Other Oxygen- and Sulphur-containing Systems

Reagents i, toluene, reflux ii, MeOGCC iTCOOMe, o-Cl CjH, reflux 

The fused oxadiazine (249) is formed, in excellent yield, by heating the nitroso-compound (248) in light petroleum 

Two publications have recently appeared on the formation of six-membered heterocycles from nitrilimines (PhN-N R) and suitably hetero-substituted olefins thus the selenate (256) gives a selenadiazine (257) and the phosphonite (258) affords a phosphadiazine (259).  

high-yielding route to 1,3-didehydro-2,l,3-benzothiadiazin4-one (260) consists of treating anthranilamide with thionyl chloride or sulphur dichloride ketones react with this cyclic ylide to give quinazolines, e.g. (261).  

Reagents i, AgOAc, PhH, reflux ii, PPhj, MeCN, at room temperature 

Thermolysis (at 120—140 °C) of 2-aryl-6//-l,3,5-oxathiazines (422), which can now be synthesized with a variety of substituents, gives 1,3-thiazadienes 

Reagents i, PCI5, CCI4, heat ii, NuH, base, CH2CI2, at r.t. 

The iV-acyl-imine (426) cyclo-adds to aromatic aldehydes and nitriles to give 1,3,5-dioxazines and 1,3,5-oxadiazines, respectively. Treatment of divinyl sulphide with thiourea affords the 1,3,5-dithiazine (427).  

Benzo[e]-l,2,4-thiadiazine 1,1-dioxide has been shown to prefer the AH-structure (432). A new, simple route to 3-oxo-derivatives of this system has been developed anilines are added to CSI (CSI is CISO2NCO) and the resultant N-chlorosulphonyl-ureas cyclized with AICI3. Yields are good to excellent, and 

Reagents i, CSI, EtN02, at -40 °C ii, AlCl, heat iii, cone. HCl, heat 

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Other Oxygen- and Sulphur-containing Systems. - M. Christl, U. Lanzendorfer, and S. Freud, Angew. Chem., Int. Ed. Engl., 1981, 20, 674. 

Other Oxygen- and Sulphur-containing Systems 367 References 370... 

The distinctions between the system of equivalents ordinarily employed in this country, and the 2 volume notation adopted in this work, may be thus expressed. In the new system, the atomic weight of carbon is 12, of oxygen is 16, of sulphur is 32 and similarly with selenium and tellurium all the other atomic weights are unaltered. The atomic expressions for all bodies not containing carbon, oxygen, or sulphur, are unchanged thus, H, N, HCl, KI, NH, c. When in an atomic formula the atoms of carbon, oxygen, and sulphur, form even numbers, these numbers are halved thus, alcohol becomes G H O, ethyl... 

Any ring system containing at least one heteroatom (i.e. an atom other than carbon - typically nitrogen, oxygen, or sulphur) can be described as heterocyclic. This broad definition encompasses both aromatic heterocycles (such as pyridine 5.1) and their non-aromatic counterparts (piperidine 1.7). 

As distinct from benzene and other ring systems which contain carbon as the only ring constituent are a number of heterocyclic ring compounds in which one or more of the carbons is replaced by an oxygen, nitrogen or sulphur atom. These too may be either saturated or unsaturated. 

A cautionary note is that, in addition to the polymer itself, the polymer additive system may contain elements other than carbon, hydrogen and oxygen. The detection of an element such as nitrogen, sulphur, halogens, phosphorus, silicon or boron in a polymer... 

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