Systems containing Other Heteroatoms

In a more general approach toward pentacyclic heteroaromatics from tricyclic ketones, treatment of the N-methylated derivative of 112 with p-tolylhydrazine, followed by Fischer indolization of the resulting phenylhydrazone in a mixture of trifluoroacetic acid and acetic acid, produced only a low yield of 114, although this method proved to be considerably mrae efficient for synthesis of analogous systems containing other heteroatoms than nitrogen (98SC1239). 

It is well known that ferrocene and related metallocene compounds undergo reversible oxidation by a variety of chemical oxidants. The particular ease with which ferrocene undergoes oxidation to its ferricinium cation allows one to determine the effect of a series of substituents on the oxidation potential of the ferrocene system. Thus a sensitive probe is available for determining the electronic effect a substituent has on the iron heteroatom and a device is made available by which one might elucidate the mechanism by which such an effect is transmitted from the substituent to the iron atom in the ferrocene system. It is unfortunate that lack of suitable derivatiyes has precluded similar studies in systems containing other transition metal atoms. 

The potential of this approach for heterocycle preparation has by far not been exhausted, as is the case for systems containing other or more heteroatoms within the frame executing the Cope rearrangement. ... 

The ring systems described in the present chapter contain other heteroatoms, and the normal Hantzsch Widman rules are applied. Compounds (10) are therefore diazaphosphinines. The order of precedence in heteroatom numbering should be noted oxygen > sulfur > nitrogen > phosphorus. In this chapter we normally place the P atom at the bottom of the ring, but this is seldom position 1, when other heteroatoms are present. 

Other Systems containing One Heteroatom. - The stannole (185) is transformed by the action of iodine trichloride into the 67r-iodolium cation (186), which has been isolated as a stable iodide, tetraphenylborate, and hexachloro-stannate. 

Miscellaneous other Systems containing Three Heteroatoms. - Catechol is converted into the 1,3,2-benzodioxathiolan (503) by the action of EtNSFj. The cyclic iminodiacyl peroxide (504) is obtained from the imino-compound MeN(COCl)2 and hydrogen peroxide. The hydroxamic acid HOCPh2-CONHOH reacts with carbonyldi-imidazole to yield the dioxazolone (505). The i.r. and Raman spectra of l,3-dimethyl-l,3-diaza-2-boracyclopentanes (506 R = Cl, Br, or NMc2) have been reported. The zwitterionic salt... 

Other Systems containing Three Heteroatoms 266 Oxadiazoles 266... 

It should be stressed that most of the published papers concerning heterocyclic systems deal with the nitrogen-containing cycles, but some of them compare properties between analogous systems with other heteroatoms and these results are presented in Section 3. 

The only heterocyclic seven-membered ring system with maximum unsaturation containing six heteroatoms is 1,3A4,5,2,4,6-trithiatriazepine (1). The methoxycarbonyl derivative 2 is a minor product (14%) of the complex reaction of tetrasulfur tetranitride with dimethyl acetylenedicarboxylatc in refluxing toluene, which gives mainly dimethyl l,2,5-thiadiazole-3,4-dicarboxylate (3, 67%) (see Houben-Wcyl, Vol. E8d, pl54ff which includes an experimental procedure). Two other products are the trithiadiazepine 4 (5%, see Section 4.4.1.1.1.) and the 1,2,4-thiadiazole derivative 5 (3%).385... 

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