What is Michael addition?
The Michael addition is a chemical reaction in which a conjugated enone or enoate reacts with an unsaturated compound, such as an aldehyde or a nitrile, to form a β-unsaturated compound. It is named after the Nobel laureate Herbert C. Michael, who first described the reaction in his research on the chemistry of conjugated dienes..
The Michael addition is a useful method for synthesizing a wide range of β-unsaturated compounds, which are important intermediates in the production of a variety of chemicals and pharmaceuticals. It is a two-step process that involves the addition of the nucleophile to the enone or enoate, followed by the deprotonation of the intermediate..
The first step of the Michael addition involves the addition of the nucleophile to the enone or enoate. This is typically done using a nucleophilic addition reaction, in which the nucleophile attacks the electrophilic carbon of the enone or enoate. The resulting intermediate is a conjugated enol or enolate, which is highly reactive and unstable..
The second step of the Michael addition involves the deprotonation of the intermediate to form the β-unsaturated compound. This is typically done using a base, such as sodium hydroxide or potassium tert-butoxide. The resulting product is a β-unsaturated compound, with the nucleophile attached at the β-position..
The Michael addition has several advantages over other methods of synthesizing β-unsaturated compounds. It is a straightforward and efficient process that can be easily scaled up for large-scale production. It also allows for the synthesis of a wide range of β-unsaturated compounds, with good yields and good selectivity..
Despite these advantages, the Michael addition has some limitations. It is not suitable for the synthesis of β-unsaturated compounds from enones or enoates with certain substituents, such as halogens, due to the high reactivity of the intermediate. It is also not suitable for the synthesis of β-unsaturated compounds from nucleophiles with certain substituents, such as electron-withdrawing groups, due to the low reactivity of the nucleophile..
Summary
The Michael addition is an important method for the synthesis of β-unsaturated compounds, and it has played a significant role in the production of a wide range of chemicals and pharmaceuticals..
