The complexed dienophile becomes more electrophilic and more reactive toward the diene, increasing the reaction rate and often improving the regio- and stereoselectivity as well. Regardless of which situation pertains, the HOMO and LUMO of the components are in phase and a bonding interaction results as can Diels alder retrosynthesis problems seen in the diagram below.
Remember me showing you guys that? So it turns out that sometimes when you run a diels-alder reaction you get a bicyclic bridged molecule as your products, as shown in this diagram right here, so, how does that happen and why would we get a bicyclic as our product?
A series of reactions then follow to transform the functionality into a desirable group. E- and Z-dienophiles, for example, give rise to the adducts with corresponding anti- and syn-stereochemistry: So, hopefully that made sense so far. In general, with respect to the energetically most well-matched HOMO-LUMO pair, maximizing the interaction energy by forming bonds between centers with the largest frontier orbital coefficients allows the prediction of the major regioisomer that will result from a given diene-dienophile combination.
Remember, that we stated how your one, three diene always has to be in the S cis conformation, is it in the right conformation? So, how would, we draw this product? Similar analyses for the corresponding inverse-demand scenarios gives rise to the analogous products as seen in cases 3 Diels alder retrosynthesis problems 4.
A diene substituted at C2 as in case 2 below has the largest HOMO coefficient at C1, giving rise to the "para" product. Despite the fact that the vast majority of Diels—Alder reactions exhibit stereospecific, syn addition of the two components, a diradical intermediate has been postulated  and supported with computational evidence on the grounds that the observed stereospecificity does not rule out a two-step addition involving an intermediate that collapses to product faster than it can rotate to allow for inversion of stereochemistry.
Notice that we already have one ring, that one ring is here. Examining the canonical mesomeric forms above, it is easy to verify that these results are in accord with expectations based on consideration of electron density and polarization.
Remember, that I told you guys that one three dienes could be regular straight chains but they could also be found within rings. The dienophile undergoes Diels—Alder reaction with a diene introducing such a functionality onto the product molecule.
Well, first of all is this diene in the right conformation to even react. The maximization of orbital interaction correctly predicts the product in all cases for which experimental data is available.
So, my first step is always to find the original diene and the way you do that is by identifying the double bond and then saying, well, this must have been the diene to begin with this was my 1, and and this one must have been my four, okay?
Since the reactants are in their ground state, the reaction is initiated thermally and does not require activation by light. Notice that the bridge was attached to which atoms? Mechanism[ edit ] The reaction is an example of a concerted pericyclic reaction.
Here is a summary of those steps: As such, the Diels—Alder reaction is governed by orbital symmetry considerations: This is a "masked functionality" which can be then hydrolyzed to form a ketone.
For normal demand Diels—Alder scenarios, with electron-withdrawing substituents such as carbonyls attached to the dienophile, the endo transition state is typically preferred, despite often being more sterically congested.
A bridge, when you have a bridge, when you have a cyclic diene. Now, that I have that diene I understand the mechanism better, I know that the diene must have reacted with a dienophile and remember that the diene always creates two new to the dienophile, so the next step is going to be to cross out the new bonds because, I know that my diene must have made two bonds.
The end product cannot not be made in a single DA step because equivalent dienophile is either unreactive or inaccessible. And, this is a backwards question, you have to think backwards. This preference is known as the Alder rule.
Lewis acid catalysis also enables Diels—Alder reactions to proceed at low temperatures, i. So, remember guys, when do you use endo and EXO only when you have what?
So, I know this is a new skill, I know I might be making it look too easy. Such a scenario is termed an inverse electron demand Diels—Alder reaction. Now, if you guys just notice this molecule here is the same one that I drew up there. So, there we go. So, when we go to react, let me just make that a little more clear one, okay?
So, we went ahead and stayed above the whole situation.
Now, what the heck do those words mean?Retro Diels-Alder worksheet A common question for retro DA reactions is shown below. If you can push a retro DA two different ways (pathway.
In this video I'm going to walk you guys through a technique that you might need to use for diels-alder problems. So, sometimes your professor, your textbook, your online homework is going to ask you to do a diels-alder retrosynthesis, that means that you're going to be given the final cyclisation product and then you're going to be asked which.
The Diels–Alder reaction is an organic chemical reaction (specifically, a [4+2] cycloaddition) between a conjugated diene and a substituted alkene, commonly termed the dienophile, to form a substituted cyclohexene derivative.
Video explaining Diels-Alder Forming Bridged Products for Organic Chemistry. This is one of many videos provided by Clutch Prep to prepare you to succeed in.
Organic Chemistry Practice Problems at Michigan State University. The following problems are meant to be useful study tools for students involved in most undergraduate organic chemistry courses. The problems have been color-coded to indicate whether they are: 1.
Generally useful, 2. Diels-Alder Practice Problems Please draw the product of each of the following Diels-Alder reactions. + Cl 2 x O O + O 2 x + + C C H H H COOH CH 3 O C OH O + +.Download