Multistep synthesis

[jennyb212]

Hey everyone! I'm really struggling with these multistep synthesis problems. Any input to push me in the right direction would be greatly appreciated.

 

For the following problems (see images below), what are the reagents to achieve this transformation.

 

 

My thoughts:

For the first image: It is supposed to occur in two steps and I believe it would involve a grignard because you add carbons, but I don't know if I should turn the alcohol into a ketone. And if I can just add a alkyne as part of a grignard reagent?

 

For the second image: This is supposed to occur in five steps. I added hexavalent Cr to oxidize the alcohol, which turned it into a secondary ketone. Then I a grignard (phenyl-magnesium-bromo), but I got stuck here because I created a tertiary alcohol, which cannot be oxidized because it has no proton to grab onto, so I'm unsure of what to do next.

 

Again, any help or push in the right direction would be appreciated! Thank you so much!!

[hypervalent_iodine]

1. Grignard isn't going to give you that product in 2 steps. What other C-C forming reactions do you know of?

 

2. I can think of a way to make it in 3 steps, but I'm not sure what sort of reactions you have learnt. Grignard is along the right lines, but as you have identified, you are then left with nothing much to alter to add the second phenyl and OH groups. Perhaps consider installing the second reactive point on C-3 first? How much have you learnt about synthesis of diols?

[jennyb212]

First of all, thank you so much for taking the time to respond to my question! I really appreciate it!

 

1) The only other C-C forming reaction that we've learned is ether synthesis and we talked about ring opening epoxides. Would either of those be helpful? Or Could I just add HBr, to get this to be an alkyl halide, and then add an alkyne, having that replace the Br, to get the product I want, or is that not how this works?

 

2) We haven't talked about synthesis of diols. How do I install the second reactive point on C-3? I'm sorry.

Edited May 9, 2016 by jennyb212

[hypervalent_iodine]

1. I think bromination is a good route. You can form carbanion bases with alkynes using NaNH2, which you can then use to substitute the Br.

 

2. What I had in mind was dehydration to the alkene, followed by formation of the diol with OsO4, oxidation of the two alcohols and then Grignard. So, 4 steps unless you count the protonation. You could also make the diol by making the epoxide and ring opening it with a hydroxide base.