Which are chemoselective reagents?
The most common sources of the hydride Nucleophile are lithium aluminum hydride (LiAlH4) and sodium borohydride (NaBH4). Note! The hydride anion is not present during this reaction; rather, these reagents serve as a source of hydride due to the presence of a polar metal-hydrogen bond.
What are chemoselective reactions?
Chemoselective: A reaction that operates exclusively on one functional group in the presence of other functional groups. This NaBH4 reduction is chemoselective because the ketone is reduced but the ester is unchanged.
What is a chemoselective reducing agent?
Under the appropriate reaction conditions, sodium borohydride is a highly chemoselective reducing agent. In general, a carbonyl group of one type can be selectively reduced in the presence of a carbonyl group of a less reactive type.
What is chemoselectivity example?
Chemoselectivity is the preferential outcome of a chemical reaction over a set of possible alternative reactions. Examples include the selective organic reduction of the greater relative chemoselectivity of sodium borohydride reduction versus lithium aluminium hydride reduction.
What is difference between regioselective and Regiospecific?
Generally speaking, if a reaction takes place that produces two or more products and one of the products predominates, the reaction is said to be regioselective. On the other hand, if one of the products completely predominates (or nearly so), then the reaction is said to be regiospecific.
What is stereospecific and stereoselective?
A stereospecific mechanism specifies the stereochemical outcome of a given reactant, whereas a stereoselective reaction selects products from those made available by the same, non-specific mechanism acting on a given reactant.
What are Synthons and synthetic equivalents?
The key difference between synthon and synthetic equivalent is that synthon is a moiety of a chemical compound that can be formed by a known synthetic process, whereas synthetic equivalent is a reagent that carries out the function of a synthon.
What is stereoselective and stereospecific reactions?
What is Regio Chemoselective?
There are three types of selectivity possible for any synthesis: (i) Chemoselectivity is deciding which group reacts. (ii) Regioselectivity is where the reaction takes place in that group. (iii) Stereoselectivity is how the group reacts with respect to the stereochemistry of the product.
What is Regiospecific chemistry?
Medical Definition of regiospecific : being a chemical reaction in which one structural isomer is produced exclusively when other isomers are also theoretically possible.
What is regiospecific and stereospecific?
Stereoselective — the reaction can result in more than one stereoisomer but has some reason to prefer one over the other(s) (E2 dehydrohalogenation preferentially forms trans products) Regiospecific — the reaction can only result in one constitutional isomer (Markovnikov addition to an alkene)
What is a stereoselective process?
A stereoselective process is one in which one stereoisomer predominates over another when two or more may be formed. If the products are enantiomers, the reaction is enantioselective; if they are diastereoisomers, the reaction is diastereoselective. The product in such a case must also be achiral (or racemic).
What is an example of chemoselective ligation?
Chemoselective ligation involves using unique pairs of mutually specific reactive chemical groups to accomplish molecular conjugation. Examples of this chemistry include hydrazide-aldehyde condensation, click chemistry (azide-alkyne) and Staudinger ligation (azide-phosphine).
What is an example of a chemoselective reaction?
An example of a chemoselective reaction is found in Scheme 1, where the tri- n -butyltin radical abstracts the O -thiocarbonyl group from the thioglycoside 1 while the potentially reactive ethylthio group remains in place. 1
What is the difference between chemoselectivity and protecting groups?
Protecting groups can be used instead of chemoselectivity but with the disadvantage of having to perform two additional synthesis steps (protection and deprotection). However, if the reagent and reaction conditions are well chosen, the chemoselectivity can be more effective than protecting groups.
What are some examples of chemoselective epoxidations of alkenes?
Chemoselective epoxidations of many alkenes carrying functional groups such as hydroxy, ether, ester, amide and ketone have been presented in this chapter. Chemoselective epoxidations of a few functionalized alkenes have proved difficult, but by using appropriate reagents and strategies the difficulties have been overcome.
