Bromocholestan-3-1 Lab Report
Mechanism 4 shows the debromination of 2α-bromocholestan-3-one to give 4. This mechanism which is similar to a Favoskii rearrangement, is likely to go via this path as other research has shown that there is often a by-product with this reaction. The by-product is cholest-4-en-3-one which requires the intermediate seen in the third molecule in the above mechanism. The intermediate is highly strained and with the presence of base a proton will be extracted which aids the collapse of the three membered ring. To gain the major product, 4, the H1 proton is removed, however it is very possible that the H4 proton is removed instead which would leave the minor product of cholest-4-en-3-one. Both products result in conjugation which will stabilise the molecule. The mechanism for this step is unlikely to go via a simple elimination as for an elimination the eliminated products must be trans to each other for facile leaving. As the bromine is equatorial in both the chair and the boat conformation the bromine is trans with neither of the hydrogens which shows this type of elimination is unlikely to occur. The other possibility is that the acidic hydrogen that is removed in the first step is not H4, but H2. This
…show more content…
would result on a negative charge on C2 which would eliminate Br leaving C2 as a carbene. This would result in a proton transfer and a collapse of the double bond forming the product. This is unlikely due to not producing a minor product as the highly strained intermediate is not formed.
Conclusion
Through the synthesis of cholesterol to cholest-1-en-3-onr via; cholestan-3β-ol, cholestan-3-one and 2α-bromocholestan-3-one the reaction gave a poor overall yield of 3%.
This shows that developing this reaction on a large scale would not be feasible because of the amount of product obtained. If cholest-4-en-3-one could be collected as a major product this experiment would allow access into creating steroids which could be further reacted to have akyl chains with differing properties16. This would allow for further pharmaceutical application. TEMPO could have further application as an environmentally oxidant when coupled with a radical to produce less by-products such as salts and toxins which are hard to remove from your product and dangerous for the
environment.
would result on a negative charge on C2 which would eliminate Br leaving C2 as a carbene. This would result in a proton transfer and a collapse of the double bond forming the product. This is unlikely due to not producing a minor product as the highly strained intermediate is not formed.
Conclusion
Through the synthesis of cholesterol to cholest-1-en-3-onr via; cholestan-3β-ol, cholestan-3-one and 2α-bromocholestan-3-one the reaction gave a poor overall yield of 3%.
This shows that developing this reaction on a large scale would not be feasible because of the amount of product obtained. If cholest-4-en-3-one could be collected as a major product this experiment would allow access into creating steroids which could be further reacted to have akyl chains with differing properties16. This would allow for further pharmaceutical application. TEMPO could have further application as an environmentally oxidant when coupled with a radical to produce less by-products such as salts and toxins which are hard to remove from your product and dangerous for the
environment.