ABSTRACT:
Carbon-carbon bond formation is the core of organic synthesis, in which organometallic reagents play a key role in the forms of 1,2-nucleophilc addition. Transition metal catalyzed couplings. These reactions have enabled the production of wide range of organic molecules in our society. Despite the enormous power of organometallic reagents in chemical synthesis, they have inherent drawbacks in the eyes of future sustainability. This account summarizes our efforts on the exploration of new scientific means over the drawbacks of these classical organometallic reactions.
INTRODUCTION:
Organometallic compounds leading to the formation of new carbon-carbon bond have secured the important place in the synthetic organic chemistry. Two classes may be distinguished at the outset. In the first of these , the metal act as template which mediates the attack of external reagent on the ligand . Without that reagent becoming bonded with the coordination sphere. Prominent examples include catalytic alicyclic alkylation, usually requiring palladium complexes, and the reaction of electrophiles with the iron acylate anions. In the second category, the new bond is formed between the ligand species, and a further subdivision is needed. The key step may be cis-ligand migration, is alkyl migration to the coordinated CO in the catalytic hydro formylation. https://pubs.acs.org/doi/10.1021/acs.organomet.3c00162
TYPES OF ORGANOMETALLIC ELIMINATION:
1. NEGISHI COUPLING:
It involves the reaction of organozinc compound within an organic halide or pseudo halide in the presence of palladium catalyst. The reaction proceeds through Trans metalation step, where the organic group from organozinc reagent is transferred to the palladium catalyst. It followed by the reductive elimination step, leading to the formation of new carbon-carbon bond.
2. SUZUKI MIYAURA COUPLING:
Another widely used organometallic elimination reaction is the Suzuki- Miyaura coupling, which utilizes an organ boron compound and an organic halide I the presence of a palladium catalyst. Similarly the reaction involves Trans metalation and a reductive elimination steps, resulting in the formation of carbon-carbon bond.
3. STILLE COUPLING:
Additionally, the stille coupling is another organometallic elimination reaction that involves the reaction of an organotin compound with an organic halide in the presence of palladium catalyst. The process follows the same mechanism as the Negishi and Suzuki-Miyaura couplings leading to the formation of carbon-carbon bond.
ADVANTAGES OF ORGANOMETALLIC ELIMINATION REACTIONS:
These organometallic elimination reactions offer several advantages in organic synthesis.
1. ABILITY TO FORM CARBON-CARBON BOND SELECTIVELY:
This selectivity arises from the specific reactivity of the organometallic reagents and the choice of reaction conditions. One key aspect of selectivity is the choice of organometallic reagent itself. Different organometallic compounds have different reactivity and can selectively react with specific functional groups or substrates. For example, organolithium reagents are often used for selective carbon-carbon bond formation with electrophilic carbonyl compounds.
2. EFFICIENT AND RELIABLE:
Organometallic reactions are efficient and reliable methods for construction of complex organic molecules. Here are few reasons why they are highly regarded in the organic synthesis; • Versatile and Broad substrate scope, Mild reaction conditions, Functional group, Scalability and Well-developed methodology.
CONCLUSION:
Organometallic elimination reactions are effective method for forming carbon-carbon bond in organic synthesis. Alkyl lithium compound and Grignard reagents are commonly used organometallic reagents in these reaction. In these reactions, the carbon atom in the organometallic reagents acts as nucleophile, attacking the electrophilic carbon in the substrate. The result is the formation of new carbon-carbon chemical bond between the organometallic reagents and the substrate. The elimination of metal containing group as a leaving group accompanies the carbon-carbon bond formation. These reactions provide a way to create complex carbon frameworks and introduce new functional groups.
Overall, organometallic elimination reaction offers a valuable strategy for the synthesis of carbon-carbon bonds, enabling chemist to design wide range of organic compounds.
REFERENCES:
Hartwig, J.F. (2010). Organotransition Metal Chemistry: From bonding to catalysis. University Science Books. https://doi.org/10.1002/anie.201004890
Astruc, D. (2007). Organometallic chemistry and catalysis. Springer Science and Business Media.
Crabtree, R.H. (2005). The organometallic Chemistry of the Transition Metals (5TH Ed.). Willey VCH. https://onlinelibrary.wiley.com/doi/book/10.1002/9781118788301
Grubbs, R.H. (2003). Olefin metathesis. Tetrahedron, 59(44)10251-10270.
Frustner, A. (Ed.). (2013). Organometallic Chemistry: from the laboratory to industrial applications. Willey VCH.
