A bit of labwork
From August 2008 comes this gem of labwork from
Org Prep Daily:
This phosphine will get you fired
Beautiful asymmetric transition metal-catalysed chemistry with phosphine ligands chiral on phosphorus dates back to Knowles and Mislow. But these P-stereogenic homochiral phosphines are usualy harder to make, so they were eventually supplanted by ligands with chirality on carbon. As a freshman I used to work for a young assistant prof in Prague - and since I was very interested in asymmetric synthesis, he suggested that I could do a thesis work with him on these ligands; We would put some chiral but racemic phosphine building block onto optically active binaphtyl piece derived from BINOL, and we would get BINAP-like ligands with both axial chirality and chirality on phosphorus. We would then try to separate the stereoisomers and see which one worked better in Rh and Ru-catalysed asym hydrogenations, and we would try to interconvert the stereoisomers to see how the kinetic vs thermodynamic induction control looks like, etc. (Chiral phosphines are conformationally labile on phosphorus above 100C whereas the 2,2′-disubst binaphtyl pieces are fairly stable and should not racemize).
The author describes the synthesys and then makes mention of the odor:
But I never encountered anything as nauseating or alien like PhePHMe: The memory is stil with me - the most sickly and sweetish smell of rancid gasoline combined with rotten water melons, with undertones of stale sweat, pig carcass, a hint of garlic, moldy oranges, russian-made aftershave and a cheap household air freshener� its a whole package, and rather sweet one � like isonitriles or cyclopentadiene but magnified thousand times. A whiff of that thing and you feel that your nose just suffered a stroke and will hopefully die and peal off so that you never smell that thing again. Inconceivable - and it does not get any better when wearing off; quite opposite in fact � just like with butyric or isovaleric acid, the reek is developing a more alarming depth and complexity with the dilution.
I had a run-in with Butyric Acid and that memory is still very much with me. Cannot imagine something worse...
Posted by DaveH at May 9, 2013 12:04 PM