Addition to unsaturated compounds

Because of their relative instabiUty, primary phosphine oxides caimot be isolated and must be converted direcdy to derivatives. Primary and secondary phosphine oxides undergo reactions characteristic of the presence of P—H bonds, eg, the base-cataly2ed nucleophilic addition to unsaturated compounds such as olefins, ketones, and isocyanates (95). 

Organosodium compounds are prepared from sodium and other organometaUic compounds or active methylene compounds by reaction with organic haUdes, cleavage of ethers, or addition to unsaturated compounds. Some aromatic vinyl compounds and aHyUc compounds also give sodium derivatives. 

In this chapter, we discuss free-radical substitution reactions. Free-radical additions to unsaturated compounds and rearrangements are discussed in Chapters 15 and 18, respectively. In addition, many of the oxidation-reduction reactions considered in Chapter 19 involve free-radical mechanisms. Several important types of free-radical reactions do not usually lead to reasonable yields of pure products and are not generally treated in this book. Among these are polymerizations and high-temperature pyrolyses. 

Addition to Unsaturated Compounds. Part XVI. a/S-Ethylenic Acids. J. chem. Soc. (London) 1950, 1624-... 

The Kinetics of Halogen Addition to Unsaturated Compounds. Part... 

Waters, H. D. C., A. R. Caverhill and P. W. Robertson The Kinetics of Halogen Addition to Unsaturated Compounds, Part XII. Iodine Catalysis of Chlorine and Bromine Addition to Ethyl Cinnamate. J. chem. Soc. (London) 1947, 1168. 

Another fundamental reaction of >C=0 involves its reactivity as a base. In the Brpnsted sense, >C=0 - may react with a proton donor to produce a neutral ketyl radical (>C(.)OH, Figure 2, reaction 2). This is an important process when the reduction of a carbonyl compound is carried out under acidic conditions or in a protic media (e.g. elec-trochemically, with less reactive reducing reagents such as Mg or Zn, or when >C=0"-is produced via PIET and R3N"+ has available a-protons). The follow-up chemistry of >C(.)OH is that of a neutral free radical (dimerization to form pinacols, addition to unsaturated compounds, fragmentations/ring-openings, etc.), and thus beyond the scope of this chapter. 

Riebsomer [72] gave an extensive list of the reactions of N02 addition to unsaturated compounds. 

However, inter-radical conversion may be extremely important, as illustrated throughout, the most important reactions being H-atom transfer or addition to unsaturated compounds. For example, OH radical attack on DNA is dominated by H-transfer to give sugar radicals, and additions to the bases (Chapter 8). 

A range of products containing (CF3)2NO groups may be obtained by addition to unsaturated compounds [286-289] (Figure 8.112). 

Cyclic acetals and their heteroanalogs, homolytic addition to unsaturated compounds 88MI67. 

It seems appropriate to inquire whether or not it is possible to carry out other Michael reactions and, generally, other nucleophilic additions to unsaturated compounds as a sequence of kinetically independent steps using one s choice of nucleophiles and electrophiles The answer is definitely yes . A rationale similar to that used to describe the Robinson annulation provides us with the key to how this goal may be attained. First of all, the initial step of the reaction, addition of the nucleophilic component across a double (or triple) bond, needs to be carried out in the absence of the external electrophiles (preferably in aprotic solvents). Secondly, a carbanionic intermediate, incipiently formed at this step, requires sufficient stabilization to survive as a chemical entity under... 

The general reaction pattern for the reduction of group 14 organometal halides is shown in Eq. (45) [166]. The one-electron reduction of metal halides leads to the formation of the metal centered radicals. The metal radicals may undergo radical coupling to produce metal-metal bonds or addition to unsaturated compounds. The metal radical may also be reduced electrochemically under some conditions to give the metal anions, which react with electrophiles. 

Dipolar addition to unsaturated compounds affords routes to unique and interesting structures. The 1,3-dipolar cycloaddition of the 0-methyl ether of dinitromethane to methyl acylate produced N-methoxy-3-nitro-5-carbomethoxy-isoxazolidine in 65% yield. Similar results were obtained with other olefins. Acetonitrile N-oxide adds to enynes to form isoxazolines and isoxazoles. ... 

Carbanions, being strong bases and nucleophiles, react readily with acids and undergo the SN2 reactions considered in Chapter 1 and the bimolecular E2 eliminations considered in Chapter 3. Other important reactions of carbanions (and nucleophiles) include addition to unsaturated compounds, especially those containing carbonyl groups, fragmentation (the reverse of addition) and elimination to give carbenes. 

It seems fair to state that the nature of the metal is more important than the R group in determining the gross behavior of R M types. Relative reactivities of organometallic compounds within a given family or horizontal period of the periodic chart have been estimated by their rate of addition to unsaturated compounds (for example, benzonitrile). The resulting empirical correlations show that R M types of the A family metals in Groups... 

C-C Linkage Reactions by Formal Addition to Unsaturated Compounds... 

---