**1. Introduction**

Insertion of various functional groups into the molecules is one of the central problems of organic chemistry. In this regard, alkene and olefin double bonds are often considered as possible

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reactive centers for the construction of C‐heteroatom fragments. The classic functionalization methods are based on the addition reaction of electro‐ or nucleophilic reagents toward the unsat‐ urated substrates, for example, halogenation, oxidation, hydrohalogenation, hydroboration, hydroamination, hydrosilylation, hydro‐ and carbometalation, etc. (**Table 1**).

halides, heterocycles, carbocycles and others [9, 12–18]. For example, the well‐known Ziegler‐ Alfol process for the synthesis of higher and linear primary alcohols from ethylene [12] has

The application of transition metal complexes as catalysts enables the reactions of OAC and alkenes to proceed under mild conditions with chemo‐ and stereoselectivity control. Among the complexes Group IV transition metals played a significant role in the development of alkene functionalization methods using OAC. Structural types of catalysts can be varied from metal salts to metallocenes and postmetallocenes (**Scheme 1**). The special milestone in this research is the discovery of metallocene catalysis, which serves as an effective tool for the

The future development of these methods needs understanding the reaction mechanisms: how the OAC nature, reaction conditions, catalyst and alkene structure regulate the substrate con‐ version, chemo‐ and enantioselectivity; what kinds of intermediates define the process path‐ ways. Among the mechanistic studies much attention has been paid to the catalytic systems

**Scheme 1.** Structural types of transition metal complexes applied as catalysts in alkene hydro‐, carbo‐ and

‐ligand structure variation and provides an opportunity to a

Alkene and Olefin Functionalization by Organoaluminum Compounds, Catalyzed...

http://dx.doi.org/10.5772/intechopen.69319

45

been realized in the industrial scale.

stereochemistry regulation via η<sup>5</sup>

cycloalumination.

comprehensive study of the reaction mechanisms.

Each type of functionalization goes under specific conditions and involves various reagents and catalysts, which obviously affects the mechanisms of the processes and product structure. Thus, this chapter is focused on the reactions of alkenes with organometallic compounds as the effective routes for the synthesis of numerous classes of organic compounds.

Reactions of alkenes with organometallic reagents run with high substrate conversion and selectivity due to the generation of active intermediates with C‐metal bonds (**Table 1**), further modification of which provides a wide range of products. The organoaluminum compounds (OACs) occupied a strong position in the chemistry of alkenes and olefins [1–11]. The acyclic and cyclic products bearing organoaluminum moiety obtained as a result of hydro‐, carbo‐ and cycloalumination require no further separation and could be readily modified to alcohols,


halides, heterocycles, carbocycles and others [9, 12–18]. For example, the well‐known Ziegler‐ Alfol process for the synthesis of higher and linear primary alcohols from ethylene [12] has been realized in the industrial scale.

The application of transition metal complexes as catalysts enables the reactions of OAC and alkenes to proceed under mild conditions with chemo‐ and stereoselectivity control. Among the complexes Group IV transition metals played a significant role in the development of alkene functionalization methods using OAC. Structural types of catalysts can be varied from metal salts to metallocenes and postmetallocenes (**Scheme 1**). The special milestone in this research is the discovery of metallocene catalysis, which serves as an effective tool for the stereochemistry regulation via η<sup>5</sup> ‐ligand structure variation and provides an opportunity to a comprehensive study of the reaction mechanisms.

