Talk:Protecting group

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This article is or was the subject of a Wiki Education Foundation-supported course assignment. Further details are available on the course page. Student editor(s): Mpodunavac, Jlchen15.

Above undated message substituted from Template:Dashboard.wikiedu.org assignment by PrimeBOT (talk) 07:20, 17 January 2022 (UTC)

Fmoc and Boc

What about Fmoc and Boc protecting groups? There are a few very common protecting groups missing

So add them. That's how Wikipedia works:) DMacks 06:02, 8 February 2006 (UTC)

Okay, someone did... DMacks 06:03, 8 February 2006 (UTC), talking to himself mainly

Acetal vs Ketal

Although originally and technically, a "ketal" was derived from a ketone and an "acetal" was derived from an aldehyde, it appears that modern usage is "acetal" as a general term for both. IUPAC's 1993 nomenclature rules agree (p102). The case at ia articles. Wikipedia is a platform for amateurs as well and Wikipedia's disclaimers can be found at the bottom of each page hand could still correctly be termed a "ketal" but we're not trying to distinguish ketal vs acetal moieties here. DMacks 05:07, 26 April 2006 (UTC)

list of protecting groups

I have started writing for my own personal use a list of common groups. It lists the group(s) being protected, the protecting group, common abbreviation, group formed, introduction reagents, removal reagents, and starting material. Obviously, this isn't exhaustive, for example, there are a million ways to remove a TMS group from an alcohol, but I have just listed F-.

Would such a list be helpful here? What would be the best way of formatting it for Wikipedia? I am wary of lists on Wikipedia pages, because they tend to get bogged with each editor's personal preferences, and errors become harder to detect. Also, I have taken the info from many textbooks and manuals, and am not sure how to source the whole thing, or where I even got it all.

Any other comments would be appreciated. 208.4.152.131 22:07, 22 January 2007 (UTC)

retro vs forward synthesis

Also I just noticed that in the reduction reaction shown. The product is shown in the beginning with a retrosynthetic arrow, and at the end of the reaction sequence. This seems to me to be not only non-standard, but confusing. Should the retrosynthetic arrow be removed? 208.4.152.131 22:07, 22 January 2007 (UTC)

Concurred. Plus the fact that there was a synthetic mistake in the image! I just replaced it by one that actually illustrates the use and value of the acetal. DMacks 22:33, 22 January 2007 (UTC)

Criticism section

Is that undeniably pointless 40-step reaction schematic a necessary component in an article which should simply state the common protecting groups and their use in synthesis?

Surely the reference itself would serve as enough without wasting needless space. One could find 500 of such reactions in any respected organic chemistry journal.

http://www.organic-chemistry.org/protectivegroups/ provides a suitable list of protecting groups, and some synthetic strategies used to employ them in synthesis. A better option would be to link a review article from acc.chem.res or another suitably respected journal on the subject.

I have removed the offending images and edited the text for clarity.

—Preceding unsigned comment added by 82.39.95.250 (talk) 21:50, 9 April 2008 (UTC)

While a full discourse about the evils of protecting groups is not needed, there is certainly something to be said on the topic. Their use is certainly considered a crutch by some chemists, and at a minimum usually represents wasted atoms ("poor atom economy"), additional synthetic steps, and/or reduced yield. An example is certainly useful in my opinion. OTOH, a full synthetic scheme is over-kill. Why not keep the textual content, since it does provide a quite striking example, is on-topic, and is cited, but not the images, which are large and only of limited use/understanding to lay readers? If someone really wants the full schemes and details, the cite is there. DMacks (talk) 23:08, 28 April 2008 (UTC)

Thanks for your kind intervention Dmacks but I disagree

• the addition is valid and notable, the Baran work gets a mention in the C&EN 2007 highlights (Chemical & Engineering News, 85(52), December 24, 2007)
• Wikipedia articles are not fan pages, you will have to deal with criticism when it is there.
• Wikipedia does not have article size restrictions.
• why is the addition pointless, offending and inappropriate according to the anonymous user
• the average reader does not have access to chemical journals, the whole point of wikipedia is to provide access to knowledge without any restrictions
• The anonymous user is happy with such publications as acc.chem.res or www.organic-chemistry.org. I agree both publications are much better than anything wikipedia has to offer but that is no reason to scrap wikiped
• is this general opposition to reaction schemes? I have contributed hundreds of them, what is their current status?
• if the images are considered too large a simple solution would be presenting them as a thumbnail, those readers interested in the full image simply expand it. Note that I have already adjusted the layout in one of my previous edits. Deletion is not an option.

