Formation of Carbon‐Hetero Atom Bonds by Free Radical Chain Additions to Carbon‐Carbon Multiple Bonds

Abstract

Free‐radical chain addition to carbon‐carbon multiple bonds to form carbon‐hetero atom bonds is an important synthetic method of wide scope. Carbon‐halogen, carbon‐sulfur, carbon‐silicon, carbon‐germanium, carbon‐phosphorus, and carbon‐nitrogen bonds have been formed by this method, In this chapter, the mechanism, scope, limitations, and experimental conditions are treated for the addition reactions that lead to the formation of the six types of carbon‐hetero atom bonds mentioned above. Since the direction of addition of free radicals to carbon‐carbon multiple bonds is common to all classes reviewed here, it is briefly explained.

Free Radical Addition of Butanethiol to Vegetable Oil Double Bonds

“…In this context, thiol−ene chemistry represents a direct and efficient method of introducing the sulfide groups into vegetable oils without additionally introducing unnecessary functionality such as hydroxyl groups. The thiol−ene reaction has been well studied for many types of double bonds − . The reaction occurs via free radical addition to double bonds and, importantly, can be performed in air without the complication of competing side reactions with oxygen.…”

Radical Alliances: Solutions and Opportunities for Organic Synthesis

“…[3,4] Various other radical additions to alkenes were then developed, hinging on the same general mechanism pictured in Scheme 1. [5][6][7] In recent times, the special case of the addition of thiols, renamed 'thiol click reaction', even though it was first described in 1905, [8 -10] has witnessed a remarkable popularity as a useful tool in organic synthesis, biology, polymers, and material sciences. [11 -13] The halogen atom transfer variant of the Kharasch reaction constitutes the basis of the Atom Transfer Radical Polymerization (commonly ATRP), a process of signal importance in polymer chemistry and the focus of intense attention.…”

“…They consist chiefly of polyhalides, with perfluorinated halides (e. g. CF 3 I) being particularly important from an industrial perspective; haloesters (especially bromo and iodo malonates and tertiary bromoesters, such bromoisobutyrates); and bromo-and iodo-nitriles. [5][6][7] Chlorides and bromides are only moderately reactive and frequently require the assistance of more or less catalytic amounts of copper complexes for improved reactivity. Iodine transfer is very fast, but many iodides, such as tertiary iodides, α-iodoketones, acyl iodides, anomeric iodides etc., are only moderately stable thermally and photochemically, liberating hydrogen iodide and iodine, which act as inhibitors.…”

The Use of the Thiol-Ene Addition Click Reaction in the Chemistry of Organosilicon Compounds: An Alternative or a Supplement to the Classical Hydrosilylation?

“…Further, this intermediate follows the chain transfer pathway (3) resulting in the main product and generation of another thiol radical. However, it can also follow the macromolecular chain growth (polymerization) pathway, which again results in a carboradical [ 19 ]. The ratio of these processes is determined by the nature of the olefinic substrate.…”

“…Hence, it follows quite naturally that the better chain transfer agent the reacting thiol is, the better the reaction occurs [ 21 ]. For example, thiol radicals with electron-acceptor substituents that can form resonance-stabilized radicals (such as phenylthiol and thioacetic acid) are more reactive than thiols with electron-donating substituents (e.g., butylthiol) [ 19 ]. This increases the stability of the resulting radical and hence ensures its longer life time and hence its higher concentration in the mixture, which in turn increases the reaction rate.…”