In
the many scientific endeavors that are driven by organic chemistry,
unambiguous identification of small molecules is of paramount importance.
Over the past 50 years, NMR and other powerful spectroscopic techniques
have been developed to address this challenge. While almost all of
these techniques rely on inference of connectivity, the unambiguous
determination of a small molecule’s structure requires X-ray
and/or neutron diffraction studies. In practice, however, X-ray crystallography
is rarely applied in routine organic chemistry due to intrinsic limitations
of both the analytes and the technique. Here we report the use of
the electron cryo-microscopy (cryoEM) method microcrystal electron
diffraction (MicroED) to provide routine and unambiguous structural
determination of small organic molecules. From simple powders, with
minimal sample preparation, we could collect high-quality MicroED
data from nanocrystals (∼100 nm, ∼10–15 g) resulting in atomic resolution (<1 Å) crystal structures
in minutes.
<p>In the many scientific endeavors that are driven by organic chemistry, unambiguous identification of small molecules is of paramount importance. Over the past 50 years, NMR and other powerful spectroscopic techniques have been developed to address this challenge. While almost all of these techniques rely on inference of connectivity, the unambiguous determination of a small molecule’s structure requires X-ray and/or neutron diffraction studies. In practice, however, x-ray crystallography is rarely applied in routine organic chemistry due to intrinsic limitations of both the analytes and the technique. Here we report the use of the CryoEM method MicroED to provide routine and unambiguous structural determination of small organic molecules. From simple powders, with minimal sample preparation, we could collect high quality MicroED data from nanocrystals (~100x100x100 nm, ~10<sup>–15</sup>g) resulting in atomic resolution (<1 Å) crystal structures in minutes.</p>
Here we apply microcrystal electron diffraction (MicroED) to the structural
determination of transition-metal complexes. We find that the simultaneous use of 300
keV electrons, very low electron doses, and an ultrasensitive camera allows for the
collection of data without cryogenic cooling of the stage. This technique reveals the
first crystal structures of the classic zirconocene hydride, colloquially known as
“Schwartz’s reagent”, a novel Pd(II) complex not amenable to
solution-state NMR or X-ray crystallography, and five other paramagnetic and diamagnetic
transition-metal complexes.
The first enantioselective Pd-catalyzed decarboxylative allylic alkylation of fully substituted N-acyl indole-derived enol carbonates generates acyclic all-carbon quaternary stereocenters in excellent yields (up to 99%) and enantioselectivities (up to 98% ee) using a new electron-deficient phosphinoxazoline (PHOX) ligand.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.