Synthesis of 1,2,3,4,5,6,7‐Heptasubstituted Cycloheptatrienes through Cycloaddition Reactions of Substituted Cyclopentadienones

Abstract

Two schemes for synthesizing heptasubstituted cycloheptatrienes with various substituents in the ring are suggested. The first method is based on cycloaddition of 2,5‐dimethoxycarbonyl‐3,4‐diphenylcyclopentadienone with substituted cyclopropenes and allows cycloheptatrienes containing two or three electron‐withdrawing substituents in the molecule to be obtained. The second method employs a cascade reaction between a substituted cyclopentadienone and appropriate vinyldiazoacetates. It allows the number of electron‐withdrawing substituents to be increased to five. In all cases, heptasubstituted cycloheptatrienes are formed as just one of the possible isomers.

The First Anionic Thia‐Fries Rearrangement at the Cobaltocenium Cation

“…As a decomplexation of cyclopentadienones from their cyclopentadienylcobalt(I) complexes is possible by treatment with cerium ammonium nitrate, [28] the reaction provides a new access to substituted cyclopentadienone derivatives as building blocks for further syntheses of compounds such as interesting aromatic systems, [39,40] cycloheptatrienes, [41,42] anellated cyclopentanones, [43] norbornenones, [44] triptycenes, [45] and various heterocycles, [46,47] often by Diels‐Alder cycloadditions [48] …”

“…[34] Two enantiomeric molecules are connected by a water molecule forming hydrogen bridges to the carbonyl oxygen atoms. with cerium ammonium nitrate, [28] the reaction provides a new access to substituted cyclopentadienone derivatives as building blocks for further syntheses of compounds such as interesting aromatic systems, [39,40] cycloheptatrienes, [41,42] anellated cyclopentanones, [43] norbornenones, [44] triptycenes, [45] and various heterocycles, [46,47] often by Diels-Alder cycloadditions. [48] In the course of our investigations with ferrocene systems it was shown that the anionic thia-Fries rearrangement does not take place with ferrocenyl mesylate or tosylate.…”

C–C Bond Cleavages of Cyclopropenes: Operating for Selective Ring-Opening Reactions

“…220,221 A different class of formal [3 + 4] cycloadditions was reported by Tomilov and co-workers using 1,2,3-trisubstituted cyclopropenes 329 and cyclopentadienones 330 to prepare heptasubstituted cycloheptatriene derivatives 331 (Scheme 47A). 222 Only a few examples of this class of compounds were prepared in useful yields and as single isomers. Nevertheless, the final location of the double bonds was substrate-dependent.…”

Diels-Alder Additions as Mechanistic Probes–Interception of Silyl-Isoindenes: Organometallic Derivatives of Polyphenylated Cycloheptatrienes and Related Seven-Membered Rings

“…Although the hepta-ester was not preparable directly via a Diels-Alder route, reaction of 2,5-dicarbomethoxy-3,4-diphenylcyclopentadienone with 1,2-dimethyl-3-carbomethoxycyclopropene did yield the corresponding cycloheptatriene, 47 , containing two methyls, two phenyls and three ester groups. Analogously, a number of cycloheptatrienes bearing multiple electron-withdrawing substituents–esters, nitriles and trifluoromethyl groups, as in 48 , were readily obtainable [ 58 ].…”