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DEAR PROFESSOR: I HAVE ONE QUESTION ABOUT THE NITRONE. IS THAT OKAY TO USE KETONE AND RNHOH TO FORM NITONE? THANKS
Dear Whomever, Yes, nitrones can be formed from ketones and hydroxylamines although the reaction is a little slower than that of an aldehyde and a hydroxylamine! M. E. Jung
dear professor: i have question about reduce NO2 group. will HCOOH and HCOH reduce it without touch double bond? or is that okay to use NaCNBH3 to reduce it without touching double bond? thanks ^^
Dear Whomever, Nitro groups are not reduced under Eschweiler Clarke conditions, namely formic acid and formaldehyde (those are the conditions to methylate amines!). You could reduce a nitro using formic acid but need Pd on C (transfer hydrogenation conditions). Usually one used H2/cat or Sn/HCl to reduce nitro groups. Also NaCNBH3 will not reduce a nitro group either (you need a very strong hydride, e.g., LiAlH4, or something like that to reduce a nitro group with hydride - check the hydride handout!). M. E. Jung
dear professor: i have question about reduce NO2 group. will HCOOH and HCOH reduce it without touch double bond? or is that okay to use NaCNBH3 to reduce it without touching double bond? thanks ^^
Dear Whomever, Nitro groups are not reduced under Eschweiler Clarke conditions, namely formic acid and formaldehyde (those are the conditions to methylate amines!). You could reduce a nitro using formic acid but need Pd on C (transfer hydrogenation conditions). Usually one used H2/cat or Sn/HCl to reduce nitro groups. Also NaCNBH3 will not reduce a nitro group either (you need a very strong hydride, e.g., LiAlH4, or something like that to reduce a nitro group with hydride - check the hydride handout!). M. E. Jung
dear professor: Do we use TFA or NAOH to convert COSBU to COOH? since we use TFA to convert COOBU TO ACID,so could we use TFA? or we could use both thanks!
Dear Whomever, We use mild NaOH to convert a thioester to an acid (RCOSR' to RCOOH). It has to be mild because we generally use it for aldol products and they can be beta-eliminated very easily to give the alpha,beta-unsaturated acid if the base is too strong. For t-butyl esters, we use trifluoroacetic acid (TFA) to give the acid, which is mild enough so that elimnation isn't a big problem. However, please note that TFA does NOT!!! convert thioesters to acids and mild NaOH does NOT!!! convert t-butyl esters to acids. So you have to use the right reagent with the right substrate! MEJ
dear professor: could u please go over the problem for fun....the one with C15H18..THANKS
Dear Whomever, I went over that problem in detail in class on Tuesday. Come to my office if you need more info. MEJ
dear professor: does OBn too big for chelation? and when Li and NH3 (l) to reduce a compound with alcohol inside will the alcohol group being the directing group or it's not a good choose for alcohol group? thanks a lot
Dear Whomever, A benzyloxy group (OBn) is not too big or too electron poor to chelate so it will chelate well. And I don't know of any technique that uses Li/NH3 to reduce 'a compound with alcohol inside'. I think you're talking about the Evans reduction using hydrogen and a cationic metal catalyst and if so, then an alcohol is the preferred group for the 'hydroxyl-directed' hydrogenation. MEJ
dear professor one the hw and and handout, one said VO(acac)3 and other said VO(acac)2 . which one is right? thanks
Dear Unknown Questioner, It's VO(acac)2, the bis(acetylacetonate) vanadyl complex. M. E. Jung
