With 2 hetero atoms other than

Boranes with Hetero Atoms Other Than Carbon... 

The structure of this chapter is as follows. As it concerns [AIJ-MTS, first discussed are the cation-exchanged samples, potentially exhibiting basic behavior, then the H-forms, the acidic properties of which are, as a whole, the main subject, finally the development of acidity upon partial exchange of cations with protons. The last section is devoted to a brief description of MTS with hetero atoms other than Al. 

H-pyrrolo[2,l-a] isoindoles quinolines quinolizines quinuclidines with 1 hetero atom other than O or N dibenzostannols dinaphthothiophenes phospholines phosphorins stibiafluorenes thieno[4, 3, 2"-4,5,6]steroids Ihietanes thiochromans thiophenes thiopyrylium salts thioxanthylium salts with 2 0-atoms benzodioxanes benzofuro[2,3-b]benzofurans chromeno [3,4-bJ chromenes coumarinocoumarones dibenzo-p-dioxins... 

Heterocyclic compounds are organic ring structures (-cyclic) that include an atom or atoms other than carbon (hetero-) in the ring. Thus, although compounds such as benzene and cyclohexane form organic rings, they do not include atoms other than carbon, and therefore do not qualify as heterocyclic. The particular number of elements in the ring varies, with... 

Following the lUPAC rules for nomenclature, the numbering of the ring begins with the hetero atom (atom other than carbon). Thus indole s numbering system is ... 

It should be expected that the orientation and rate of electrophilic substitution in the isoxazole nucleus would be affected by both hetero atoms. Because of the electron-accepting effect of the nitrogen atom, electrophilic substitution of the isoxazole nucleus should proceed less readily than in the case of benzene and should occur essentially at the position jS to the nitrogen atom, just as in pyridine and other azoles. Simultaneously the electron-donating oxygen atom should facilitate such reactions in isoxazole as compared with the substitution in pyridine. These predictions are confirmed by the available experimental evidence. 

The term hetero rearrangement is not limited to those reactions in which only the initially electron-deficient atom is something other than carbon, but may be applied to rearrangements in which any of the carbon atoms of formula L have been replaced with other elements. 

---