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10 votes
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By what mechanism do acids deprotect primary silyl ethers?

Fluoride-mediated deprotection of silyl ethers proceeds through a pentavalent silicon pathway:[1] This mechanism proceeds the same for both primary and secondary silyl ethers, and there's no reason ...
ringo's user avatar
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10 votes

Can protection group be used in a Wolff–Kishner reaction?

@Halake: The protection of adipaldehyde as the monoacetal was solved by Schreiber and Claus some years ago [Also see, Schreiber, S.L.; Claus, R.E.; Reagan, J. Tetrahedron Letters, 1982, 23, 3867.] ...
user55119's user avatar
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8 votes

How are neutral amines effective bases in organic chemistry?

There are several interesting aspects to your question. How are neutral amines effective bases in organic chemistry? First of all, recall the definition of a base. Anything which accepts a proton (...
AChem's user avatar
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7 votes
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Reaction of glucose acetal with acetic anhydride

I think there's nothing to discussed about this further as all comments directing to the correct answer: $x = 4, \ y = 6,$ and $ z = 5.$ I think it's better show in the structures: Glucose is ...
Mathew Mahindaratne's user avatar
6 votes
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Organic chem mechanism

This is straightforward enough: The $\ce{NaOMe}$ deprotonates the $\ce{OH}$ group on $\ce{C}$5, the alkoxide then does an intramolecular nucleophilic attack on the ester to give the lactone. This is ...
Waylander's user avatar
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6 votes

Reaction of glucose acetal with acetic anhydride

Starting from any cyclic form of glucose, there are two key ways to form the acetal in sequence (i). Taking glucopyranose as a starting point, here is a reaction scheme: Initially, you could argue ...
Jan's user avatar
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5 votes
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Is formation of cyclic carbonate from trimethyl orthoformate and vicinal aromatic 1,2-diol possible?

Trimethyl orthoformate is at the wrong oxidation level to give a cyclic carbonate. You need phosgene or a dialkyl carbonate. The efficient preparation of catechol carbonate from catechol (benzene-1,2-...
Waylander's user avatar
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5 votes

Effect of protecting group on diastereoselectivity of LiAlH4 reduction of α-hydroxyketones

I think Jan did an excellent job of answering your question, however I am writing a slightly longer answer largely with more details concerning the Felkin–Anh rule, just so that someone who is not ...
getafix's user avatar
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5 votes
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How to form an acetal from an enol ether?

Steps (Source: from comment made by Zhe) Tosic acid protonates alkene to form oxocarbenium through resonance. One of the alcohols from ethylene glycol attacks the activated carbonyl and ...
Trufflehog's user avatar
4 votes

Synthesis for turning synephrenine into N-methylphenethylamine

Suggested route - step 1 acetylate the amine with 1 eq of acetyl chloride in pyridine. step 2 hydrogenation of the benzylic alcohol over Pd/C in the presence of acid or use TFA/triethylsilane step 3 ...
Waylander's user avatar
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4 votes

Effect of protecting group on diastereoselectivity of LiAlH4 reduction of α-hydroxyketones

The $\ce{TBDPS}$ group (tert-butyldiphenylsilyl) is a very bulky protecting group. A silicon atom is bonded to the oxygen, which already acts as a larger carbon atom. That is then substituted by three ...
Jan's user avatar
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3 votes

What are protecting groups in organic chemistry?

The term protecting group is not absolutely strictly defined. In general, anything can be a protecting group if it fulfills the following conditions: it is attached somewhat easily and adequatly ...
Jan's user avatar
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3 votes

What are protecting groups in organic chemistry?

Functional groups become protecting groups out of practicality. I would define an ideal protecting group (PG) as a functional group that is easy to introduce/attach to a given, other functional ...
TAR86's user avatar
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3 votes
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Can an ether be selectively hydrolysed in the presence of an ester?

There are certain ethers which are somewhat easier to remove than others. If you stipulate that the ether must have a CH2 group immediately adjacent to oxygen, then a couple of possibilities, off the ...
orthocresol's user avatar
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3 votes

Can protection group be used in a Wolff–Kishner reaction?

I'm assuming you've carried out ozonolysis followed by mild reduction (e.g. using $\ce{Me2S}$) to generate a dialdehyde and now want to convert it to a monoaldehyde. Wolff-Kishner requires basic ...
GingerBadger's user avatar
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3 votes
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Friedel–Crafts acylation of substituted anisole

I think it is clear that you want to acylate a trisubstituted benzene compound. It is also clear that the ring consists of two oxygen atoms, one of which is methoxy group. That makes the acylation ...
Mathew Mahindaratne's user avatar
2 votes
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Mechanism of deprotection of enol thioether

Mechanism: 1 -hydroxide anion adds to the =CHSBu carbon in a Michael addition giving the enolate anion of the carbonyl and -CHOH(SBu). 2- The enolate anion deprotonates the newly arrived -OH group to ...
Waylander's user avatar
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2 votes

Performing a reaction on one side of piperazine ring

Making your own BOC piperazine is not hard, the general principle is to do the reaction with the monohydrochloride - there is a good procedure here from piperazine, piperazine di-HCl, t-BuOH and ...
Waylander's user avatar
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2 votes

Do side chain carboxylic acids need to be protected in peptide synthesis?

Yes, the side chain carboxylic acid requires protection. The two most commonly used peptide coupling strategies use Boc or Fmoc on the amide. The side-chain carboxylate is typically protected as a tBu ...
Jan's user avatar
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2 votes

What happens to the t-butyl cation in the TFA deprotection of a t-butyl ester?

I realize this question is old but the mechanism is nicely described here (steps 1-3): http://www.umich.edu/~chemh215/W06HTML/SSG2/ssg6/main_files/Page346.htm Briefly, the released t-butyl carbocation ...
Nate's user avatar
  • 271
2 votes

Wittig reaction with an alkyl dibromide

It seems that the method to circumvent this problem is indeed to use a protecting group to protect one end of the alkyl chain, which is the end to be converted to a bromide after the Wittig reaction. ...
Tan Yong Boon's user avatar
1 vote
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How are neutral amines effective bases in organic chemistry?

MOMCl reacts via an SN1 reaction and alcohol is the nucleophile, not an alkoxide. The amine serves to scavenge HCl. ADDENDUM: Typically, a generic alcohol in an inert solvent is treated with MOMCl 1 ...
user55119's user avatar
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1 vote
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Trimethylsilyl iodide - Alkyne Reaction

TMSI was used successfully without damaging the alkyne as per this protocol. http://pubs.acs.org/doi/abs/10.1021/cb400261h
Hazinga's user avatar
  • 397
1 vote

What happens to the t-butyl cation in the TFA deprotection of a t-butyl ester?

The reaction is, in principle, catalytic in TFA. If t-butyltrifluoroacetate is the by-product, then the catalyst is consumed. If only isobutylene is formed, catalytic is OK. Using excess TFA covers ...
user55119's user avatar
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1 vote

Decomposition of acetonide protecting group in chloroform

Deuterochloroform (and indeed 'normal' chloroform) are known to be mildly acidic if left standing for any length of time: Chloroform: It reacts slowly with oxygen, or oxidising agents, when exposed ...
NotEvans.'s user avatar
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