Haloalkanes, alkenes, radical addition

Scheme 27 Radical addition of haloalkanes to alkenes by Kumar [ 18]...

Free-radical addition of haloalkanes to soHd-supported alkenes as the key step in... 

Radical additions. Activated haloalkanes add to alkenes in solvent-free systems in 4 process initiated by electron transfer from copper. 

Metzger, J.O., and R. Mahler, Radical Additions of Activated Haloalkanes to Alkenes Initiated by Electron Transfer from Copper in Solvent-Free Systems, Angew. Chem. Int. Ed. Engl. 34 902-904 (1995). 

Unsaturated fatty compounds such as oleic acid [la], 10-undecenoic acid [2a], pet-roselinic acid [3a], erucic acid [4a], and the respective esters, alcohols, and native oils (Fig. 1) are alkenes and contain an electron-rich double bond that can be functionalized in many different ways by reactions with electrophilic reagents. It is therefore remarkable that >90% of oleochemical reactions have been focused on the carboxylic acid functionality and < 10% have been reactions of the alkyl chain and the C,C-dou-ble bond (1). A review on radical additions to unsaturated fatty compounds that appeared in 1989 (2) quoted only very few C,C-bond-forming reactions giving branched and chain-elongated fatty compounds. Since then, modem preparative radical chemistry has been developing and has been applied also to fat chemistry (3-5). We report here on radical additions of activated haloalkanes such as alkyl 2-haloalka-noates and 2-haloalkanenitriles to unsaturated fatty compounds [l]-[4] initiated by electron transfer from copper in solvent-free systems. These additions were also car-... 

The complex, Ir[(dF(CF3)ppy)2(dtbbpy)]PF6 acted as a good photoredox catalyst for atom transfer radical addition of haloalkanes to alkenes. ... 

Physical Properties of Haloalkanes Preparation of Haloalkanes by Halogenation of Alkanes Mechanism of Halogenation of Alkanes Allylic Halogenation Radical Autoxidation Radical Addition of HBr to Alkenes... 

Cyclopentenes behave differently and often act through radical mechanisms this can lead to photoreduction to cyclopentanes, or photoaddition of the kind exemplified by norborneneand propan-2-ol 12.57). The photoadduct in this process is linked through the carbon atom of the alcohol, and not the oxygen atom. A related addition to acetonitrile 12.58) takes place when norbornene is irradiated in the presence of a silver(i) compound. It is likely thal a metal complex of the alkene is the real irradiation substrate, and the same may be true for copper(i)-promoted additions of haloalkanes to electron-deficient alkenes (2.59). When dichloromelhane is used in such a reaction the product can be reduced electrochemically to a cyclopropane (2.60), which is of value because the related thermal addition of CH.I, to alkenes in the presence of copper does not succeed with electron-poor compounds. 

In this chapter, we begin with the structure and physical properties of haloalkanes. We then study radical halogenation of alkanes as a vehicle to introduce an important type of reaction mechanism, namely the mechanism of radical chain reactions. Reactions of oxygen with alkenes and a radical mechanism for HBr addition to alkenes complete the chapter. 

---