Andro to TNE...Spidey??

[spidey]

You are reducing andro with NaBH4, right? You will end up with some over-reduced diol. The MnO2 (Mn(IV)oxide) will oxidize the diol in your product mixture to TNE.

So, no, you don't "need" it if you are willing to settle for some amount of androstenediol in your product.

[candle25]

My first attempt at this went aweful. I spilled lots of the crude product during the filtration process. Gravity filtration of this is impossible so I ended up using a vacume filter. My kitchen stank of evaporated MeOH & the acetic fumes burned my eyes. This isn't something to attempt without the proper equipment! My yield in the end was only around 2.5g of a white, epoxy type material. For MP testing I used Ethylene Glycol since its BP is 199C and pure Test's MP is 155C. The melting range of my product was 125C-127C which means that I didn't make TNE at all .

I did the experiment just as I have it written out in the first post. I don't understand what went wrong. Maybe my glassware wasn't clean anough? Maybe the temp that I did the reaction at? Everything seemed to go well untill the MeOH evaporation process. I had to get a rolling boil just to get it to evaporate. A white foam formed around the edges of my evap dish while I was evaporating the MeOH. You have any suggestions Spidey? Anyone? I have plenty of the chems left, so I can do it several more times.

[candle25]

I did a little more research today and found that NaBH4 degrades quickly in MeOH. I also found that NaBH4 is stable in EtOH. Would it then be better to react the Andro & NaBH4 in EtOH? I really want to try this again, but I need to have it nailed down before I attemt it. I also ordered 15g Mn (IV) Oxide yesterday. So if I need to redissolve the crude product in dichloromethane and treat it with the Mn.

Found this as well:
"Chemoselective Reductions with Sodium Borohydride. Aldehydes vs. Ketones." D. E. Ward and C. K. Rhee, Synthetic Communications, 1988, 18, 1927-1933.

Abstract: Aldehydes can be reduced in the presence of ketones by sodium borohydride in 30% ethanol in dichloromethane at -78 C. The selectivity is generally greater than 95%.

"A General Method for the Selective Reduction of Ketones in the Presence of Enones." D. E. Ward, C. K. Rhee, and W. M. Zoghaib, Tetrahedron Letters, 1988, 29, 517-520.

Abstract: Ketones can be reduced in the presence of conjugated enones by sodium borohydride in 50% methanol in dichloromethane at -78 °C. The selectivity is generally excellent. In favorable cases the reaction can be carried out at room temperature in dichloromethane with acetic acid as catalyst.

[spidey]

Originally posted by candle25
My first attempt at this went aweful. I spilled lots of the crude product during the filtration process. Gravity filtration of this is impossible so I ended up using a vacume filter. My kitchen stank of evaporated MeOH & the acetic fumes burned my eyes. This isn't something to attempt without the proper equipment! My yield in the end was only around 2.5g of a white, epoxy type material. For MP testing I used Ethylene Glycol since its BP is 199C and pure Test's MP is 155C. The melting range of my product was 125C-127C which means that I didn't make TNE at all .

I did the experiment just as I have it written out in the first post. I don't understand what went wrong. Maybe my glassware wasn't clean anough? Maybe the temp that I did the reaction at? Everything seemed to go well untill the MeOH evaporation process. I had to get a rolling boil just to get it to evaporate. A white foam formed around the edges of my evap dish while I was evaporating the MeOH. You have any suggestions Spidey? Anyone? I have plenty of the chems left, so I can do it several more times.

Just because your melting point was low doesn't mean you didn't have some product. It just means it wasn't pure.

NaBH4 is not completely stable in ethanol either but it is more stable in ethanol than methanol.

Do you have analytical TLC plates? You really need some way of judging when your reaction is complete.

[candle25]

No. I have no TLC plates. Are they expensive? I might buy some if they don't cost too much. Do you think that I didn't let it react long enough? I can let it react longer next time. Thanks for helping out with this experiment. You are the only person on 4 boards that pays any attn to chem related questions.

[spidey]

I would buy the aluminum backed flexable plates you can cut with scissors. They are generally bought as packs of 25 (25x25cm) and I can get 24 individual TLC plates from one 25cmx25cm sheet.

The cost from Fisher Scientific is $132.14. That may seem expensive but not when you consider that is 600 individual TLC plates when you cut them up. That should be a lifetime supply for you.

Catalog number is M5554-7 for Silica gel-60 TLC plates, packs of 25 sheets with fluorescent indicator.

To do TLC, you will need a clear jar with a lid to use as the developing chamber and a staining agent or UV-lamp.

10% KMnO4 in water will do as a staining agent. You dip the developed plate in the KMnO4 solution and then heat with a heat-gun or hot-plate until the spots show up as yellow spots on a pink or maroon background. Careful not to overheat or the whole plate will turn yellow and you won't be able to see anything.

If you need detailed directions on how to use TLC to check the progress of your reaction, let me know.

[candle25]

I might be able to order them through my job and write it up as a lab expense. The only problem I see with this method is that it is starting to become unpracticle. The expenses for all the reagents and tools I have bought (well had bought..lol) for this experiment are getting to be higher and higher. I personally have a small, decent lab at home, but I doubt the average guy will have all the equipment that you or I have access to. I'll look into the plates and post back when I get them. I was reading in an organic sythisis book yesterday at work about how to use TLC plates to tell if a reaction is completed. If I have any questions I'll post them as well.

[spidey]

Think about it like this:

It is expensive initially but the equipment and reagents you buy are enough to make enough AS for literally dozens of cycles. How much would you spend buying the AS from a source for 12 cycles?