The low-lying excited singlet states of the keto, enol, and keto-imine tautomers of cytosine have been investigated employing a combined density functional/multireference configuration interaction (DFT/MRCI) method. Unconstrained geometry optimizations have yielded out-of-plain distorted structures of the pi --> pi and n --> pi excited states of all cytosine forms. For the keto tautomer, the DF...

Proton tautomerism is a general phenomenon in organic molecules and plays a vital role in many fields of chemistry and biochemistry. The tautomerism of salicylideneanilines [eq(1)] has attracted a considerable attention because it is closely related to thermoand photochromism. Salicylideneanilines greatly favor the enol form over the cis-keto form in the gas phase. We demonstrate here that the ...

Schiff-base macrocycles that combine keto-enamine and enol-imine tautomers within the same ring were synthesized and characterized. These new macrocycles form host-guest complexes with organic cations and unexpectedly form a lyotropic liquid crystal in organic solvents such as chloroform and toluene.

The title compound, C21H24O9, crystallizes with two independent mol-ecules in the asymmetric unit which are almost centrosymmetrically related to each other. The ethano-ate group in one of the two mol-ecules is disordered over two positions with a site-occupation factor of 0.880 (7) for the major occupied site. In the crystal, the 1,3-diketone group exists in the keto-enol isomeric form due to ...

X-ray analysis reveals that the title Schiff base compound, C(17)H(19)NO(3), possesses both OH and NH tautomeric character in its mol-ecular structure. The occupancies of the enol and keto tautomers are 0.62 (3) and 0.38 (3), respectively. The presence of the minor keto form could not be confirmed from the IR spectrum. The mol-ecule is approximately planar, the dihedral angle between the planes...

Difluoromethanesulfonyl hypervalent iodonium ylides 2 were developed as electrophilic difluoromethylthiolation reagents for a wide range of nucleophiles. Enamines, indoles, β-keto esters, silyl enol ethers and pyrroles were effectively reacted with 2 affording desired difluoromethylthio (SCF2H)-substituted compounds in good to high yields under copper catalysis. The reaction of allyl alcohols w...