Heterocyclic compounds four-heteroatomic rings

Sulfur containing heterocycles are also common Compounds m which sulfur is the heteroatom m three four five and six membered rings as well as larger rings are all well known Two interesting heterocyclic compounds that contain sulfur-sulfur bonds are hpoic acid and lenthiomne... 

There is much current interest in four-membered ring compounds containing heteroatoms that are isoelectronic with a cyclobuta-l, 3-dienediide. The first thermally robust parent homocyclic dianion [ CfSiMe,), " was only reported in 2000 the first neutral heterocyclic analogue [P(C6H2Bu 3-2,4,6) p-C( Cl) ]2, containing a Group 14 element (C) dates from 1995 Extensions to the 4" and 5" quantum group elements Ge and Sn respectively, were published in 2004. 

The compounds with five-membered rings containing three or four heteroatoms including at least one phosphorus were first systematically reviewed in Chapter 4.22 of CHEC-II(1996) by Schmidpeter <1996CHEC-II(4)771>. In CHEC(1984), only few examples of 2//4,2,3-diazaphospholcs were mentioned in the general chapter on phosphorus heterocycles <1984CHEC(1)493>. 

This is the largest class of compounds in this category. The heterocyclic ring can contain from two to four heteroatoms. Many types of derivatives of the parent compounds found in Table 5 are known in which functional groups such as carbonyl and carboxylic groups, for example, extend... 

Abstract 1,2-Heteraphosphacyclanes have drawn the attention of synthetic chemists due to their association with various biological activities and their unusual properties. The focus of this chapter is on the synthetic approaches to heterocyclic compounds of this type, which are principally different for the compounds with three-membered, four-membered and larger ring size and differ greatly depending on the nature of the heteroatom in the ring. 

The second largest class of eight-membered ring heterocycles containing four or more heteroatoms is 1,3,5,7-tetraoxocanes. The parent compound is used commercially as a monomer and substituted derivatives are useful pesticides. Again, a large body of information exists on these systems and only material related to structure, reactivity, and synthesis will be covered here. Surprisingly, few papers related to the synthesis of tetrazocanes or tetraoxocanes have appeared since 1982. 

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