Problem 6 Easy Difficulty

Reserpine is a natural product that has been used in medicine to control high blood pressure and to relieve psychotic symptoms. Part of a 21-step synthesis of the natural product reserpine, published by the American chemist R. B. Woodward, is shown below. (Section 21.3)
(a) Give a reaction mechanism that explains how 4 is converted into 5. (Hint: the reaction) involves an intermediate bromonium ion).
(b) The first step in the conversion of 5 into 6 involves deprotonation of 5 and elimination of bromide ion to form an alkene. Suggest a structure of the intermediate alkene.
(c) Give a reaction mechanism that explains how 6 is converted into 7 . (Hint: the reaction involves an intermediate bromonium ion).

Answer

Related Courses

Organic Chemistry

$Book Cover for Chemistry $^{3}$ : …$

Chemistry $^{3}$ : Introducing inorganic, organic and physical chemistry

Chapter 21

Alkenes and alkynes: electrophilic addition and pericyclic reactions

Discussion

You must be signed in to discuss.

Top Organic Chemistry Educators

Watch More Solved Questions in Chapter 21

Problem 1

Problem 2

Problem 3

Problem 4

Problem 5

Problem 6

Video Transcript

Hello everyone. Let us see the following question. The respirator is a natural product that has been used in a medicine to control high blood pressure to relieve a psychotic symptoms. Part of 21 step synthesis of a natural product respiration published by american chemist R. B. Woodward is shown below. So let us see the structure of the preparation strategy of respiratory arrest. The rest reserve. Fine. Sorry, Mrs Irvine, is that fine? Okay, the production is given below so we can see the preparation of razor pine here. So this is as given in that question. So let us see question A The question is the statement give a reaction mechanism that explains how four is converted to fight. So four structure four year given is converted to five. We have to explain C. As we can see here, there is question for to fight how it is converted we can see the components here. This is as it is. This structure also similar as it is here, hydrogen also similar only thing, the double bond is broken here here in the double place of double bond. There is addition of blooming br plus and B. R minus, which follows definitely electra filic edition mechanism. So after Elektra filic addition mechanism from the anti direction blooming is added, one is added from a bow and another decided from below. So definitely the double bond is simply broken into single bond. So let me draw the single bond very clearly this is not a double born. So double bond breaks into single bonds. So after that you see there is one ohh, which is already in the veg direction, what is veg, which is about the plane? So already I know that this brahman is inventor direction. So this brahman is below the plane as shown here. Now this edge and this be our we can remove due to inter molecular hydrogen bonding. We can remove as H B. R. So what is removed, followed by elimination. So removal of HBR is called elimination reaction elimination during elimination. What happens oxygen gets a negative charge as the broom includes hydrogen gets sorry here, carbon gets positive charge. So this oxygen bonds with this carbon. So we can see as it is facing the same side, the blooming and over age group are facing the same side, it would be very easy for the H bonding. Hence it leads to the elimination of HBR and there is formation of epoxy components. So this is a part of question. A Now let us see the question is, what actually electra filic addition mechanism. Okay, followed by for lower bay elimination of elimination ah H B R. So let us see the question be in question, be the first step in conversion of five into six involves the proto nation of five and elimination of Brahma Deana Valk in as we discussed, such as the structure of intermediate alkaline. So in the production of 5-6, we can see that 5-60, there is a broom in here and in that place, oh emi group is dead. So if this blooming is gone. So this carbon is alpha carbon which is a positive, we know that there is a hydrogen here. We also know that there is a hydrogen here. Now these both places are beta places, this is beta one and this is a beta two. Now from where if hydrogen is remote, we can form either a double bond at this Vita one and alpha place or better to an alpha place. But we know that there is a carbon in so this is an electron withdrawing group. If there is a double bond here, it would favor alternative resonance. So definitely double bond forms here at this point. Therefore hydrogen from bitter to has to be eliminated which leads to the formation of this double bond at this structure. So let me draw the structure of double bondage to alki in here. See there is a cyclo structure area. So there is oxygen here. So here, yet there is hydrogen. So there is a oxygen here, they received double bond, so has to be double born at this point. So I'm drawing that with the red color. So there has to be a double bond at this point. Now, what happens is we will take a ch three ohh metal alcohol which is mentioned in the question already now as there is a carbon in group, this is taking the bond bear, hence the bond breaks at this point. So this carbon becomes negatively charged. This carbon becomes positively charged. Now we know that the electro file hydrogen which adds at this point. Okay and the nuclear file O. C. H 30. Being minus adds to this carbon which leads to the formation of this particular product. So this is the structure of particular alkaline, which is a part of the question B. Now let's see the question, see the question see is give a reaction mechanism to explain how six is converted to seven. So let us see how is 6 46. This is six where there is all metal group which is converted to seven in seven. We can see that this uh literal group is like this. There has to be just the cleavage of this grouping group. There is addition of grooming and so that means broom in water that is leading to be our plus and B. R minus. And then there is ohh minus. So we know that when there is double born here, if it has to be broken like this. So if it is broken like this we know that there is a withdrawing group here because of that bond breaks like this which leads to minors here and plus here. Okay wherever plus charges. The nuclear file will attack wherever minus charges their electro file will attack. Okay first it follows electrification mechanism therefore it is favored by E. Bliss 87. So always electro file adds to the carbon Because this carbon is SP two hybridized, cannot bear positive charge, but it can have negative charge, so first two positive charges to be stabilized. Therefore, therefore, what happens is, uh sorry, This is broken into positive and negative charges speak to hybridized carbon cannot be positive. Therefore, first electro file adds to this lone pair of electrons and which makes the stable carbon catalon, followed by additional so it leads to E plus edition. Thank you.

We have video lessons for 18.66% of the questions in this textbook

$Book Cover for Chemistry $^{3}$ : …$