A dieneβplatinum complex, (COD)Pt(TFA)2, serves as an efficient and chemoselective catalyst for Ξ±,Ξ²βdesaturation of cyclic ketones through direct Ptβenolate formation. Distinct from known ketone dehydrogenation methods, a wide range of sensitive functional groups are tolerated. Mechanistic studies suggest a fast reversible Ξ±βdeprotonation followed by rateβdetermining Ξ²βH elimination.
Abstract
The development of a platinumβcatalyzed desaturation of cyclic ketones to their conjugated Ξ±,Ξ²βunsaturated counterparts is reported in this full article. A unique dieneβplatinum complex was identified to be an efficient catalyst, which enables direct metalβenolate formation. The reaction operates under mild conditions without using strong bases or acids. Good to excellent yields can be achieved for diverse and complex scaffolds. A wide range of functional groups, including those sensitive to acids, bases/nucleophiles, or palladium species, are tolerated, which represents a distinct feature from other known desaturation methods. Mechanistically, this platinum catalysis exhibits a fast and reversible Ξ±βdeprotonation followed by a rateβdetermining Ξ²βhydrogen elimination process, which is different from the prior Pdβcatalyzed desaturation method. Promising preliminary enantioselective desaturation using a chiralβdieneβplatinum complex has also been obtained.
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Okay so I am reviewing some material from Orgo, (I took it a year ago). I came across this reaction, which I don't remember at all seeing. I labeled all the steps, and I am confused about what is going on in step (B). What I got from the book is that the carbonyl carbon is sightly positive in its polarity due to the Oxygen's electronegativity. And that because of this the Carbonyl carbon becomes an electrophile that can be attacked by a nucleophile, like a strong Base. Up to this point I feel good with the info, however what is going on from step B to C. Again its been a while since looking at orgo, so I admit that I have a couple of gaps. All help is greatly appreciated!
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For example, can an amide be said to be in the keto form, and is the tautomerized version of the amide still called an enol even though it does not contain a C=C double bond (but rather a double bond to a nitrogen)?
Since enols are weak nucleophiles, is there a chance that this occurs which may interfere with the reaction?
Journal of the American Chemical SocietyDOI: 10.1021/jacs.1c01797
Sinem Guven, Gourab Kundu, Andrea WeΓels, Jas S. Ward, Kari Rissanen, and Franziska Schoenebeck
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What makes a keto form more stable than an enol form?
When I was doing my project this year, I had to prepare a beta-keto ester from 1-tetralone with NaH and diethyl carbonate, after columning it the proton NMR showed a ratio of 7:1 enol:keto (which is the opposite of what I've always been taught should happen), and as such when it was left out on the bench the enol form crystallised out in a big way (unfortunately didn't take any pics) and I managed to get a crystal structure (http://imgur.com/7VTE852).
Any idea why this is? Possibly something to do with the formation of a 2nd H-bonded 6-membered ring in the enol form which is thermodynamically stable?
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Hey, I'm trying to figure out the compound/type of reaction needed to get from the molecule at the top to the one at the bottom (Step I).
The main issue is that I can't think of an alkylation which converts a ketone to a C/C double bond without leaving a methyl group.
If it were an aldehyde, then it would be a rather simple Wittig reaction, but a Wittig reaction forms a double bond at the C atom with the carbonyl group and would leave in this case the methyl group as a side chain.
I've been looking through my notes/textbook for about 40 minutes now, so if I haven't misunderstood the Wittig reaction somehow or overlooked something, then I'm completely clueless.Just telling me the name of the reaction would be enough help.
Thanks for any help.
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I have a product I'm trying to synthesize that involves the alpha-amination of a ketone. Most of it's worked out but we're getting low yields from this step. We're trying to do an intramolecular ring-closure (6-membered ring) reaction where we brominate the ketone under acidic conditions before adding base so that the secondary (methyl) amine attacks.
One of the main issues is that the brominated compound can't really be isolated (too hygroscopic and presumably quite reactive) so we're trying to find reaction conditions that can be used for the bromination step into the basification step.
Basically wondering if anyone has any advice for bromination in a situation like this (I'm wondering if the elimination to form an a,b-unsaturated ketone is competing with nucleophilic attack of the amine) or more generally on the alpha-amination of a ketone. Mostly we're considering different solvent systems, bases etc. but miscibility etc. are concerns. The standard conditions we'retried are Br2/HB2 in HOAc and then a bicarbonate salt. I've used scifinder/reaxys to some success but before trying some of the other ideas I've come up with (umpolung with an enolate, copper bromide) figured I'd consult people here with more hands-on experience with me.
I don't want to step on anybody's toes here, but the amount of non-dad jokes here in this subreddit really annoys me. First of all, dad jokes CAN be NSFW, it clearly says so in the sub rules. Secondly, it doesn't automatically make it a dad joke if it's from a conversation between you and your child. Most importantly, the jokes that your CHILDREN tell YOU are not dad jokes. The point of a dad joke is that it's so cheesy only a dad who's trying to be funny would make such a joke. That's it. They are stupid plays on words, lame puns and so on. There has to be a clever pun or wordplay for it to be considered a dad joke.
Again, to all the fellow dads, I apologise if I'm sounding too harsh. But I just needed to get it off my chest.
Additional information: I was wondering if it is possible to obtain the enolate and let this react with itself (provided it has a ketone and aldehyde group present). No catalyst is added as the enolate would be formed during the 1,4-addition.
Sorry for any grammar mistakes, English is not my native language.
Hey guys, I read online that in conditions of pH < pKa, keto form is preferred over enol form due to protonation. Can someone please explain what this means?? I thought keto form was referring to aldehydes and ketones and enol was referring to alcohol, so wouldn't an alcohol be protonated?
Do your worst!
I was just thinking, while they (as far as I understand) exhibit exactly the same physical properties bar optical rotation, they technically have different molecular structures (same constitution, different 3D arrangement) which is especially felt considering enzymes and receptors can be highly specific toward a single enantiomer and not the other. My brain says they must be different compounds because they don't have exactly the same properties, but my heart/gut/intuition says they're the same, but just different forms? Another thing, ketones and their respective enol tautomers are technically constitutional isomers, yet are considered forms of the same compound, and are practically considered the same compound. I was hoping to get your thoughts on this. Thanks!
They were cooked in Greece.
I'm surprised it hasn't decade.
For context I'm a Refuse Driver (Garbage man) & today I was on food waste. After I'd tipped I was checking the wagon for any defects when I spotted a lone pea balanced on the lifts.
I said "hey look, an escaPEA"
No one near me but it didn't half make me laugh for a good hour or so!
Edit: I can't believe how much this has blown up. Thank you everyone I've had a blast reading through the replies π
Don't you know a good pun is its own reword?
It really does, I swear!
Because she wanted to see the task manager.
Heard they've been doing some shady business.
but then I remembered it was ground this morning.
Edit: Thank you guys for the awards, they're much nicer than the cardboard sleeve I've been using and reassures me that my jokes aren't stale
Edit 2: I have already been made aware that Men In Black 3 has told a version of this joke before. If the joke is not new to you, please enjoy any of the single origin puns in the comments
BamBOO!
Theyβre on standbi
A play on words.
My daughter, Chewbecca, not so much.
Pilot on me!!
Christopher Walken
Nothing, he was gladiator.
Or would that be too forward thinking?