Thanks V8rik (talk) 16:29, 29 April 2008 (UTC)

If this particular work is itself notable (highlighted in secondary/tertiary sources like C&EN) especially as an outstanding example of what it's being used to explain (rather than just an editor-selected example), then I would support its inclusion on those merits alone. The layout does need some help (it's almost 50% wider than my laptop screen. Also, a bit more explanation about how this is a whole reworking to avoid a problematic area (cf. just changing conditions to avoid having N react) would be good. At least for the first tosyl use, to casual inspection, the PG-free route uses more steps to get from start to comparable intermediate. Could "Protecting-group-free chemistry" stand as its own article? There certainly must be some review articles (maybe getting towards biomimetic synthesis...our biomimetic article is silent on chemistry applications). DMacks (talk) 16:46, 29 April 2008 (UTC)

To clarify, I do support inclusion of the diagrams (just not this size side-by-side layout) and explanation of what they illustrate, given that the specific thing being illustrated is the notable example. DMacks (talk) 18:13, 29 April 2008 (UTC)

• Thanks for your input and you are making fair points but the pressing matter is the action of the anonymous user. Do you feel that this user made a valid edit (deleting the content) based on the arguments provided (assuming we are dealing with one and the same user) Thanks. V8rik (talk) 21:31, 30 April 2008 (UTC)

I do not agree with any of anon's stated reasons for removal. The basis of his removal is that it is an "undeniably pointless 40-step reaction schematic". I disagree--the scheme illustrates an important issue relating to the topic of the page. Anon states that this page is "an article which should simply state the common protecting groups and their use in synthesis" but again, I disagree. That topic is "Protecting group"(s), not just certain aspects of them. Even if it were for some reason limited to that scope, however, a discussion of avoiding their use is still part of "their use in synthesis". DMacks (talk) 21:57, 30 April 2008 (UTC)

Response

(From the anonymous user who has an account now!) Mattybhoy 69 (talk) 12:18, 15 May 2008 (UTC) I still dispute the necessity of that reaction schematic - There are a huge number of authors in the chemical literature studying the applications of protecting groups in synthesis, many of whom would love to be able to bypass protecting groups. This Baran fellow is not the only one. I completely agree with the need for the text explaining alternatives for protecting group strategies, because it is important and topical. Hence, the Baran paper is a suitable cite. However, 'it gets a mention in C&E news' is, in my opinion not sufficient to make it stand out as a synthetic strategy in its own right. For that particular molecule, yes, it works, but what about the application of this synthesis in more general chemistry? can any of you stand up and say with that reaction scheme you could go into a lab and use the principles (not that specific reaction) to synthesise other useful molecules? I suspect not. However, despite my edit, someone has since restored the original badly worded and gramatically incorrect text, and furthermore, the author of the diagram has failed to identify the SiMe3 protecting group in step 1 and the acetyl protecting group in step 9 used to generate the cyanide.

Please do not go over the top and state that my removal of that synthesis is some kind of rebuttal of the addition of all reaction schemcatics - that is clearly not the case. Take for example the page about the Suzuki-Miyaura reaction - there is a relevant catalyic pathway, some reagents commonly employed and some reaction conditions. One does not NEED a 20 step synthesis of some random natural product just to illustate how the reactions work.

The people reading this articles will be mostly chemists - they will want clarity. This can be summarised as: What functionality does my protecting group protect? How do I put on a protecting group? How to take off a protecting group? How stable is my protecting group with respect to my reaction conditions?

surely that is all that is required is it not?

Additionally, I find it thoroughly amusing that V8rik you says that 'deletion is not an option' - If I were to post up schematics of 10 well-publicized examples of protecting groups used in organic synthesis (which I could do in ChemDraw in about 10 minutes) they would be deleted like a shot. The irony.

comment

If I had the chance to to a synthesis without expensive and step adding protection I always tried this first, because its cheaper and with every 99% yield protection group addition and abstraction you loos substance. So the criticism points out that chemists would use pointless protection groups because they are fun, although there are alternatives possible? Protection groups add steps and kill yield this is why you use them if no alternative is given. This is the same thing like the click chemistry, if there is a 100% yield reaction without producing waste, every chemist would use it.--Stone (talk) 09:05, 13 May 2008 (UTC)

Why protecting alcohols?

