[saint_john]

Can anybody tell me what reagents would be required to obtain the product from the starting molecule.
( i have attached a picture of the reaction)

I would appreciate any explanations or hints
thanks !

[mschelthoff]

The first thing to do is disconnect the final product in a position where bond formation takes place. Once you've determined where the bond is formed, decide what part of the molecule could function as a nucleophile, and conversely what part could function as an electrophile. For instance, if you were to designate the alpha-carbon off the carbonyl as the nucleophile, what could make that carbon nucleophillic? Reason it through.

[discodermolide]

Can anybody tell me what reagents would be required to obtain the product from the starting molecule.
( i have attached a picture of the reaction)

I would appreciate any explanations or hints
thanks !

Think about the acidity of the hydrogens on the ketone methyl group

[mifeng]

Br-R is more reactive than -COCH3 under alkaline conditions.
it is impossible to get the target compound from the materials you mentioned.

[discodermolide]

Br-R is more reactive than -COCH3 under alkaline conditions.
it is impossible to get the target compound from the materials you mentioned.

No it is not. Use a strong non-nucleophillic base to deprotonate an  alpha methyl hydrogen, you get the enolate of the ketone which will cyclise onto the bromide

[cupid.callin]

is it necessary to use only one step?

[discodermolide]

is it necessary to use only one step?

You deprotonate at -78°C, stir 30 mins or so then let it warm slowly to -20 - 0°C. If the solvent is THF or ether you should see a ppt of the bromide of the cation, usually Na. As base I would use sodium or potassium hexamethyldisilazide (M+(NTMS2)-. You can also use lithium 2,2,6,6,tetramethylpiperidide.

[saint_john]

would CH₃O^- work as reagent for this reaction ?

[discodermolide]

would CH₃O^- work as reagent for this reaction ?

Probably not a strong enough base. And you will get side reactions, displacement of bromide or elimination of HBr. Which is why I specified a non-nucleophillic base.