25.04.18 Problems with Stereochemistry

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25.04.18 Problems with Stereochemistry
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Part Number
6
Number of Parts
9
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CC Attribution 3.0 Germany:
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Release Date
2018
Language
English

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Abstract
Mitsunobu Reaction, Problems with Stereochemistry and Ring Closure Reactions
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Reaction mechanism Stereochemistry Carboxylate Set (abstract data type) Wursthülle Hydro Tasmania Chemistry Molecule Solvent Isomer Magma Benzene Elektronentransfer Ausgangsgestein Derivative (chemistry) Dyeing Azofarbstoff Hydride Totalsynthese Carbon (fiber) Fed-batch-Verfahren Ice front Chemical reaction Alcohol Electronic cigarette Reducing agent Sodium Ingredient Hydrogen Gesundheitsstörung Blue cheese Functional group Boron Methanol
Metallorganische Chemie Heterocyclic compound Phosphine Death Phosphorous acid Hydro Tasmania Molecule Noble gas Isomer Oxide U.S. Securities and Exchange Commission Fatty acid methyl ester Diethanolamine Chemical property Walking Corticosteroid Sulfur Chemical reaction Alcohol Nucleophilic substitution Uranpecherz Acid Tiermodell Chemical compound Acetone Cobaltoxide Acetate Ligand Ester Carboxylate Sunscreen Substitutionsreaktion Chemical plant Wursthülle Organische Verbindungen Diet food Ageing Redox Nanoparticle Butcher Conjugated system Process (computing) Palladium Dyeing Setzen <Verfahrenstechnik> Potenz <Homöopathie> Stickstoffatom Bromide Backhoe Darmstadtium Hybridisierung <Chemie> Triphenylphosphin Functional group Sulfoxide Chemical structure
Dimethylamin Digital elevation model Kohlenhydratstoffwechsel Ethylene oxide Death Hydroxyl Chloride Food Chemistry Grade retention Molecule Diet food Sodium hydroxide Amine Schwefelorganische Verbindungen Mixture Dipol <1,3-> Oxide Pyridine Naturstoff Dyeing Chain (unit) Hydride Stickstoffatom Hydroborierung Heterodimere Ketone Epoxidation Walking Sulfur Katalase Addition reaction Protonation Systemic therapy Lone pair Water Hydrogen Gesundheitsstörung Functional group Rifampicin Chemical compound Sulfoxide Acetone Breed standard Chemical structure Base (chemistry) Stereoselectivity
Cyanide Sense District Prochiralität Gold Methoxygruppe Hypobromite Molecule Klinisches Experiment VSEPR theory Diet food Cryogenics River Elimination reaction Oxide Setzen <Verfahrenstechnik> Octane rating Walking Pedosphäre Reducing agent Functional group Azo coupling Tetrahydrofuran Cobaltoxide Thermoforming Stereoselectivity
Setzen <Verfahrenstechnik> Molecularity Bromide Copper Chemical reaction Chemistry VSEPR theory Molecule Acid Gesundheitsstörung Functional group Azo coupling Chemical compound Tartaric acid Tool steel Oxide
Thylakoid Setzen <Verfahrenstechnik> VSEPR theory Water Weinfehler Electron Functional group Cell (biology) Azo coupling Tool steel Oxide
Acetate Ethylene Carboxylate Substitutionsreaktion Chemical plant Hydroxyl Chloride Lightning Wursthülle Titanium carbide Chemistry Steric effects Ageing Human subject research Isomer Tool steel Side chain Oxide Process (computing) Setzen <Verfahrenstechnik> Naturstoff Stickstoffatom Perchloric acid Walking Totalsynthese Titanium Ice front Protonation Chemical reaction Wine tasting descriptors Death Electronic cigarette Nucleophilic substitution Water Systemic therapy Hydrogen Acid Gesundheitsstörung Tiermodell Zinc Yield (engineering) Functional group Azo coupling Dimethylzinc Aage Bromine Base (chemistry) Condensation
Potenz <Homöopathie> Stickstoffatom Walking Alkansulfonate Solution Klinisches Experiment Branntwein Lactitol Azo coupling Urea Elimination reaction Cobaltoxide Side chain Process (computing)
so come to part 6 of the lecture on competing reactions the heading all full part of 6 all further the article of 4 so yeah about dead ends and 2 did too is in total synthesis and 2 there is 1 effect of problems Mysterio chemistry problems which 1 has not maybe not foreseen so here in this 1st reaction it's about the reduction of the carbon I drew so how would the per such an reduction usually sodium Borel hydride as a relatively mild reducing agent is sufficient and indeed so during boron hydrides in methanol to can apply this complex hydride even in such an acidic solvents you have to use it in its 1st I'm done at 0 degrees a nice 90 % viewed all of this secondary alcohol was obtained unfortunately it is not the studio isomer which was needed so we have were wrong stereochemistry had was position that are in need all of this more so can be explained the outcome of this reaction while as we know the hydride should to a at DEC carbon lies group the trajectory of the bloody Brunet's angle 107 degrees I've a from Hilo or from behind the blackboard however in this case the VOS twill hydrogens behind the blackboard you have the roof like the parents all of that molecule and yellow from from here it's it's like that there are the hydrogens and here is the truth OK so that means that the UK reducing agent should also approached from behind the blackboard finally leading to work had observed group in front of a black so for having the chance that you get the opposite steer your isomer that we would have to change when mechanism and 1 way to do so there's still trying the reduction under Böge reaction conditions France's sodium in Physik fit ammonia going for SET single electron transfer processes while they tried to batch was the group of 5 aim is B. Smith a very famous group for on the total synthesis and tried these birds like reaction conditions you will some of you at least have a practice in the undergraduate lab for are mainly used for the reduction when fed you'd derivatives to rule unconjugated die hydro benzene derivatives so they tried it but in vain it didn't work so what else could 1 do you there is the so-called Matsuno blue reaction very interesting reaction we should have a look for the mechanism and the grief ingredients is the need for that what we 1st of all need to azo dye carboxylic acids die s 2 normally normally all very often abbreviated as that die f EU azo dye carboxylate heat so the this is treated they've tried venues phosphine so what will happen in that case
