Hantzsch-Widman system of nomenclature

IUPAC Commission on Nomenclature of Organic Chemistry, Revision of the extended Hantzsch-Widman system of nomenclature for heteromonocycles, Pure Appl. Chem., 55, 409-416 (1983). 

Hantzsch-Widman System of Nomenclature for Heteromonocycles, Pure Appl. 

Hantzsch-Widman System of Nomenclature for Heteromonocycles, Pure Appl Chem., 1979, 51, 1995. U... 

The name phosphorin is used to describe compounds which follow below, because it is still in general use, but it must be noted that in the revision of the extended Hantzsch-Widman system of nomenclature for heteromonocycles, phosphorin becomes phosphinine (Pure appl. Chem., 1983, 55, 409). An investigation of the nature of the bonding in A -phosphorins (W. Schafer et al., J. Amer. chem. Soc., 1976, 98, 4410) and studies supporting the phosphonium ylide structure (1) for -phosphorins (A.J. Ashe and T.W. Smith, ibid. p.7861 ... 

There are 19, largely nonmetallic, elements encompassed by the Hantzsch-Widman system the prefixes to indicate them are shown in Table 2. These prefixes, all of which end in a (which may be lost by elision), are the same as those used in replacement nomenclature (Section 1.02.2.3). 

The nomenclature of boron compounds involves some intricacies. IUPAC rules allow the terms borabenzene or borinine for 2 the older name borin has become obsolete with the recent revision of the extended Hantzsch-Widman system (6). Anions 4 are termed boratabenzene ions an alternative would be borininate instead of the earlier borinate (7). 

SPECIALIST HETEROCYCLIC NOMENCLATURE Rule B-l. Extension of Hantzsch-Widman System... 

Another example of the prevailing use of "unnecessary" affixes in IUPAC inorganic nomenclature occurs in the extended Hantzsch-Widman system. Here a Greek capital delta (A) is inserted to denote a double bond in a heterocyclic ring. For example, the four-member ring which IUPAC would name as A3-l, 2-Azarsetine (Figure 27) in the proposed system is simply ... 

The Hantzsch Widman system is often used for the nomenclature of organic rings. This indicates the ring size by specific sufSxes the first suffix given is used for saturated rings, the second for unsaturated rings ... 

For cyclic systems, the prefix cyclo in connection with the name of the corresponding chain compound, or the Hantzsch-Widman (H-W) nomenclature system (see Section IR-6.2.4.3), may be used. 

The parent isoxazolidine (1) can be named as 1,2-oxazolidine according to the extension of the Hantzsch-Widman system. However, since the corresponding heterocycle (2) with the greatest number of non-cumulative double bonds is conventionally called isoxazole, 1 is most frequently referred to as isoxazolidine, which is used in Chemical Abstracts (CA). The hydro-isoxazole or -isoxazoline nomenclature is used solely in connection with the condensed ring for instance, compound 3 may be called either octahydro-l,2-benzisoxazole (CA nomenclature) or 4,5-tetramethyleneisoxazolidine (as a derivative of the isoxazolidine), or 7-oxa-8-azabicyclol4.3.0]nonane (3 ) (Stelzner method). A bis-isoxazolidine is called tetrahydro-2//-isoxazolo[2,3-6]-isoxazole (4) (CA method), or conventionally isoxazolizidine (4 ). 

The Hantzsch - Widman system serves for the nomenclature of heterocyclic compounds. The affixes for the Hantzsch - Widman system are shown in Table 14.2. 

At this point, we can introduce an entirely different system of nomenclature that is nevertheless accepted by lUPAC and is extremely valuable in multicyclic and bridged saturated systems. This is the replacement system, where the hydrocarbon name that would correspond to the entire ring structure, as if no heteroatom were present, is stated, and then given a Hantzsch-Widman prefix and number for the heteroatom(s). Thus, phenanthridine shown previously has the ring framework of the hydrocarbon phenanthrene, with N at position 5. The replacement name would be 5-azaphenanthrene. 

The molecules of Chapters 1 and 2 were species that defy one of the basic principles of the structural theoiy of organic chemistiy (or at least the theory in its simplest form, based on experience, without invoking electronic theory) the valences of tetracoordinate carbon are directed toward the comers of a tetrahedron. They are molecules that, within the confines of the theory, should not exist. The subject of this chapter, in contrast, appears to defy no rules of the stmctural theory oxirene (this is the usual name it is based on the clumsy Hantzsch-Widman system, in which heterocyclic rings of 3, 4, etc. atoms are given special names like oxirane, oxirene, oxetane, etc. An alternative system utilizes the currently neglected logical and convenient method of replacement nomenclature oxacyclopropane, oxacyclo-propene, oxacyclobutane, etc. ), 1, looks at first glance like a normal molecule. No unusual stereochemical constraints are imposed on the molecule, all atoms have... 

As lactones are cyclic esters, so lactams are cyclic amides. Again, as was the case with lactones, the nomenclature of the lactams is based on the use of Greek letters to show ring size, substitution of nitrogen for carbon in a cyclic array (thus using the prefix azacyclo ), or the Hantzsch-Widman system (vide supra). Some examples follow in Table 5.14. 

Advanced Chemistry Development Labs. Heterocyclic Systems. Rule B-1. Extension of the Hantzsch-Widman System, http //www.acdlabs.com/iupac/ nomenclature/79/r79 702.htm (accessed February 17, 2015). 

We summarize here the rules of the so-called Hantzsch-Widman nomenclature system for heterocycles, which currently is the fashionable procedure, although relegated to second-class status by a recent, very practical approach to organic nomenclature.1... 

Heterocyclic systems can be named by various methods, depending on ring size, the presence or absence of metal atoms, the availability of trivial names, etc. For this index the naming of the heterocyclic parents has generally followed the practices of IUPAC and Chemical Abstracts. Thus Hantzsch-Widman names have been employed for all monocyclic systems and for the other systems when the smallest ring size is five atoms or more, but replacement nomenclature has usually been followed for bicyclic and higher systems when they contain three- and four-membered rings. 

Owing to the numerous possibilities in which a 1,4-diene can be assembled, especially when heteroatoms are included, a nomenclature issue arises that needs to be addressed from the outset. According to the Hantzsch-Widman nomenclature system in combination with the lUPAC rules, hetera-di-ir-meth-ane reactions are those transformations in which a particular heteroatom replaces the caiixin atom of the 1,4-diene moiety the position is specified by means of a numerical prefix. We will use this suggested nomenclature for the di-Tr-methane photorearrangement as indicated for the substrates shown in Scheme 1. 

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