**3. Asymmetric alkene carbo‐ and cycloalumination, catalyzed by enantiomerically pure Group IV metallocenes**

The development of stereoselective catalytic methods for the synthesis of cyclic and acyclic OAC using chiral transition metal η<sup>5</sup> *‐*complexes is an actual field of chemistry. Among these, chiral Ti and Zr complexes found application in the enantioselective functionalization of alkenes with organomagnesium and ‐aluminum compounds [7–11, 34, 64, 65].

Study on the olefin carboalumination with AlMe<sup>3</sup>

**46**, *p-S,p-S*

**Zr Cl Cl**

B(C6F5)4

+

**39**, *R,p-R,p-R*

H H

H H

plex **45** [71]. The reaction of alkenes with AlMe<sup>3</sup>

achieved in the styrene methylalumination, catalyzed by the [Ph<sup>3</sup>

**45**, *p-S,p-S* **47**, *p-S,p-S* **48**, *p-S,p-S* **49**, *p-S,p-S*

**Si**

**40**, *p-R,p-R*

**Zr Cl**

> **Zr Cl Cl**

**n**

H

**Zr Cl Cl Zr Cl Cl Zr Cl Cl**

[43]

H

**R'= Alk, n=2-6**

H H

H H

<sup>H</sup> <sup>H</sup>

[43,44,66-68,73-75] [43] [66,71,72]

**33,** *p-R,p-R*

**Zr** O O

H

**<sup>O</sup> Ti Cl**

[76]

**Cl <sup>N</sup> H Si**

> **Zr Me Me Al Me Me**

[43, 44, 66–78].

**32a**,**b***, p-S,p-S* X= Cl (**a**), Me (**b**)

**Zr <sup>X</sup> <sup>X</sup>**

H H H

**[Zr\*], AlR3, MAO**

**[Zr\*], Et2Zn, MAO**

H H

H H

**Zr Cl Cl Si Zr**

**Scheme 8.** Enantiomerically pure Zr and Ti complexes as catalysts in the reactions of alkenes with AlR<sup>3</sup>

**EtnAlCln-3, Mg [Zr\*], AlEt3**

**[Zr\*], AlMe3**

of complexes **42, 44** in the alkene carboalumination with AlEt<sup>3</sup>

chain‐end functionalizability has been presented in Ref. [72].

*ansa‐*zirconocenes **45**–**49** showed that the highest enantioselectivity (about 80%*ee*) was

**n**

**<sup>37</sup>**, *p-R* **<sup>35</sup>**, *p-S* **34,** *p-R,p-R*

**Cl Zr Si**

**42**, *S, p-S, p-S* 

[66,69,70]

**Zr Cl Cl**

**36**, *p-S*

**Zr Cl Cl**

H H H

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

H

[77]

**Cl Cl**

[71,72] [68]

[43] [68] [68] [68,78]

**<sup>41</sup>**, *S, p-S, p-S* **<sup>43</sup>**, *S, p-S, p-S* **<sup>38</sup>**, *p-R,S* **<sup>44</sup>**, *p-S, p-S* 

**Si**

**Zr <sup>O</sup>**

**THF [Zr\*], EtMgBr (Et2Mg)**

**THF [Zr\*],**

> H H

methylalumination products in 66% yield and with enantiomeric purity of 65%*ee* [68]. Using

derivatives with enantiomeric excess of 50–51%*ee*. The reaction provided optically active dia‐ steromerically pure functionally substituted alkylated alkene dimers as well [68]. The strategy of all‐syn deoxypropionate motif construction, found in a number of natural products, by the asymmetric oligomerization of propylene in the presence of **42** with both stereoselectivity and

Thus, the chemo‐ and enantioselectivity of these reactions are substantially affected by the cata‐ lyst and alkene structures, OAC nature and reaction conditions (temperature, reactant ratio

in the presence of conformationally rigid

[71,72]

**Zr Cl Cl**

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

H

**O O**

]‐activated com‐

(R = Me, Et)

