[nexisrocks]

Hello,

I've been mulling over this problem for awhile now.  I was given a reagent and product, and I need to find a retrosynthetic pathway between the two.  However, I can't seem to come up with anything.  Here is what I was given:



I thought perhaps I could use an oxy-cope rearrangement, however I can't seem to get that to work.  I thought perhaps the ring with the carbonyl had to be broken, and then you could possibly perform a cuprate addition to add the rest of the large ring, or perhaps a robinson annulation.

Any help would be greatly appreciated!

[Rico]

Hello nexirocks

Your idea about using an oxy-cope rearrangement is actually a good idea! Treat the starting material with vinylmagnesiumbromide and the addition product will rearrange via a [3,3]-sigmatropic oxy-cope rearrangement to an enolate, that upon quenching with water gives the wanted product (see jpeg attached). Since the formation of the enolate-anion is very energetically favourable the rearrangement runs even at room temperature. Moreover the sterochemistry of the newly formed chiral center is controlled by the stereochemistry of the chiral spiro-center (if you have problems vizualising this, i would recommend that you make a molecular model)

Rico

[nexisrocks]

Oh, perfect!  I see how to do it now.

Thanks so much!