However, unlike Delfourne et al. my final product wasn't clean after a simple work up. Succinimide was simply precipitating everywhere and hence some silica was required. In the end a filtration through a silica plug proved sufficient to give clean product on a reasonably large scale (18 grams) in excellent yield (97%). So despite the fact that a simple work up wasn't sufficient to clean the product up this is an easy to do reaction that I would recommend to anyone who's tired of stinky old Swern. D!
This blog is devoted to the discussion of all aspects of synthetic organic chemistry and related sciences. Curly Arrow is run by a synthetic organic chemist based in Copenhagen, Denmark. Contributions from readers are always welcome and should be emailed to curlyarrow@gmail.com
Friday, April 20, 2007
Tempo Oxidations Part II
However, unlike Delfourne et al. my final product wasn't clean after a simple work up. Succinimide was simply precipitating everywhere and hence some silica was required. In the end a filtration through a silica plug proved sufficient to give clean product on a reasonably large scale (18 grams) in excellent yield (97%). So despite the fact that a simple work up wasn't sufficient to clean the product up this is an easy to do reaction that I would recommend to anyone who's tired of stinky old Swern. D!
Monday, April 16, 2007
Fun with singlet oxygen
Now the above reaction is obviously totally irresponsible and was only on for less than a minute so that I could take the picture. We are dealing with a fancy piece of glassware that has oxygen bubbling through it whilst two flood lamps are hammering photons away generating singlet oxygen and in the process heating the fume hood up big time. Hence, aluminium foil on the bottom of the hood is required to literally avoid a melt down and I'll be hooking a pump up that sends ice water through the cooling jacket. Moreover, I'm synthesising an endoperoxide - AAaARRRrGGGHhHh PEROXIDE - yeah I know but they are really quite stable. In fact our friends at the defence force haven't been able to blow them up so we aren't too worried. However, to avoid any nasty surprises we try not to make more than 5-10 grams of endoperoxides at any time. So as I said totally irresponsible hence I proceed to wrap this beautiful reaction up in two blasts shields covered in aluminum foil, pull the sash down and hook a cooling box/pump up to the glass ware and the final set up looks like this:
Well at least I know it's beautiful behind all that plastic and aluminium foil. This particular day I was doing the following photolysis:
Reactions of this type generally work quite well giving yields in the 40-70% range and since dienes are easily accessible using classic Wittig chemistry we consider making endoperoxides quite trivial. So why was I making this particular endoperoxide? Well if I told you I would have to kill you. There should be a paper coming out later this year featuring amongst others this particular endoperoxide turning into a supa cool cyclopropane in one (yes one) synthetic step so keep your eyes open for that paper. Some of you are probably wondering what Rose Bengal is. Behold the halogenated beast:We tend to use the bis-triethyl ammonium salt (as shown) because it is nicely soluble in organic solvents such as dichloromethane. D!