[Death Rider]

Hi, I got an assignment to synthesize this whatchamacallit out of cyclopentanone. I am asking for  your  help in naming it and just brainstorming possible ideas how could this be done. I suppose we will be needing a reducing agent to get the alcohol group, but the question is whether it is before or after connecting the side branches.
I got a tip from my superior that it could take about 2 steps to make and that this is some known existing material, which I suppose should have a certain name. So, what are your ideas?

[Schrödinger]

I have the answer, but I want you to try harder. So here's a hint : Use benzaldehyde - C₆H₅CHO in both the steps. I leave it to you to try and figure out the reaction.
Later, reduce the ketone (MPV reduction http://en.wikipedia.org/wiki/MPV_reduction#Reactions)

[cyp]

2 aldol condensations, then reduction of the ketone.

[Death Rider]

So true! Pentanone + 2xBenzaldehyde in base conditions such as NaOH and I might just have it But still, is there a short name for this product? Cause currently a IUPAC name is humongous and pretty useless 

[vhpk]

I suppose dibenzalcycloheptanol, but I've googled and no results for the name :-?

[cpncoop]

The name suggested isn't correct... I'll give you a hint though - the ring system is 2,5 substituted with benzylidene groups.... 

Also, I would consider a base other than NaOH for this type of reaction.

[Arctic-Nation]

Also, I would consider a base other than NaOH for this type of reaction.

You think? For dba NaOH is used. No idea of the usual yield, though.

[cpncoop]

I was thinking of a different base (an alkoxide or something) only because w/ NaOH you're forming water during deprotonation which will drive the equilibreum in the wrong direction during the reaction.  If you can get away with NaOH, it's certainly cheap enough.

[cyp]

A student at SEMSU . . . performed three different aldol condensation reactions on cyclopentanone to make three different products. For each condensation reaction, a different aldehyde, along with barium hydroxide, were reacted with cyclopentanone in ethanol. The products formed were, 2,5-Dibenzylidene cyclopentanone, 2,5-Di-(4-methyl benzylidene) cyclopentanone and 2,5-Di-(4-methoxybenzlidene) cyclopentanone.

Does the Ba(OH)2 deprotonate ethanol and then ethoxide catalyze the condensation, or does the ethanol mainly serve as a proton source and counterion for barium?

Also, does using a base with two equivalents play a role in the in the two-sided symmetry of the overall  reaction?

[orgopete]

The concentrations of hydroxide and ethoxide will be governed by the concentrations of water and ethanol and their acidities. Because they have comparable acidities, both species will be present.

The reaction is catalytic in hydroxide, so two equivalents from 1 mole Ba(OH)₂ or 2 moles of NaOH should not have an effect on the overall stoichiometry. Although I do not know the equilibrium constants for these bases, I would expect that barium and sodium hydroxide should have an effect on hydroxide concentration similar to water and hydrogen fluoride on hydrogen ion concentration, though with a different magnitude.

[fawad0418]

probably use NEt3...if u want bit stronger base use LHMDS

[Dan]

I have my doubts about triethylamine... with the pKa of triethylammonium being around 10 it probably won't be strong enough to generate the enolates in significant quantity - the pKa of cyclopentanone is probably around 20, we're looking at at about 10 orders of magnitude difference. I have done a few aldol reactions and always used potassium carbonate in refluxing aqueous methanol (pKa ~ 16, the base here is going to be methoxide/hydroxide), although in those systems I was creating quaternary centres so there was no dehydration possible.

Incidentally, you might get lucky and eventually reduce the ketone by a crossed Cannizzaro reaction with benzaldehyde in the same pot under those conditions... otherwise I'd go for a Luche reduction.

[Death Rider]

After searching through last 80 years of chemical abstract indexes I was able to find only 5 feeble entrances concerning this substance. Do you have any ideas where could I find some more info?
Btw, up to 1965 it was called 2,5-dibenzylidene cyclopentanol, but afterwards they changed a lot of names and it became 2,5-bis[phenylmethylene] cyclopentanol

[srihari]

 I'm not at all conversant with practical aspects
I'd like to learn .

Abstract the proton in the first step , don't add excess of LDA and then add benzaldehyde and heat ( to get alkene )
now again add a stoichiometric amount of LDA and repeat the process .

and then use a selective reductive agent such as NaBH4 in CeCl3 solution etc...
is this a possible way to do the above synthesis  ??

regards
Srihari

[Death Rider]

You see, my assignment is to find several ways of synthesis and then choose the best one AND I have to start with cyclopentanone. It's pretty clear that there is only one way of producing the pre-reducated final substance. I've got till end of the month to wrap everything up and I pretty much have everything done Afterwards I will present my work to the public so that 2,5-bis[phenylmethylene] cyclopentanone would catch google's sight I was able to get the full paper on "Allylic Alcohols Via the Chemoselective Reduction of Enone Systems with Sodium Borohydride in Methanolic Tetrahydrofuran" which I will post as soon as I will have the technical capabilities, but basically what it says is that you perform reduction with NaBH4 in a methanol and THF mixture and you get yields up to 88% and the process takes a 20 minutes
As I now have the info on how to make it, I need to find corresponding papers that prove it, maybe some alternative reduction mechanisms to cast aside as unfit and I need chemical, physical and medical properties on both, enone and enol structures and that would be it