**Zr Cl Cl**

**Si**

55

afforded 2‐ethyl‐substituted

C][B(C<sup>6</sup> F5 )4

catalyzed by **44** in the presence of МАО gave

Thus, in the reaction of alkenes with organoaluminum compounds C<sup>2</sup> ‐ and C<sup>1</sup> ‐symmetric conformationally labile (**32**–**37**) and rigid (**38**–**49**) enantiomerically pure complexes were used as catalysts (**Scheme 8**). Thus, the high enantioselectivity (up to 95%*ee*) of alkene car‐ bometalation by AlR<sup>3</sup> (R = Me, Et) was achieved in the reactions, catalyzed by conforma‐ tionally labile complex **32a** in chlorinated solvents [43, 44]. Later, it was demonstrated that the replacement of AlMe<sup>3</sup> by AlEt<sup>3</sup> in the reaction catalyzed by complex **32a** results in the *R* to *S* change of the absolute configuration of the β*‐*stereogenic center in the carboalumina‐ tion products [66–68]. Furthermore, the cycloalumination of terminal alkenes gives alumi‐ nacyclopentanes with 24–57%*ее* [44, 66, 67, 69]; the maximum enantioselectivity (∼57%*ее*) in cycloalumination was found in the reaction of vinyl‐substituted hydrocarbons with AlEt<sup>3</sup> conducted in CH<sup>2</sup> Cl<sup>2</sup> [67].

Alkene and Olefin Functionalization by Organoaluminum Compounds, Catalyzed... http://dx.doi.org/10.5772/intechopen.69319 55

**Scheme 8.** Enantiomerically pure Zr and Ti complexes as catalysts in the reactions of alkenes with AlR<sup>3</sup> (R = Me, Et) [43, 44, 66–78].

by OACs goes via several stages and gives alumolanes. The probability of this process was

The development of stereoselective catalytic methods for the synthesis of cyclic and acyclic

chiral Ti and Zr complexes found application in the enantioselective functionalization of

conformationally labile (**32**–**37**) and rigid (**38**–**49**) enantiomerically pure complexes were used as catalysts (**Scheme 8**). Thus, the high enantioselectivity (up to 95%*ee*) of alkene car‐

tionally labile complex **32a** in chlorinated solvents [43, 44]. Later, it was demonstrated that

to *S* change of the absolute configuration of the β*‐*stereogenic center in the carboalumina‐ tion products [66–68]. Furthermore, the cycloalumination of terminal alkenes gives alumi‐ nacyclopentanes with 24–57%*ее* [44, 66, 67, 69]; the maximum enantioselectivity (∼57%*ее*) in cycloalumination was found in the reaction of vinyl‐substituted hydrocarbons with AlEt<sup>3</sup>

*‐*complexes is an actual field of chemistry. Among these,

in the reaction catalyzed by complex **32a** results in the *R*

(R = Me, Et) was achieved in the reactions, catalyzed by conforma‐

(R = Me, Et), catalyzed with Zr η<sup>5</sup>

‐ and C<sup>1</sup>

‐complexes.

‐symmetric

shown experimentally using low temperature NMR spectroscopy [56].

**enantiomerically pure Group IV metallocenes**

by AlEt<sup>3</sup>

OAC using chiral transition metal η<sup>5</sup>

**Scheme 7.** Mechanisms of reactions of alkenes with AlR<sup>3</sup>

bometalation by AlR<sup>3</sup>

54 Alkenes

conducted in CH<sup>2</sup>

the replacement of AlMe<sup>3</sup>

Cl<sup>2</sup> [67].

**3. Asymmetric alkene carbo‐ and cycloalumination, catalyzed by** 

alkenes with organomagnesium and ‐aluminum compounds [7–11, 34, 64, 65].

