Ring-confused systems

Levels greater than 150 mcg mL may result in symptoms of mild salicylism, namely tinnitus (ringing sound in the ear), difficulty in hearing, dizziness, nausea, vomiting, diarrhea, mental confusion, central nervous system depression, headache, sweating, and hyperventilation (rapid, deep breathing). 

Novel steroidal pyridazines are readily prepared from ADC compounds and steroidal A2,4-dienes,163 A14,1 -dienes,164 and A16,20-dienes.165 ADC compounds are also commonly used in the protection of the steroid 5,7-diene system (see Section V,A). These Diels-Alder adducts of steroidal dienes and azo dienophiles should not be confused with the so-called azasteroids, which are also prepared from ADC compounds. Cyclic ADC compounds such as the pyrazole-3,5-diones (7), and the diazaquinones 12 and 13 readily add to dienes to give bicyclic pyridazine derivatives,166168 and these reactions have been adapted to the synthesis of 5,10-diazasteroids (106).42 Similarly, the 13,14-diaza- (107) and 13,14,16-triazasteroid (108) ring systems have been prepared.169... 

The nomenclature of the family of compounds to be discussed below has for long been the cause of much confusion. The systematic name for a six-membered ring containing one sulfur atom is thiin, but Chemical Abstracts uses the name thiopyran, while many earlier publications have used the replacement nomenclature thiapyran (which is strictly inaccurate as thia implies replacement of carbon, rather than oxygen, by sulfur). Throughout this chapter the terms thiopyran and thiin will be used interchangeably, while thiadecalin nomenclature will be found convenient for the perhydrobenzothiopyran systems. 

Diffusion by the interstitial mechanism and by the interstitialcy mechanism are quite different processes and should not be confused. Diffusion by the vacancy and interstitialcy mechanisms requires the presence of point defects in the system, whereas diffusion by the ring and interstitial mechanisms does not. 

Obtusenyne, via ring-closing diene metathesis, 11, 235 (9-confused oxaporphyrin systems, and silver(III) complexes,... 

The N-confusion concept can be generalized to heterocyclic rings other than pyrrole. The resulting systems, known as X-confused porphyrinoids (Fig. 30), structurally... 

In a later synthetic effort, a doubly N-confused sapphyrin 113 was obtained, wherein both confused rings belong to the bipyrrolic fragment of the macrocycle [255], In this system, a methoxy group is attached to one of the external a-pyrrolic positions, creating a peripheral sp3 center. This structural feature, which is presumably due to spontaneous addition of a methanol molecule during the synthesis,... 

The numbering of the skeleton in a ring system is generally a consequence of the way in which the skeleton is named. In order to avoid confusion as to the peripheral numbering sequence and locations of substituents in the fused systems, structural formulae are drawn as in Chemical Abstracts in accordance with the rules of heterocyclic nomenclature. Thereby the reader is not required to possess detailed knowledge of the elaborate series of priorities used in the structural presentation and numbering of ring systems. 

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