triphenyl phosphine there is the soft you agree your final those who already attended the lecture on catalytic Caere organometallics know that you have this example of the isomerization of EU bones to dieting poems formerly thought to be catalyzed by palladium acetate and they draw on globally Troost group found out it wars the phosphine catalyzed process of ligands at models but did job so also here attacking this conjugated system just as the new crew file all of this happens in equilibrium and the we now have formal you positive charge as that of phosphine around here the nitrogen and ionic charge but in the presence of 1 carboxylic acid this will get protonated and then the of calls have the carboxylate as B culture and I am the MIT soon normal reaction is a reaction for activating for the nucleophilic substitution primary primary and secondary out calls for assistance to reactions so we also have Onopko hold presence so the alcohol then really acts therefore this force for on your own reagent making use of the ox or felicity of the phosphine so I let me think about it I think we can that we trolled process so what had happened obviously you the ayes or die carboxy carboxylate has been reduced true to the hydro signal compound on the other hand the phosphine has been oxidized if in this redox process not as I said generally this oxygen we also formerly part all post secondary or primary particle that means here that substituent our is an aliphatic 1 wall at least it is C 3 up hybridizer C. 3 hybridized cobbler him in such cases that s than to process could take place and does indeed this that carboxylate as the nucleophile producing triphenylphosphine oxide and 1 event and an ester like that on the other hand because the tears and test and to process still you read your in formation at that center is in reverse and this is the important in terms of factor wide it's a noble reaction so interest in this case of we already know a similar reaction like that yes indeed from organic chemistry 1 the other was also
reaction so I hope you remember heading for instance plants you go light that that reacts this nice reagent that the phosphine as look could you file reacts here so also a false for on your because of the role White contact and I and in this case and now I hope you see the perilous situation here you have the leaving group of good leaving group similar to the it's a normal reaction now not the carboxylate it was would also group of a carboxylic but not the th the bromide and even the role might is look real enough to make that substitution reactions the of fame is produced hand this phosphonic acid as to which then can later on be applied no the dish type the teach Warner Emmons and so on type processes after Dutrow tonight in here how so that's why there is some power parallely t between single reaction and the abuse off reaction so what about here well OK make it's a noble process here nucleophilic substitution the 4 carboxylate hydrolyzed that has to and you should have the 0 age group on the other side great to this product they tried that and it didn't work so we couldn't get this done so that is to the side to what go for the different approach so they did so in the 1st step they apply at an interesting reagent I would guess most of you haven't seen that before it's the so-called Nugent from its structure of its and OCR sets the region so three-member nitrogen heterocycles this and as a reading and having ox subgroup in there meaning exchanging a methylene group by an oxygen here means that science OCs up zur reading and this ox aziridine have has the nice property that it can do liver this oxygen can oxidize that molecules so which part of a molecule that is most easily oxidized His of calls the sulfur so in that case the needed get to the sulphoxide I hope you remember from organic chemistry to another interesting reagent Fuller delivering oxidatively 1 oxygen 2 3 blended heterocycle it's this time of full dialog hearing very nicely introduced and it delivers the oxygen and that an acetone remains which is not bad acidic this is the advantage compared to CPB a very of a carboxylic acid remaining Prime and all over I would like to remind you of
the she epoxidation developed by Professor Yuen she there he is 1st oxidizes they've been in the show got moiety the keto functionality the the cour fate Papic soul sulfur compounds which deliver 1st would also oxidized acetone to down the food oxirane and this moiety you have done this in the guy role part of of the sugar molecule
