The synthesis of 13 trans-dimethyldihydropyrenes (bridged [ 14lannulenes) fused to one or more benzene, naphthalene, phenanthrene, phenalene, or quinoxaline rings and 6 cis-dihydropyrene derivatives from benzenoid precursors using either a thiacyclophane route or an electrocyclic addition of a furan to an annulyne followed by deoxygenation is reported. Their 'H NMR spectra are studied in detail to obtain correlations between 3 J~,~ coupling constants and the intemal methyl proton chemical shifts and also between the latter and the more distant external annulene ring proton shifts. These linear correlations are then used to obtain a relationship between the relative aromaticity of benzene and the fused ring in question, such that the aromaticity of the fused ring can be estimated relative to that of a benzene ring simply from a measurement of chemical shift in the fused annulene.
A two-step method is presented for the oxidation of the 2-methylene position of 2,3-cycloalkenopyridines. The pyridyl ketones thus obtained may be reacted with 2-aminonicotinaldehyde to yield 3,3'-annelated derivatives of 2-(2'-pyridyl)-1,8-naphthyridine. Treatment of cyclic -diketones in a similar manner provided 3,3'-annelated derivatives of 2,2,-bi-l,8-naphthyridine. Analyses by NMR indicate that when the 3,3' bridge contains four methylene units the molecule is conformationally rigid at room temperature. UV and pKB data indicate interactions between the two heteroaromatic rings which vary as a function of the dihedral angle between the rings.
Friedlánder condensation of /3-aminoacrolein with a-oxo-2,3-cycloalkenopyridines or thermolysis of the 0allyloximes derived from these ketones leads to the formation of 3,3'-bridged-2,2'-bipyridines 2a-d. Reaction of 2a-d with 1,2-dibromoethane gives rise to the corresponding l,l';3,3'-doubly bridged diquaternary salts. The NMR spectra of the dimethylene-and trimethylene-bridged compounds are consistent with structures which are conformationally mobile at room temperature, while the tetramethylene-bridged system is conformationally rigid up to 150 °C. The basicity and ultraviolet absorption spectra of 2a-d may be related to the dihedral angle defined by the two pyridine rings and the resulting conjugative stabilization.
The reversible valence isomerization of cyclophanedienes to
dihydropyrenes is discussed for a
number of [a]- and [e]-annelated examples, 5 →
6 and 7 → 8, and is related to AM1
and MM2+Pi
calculations. Only in [e]-fused systems is the isomerization
easily seen to be reversible. Electrophilic
substitution of dihydropyrenes is discussed. Nitration of the
highly annelated 20 gives a mixture
of 8- and 7-nitro derivatives, while NBS/DMF bromination of the
benzo[a]dihydropyrene 3
gives
mostly 12-bromo derivative.
Zwischen der Abschirmung der chemischen Verschiebung von inneren Protonen der benzanellierten Dihydropyrene (l )‐(V) und der mittleren Abweichung von der π‐Bindimgsordnung für den Makrocyclils von [14]Annulen besteht ein linearer Zusammenhang; vergleichbare Ergebnisse werden für die Dehydro[l4]annulene (VD‐(VIII) erhalten.
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