We should state to every group why a chemist wants it protected.

Alcohol

• acidic H from the OH interferes with hydride donors for example Lithium aluminium hydride
• OH forms strong hydrogen bonds and makes the substances hydrophil, this makes it difficult for seperation of the substance from water and for purification with certain chromatographic methods

...... --Stone (talk) 09:05, 13 May 2008 (UTC)

This would be an interesting extension of the page, although there would be a lot of material if one wanted to be thorough.ChemistHans (talk)

Orthogonal protection

I find this section misleading, the example given is a highly specialized (although interesting) case and is not even orthogonal in nature, which I believe requires that either protecting group for a pair of identical functions be removable without affecting the other, which is not possible here. This needs a proper summary of the concept and some real examples. ChemistHans (talk) 16:53, 15 May 2008 (UTC)

I find much of the content in this section to be confusing. Perhaps I don’t know all the details necessary to understand the concepts, but then again, I shouldn’t have to. My main point is that the article talks about an example of orthogonal protection & continues in the next paragraph to describe both the same technique & a new 1. I had to reread the paragraphs a number of times just to understand the way the ideas flow. Again, this may just be my perspective & no one else’s, but I believe some paragraph restructuring, rewording, & maybe some more information would be greatly appreciated by myself & those who don’t already know much about chemistry. Dfcorrea00 (talk) 22:29, 25 September 2017 (UTC)

suggest page be pulled for major revision

With due respect to current contributor(s), I would suggest this page is not ready for viewing.

The entry lacks the uniform quality of coverage otherwise readily available for this subject, and so demanded here; present quality is such that in it cannot be taken seriously by students in the field with more than a basic background, and is seriously misleading for those of just basic training. (The Oxford and Cambridge primers' opening chapters do the subject far greater justice.)

The earlier discussion entry about missing groups and concepts, and about the shortcoming of description and example for orthogonal protection is only the beginning. As well, the relative overstatement of Phil Baran's recent contributions (as much as I admire them) -- consider their percent of the total of this entry -- unnecessarily overshadows decades of significant and high-impact accomplishment made through application of protecting groups. This includes, off top of my head, all of modern biological polymer synthesis (DNA, peptides, etc), as well as modern industrial drug manufacturing, and most modern methodology and natural product synthesis research (including some of Baran's own work). Certainly, there will be better ways to do things down the road, but that does not deny the status quo and important history of the concept and practice.

Hence, on the whole, the scope and perspective are so far lacking that the present article does more harm than good. I would therefore recommend the current contributors give it a hard weekend of work, or pull it. An interim one paragraph citing Green and Wuts and Kocienski would due until a proper treatment can be prepared.

Apologies at the directness of this statement, but others of adequate training have either not read it, or not cared enough to comment. M-ED (Prof) —Preceding unsigned comment added by Meduban (talk • contribs) 04:56, 23 May 2008 (UTC)

Even taken to an extreme of "It's horribly written, mis-emphasizes minor points, omits major ideas, doesn't cite lead works", that's not a valid reason to delete it until there is something better to replace it. If there's a minor addition that would be a big help, thanks for making them! If the page would be better rewritten from scratch, that can be done and then the existing page replaced when the new one is ready. If there are specific paragraphs that need overhaul, let's work them out. But I strongly disagree with "no information is better than poorly written mis-focused information that doesn't do justice to subject and isn't well-targetted to the audience." DMacks (talk) 05:30, 3 June 2008 (UTC)

Tosyl

I thought that Tosyl is a protecting group for alcohols, not amines. The page for the chemical itself seems to agree. Tomásdearg92 (talk) 22:21, 16 April 2013 (UTC)

N–Ts is a standard one. I added a comment with ref to the tosyl article. DMacks (talk) 01:37, 17 April 2013 (UTC)

Ah, thank you. You learn something new every day! Tomásdearg92 (talk) 02:35, 17 April 2013 (UTC)