Reaction with unsaturated

The Ritter reaction with unsaturated carbenium ions under either silver-assisted solvolysis or photolytic conditions leads to excellent yields of isoquiaolines (173). The ease of preparation of the requited vinyl bromides makes an attractive route to highly substituted isoquiaolines. 

Pyridazine carboxylates and dicarboxylates undergo cycloaddition reactions with unsaturated compounds with inverse electron demand to afford substituted pyridines and benzenes respectively (Scheme 45). 

Cycloaddition reactions also have important applications for acyclic chalcogen-nitrogen species. Extensive studies have been carried out on the cycloaddition chemistry of [NSa]" which, unlike [NOa]", undergoes quantitative, cycloaddition reactions with unsaturated molecules such as alkenes, alkynes and nitriles (Section 5.3.2). ° The frontier orbital interactions involved in the cycloaddition of [NSa]" and alkynes are illustrated in Fig. 4.13. The HOMO ( Tn) and LUMO ( r ) of the sulfur-nitrogen species are of the correct symmetry to interact with the LUMO (tt ) and HOMO (tt) of a typical alkyne, respectively. Although both... 

Azidofurazans and -furoxans undergo dipolar cycloaddition reactions with unsaturated compounds, in some cases regiospecifically. Thus, reaction of 3-amino-4-azidofurazan with l-morpholinyl-2-nitroethene (toluene, reflux, 70 hours) gives 4-nitro-l,2,3-triazole 204 in 87% yield (99MI1, 000KGS406). Cycloaddition of the same azide to alkynes was accomplished by formation of a mixture of position isomers 205 and 206. Regiospecific addition was observed only in singular cases... 

Cyanoisopropyl radicals generally show a high degree of specificity in reactions with unsaturated substrates. They react with most monomers (c.g. S, MMA) exclusively by tail addition (Scheme 3.4). However, Bcvington et al.11 indicated that cyanoisopropyl radicals give ca 10% head addition with VAc at 60 °C and that the proportion of head addition increases with increasing temperature. 

Hydroxy radical and sulfate radical anion, though they may sometimes give rise to similar products, show quite different selectivity in their reactions with unsaturated substrates. In particular, the sulfate radical anion has a somewhat lower propensity for hydrogen abstraction than the hydroxyl radical. For example, the sulfate radical anion shows little tendency to abstract hydrogen from mcthacrylic acid.232... 

Metal vapor chemistry showed that the lanthanides had quite an extensive chemistry with unsaturated hydrocarbons. Some of the early surveys of metal vapor reactions with unsaturated hydrocarbons included some lanthanide metals and showed that reactivity was present for these metals (14-18). Subsequent synthetic studies in which the products were isolated and characterized led to some of the most unusual organolanthanide complexes currently known (19-28). 

Reaction with unsaturated selenides.2 Organotin compounds are useful in synthesis because they undergo Sn/Li exchange and also various condensations with electrophiles. A new route to organotrimethyltin compounds involves reaction of (CH3)3SnLi (1) with various selenides. 

The unstable per-acid, which like all per-acids is much weaker than the corresponding carboxylic acid, is taken up in chloroform after acidification of the solution of the sodium salt. The chloroform solution serves in the reaction with unsaturated substances which has already been formulated on p. 111. Ethylene itself does not give this reaction. 

The 4-substituted-5-sulfonylimino-l,2,3,4-thiatriazoles also rearrange on reaction with unsaturated reagents [75JOC1728 80AG(E)276 82T3537 ... 

Section C of Scheme 9.4 give some other examples of cyclization involving iminium ions as electrophiles in reactions with unsaturated silanes. 

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