• nom: @Michael D. Turnbull: No sources, orphan, hardly any views on this non-notable topic (Wikipedia does not have articles for any of the compounds shown)
• 2nd: @Project Osprey: Many of these structures are also unlikely to be stable (enolates, hemiacetals etc.), looks like stamp-collecting
• con: @Spinningspark: This article https://books.google.co.uk/books?id=BbUfAQAAMAAJ&q=%22pyran+alcohol%22 indicates at least seven isomers exist, although the nomenclature is different

I don't have access to that Journal of Organic Chemistry of the USSR. Volume 11, Part 1 ref and the link doesn't give me a preview that highlights those terms. Could Spinningbark or someone else give us some specific quotes/details of their existence and the alternate names so we can look for them in other sources? DMacks (talk) 15:27, 12 January 2022 (UTC)[reply]

I've only got snippet view, but I can give you some quotes;

At the same time appreciable quantities of the pyran alcohol (V) (Fig. 1) are formed during the condensation of the unsaturated alcohol (II) with formaldehyde even in the early stages of the reaction....

— p. 149

...from which the pyran alcohol (V) and subsequently (VI) and (VII)) can be easily obtained.

— p. 150

I'm assuming the roman numbers refer to isomers, but I'm not entirely sure. They could just be annotation on a diagram. SpinningSpark 15:58, 12 January 2022 (UTC)[reply]

Almost all of these are enols and they only exist fleetingly, in equilibrium with their ketones. There's also a top-level page on pyrones, a mention of these enolates could be placed there, but there's no real content for this page. --Project Osprey (talk) 16:08, 12 January 2022 (UTC)[reply]

(edit conflict)

In my opinion we are wasting our time here. The article cites no sources and displays an astonishing lack of knowledge of organic chemistry. For example these two compounds are simply alternative drawings of two minor tautomers of the compound 2H-Pyran-3(4H)-one, here on Chemspider. The issue is not whether these substances could exist but whether they are notable in the usual Wikipedia sense. I see no evidence for that: none of our articles on C5H6O2 refer to any of these materials. As Spinningspark has de-prodded my nomination, the next step is to move to WP:AfD and have a longer discussion there. I'll do that unless someone now provides convincing evidence for retention. Mike Turnbull (talk) 16:12, 12 January 2022 (UTC)[reply]

That notation refers to specific chemicals defined elsewhere in the article (typically in a diagram or preceding prose). One of the common mistakes I see wikipedia editors and students make is string-matching a posited chemical name, where it winds up being merely lay-language descriptive or a substring of the actual chemical name. For example, there are tons of compounds that have both pyran and alcohol structures in them, so an article about such a chemical might use that adjectival phrase without meaning any of the chemicals this WP article is talking about. JOC-USSR volume 11 is 1975 and archive.org has its table of contents. The article on pages 148–152 of the English edition is:

• "Mechanism of Formation of Pyran Compounds duing Synthesis of 4,4-Dimethyl-1,3-dioxane" by V. W. Zakoshanskii, G. S. Idlis, S. K. Ogorodnikov, O. E. Batalin, Yu. M. Blazhin

I obviously agree with Mike that "notability" is a WP standard. On commons, the images are cited to chemspider, but I can't even find them on that site (is why I wanted synonyms in order to look for refs there). By SciFinder, that ref has tetrahydro-4-methyl-2H-pyran-4-ol (CASNo 7525-64-6) as a product of several reactions that sound like what those quotes describe (the reactions use various alcohol-containing structures and a form tetrahydropyran ring). It is not any actual "pyranol" isomer itself. DMacks (talk) 16:40, 12 January 2022 (UTC)[reply]