Isothiazoles monocyclic

A few isothiazoles, 2,1-benzisothiazoles and monocyclic sultams have been prepared by methods involving formation of the 4,5-bond. Thus, condensation of a-cyanooximes (179) with ethyl mercaptoacetate or related compounds gives a compound (180) which cyclizes... 

For such purposes as locating substituents, monocyclic heterocycles having only one non-carbon atom are numbered starting with the hetero atom as 1. If there is more than one hetero atom of the same kind, the more saturated hetero atom takes precedence (cf. imidazole in Table 1). In isoxazole and isothiazole, the divalent atom takes precedence, in conformity with the pnaciples of the Hantzsch-Widman system (Section 1.02.2.2). 

Isoquinolinones and their saturated derivatives, 52, 155 Isothiazoles, 4, 107 recent advances in the chemistry of monocyclic, 14, 1... 

The electron-withdrawing effect of the isothiazole unit is evident in the proton chemical shifts of H-3 and H-4 in 5-phenylfuro[3,2-d]isothiazole (15), V-methyl-5-phenylpyrrolo[3,2-parent monocyclic heterocycles <80BSB773,85KGS223). As expected, changing the orientation of the isothiazole subunit (i.e., thieno[2,3-c]isothiazole (17)) vis-a-vis the thiophene subunit has little effect on the chemical shift of H-4 (see structures (14a) and (17)) <82AJC385>. 

In fully-conjugated 5 5-fused heterocycles the ring protons are found in the aromatic region but their position is influenced by the adjacent ring. Thus, in the series 111-113 the isothiazole unit has an electron-withdrawing effect and the left-hand ring protons are deshielded relative to the parent monocyclic heterocycles (Figure 18) . 

Oxazole chemistry, advances in, 17, 99 Oxazolone chemistry new developments in, 21, 175 recent advances in, 4, 75 Oxidation of monocyclic pyrroles, 15, 67 Oxidative transformations of heteroaromatic iminium salts, 41, 275 3-Oxo-2,3-dihydrobenz[d]isothiazole 1,1-dioxide (saccharin) and derivatives, IS, 233... 

Synthesis and reactions of lithiated monocyclic azoles containing two or more hetero-atoms. Part 1 Isoxazoles , Iddon, B., Heterocycles, 1994, 37, 1263 Part III Pyrazoles , Grimmett, M. R. and Iddon, B., ibid., 1994, 37, 2087 Part V Isothiazoles and thiazoles , Iddon, B., ibid., 995,41, 533. Heinisch, G., Holzer, W. and Pock, S., J. Chem. Soc., Perkin Trans. 1, 1990, 1829. 

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