On Break

As I’m sure regular visitors have noticed, things haven’t been too exciting around here for a while. In lieu of boring you with all the gory details, I’ll just say that MGW is going on a little “break” for the time being. Regular posting should resume sometime in the summer. Until then, enjoy this. LSD optional.

WNPS Solution

The chemistry world can be a very small place. Last semester, for example, I TA’ed for a professor who had my undergrad organic professor as her organic TA in undergrad. What does this have to do with Wednesday’s problem? To put it plainly, I don’t remember ever learning oxymercuration from the aforementioned prof. In all fairness to RBG I spent many hours asleep in that class, having it a mere eight hours after the 12-4am dorm night-desk shift. Still though, before last semester, mercury was basically the element that filled thermometers to me and little else. But Wednesday’s problem demonstrates that under the right conditions, mercury can do magic!

The cornerstone of the problem is the Ritter reaction, in which an isonitrile attacks an electrophile before being attacked by some nucleophile (classically, water) at carbon. The overall transformation leads to substituted amides in the classical case, but with other nucleophiles around, interesting architectures can fall out. In Stevens’s case, mercury-mediated fragmentation of the pinene skeleton generated both the electrophile (a carbocation) and the nucleophile (a double bond) in one fell swoop! The fragmentation can be rationalized by the release of ring strain associated with the starting cyclobutane. Attack by the isonitrile and trapping by the alkene, with loss of mercury to form the exocyclic alkene, leads to the intermediate X, an imine. The imine is then reduced on its top face to form the final product. Stevens makes a big deal of the reduction stereochemistry in the paper, although it makes sense to me considering the “roof-like” bicyclic structure of the imine.

Same time, same place, next week…be there or be square.

WNPS: How I Learned to Stop Worrying and Love Carbocations

Tonight’s problem comes once again from Harvard’s challenging organic problems website.

In the early 1980’s, Robert Stevens’s group at UCLA studied nucleophilic additions to and reductions of tetrahydropyridiniums, which could potentially yield alkaloid products. Actually getting to these cyclic imines and iminium ions in the first place can be an interesting exercise in arrow-pushing. It certainly was in the case of makomakine, which the Stevens group made from beta-pinene in only two steps! Barret Valentine would be proud.

Mercuric ion, being a Lewis acid, does interesting things with that double bond to start things off. From there, the arrows get crazy! See if you can draw a mechanism for the transformations below and come up with the intermediate X. One million EXP if you can!

From the Lab to the Court

As an avid Kentucky basketball fan, I guess it’s about time for me to weigh in on this year’s season. What better time than after a spectacular win against a solid Creighton club (that jumped on all of our idiotic mistakes)?

Ironically, we have more wins right now than we would have had if we’d made the NCAA tournament. And I’m OK with that–to me, the longer the season goes, the better. The NIT has given our young guys like Darius Miller and DeAndre Liggins a chance to mature, and stars like Patterson and Meeks a chance to experience the glory of collegiate tournament basketball, which, if you ask me, beats the hell out of an early exit to the NBA any day.

A lot of people in Lexington have been blaming Billy Gillispie for our recent woes. I haven’t watched enough of UK’s games this year to comment on his coaching style, which has earned the disdain of many a basketball expert, but I can’t say I have a problem with the guy. The problem with UK basketball transcends Gillispie and even the players themselves. Rupp Arena, these days, is basically a stinkhole of old farts (and old money) and useless, pathetic fans. Coming to Illinois and watching a season in Assembly Hall has proven this to me.

Imagine coming from Lexington, Kentucky, and watching a talentless squad struggle against Lewis University (who?) in their second exhibition game of the season. Sounds like a long season, right? Basketball was supposed to be one of my few releases from chemistry, and at that point, it was looking like just another chore. And yet, four months later, that same talentless team finished second in the Big Ten and earned an NCAA tournament berth, which is more than Kentucky can say. And I give just as much credit to the fans in Assembly Hall as I do to Bruce Weber and the team for their impressive year. The team came together and they learned how to win in spite of their weaknesses. They played fierce defense and made shots when they mattered…and behind them every step of the way was another chorus of “Oskee Wow Wow” or a rousing “ILL-INI” cheer. Coincidence? Absolutely not!

Contrast this scenario with the situation at Kentucky, a squad jam-packed with basketball talent but lacking the passion, chemistry, and desire to win basketball games. That all starts with the fans. Although the astronomical expectations in Lexington have not changed, the average fan’s relationship with these expectations has: raucous cheers have been replaced by groans and whining. The players and coaching staff can sense that, and it rubs off on them. The whole “southern basketball tradition” bullshit is getting old, and it’s certainly not winning basketball games!

All that said, I’m pleased with how the season’s gone overall. It seems to me the entire team and coaching staff just got lazy towards the end of the season–the team peaked early. That happens. But as the talent level at Kentucky continues to rise (thanks to Gillispie’s superb recruiting, which is something BG haters should consider), seasons in the upcoming decade like ‘08-’09 should be (and will be) considered intolerable. No reason to worry about the future til it gets here, though!

WNPS Solution

Wednesday night’s problem featured a variant of the venerable Staudinger reaction, which can be used to reduce azides to amines or generate iminophosphoranes which can participate in aza-Wittig reactions, which form imines rather than alkenes. The reactivity of azides is apparently more subtle than one might think, if this reaction has anything to say about it.

In the presence of base and electrophilic phosphorus, substitution first takes place to generate a phosphite. The phosphite then attacks the “hanging” nitrogen of the azide, which neutralizes the central nitrogen and leaves the phosphorus poised for attack by the negatively charged azide nitrogen, which generates the heterocycle shown (what would the name of this heterocycle be…?). Retro [2+2] cycloaddition from this dihydrotriazaphosphete releases nitrogen gas and gives the “curious intermediate” alluded to, an iminophosphorane. [3,3] sigmatropic rearrangement then generates the product.

The selectivity for the E olefin can be rationalized by a six-membered transition state that places the methyl group equatorial.

Interesting stuff! Tune in next week for another Wednesday Night Problem Session…