Setting the Record Straight

OK.  Enough chemistry for now.  I’ve been reading comment after comment in various newspapers (letters to the editor, electronic comments on articles, etc.) from stupid dittoheads saying that the Community Reinvestment Act (CRA) was the cause of the subprime mortgage meltdown and that it should be repealed as part of any bailout bill.  These people are woefully uninformed and actually need to read legislation rather than just repeat some bullshit that a high priced hypocrite tells them.

You can find the actual text of the act here.  The argument I’ve read is that the CRA forced banks to make risky loans to those pesky minorities (why can’t they just rent like they are supposed to?).  This is simply untrue.  The act requires that banks stop the practice of redlining by forcing them to offer loans to people from their entire geographical area (defined by where they have branches).  There have never been quotas detailing how many loans to minorities or low income customers they must make.  If someone is a bad credit risk, they can still be denied a loan at no cost to the bank’s compliance record.  If some banks chose to make risky loans, that was their choice.  They simply were no longer allowed to discriminate on the basis of SES or race (the corollary here is that a low income borrower wouldn’t be able to get as big of a loan for obvious reasons).

Moreover, fully 80% of subprime mortgages originated from financial institutions not covered by the CRA.  Equally damning to the dittohead argument is that subprime lending only intensified (in terms of dollars) after 2004, when the CRA was defanged.

How Many Nitrogens is Too Many Nitrogens? Part I

In a recently published article in ACIEE, a group from – I kid you not – Idaho reports the synthesis of several compounds that contain almost all nitrogen. Needless to say, these compounds are highly explosive and were, um, interesting to work with. Props to the students on this paper, assuming they still have a hand to perform a terrorist fist jab in the first place. This paper has been blogged about elsewhere, but it got me to thinking about other feisty compounds I’ve either heard about or prepared.

The first of these has to be octanitrocubane and its immediate cousin heptanitrocubane. Professor Philip Eaton was the first and maybe the last to prepare these compounds, and I was lucky enough to attend a “retrospective lecture” chronicling his career and life. It was probably the only seminar I’ve ever been to that made me pumped up to do chemistry and go scurrying back up into the lab to set up a bunch of reactions.

Anyway, much like nature makes berries bright red to warn you not to eat them, heptanitrocubane only successfully crystallizes in its anhydrous form from fuming nitric acid slowly diluted with sulfuric acid. Jesus that is the worst recrystallization ever. If that isn’t a warning to stop making the stuff, I don’t know what is. Even Ralph would know to turn heel and run.

My personal favorite is 5-diazotetrazole. Not only is the tetrazole nucleus explosive, so is the 5-aminotetrazole that the diazo compound is prepared from. A friend of mine (seriously, it wasn’t me, I have more sense than to work with this thing!) was trying to displace the diazo group with chloride. They performed the reaction on a tiny scale and still managed to blow a hole in the back of their hood and put a serious hurting on the blast shield they thankfully used. Needless to say, that analogue was set aside for another day. Sometimes that analogue just isn’t worth it…

Finally, there are the “explosive” compounds. The ones where your hands get sweaty and your heart races when you work with them. A short list might include: IBX, metal perchlorates, aryldiazonium salts, azides, and maybe KH, which is more burny than boomy. Anything I’m forgetting?

Reductive Amination Made Associate-Proof

On the flip side of organic chemistry, there are workhorse reactions that seem to work like the old Beetle you see on your block. It is an act of God that the thing still runs, and I feel similarly that this prep has NEVER failed. By failed I mean I got less than a 75% yield and a spot to spot reaction. Yeah, it is that baller.

So, how did I invent this freak of organic chemistry? Well I didn’t invent it, but I don’t have the original paper anymore and I don’t remember the reference, so I suppose I’m taking credit for someone else’s optimization. Well, whoever you are, thank you, thank you from the bottom of my once-was-a-well-paid-industry-associate heart.

The first key is to use sodium triacetoxyborohydride as the reducing agent instead of the evil and stupid sodium cyanoborohydride. That is, unless you like liberating hydrogen cyanide during quench or even upon opening the container, or if you plan on going for a vacation that week since I’ve had reductive aminations take 5-6 days with cyanoborohydride. [1]

The second consideration is the use of the somewhat exotic 1,2-dichloroethane as solvent. I have no idea why this works so much better than other solvents I tried, but it does. Also, it dissolves essentially everything except the tumor it is growing inside you, so you don’t have to worry about whether your pyrazine containing amines will dissolve. Less thinking means more reductive aminations which means more bonus at the end of the year.

The third awesomeness is that you can use amine salts, which are way more stable then their freebase cousins. Also, it means when you deBoc-ed yesterday, you didn’t need to mess around trying to neutralize your precious, water soluble, and volatile amine. Just add a couple equivalents of TEA and dump in the triacetoxyborohydride!

Finally, and probably most importantly, you get to write “STAB” (Sodium TriAcetoxyBorohydride) in your notebook, which, face it, makes everything all better. If you really want to freak your labmates out, start chanting “stab, stab stab” faster and faster as you add the reagent.

Sodium triacetoxyborohydride, the assassin’s choice for reductive aminations.

[1] – however, if you have an amine that only sluggishly forms the requisite iminium, cyanoborohydride is better as it will only very slowly reduce your aldehyde, which STAB will do at a rate that can in a few cases be problematic. Also, I have never tried it to reduce an imine. In those situations, I just form the imine in DCM + MgSO4 from the primary amine and aldehyde and then add sodium borohydride after filtration and solvent-exchange for THF/ethanol.

The Ohira-Bestmann Reaction: Pro or Con?

A major portion of my research on the way to getting a fancy hoodie and sweet-ass piece of paper deals with the reactions of alkynes. For those of you not in the know, an alkyne is what chemists call two carbons with three bonds between them. Think of it as a giant clusterfuck of electrons sandwiched between two carbon nuclei.

But I digress, making these things can be a bit trying and there really aren’t many ways to do it well. However, there is one method for making terminal alkynes that I have a particularly schizophrenic relationship with; the Ohira-Bestmann Homologation.

Sometimes it works, sometimes it doesn’t. You have to make the diazophosphonate from tosyl azide (think explody meets colorless maple syrup). The yields are never as high as you think they will be. If the other method to make alkynes from aldehydes wasn’t the dreaded Corey-Fuchs, I would never run this bitch again.

Stop making up academic subjects!

Clearly the ivory tower has enough interdisciplinary programs of study.  However, if you just can’t get enough, you can find rants, raves, and occasionally a useful word or two about organic chemistry, educational policy, and sociology here.