The future development of these methods needs understanding the reaction mechanisms: how the OAC nature, reaction conditions, catalyst and alkene structure regulate the substrate con‐ version, chemo‐ and enantioselectivity; what kinds of intermediates define the process path‐ ways. Among the mechanistic studies much attention has been paid to the catalytic systems

reactive centers for the construction of C‐heteroatom fragments. The classic functionalization methods are based on the addition reaction of electro‐ or nucleophilic reagents toward the unsat‐ urated substrates, for example, halogenation, oxidation, hydrohalogenation, hydroboration,

Each type of functionalization goes under specific conditions and involves various reagents and catalysts, which obviously affects the mechanisms of the processes and product structure. Thus, this chapter is focused on the reactions of alkenes with organometallic compounds as

Reactions of alkenes with organometallic reagents run with high substrate conversion and selectivity due to the generation of active intermediates with C‐metal bonds (**Table 1**), further modification of which provides a wide range of products. The organoaluminum compounds (OACs) occupied a strong position in the chemistry of alkenes and olefins [1–11]. The acyclic and cyclic products bearing organoaluminum moiety obtained as a result of hydro‐, carbo‐ and cycloalumination require no further separation and could be readily modified to alcohols,

hydrometalation

carbometalation

cyclometalation

M = Li, Mg, Al, Zn, Zr, etc. M = Al (OAC) Catalysts: [Ti], [Zr], [Co], [Ni] Catalysts:

M = Li, Mg, Al, Zn, Zr, etc. M = Al (OAC)

M = Mg, Al, Zr etc. M = Al (OAC) R = Alk, Alkenyl Catalysts: Catalysts: [Ti], [Zr], [Hf] (η<sup>5</sup>

Section 2.1.

Sections 2.2, 3

Sections 2.2, 3

Catalysts: (η<sup>5</sup> ‐L)<sup>2</sup> ZrCl<sup>2</sup>

> ‐L)<sup>2</sup> ZrCl<sup>2</sup>

(η<sup>5</sup> ‐L)<sup>2</sup> ZrCl<sup>2</sup>

hydroamination, hydrosilylation, hydro‐ and carbometalation, etc. (**Table 1**).

**Substrate Reagent Product**

**Hal**<sup>2</sup>

44 Alkenes

**[O]**

**H‐X**

SiR<sup>3</sup>

**M‐H**

**M‐R**

**M‐R**

X= Hal, OH, SO<sup>4</sup>

, PO(OR)<sup>2</sup>

, NR<sup>2</sup> , BR<sup>2</sup> ,

etc.

R = Alk, Ar, Allyl Catalysts: [Cu], [Ti], [Zr], [Ni], [Fe], [Co]

**Table 1.** Alkene and olefin functionalization via addition reactions.

the effective routes for the synthesis of numerous classes of organic compounds.

**Scheme 1.** Structural types of transition metal complexes applied as catalysts in alkene hydro‐, carbo‐ and cycloalumination.

based on zirconocenes due to several reasons. First, a broad range of catalytic reactions can be implemented in these systems, from hydro‐, carbo‐ and cyclometalation to polymerization of unsaturated compounds. Second, these systems are convenient for fundamental investi‐ gations, since η<sup>5</sup> ‐ligands bound to zirconium atoms act like magnetic probes indicating the electronic state of the transition metal atom and reflecting the molecule symmetry. Third, the reaction times and intermediate lifetimes appear to be convenient for nuclear magnetic resonance (NMR) monitoring, which is the most informative method for the studies of homo‐ geneous catalytic reactions. Moreover, the systems are substantially free of paramagnetic species, which, for example, in the case of titanium complexes, preclude observation of the genesis of intermediates due to pronounced NMR signal broadening.

Thus, the chapter presents the results on the experimental and theoretical studies of the mechanisms of alkene hydro‐, carbo‐ and cyclometalation by organoaluminum compounds (AlR<sup>3</sup> and XAlBui 2 ), catalyzed with zirconium η<sup>5</sup> ‐complexes. The factors that determine the intermediate reactivity and, consequently, the activity of the catalytic systems, reaction pathway and enantioselectivity are considered. The prospects of the development of stere‐ oselective methods using these catalytic systems for the alkene and olefin transformations are discussed.

### **2. Mechanisms of alkene functionalization, catalyzed by zirconium η5 ‐complexes**