and the she epoxidation this that an app oxidation of a car all information gunman an answer selective epoxidation of the current information stems from the sugar more here so let's go on here the idea that is that the do they mean 8 water here this is already more acidic by the oxidation but 1st of all we have to transform the odd AXA Group into a better leaving group on standard procedure there's there's treating it this this you chloride the presence of a base mixture of try out for the mean and dimer full amino pyridine D. N In-taek a thing and Serge than an additional strong world babies the DBU will die eighties by Psychlo ones decaying some of you I know use that regularly for any of us going to for that structure here but see you on this free electron pair at about nitrogen is the basic Center because after protonation we have done the conjugated to cat so over all eliminating water means they must be smooth group was heading for this olefin but for the final product they are indeed not all of the sulphoxide but the reduced 1 so how could you reduce that without affecting that double there is a nice reagent the difference try from or wrote the city the hydrides then acetone and the reducing agent those so do you and I . it transfers that cell phone in principle in this dipole Moodle compound which then the newest simply iodine so the sulfur is reduced then on the other hand the ideal diet is oxidized to iodine the next step this this simply Our hide rule people relations th have followed by the usual oxidation on a basic conditions sodium hydroxide and hydrogen tap oxide and as you know this oxidation of the org honorable room com prone groups this this under retention and systems the hydroboration will take place on top of a room so so not handle that means the ball sit here behind the blackboard and therefore finally the hydroxyl group to and this is just the steal your eyes and there the Smith group was aiming for to get to the final natural product that's some steps more of that that there's a better go to the next example of stirred about problems the stereo chemistry Coleman's group wanted to synthesize a molecule the Cairo
axes and wanted to synthesize about the nuns is selected to be precise they needed that di st you you select TVT sense also already a trial center present so 2 of those molecules 1st treated the what to this you would get the lithiated at this position then offering couple of cyanide proper 1 cyanide and T and mediate complex this app at low temperatures and then oxidizing still have that low temperature lives molecular oxygen so what will happen you have the form a diet our group poop rate and the the oxidation you very endurance the principle the money coupling reductive elimination forming women coupling so I'm by the womb uncoupling steps the our room axis is integers from the let's see so here he hat at the Carroll axis and it looks like like that this methoxy group goes outside the blackboard he ever methoxy group this inside the black the current information this ad I'll we is for the axial let's see I have to check for prior information on on that solid yeah it's the same as here and what a great so I'll selectivity that means just by chance this point Kiral information has influenced here be dire stereoselective formation offered axis this this nice almost pure heat up Steve you isomer unfortunately it was the wrong 1 river indeed off the axis so this followed drawing that whole thing once again I just moved explain how they did it and it was rather easy default nice it groups highly diets do you selective so if the change it here than gold stopped if the other in and soon you should consequently get to V. S dynasty you you past that that axis but then of calls prochiral information here is wrong but it is more easily to the bill arise here to get to the other steer you isomeric at the point Carleson did manage the car axis you can of calls press sphere but he did that that's not what what you want to OK so and Vigneault no fought hard to change the GA information he had to the opposite it's said it's an overreaction so these are groups have been none are protecting groups break
leave to protecting groups off make the double admits a noble reaction here and there and finally get the right so as to realize I guess in addition and I would like to show you another approach for our Kiral axes was developed by a bruised Lipschultz and he is 1 of the pioneers of sophisticated to the copper chemistry while in Santa Barbara had to 10 19 93 so
this summer grown enough tool Walls Kumble coupled the this carol compound and calls you will notice that you can easily synthesized there's starting from tartaric acid brought so you're producing the acid functionality and putting on bands protecting groups the coupling that to give this molecule there is achieved also referred me to normal type of reaction making leaving groups out of that and having done the Sandel late finally made attacking as the nucleophile so now we have a bromides and Peru bromide in a bromide and this was used for them in trot molecular womb uncoupling actually the same conditions as we have discussed before so total theorems and that in a couple of Sinai at and than oxidation
forming viral axes Paul was achieved with 70 8 % you so here the Lipschitz group they have 1st it's a noble the hand the formation of a by a root access and in the
example before had to 1st the lumen coupling and it's and will strangely cells cleaving that part all the gift the finance Americans clearer by enough afterward I hope you all know all normally buying afterward is synthesized It's better enough tool treated I ran 3 crew alright has done 1 electron oxidant and to do so normally treated as solid press water and meeting it up to maybe 50 degrees that that's enough gives excellent unit off the press make by enough tools and this has to be done separated in its announcements so how but cleavage the worked very well and as reagents that Lipschitz paper was telling and the secondly Goerge minus so I was thinking is some special my fault I having to route about what they they don't tell on to the aims I find iPhone only this example exclusively I think
