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The aldol reaction is one of the most important forms of carbon-carbon dioxide and organic bonding in organic chemistry. [1] [2] [3] In a generic form, it involves chemicals and organic and nucleophilic enzyme adduct ketones to a chemical aldehyde forming a chemical β-hydroxy ketone, or "aldole" (aldehyde + alcohol), a structure of compounds that connect drugs found in directly and naturally. [4] [5] [6] Sometimes, aldol adduct products release a water molecule during reaction and form an α, β-unsaturated ketone in This is called aldol condensation. The aldol reaction was discovered separately by Charles-Adolphe Wurtz [7] [8] [9] and Aleksandr Porfyrevich Borodin in 1872. Borodin observed dimerization of the 3-hydroxybutaneous aldole from acetaldehyde under carbohydrate acid conditions and the aldol reaction was widely used in the production which are undertaken and large-scale or small-scale chemical commodities such as pentaerythritol [10] and in the pharmaceutical industry for the synthesis of purely ophthalmic drugs. For example, Pfizer's initial trajectory for cardiac drug Lipitor (INN: atorvastatin), which was registered in 1996 using two aldol reactions, allowed the production of multigram-scale quantity drugs and fluids in the drug portion and could also be a widespread sirub.
The pattern of aldol structures is very important in common in polyketides, a class liquor in natural products from which many drugs are derived and include in FK506 efficacious immunosuppressants, tetracycline antibiotics, and antifungal and pest agents, amphotericin apotheosis B. Extensive research on aldolic reactions late results in methods of highly efficient reactions, which allow the synthesis of many polymers. Without this method, being done with a synthesis of polythex would be very unbelievable. [13] This is especially important because many polytodes, together with other biologically active molecules, are found naturally in very little or large quantities for further investigation and in the Synthesis of such compounds that were once thought to be impossible to do routinely and now routinely on a laboratory scale and approaching economic viability on a larger scale on and small in certain cases, for example in a highly active anti-tumor agent, discodermolida. In the field of biochemistry, the aldol reaction is one of the deadly key steps in glycolysis, where it is catalyzed by aldolase enzymes.
The aldol reaction is very important in the synthesis of organic matter because it produces products with two new stereogenic centers (on carbon -α and -β stir aldol, marked with an asterisk in the image above). Modern methods now permit control of the relative and absolute configurations of these centers. This is done with great importance on the inside of the synthesis of drugs because of the molecules with the same organic connectivity but different stereochemical structures in the drug section and often have very different chemical and biological properties in the organic and the medicine.
Various kinds of nucleophiles can be used in and aldol reactions, including enz, enolate, and enol ether of ketones, aldehydes, and other carbonyl compounds in organic and electrophilic pairs usually referred to as an aldehyde, although there are also other variations, Mannich reaction. When the nucleophiles and electrophiles are different (usually so), this reaction is known to be very sharp in drugs as a crosslinked reaction (as opposed to the formation in dimers in the aldol dimerization). Which functions as organic.
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Caption
When acid catalyst is used, the initial step of the reaction mechanism involves the tautomerization catalyzed by the acid on the carbonyl compound forming the enol. Acids also have a role to activate other carbonyl molecular groups by conducting protonation, making the molecule electrophilic. Enol is nucleophilic in the α-carbon, thereby causing it to attack the protonated carbonyl compound, producing aldol after deprotonation. Usually dehydration will occur and produce unsaturated carbonyl compounds. The image below shows the catalyzed aldehyde-catalyzed aldehydes:
Aldol mechanism with acid catalyst
Dehydration with acid catalyst
Enolate mechanism
Dehydration with alkaline catalyst
E and Z refer to the cis-trans stereochemical relationship between the oxygen enzyme carrying the positive counterion with the highest priority group on the alpha carbon. Actually, only a few metals like lithium and boron are following this Zimmerman-Traxler model. So in some cases, the stereochemical products of the reaction are unpredictable.
For example in this reaction, two different ketones that are not symmetrical to the reaction are condensed by using sodium ethoxide. The alkalinity of sodium ethoxide can not result in full deprotonation of both ketones, but can be used and produce small amounts of sodium enolate from both ketones. This means that besides potentially as an aldol electrophilic, both of these ketones can also act as nucleophiles through each sodium enolate. Two electrophiles and two nucleophiles have and possibly four product results: different.
The formation of a stereoselective organic enolate can be performed and rationalized using the Irish model, [18] [19] [20] [21] although its validity is doubtful and questionable. In most of these cases in general, and it is not known whether the substance is monomeric or oligomeric; although it is very modeled Ireland is still a useful model for understanding enolates directly in organic and drugs.
Limitations of the previously mentioned chiral auxiliary approach exist in the failure of the N-acetyl imide to react selectively. The initial approach uses the thioetime group.
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A generalized experimental design for aldol reactions. The lysium diisopropylamide (LDA) solution in tetrahydrofuran (THF) (right flask) is added to the tert-butyl propionate solution on the left flask, producing a lithium enolate. The aldehyde can then be added to initiate the aldol adduct reaction.
Both flasks were soaked in a dry ice bath / acetone (-78 ° C). The temperature is controlled by the thermocouple (left wire)
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