Halo-nitro compounds, from

Sulfoxidation. Heteroatom oxidation catalyzed by (halo)peroxidases has been observed in a variety of organic compounds. Ai-Oxidation in amines, for instance, can lead to the formation of the corresponding aliphatic A-oxides or aromatic nitroso or nitro compounds. From a preparative standpoint, however, sulfoxidation of thioethers is of greater importance since it was shown to proceed in a highly stereo- and enantioselective fashion. Moreover, depending on the source of the haloperoxidase, chiral sulfoxides of opposite configuration could be obtained (Scheme 2.179). 

Isoxazolines A-oxides have been synthesized from primary aliphatic nitro compounds and alkenes by a two-step procedure consisting of 1,3-DC of a 1-halo-substituted silyl nitronate followed by halosilane elimination <06S2265>. 

Dipole moments for several mono- and disubstituted pyrrolo[2,3-3]pyridines, 26, have been calculated using the PM3 method <1997JFA2345>. The values range from approximately 1 D for 3-halo-substituted compounds to 5.14 D for the 3-nitro deriv ative (see Table 1, Section 10.06.2.2). 

Compounds which are vanishingly weakly basic in H20, such as nitro-anilines, nitro-aromatic or halo-nitro-aromatic compounds are protonated to a greater or less extent in superacids, allowing them to be used as indicators in Hammett Acidity Function measurements. Cl- which has essentially zero base strength in H20 is protonated by the superacids to HC1, which being monomolecular is expelled as a gas from the highly associated solvents. This provides a commonly-used important route to synthesis of anhydrous fluorides, fluorosulfates and triflates. 

Aromatic sym-disubstituted hydrazines are obtained by reduction of azo compounds, which in turn are intermediates in properly controlled reductions of nitro compounds. The over-all reduction can be accomplished with zinc dust and alkali or electrolytically. For example, hydrazobenzene, the simplest member, is made by both procedures. Chemical reduction is carried out on o-nitrobromobenzene to form 2,2 -dibromohydrazobenzene (57%), the halo groups remaining intact. Many examples of the electrolytic procedure have been cited the yields vary from 50% to 95%. To a limited extent, a magnesium-magnesium iodide system has been employed as a reducting agent for the azobenzenes. ... 

The leaving group is typically halogen if the nucleophile is derived from active methylene compounds or nitro compounds. a-Halo enolates are used for this reaction. The reaction is usually performed in a one-pot procedure however, a two-step sequence with the oxidation of conjugate adducts, intermediates for cyclopropanation, can... 

Figure 2.8 Average radius Rav and effective or trispyrazole [22], oxygen atoms of the charge Zf resulting from the REC correction POM series LnW10 and LnW22, [23] and halo-of different homoleptic compounds nitro- genides F , Cl-, Br" anions [21]. genated ligands of the type bis-pyrazole...

As a preparative method the direct decarboxylation of olefinic acids is almost limited to the formation of styrenes and stilbenes from substituted cinnamic acids. Thermal decomposition of cinnamic acid gives styrene (41%). The yield is nearly quantitative if the reaction is carried out in quinoline at 220° in the presence of a copper catalyst. The yields of substituted styrenes where the aryl radical contains halo, methoxyl, aldehyde, cyano, and nitro groups are in the range of 30-76%. cis-Stilbene and cis-p-nitrostilbene are prepared in this way from the corresponding a-phenylcinnamic acids (65%). One aliphatic compound worthy of mention is 2-ethoxypropene, prepared by heating -ethoxycro-tonic acid at 165° (91% yield). The mechanism of acid-catalyzed decarboxylations of this type has been studied. Isomerization of the double bond from the a,/5- to the /5, y-position before decarboxylation very likely occurs in many instances. ... 

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