A protecting group or protective group is introduced into a molecule by chemical modification of a functional group to obtain chemoselectivity in a subsequent chemical reaction. It plays an important role in multistep organic synthesis. … This step is called deprotection.

How can we protect carbonyl groups?

How can we protect hydroxyl group?

In the case of alcohols the hydroxyl group may be protected by formation of an ether, an ester, or an acetal.

How do you protect an ester group?

Ester is a protecting group for acid. In presence of ester the methyl group can be oxidized by heatimg ester with KMnO4 in presence of Mg catalyst for 3 hrs. then filtered to remove black MnO2 . The filtrate is neutralized by HCl to get acid.

Can deprotection be PMB?

–p-Methoxybenzyl (PMB or MPM) group can be protected or deprotected under the same conditions as benzyl group. It can also be deprotected under mildly oxidizing conditions using DDQ (dichlorodicyanobenzoquinone) or strongly acidic conditions.

How can we protect alcohol?

The most common protecting groups for alcohols are the silyl ethers. Here is the idea behind it. We take a silyl chloride, do a substitution using the alcohol as a nucleophile and then the alcohol converted into a silyl ether can be used in the presence of any strong base including the Grignard reagent.

How do you protect an aldehyde?

Aldehydes and ketones were protected as their thioacetals in the presence of a catalytic amount of iodine. These mild reaction conditions were also applied in the transthioacetalization of O,O-acetals, O,O-ketals, O,S-acetals, and acylals.

Which is used for protection of carbonyl functional group?

Therefore, methods are developed for the protection of carbonyl compounds and various protective groups can be used [1]. Acetal, 1-3-dioxalane, mixed ketal and thioketal are the widely used protective groups. Aldehydes and ketones are the most common groups that are protected by these methods.

How do you protect an aldehyde group?

The silyl ether protecting group can be removed by reaction with an aqueous acid or the fluoride ion. By utilizing a protecting group a Grignad reagent can be formed and reacted on a halo alcohol.

What are amino protecting groups?

The most common α-amino-protecting groups for solid-phase peptide synthesis (SPPS) are the 9-fluorenylmethoxycarbonyl (Fmoc) and the tert-butyloxycarbonyl (Boc) groups, used in the Fmoc/tert-butyl (tBu) and Boc/benzyl (Bn) strategies respectively.

How can we protect phenol?

Ethers are the most widely used protective groups for phenols and in general they are more easily cleaved than the analogous ethers of simple alcohols. Esters are also important protective groups for phenols, but are not as stable to hydrolysis as the related alcohol derivatives.

How do I remove tert butyl group?

The catalyst is easily recovered and reused several times without loss of activity. In addition, the tert-butyl group is removed very quickly from alcohols and phenols in methanol in the presence of Er(OTf)3 using MW irradiation.

Why is protecting a group important?

Protecting groups are used in synthesis to temporarily mask the characteristic chemistry of a functional group because it interferes with another reaction. A good protecting group should be easy to put on, easy to remove and in high yielding reactions, and inert to the conditions of the reaction required.

What does BN stand for in chemistry?

Boron nitride, (chemical formula BN), synthetically produced crystalline compound of boron and nitrogen, an industrial ceramic material of limited but important application, principally in electrical insulators and cutting tools.

Can be used as protecting group for protection of chiral alcohol?

Ethers can also be used for alcohol protection. Two common ether-based protecting groups are THP- (tetrahydropyranyl-) and MOM- (methoxymethyl-).

How do you Deprotect benzyl group?

Benzyl ethers can be removed under reductive conditions, oxidative conditions, and the use of Lewis Acids. … Benzyl protecting groups can be removed using a wide range of oxidizing agents including:

  1. CrO3/acetic acid at ambient temperature.
  2. Ozone.
  3. N-Bromosuccinimide (NBS)
  4. N-Iodosuccinimide (NIS)

Which reagent is used for oxidative removal of PMB?

Dicyanodichloroquinone (DDQ) is the most frequently used and most effective quinone for such applications. The most common use of DDQ in synthetic chemistry is the oxidative removal of p-methoxy benzyl groups, which allows the use of PMB as a protecting group orthogonal to almost all others.

How do I get rid of THP protecting group?

To remove THP (protecting a primary -OH in a compound with an additional ester group) you can use Amberlyst -15 as a mild acid reagent.

Why do alcohols need to be protected?

You would need to protect an alcoholic -OH group (actually you inactivate the hydrogen) when it would interfere with a reaction at another site on the molecule. An example is with a Grignard reaction.

How can we protect primary alcohol?

Silicon ethers are the most commonly used alcohol protecting groups. The O-Si bond formed is strong and less reactive to strong bases compared to the O-H bond in the parent alcohol.

How do you get rid of an alcohol protection group?

The silyl ether protecting group can be removed by reaction with an aqueous acid or the fluoride ion. By utilizing a protecting group a Grignad reagent can be formed and reacted on a halo alcohol.

Can you protect a ketone?

Cyclic acetals and ketals are the most useful carbonyl (aldehyde or ketone) protecting groups. Common diols used to form ketals are show below in order of their relative rate of formation.

Why do we protect ketones?

The idea is that if want to make a Grignard reagent on a molecule that contains an aldehyde or ketone, we need to protect that aldehyde or ketone beforehand so that it doesn’t react with itself. Let’s walk through the example above.

What does NH4Cl do in organic reactions?

The addition of NH4Cl to a solution of ammonia shows the effect of adding a common ion to a system at equilibrium. Addition of NH4Cl adds NH4+, driving the reaction to the left and consuming OH-.

Are generally used to protect 1/2 diol?

1,2- and 1,3-diols are generally protected as 5- or 6-membered cyclic acetal compounds.

Which of the following is used for protection of OH group?

Consistent with atom economy, the methyl group is frequently used to protect carboxylic acids and the acetylating group is used to protect hydroxyl groups.

How can we protect amine groups?

Carbamates are useful as protecting groups for amines, and the most commonly employed are -Boc, -Cbz, and -Fmoc. The -Cbz (carboxybenzyl) protecting group was first used by Max Bergmann and Leonidas Zervas in 1932 for the synthesis of peptides, and is sometimes abbreviated “-Z” in honor of Zervas.

How do you protect an aldehyde but not a ketone?

Protect the aldehyde. The best choice is probably as a 1,3-dioxane acetal by reacting your compound with 4 equivalents of 1,3-propanediol, 1 equivalent of triethyl orthoformate, and 0.01 equivalent of tetrabutylammonium tribromide.

Why acetals are used as protecting groups?

Acetals are used as protecting groups for carbonyl groups in organic synthesis because they are stable with respect to hydrolysis by bases and with respect to many oxidizing and reducing agents.

How do Grignard reagents work?

Grignard reagents add to carbonyl compounds to give primary, secondary, and tertiary alcohols. A primary alcohol is synthesized by reacting the Grignard reagent, R′─MgX, with formaldehyde. Reacting a Grignard reagent with an aldehyde gives a secondary alcohol.