Thus, in the reaction of alkenes with organoaluminum compounds C<sup>2</sup>

Study on the olefin carboalumination with AlMe<sup>3</sup> in the presence of conformationally rigid *ansa‐*zirconocenes **45**–**49** showed that the highest enantioselectivity (about 80%*ee*) was achieved in the styrene methylalumination, catalyzed by the [Ph<sup>3</sup> C][B(C<sup>6</sup> F5 )4 ]‐activated com‐ plex **45** [71]. The reaction of alkenes with AlMe<sup>3</sup> catalyzed by **44** in the presence of МАО gave methylalumination products in 66% yield and with enantiomeric purity of 65%*ee* [68]. Using of complexes **42, 44** in the alkene carboalumination with AlEt<sup>3</sup> afforded 2‐ethyl‐substituted derivatives with enantiomeric excess of 50–51%*ee*. The reaction provided optically active dia‐ steromerically pure functionally substituted alkylated alkene dimers as well [68]. The strategy of all‐syn deoxypropionate motif construction, found in a number of natural products, by the asymmetric oligomerization of propylene in the presence of **42** with both stereoselectivity and chain‐end functionalizability has been presented in Ref. [72].

Thus, the chemo‐ and enantioselectivity of these reactions are substantially affected by the cata‐ lyst and alkene structures, OAC nature and reaction conditions (temperature, reactant ratio and solvent). Presumably, the key factor determining the dependence of enantioselectivity on the solvent nature and OAC structure is the conformational behavior of the η<sup>5</sup> *‐*ligands in bimetallic Zr, Al‐intermediates, which control the reaction pathways. The effect of a solvent nature on the rate of intramolecular exchange between conformers of neomenthyl‐substituted zirconocenes **32a**, **35** and **36**, which are formed as a result of the rotation of the indenyl frag‐ ments relative to [ZrCl<sup>2</sup> ], has been shown by the means of dynamic nuclear magnetic resonance (DNMR) spectroscopy [68]. Comparison of the conformer composition and dynamics of the complexes with their activity and stereoselectivity in the reactions of OACs with alkenes led to the conclusion that the enantioselectivity of the reactions is determined by the kinetic factor, namely, by the rate of interaction in a pair: conformer of catalytically active center‐substrate. Thus, in order to achieve high enantioselectivity in the studied reactions, the catalyst molecule should have a specific conformational mobility for the formation of a suitable rotamer, which lifetime will be sufficient for the alkene insertion.

In this connection, further optimization of the ligand environment, namely the search for appro‐ priate conformers that could be formed via either introduction of suitable substituents into the indenyl ligand or upon binding of ligands could advance these studies toward the design of more efficient catalysts for alkene functionalization by organomagnesium and ‐aluminum reagents.

Fourth, the activity of catalytic systems and the degree of asymmetric induction in catalytic alkene functionalization by OACs is substantially affected by the intramolecular ligand mobil‐

**Scheme 9.** Exchange processes in bimetallic intermediates as factors that determine the properties of catalytic systems.

**Active species**

**(H) (H)**

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

**Dormant state**

**(H) (H)**

57

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

Thus, the regulation of activity, chemo‐ and stereoselectivity of the studied systems is the problem of fine tuning of the catalytically active center, in which should be a balance between

Lyudmila V. Parfenova\*, Pavel V. Kovyazin, Tatyana V. Tyumkina, Leonard M. Khalilov and

Institute of Petrochemistry and Catalysis, Russian Academy of Sciences, Ufa, Russian Federation

[1] Woodward S, Dagorne S, editors. Modern Organoaluminum Reagents. Preparation, Structure, Reactivity and Use. Berlin Heidelberg: Springer‐Verlag; 2013. p. 312. DOI:

[2] Tolstikov GA, Dzhemilev UM, Tolstikov AG. Aluminiyorganicheskie soedineniya v organicheskom sinteze (Organoaluminum compounds in organic synthesis). Novo‐

sibirsk: Akad. izd. GEO; 2009. p. 645. ISBN 978‐5‐9747‐0147‐4

The authors thank the Russian Foundation of Basic Research for financial support.

ity and conformational composition of the bimetallic intermediates.

electronic and steric factors of the catalyst, OAC and the substrate.

\*Address all correspondence to: luda\_parfenova@mail.ru

**Acknowledgements**

**Author details**

**Dormant state**

Usein M. Dzhemilev

**References**

10.1007/978‐3‐642‐33672‐0
