Organic Chemistry

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27. Transition Metals

Sonogashira Coupling Reaction

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Sonogashira Coupling Reaction

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In this video, we're gonna take a look at the synagogue zero coupling reaction. Now, in the synagogue zero coupling reaction, we have the coupling between and a real halid or vinyl Halide with a terminal al kind. Now, unlike other coupling reactions, this one utilizes co catalysts. Now, co catalyst, they work as a pair of cooperative catalyst that help to improve one another's performance within the coupling reaction. Now we're going to say within this reaction, we use palladium as our primary or main catalyst and then we use our cup are copper catalyst as the co catalyst uh to form a by a real or buy vinyl alka Neil product. If we take a look on the left at the generic setup for a cross coupling reaction, we have our carbon Halide which is represented by our one X reacting with our coupling agent. Are to see with the help of our transition metal catalyst so that we can form our coupling product of R one R two with C X. As a byproduct applying this generic setup for a cross coupling reaction, we're gonna use the coupling reaction. So here we still have our carbon Hallett. Our coupling agent in this case though is a terminal al kind. Now remember terminal kind just means that at least one of the triple bonded carbons possesses a hydrogen. Now we're gonna have our palladium catalysts working cooperatively with our copper one catalyst and some base so that we can form our coupling product here, which just has R R one and R two groups connected to the use of a triple bond and then of course, we're gonna have our byproducts here. Now, when it comes to describing what each of these groups are, we say that our our one group is just represented by a vinyl or a real group. R two could also be a vinyl and a real group here. R. C group in this case has to be the hydrogen that is part of the terminal out Guy X. As usual when it comes to our carbon, Khallad is one of the four good leaving groups, so chlorine, bromine, iodine or trifle eight. The base that we typically use in this reaction is triathlon. Mean, so we have the general layout of tachira coupling reaction. We're gonna use this basic setup to understand how to get to our final product quickly before we get to the actual mechanism for this particular cross coupling reaction.
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example

Sonogashira Coupling Reaction Example 1

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looking at the general setup for Sin Okushiri coupling reaction. We can see that fundamentally what's happening. We have our X group and our H group being lost. So that this terminal kind part which is attached to our two can combine with our one. Use that in order to determine what our product would be in terms of this particular theory coupling reaction question. Alright. So here we have our terminal kind which has a hydrogen. We don't see In this case the X Group is represented by our Trifle eight. Alright, so this would represent, so this would be a church green. So here since this is our X group, that would mean that what's attached to it would represent our our one and then here this would be our are to this portion here. So we know that all that's gonna really happen if we think about it in the simplest of terms as we know that we're gonna have these being lost and then R. R. One and R two groups bonding together. So our product would look like this. Strong are one group first and then we're gonna connect terminal kind which is still connected to this Benzie ring and the methyl group attached. Okay. And realize here that the Elkin had an E configuration in here. It's still maintaining that same E configuration. So this is pretty common when it comes to the reductive elimination step where we have the retention of our stereo chemistry when we first talked about the basic layout for a cross coupling reaction mechanism. Now that we know just the basic way of looking at a synagogue sherry coupling reaction to produce our product. We can now look at the mechanism involved to create these types of more conjugated products.
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Sonogashira Coupling Reaction

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the so no cashier a coupling reaction is pretty unique because it utilizes co catalysts. Now we're going to say that this coupling reaction is a palladium catalyzed reaction of a copper one alcatel complex with a vinyl or real halid. Now we need to realize what's the function of these two catalysts. Well, we're going to say here that the palladium catalyst, all it's going to do is it's going to partake in the oxidative addition step. So it's prepping R R one X group for the coupling reaction. So it's working with the carbon Hallett the copper one catalyst. What it does is it's prepping our coupling agent, so our R2C group and by prepping the R one and R two group that's gonna lead them to combining later on to create our coupling product. So we're gonna say here that the nose got Tachira coupling reaction starts out with a step zero where we have the preparation of our coupling agent through the use of our copper one catalyst. So what's going to happen here is that our our kind carbon is weakly acidic, therefore the triathlon. Mean that we use will dip rotate it, we wind up getting here are two connected to our triple bonded carbon, which now possesses a negative charge. Here we have copper one iodide. Remember this is an ionic compound. So it's not really together, it's just too free floating ions that are close together because of opposite charges. So as a result of this, this negative carbon will grab onto this positive copper. So what we're gonna get at this point is we have our our two group connected to our al kind which is now connected to our copper. We're gonna say here that are are two group has been primed or it's been activated so that it can later on react within this coupling reaction. Now we head into step one here which is our oxidative addition step where things are what we are accustomed to seeing in terms of a cross coupling reaction. We have our palladium with its deorbit electrons with that lone pair. They're going to attach to my ex group here and this is gonna break and attach right back to the palladium. So we're gonna get our palladium still connected to its two Liggins connected to the X. Group And now connected to our one. This leads us into step to transmit elation. Where are primed are two group or copper one. Al kamil compound is gonna react now with the transition metal complex from the oxidative addition step. So here we're gonna have our our two group being transferred from the copper to the palladium. So remember that's gonna cause this pond here to break. It's gonna attach to the palladium at the same time this X. Leaves and attaches to the copper. So we wind up getting is we're going to get r one still connected to palladium With its two Liggins attached. And now my R two group is attached. And then finally we have our final step which is reductive elimination where we create our coupling product. So what's gonna happen is this compound here We're gonna have the R. one group attaching to this carbon and then having this bond breaking going to the palladium. So what we're winding what we're gonna wind up getting is r. r. one attaching To the al-indind, which is part of our two and then the regeneration of our transition metal catalyst, which is a dragging force for this to go through another cycle in terms of the cashier a coupling reaction. So remember this reaction is pretty unique through the use of the two um catalysts. So they work in conjunction with one another to help prime my R. One group in our two group. So at the end they combine together to form my coupling product. So we have the addition of that uh step zero, which we usually don't see in terms of coupling reactions, but in this case we do have it and then followed by our three normal steps of oxidative edition, trans methylation and reductive elimination. To round out the four steps involved in the so no cashier a coupling reaction
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Problem

Determine the product from the following Sonogashira Reaction.

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Problem

Determine compounds A, B, and C from the following reaction sequence.

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