ii need to synthesize a chalcone and acetal compounds from a dialdehyde- diketone and dialdehyde-bis(diols). it always forms a oligomer with 4-7 average units. is it possible to just stop it at one unit , without using any protection strategies
It possible to synthesize a single unit of chalcone when a dialdehyde compound reacts with diketone compound taking one mole of one mole of aldehyde and one mole of ketone.
It is possible using high dilution technique.. Taking ketone in large excess NaOH aq- EtOH solution (1:1), add dilute solution of aldehyde slowly (during 1h) drop by drop with vigorous stirring.
Dear Vara Prasad Rebaka thanks for posting this interesting technical question on RG. In order to give you a qualified answer it would certainly be helpful if you could provide a schematic diagram showing the starting material of your planned reaction. In general, the dilution technique as suggested by Nayim Sepay could be a useful approach in your case. This techniques is normally employed to make large ring molecules while avoiding the formation of polymeric materials.
Good luck with your work!
Yes , it's possible. But to get better yield and pure product you have to use the mono-protected aldehyde (as half acetal) and mono protected ketone (as half ketal) of the dialdehyde and diketo precursor. The dialdehyde can be converted to mono protected acetal by reaction with one equivalent of ethylene glycol and one equivalent of dialdehyde and catalytic p-toluenesulphonic acid in refluxing benzene. In the same way mono ketal derivative of the diketone can be made. Now these two substrates can be condensed with NaOH in ethanol. it will lead to the chalcone / condensed product of single aldehyde and single ketone unit. Now the acetal and the ketal units can be deprotected /unmusked to regenerate the aldehyde and the ketone functionality (if required). Exactly I don't know your compounds but using a representative dialdehyde and a diketone derivative I have given a schematic presentation of the reaction. Similar chemistry can be followed for your dialdehyde and diketone too.
Not only such type of chalcones , these two protected carbonyl compounds can be coupled ( with TiCl4. Zn dust in 1,2-dimethoxyethane under reflux via McMurry coupling ) among free -CHO and -COCH3 functionality to produce Ar-CH=C(CH3)-Ar type of conjugated dicarbonyl compounds too .
It is tricky. But, you can try following different parameters like in dilution, maintaining equivalents, and selective protection of one group from aldehyde or ketone.
It depends on the control of your reaction. Use the one reactive species in way less than (may be half) the required moles, and start at low temperature, would be better to go around -40 dC, keep a tab of the reaction through the TLC and work it up at appropriate TLC appearance, It may turn out to be difficult/cumbersome to purify but in all probability will lead to product, do not try to get all reactants consumed up!
Dear Vara Prasad Rebaka your interesting chemical question has meanwhile received a number of potentially useful expert answers. For the readers of this thread it would be quite interesting if you would tell us if any of these answers were helpful in solving your problem and if you succeeded in synthesizing the desired product in the meantime. By the way, it is polite and a good habit on this platform to recommend those answers which have been particularly useful answering your question.
Good luck with your work and best wishes, Frank Edelmann
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