Bipyridyls optical resolution

It was pointed out that the ultra-violet spectra of 2-arylpyridine quaternary salts and 1-oxides indicate the presence ofsteric inhibition of resonance, and the same is true of those of 4-aryl-3,5-diethoxycarbonyl-2,6-lutidines4 . These examples recall, of course, the hindered diphenyls, and in pursuing the similarity a number of attempts have been made to achieve optical resolutions of suitably substituted arylpyridines . Success was achieved with the 3,3 -bipyridyl (68), and salts of (69) with different rotations were... 

The double proton transfer of [2,2 -Bipyridyl]-3,3 -diol is investigated by UV-visible pump-probe spectroscopy with 30 fs time resolution. We find characteristic wavepacket motions for both the concerted double proton transfer and the sequential proton transfer that occur in parallel. The coherent excitation of an optically inactive, antisymmetric bending vibration is observed demonstrating that the reactive process itself and not only the optical excitation drives the vibrational motions. We show by the absence of a deuterium isotope effect that the ESIPT dynamics is entirely determined by the skeletal modes and that it should not be described by tunneling of the proton. 

One example is the optically active amino acid derivative (S)-20n which contains a bipyridyl substituent (Scheme 3.14). The alkylation reaction in the presence of the cinchona alkaloid catalyst 33 proceeds with 53% ee (83% yield of (S)-20n) and gave the desired enantiomerically pure a-amino acid ester (S)-20n in >99% ee after re-crystallization [43]. Subsequent hydrolysis of the optically pure (S)-20n furnished the desired unprotected a-amino acid 35. A different purification method, subsequent enzymatic resolution, reported by Bowler et al., furnished the a-amino acid product 35 with enantioselectivity of 95% ee [44],... 

This appreciation led to a rapid increase in the range of resolved chelated ions, like [Fe(bipyridyl)3]2+ or [Co(C204)3]. However, the "hexol" remained the only resolved inorganic molecide until Fr erick G. Mann (27) in 1933 achieved the resolution of the anion ds-[Rh(HNS02NH)2(0H2)2] using the cation of an optically... 

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