A series of 13 aromatically monosubstituted [3.3]paracyclophanes have been prepared for study of their spectral and π-base properties. Nitration, acetylation, and bromination of [3.3]paracyclophane (I) led to monosubstituted derivatives which, in turn, were converted to the other compounds. Reduction of 5-nitro[3.3]paracyclophane (II) gave 5-amino[3.3]paracyclophane (III) characterized as its acetyl derivative (IV). This same compound (IV) was prepared from 5-acetyl[3.3]paracyclophane (V) by a Schmidt rearrangement, and this cycle of reactions demonstrates that no rearrangements occurred during the original electrophilic substitutions of the [3.3]paracyclophane nucleus. Clemmenson reduction of acetyl derivative V gave 5-ethyl[3.3]paracyclophane (VI), whereas oxidative cleavage by the bromoform reaction provided 5-carboxy[3.3]paracyclophane (VII), methylation of which gave 5-carbomethoxy[3.3]paracyclophane (VIII). Treatment of 5-bromo[3.3]paracyclophane (IX) with cuprous cyanide in quinoline at 225° gave 5-cyano[3.3]paracyclophane (X). Metalation with butyllithium of bromo compound IX provided the lithio derivative, methylation of which with dimethyl sulfate gave 5-methyl[3.3]paracyclophane (XI). Oxidation of this lithio derivative with nitrobenzene provided 5-hydroxy[3.3]paracyclophane (XII) characterized as its methyl ether, 5-methoxy[3.3]paracyclophane (XIII), and acetyl derivative, 5-acetoxy[3.3]paracyclophane (XIV). In the nitration and acetylation reactions the first substituent entered the ring under conditions milder than usual. The presence of an acetyl group deactivated both rings toward further electrophilic attack in either ring. The nmr and mass spectral properties of the above compounds are reported. The 5-substituted [3.3]-paracyclophanes, unlike the 4-substituted [2.2]paracyclophanes, exhibited normal chemical shifts for protons ortho, para, and pseudo-gem (proton closest to substituent in transannular ring) to the substituent. The protons pseudo-gem to the amino and bromo substituents were exceptions, and exhibited downfield shifts less than half as great as those found for the pseudo-gem protons in the corresponding 4-amino- and 4-bromo[2.2]paracyclophanes. These differences are interpreted in terms of the differences in geometry of the [3.3]- and [2.2]paracyclophanes. All of the substituted [3.3]paracyclophanes and the parent compounds gave strong parent peaks in their mass spectra. The parent hydrocarbon also gave peaks that correspond to a fragmentation to two entities, one equal to half the parent mass and the other to half the parent mass minus one. The substituted compounds fragmented similarly. The structures of these entities are discussed. © 1969, American Chemical Society. All rights reserved.