they have been invented to fall that didn't of anything more about it so we could guess what will happen there there it is and be as who looks light radical process at least if they have AID and also there just and B. S and some acid then you would get electrophilic aromatic bromination here nothing should happen there but in the side chain so what this you may mean that it's a radical processes so where the brawl mine radically be attached prefer Schally normally in Bensalem position I think that will happen but nevertheless we have also in principle in principle hydrogens and if you can also bromine made here and there is a substitute for that than in a nucleophilic substitution of hydroxylate you will get a tool he me acetals and an equilibrium there just fall apart and you get nicely that product OK that's the least my guess how this cleavage with next subject the 7th and last subjects following 0 this article about dead ends and as a set D 2 is in total synthesis reluctant ring closure so ring closure is bad I don't want to proceed 1 example which in principle could also be an example for problems the stereo chemistry the epic ke tone functionality here and in all the high variance and this has been treated the titanium strike role right and Foxy cafe in the presence of zinc copula has reducing agent 45 hours room temperature so what do you think will happen 1st gas will always be McMurray reaction and Kay but under moderate reaction conditions the steady new strike alright right it is possible tool half face stopped when McMurray reaction and to go for the pin up called coupling products from the pinnacle and this this and case here from did call formation so it was indeed a plant to have the pinnacle of their 2nd this reaction has been performed in the lap of the X Pruitt for McMurry type processes McMurray's nap itself they knew what they were doing but they broke also doing it by chance going for certain steer isomers this loss 1 of 4 isolated isomers which could be identified and that is the 1 with the highest yield 21 per cent but they also used this 1 this the real information for producing was synthesizing the certain natural products but the 1 they had originally in mind had exactly the opposite studio information at those centers so the old age group in from both in front this was unfortunately only isolated the 7 per cent a year so 3 times that much as much the 1st and so the Mcmurry group tried to
isomerize positions and they did that successfully again this these you miss you chloride Inc. as a base so then of calls the secondary call the methylated in preference and then a 2nd please treating that were of the strong based they got this oxide so they Changed the steering information already at this position and then the next step age too long the of but perchloric acid protonate here and the water nuclear 5 coming from the other side show to the finally having changed both position 1st steps with 68 per cent year on the 2nd step 70 7 per cent so double steal all in version last example for 2 days if we began a ring closure reaction which didn't work as it was planned who do and interesting sparrow psychic system Carino in the center an easy any conceivable protecting groups and the nitrogen what it is I think a rather interesting protecting groups abbreviated has to be seen and this those that kind of group so and MIT from problem oxide proved this side chain and of course if you would treat that with some through right than ethylene would be eliminated 4 carboxylate and having here the nitrogen while OK it's done rooms you too a guy easily to be the they hoped for the direct condensation science this this natural product so bad it didn't work 2 reasons can be discussed so should be discussed maybe the steric interaction how ever how will units here we have that Spira cycle kind of calls this standing like that 1 in France someone goes behind but it is not standing right Captain teach you know there but the bit like like that that means that those hydrogen and my point a little bit too loose than that position there and just having still some hindrance the on column I think of Wonder would put in model into the computer which is so this will be easy to to notice but even more important presumably all of these electronic interactions
since that column on here you could see as the double the newly ghost urea conjugated to about the mean and this OK so so and the solution to the problem the walls avoiding this spero psycho that a Psychlo ization step and making changes here at both positions concerning that nitrogen found that nitrogen making that govern here's some would more or the lecture for the having enough oxygen appear Tauzin 18 this nitrogen and having here look protected ICRC
protected problem the power to rule sulphonic acids in the city tonight trial the 51 per cent viewed was obtained of the psych lies product well the a couple of steps had to follow the most important step walls using this nucleophile attacking here the fun edition elimination the process having that on this side chain and then oxidative 3 yet oxidatively coupling at this position to the spirit cycle while OK I think this is enough for today thanks for listening to see you next week Tuesday a
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AV-Portal 3.21.3 (19e43a18c8aa08bcbdf3e35b975c18acb737c630)
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