctenes and Tetrabenzo[a,c,e,g]cyclooctenes

“…A coplanar geometry of the radical anion of 48 has also been characterized. 32 The existence of a strained acetylenic bond in 48 was also verified by a facile Diels-Alder reaction of 48 with diphenylisobenzofuran, furnishing the corresponding adduct 49. A similar reaction of 48 with furan generated 50 (Scheme 13).…”

“…As anticipated, the resulting proton hyperfine data are consistent with a coplanar structure. 32 Bromination of 21 gave dibromide 45. A mixture of dibromides 46 was also generated in 68% yield when 38 was brominated with five equivalents of NBS in boiling CCl 4 in the presence of dibenzoyl peroxide.…”