Synthetic Organic and Carbohydrate Chemistry, Stereochemistry

Our group's research has two main directions: (i) development of new methods of C-C bond formation using reactions of episulfonium ions and other stabilized cyclic intermediates and (ii) synthesis and applications of optically active cyclopalladated compounds.

(i) Development of New Methods of C-C Bond Formation Using Reactions of Episulfonium Ions and Other Stabilized Cyclic Intermediates

Studies of episulfonium (ESIs, Scheme 1) and other stabilized cyclic intermediates are quite important because their use often allows researchers to improve regio- and stereoselectivity of organic reactions. ESIs are usually generated from the corresponding b-(arylthio)alkyl halides, which are synthesized by addition of ArSCl to alkenes. It has been known for many years that ESIs react with a variety of nucleophiles, including C-nucleophiles(C-Nu). Goals of our studies are to broaden the types of ESIs' precursors (e.g., vinyl ethers, allenes, unsaturated carbohydrate derivatives, etc) and C-nucleophiles capable of reacting with ESIs. Currently, we are applying reactions of ESIs and other stabilized cyclic intermediates to the stereoselective synthesis of C-glycosides and related carbohydrate derivatives.

(ii) Synthesis and Applications of Optically Active Cyclopalladated Compounds

Cyclopalladated compounds (CPCs) have been of a considerable interest since the discovery of the first cyclometallated derivative in 1964. Their chelate structure with one covalent Pd-C bond along with a coordination bond(s) with a heteroatom (N, P, S, As or O) imparts to them a very high air and moisture stability. In general, CPCs possess a number of important properties and have been used in a number of important applications.

Our research is focused on the preparation and applications of new optically active CPCs. First, we synthesize structurally different palladacycles derived from various ligands (e.g., oxazolines, Figure 2). Next, we investigate applications of our chiral CPCs ( i ) for structural modifications of known optically active substrates using the reactivity of the Pd-C bond, ( ii ) as catalysts or precatalysts, ( iii ) as templates in asymmetric synthesis, ( iv ) as resolving agents, and ( v ) as chiral derivatizing agents for enantiopurity determination.

REPRESENTATIVE PUBLICATIONS

Liu, H.; Smoliakova, I. P.; Koikov, L.N. “A One-Pot Synthesis of b - C -Glucopyranosides from exo -Glucal, p -Tolylsulfenyl Chloride, an a -Methoxyalkene and an External Nucleophile.” Org. Lett. 2002 , 4 , 3899-3902.

Koikov, L. N.; Smoliakova, I. P.; Liu, H. “One-Pot Synthesis of C -Glycosides from D-Glucal, p -TolSCl and Aromatic/Heteroaromatic Compounds in the Presence of Lewis Acids.” Carbohydrate Res. 2002 , 337 , 1275-1283.

Peterson, D.; Keuseman, K. J.; Kataeva, N. A.; Kuz'mina, L. G.; Howard, J. A. K.; Dunina, V. V.; Smoliakova, I. P. “Homochiral Cyclopalladated Complexes of ( S )- tert -Butyl-2-phenyl-2-oxazoline. X-Ray Study of ( S,S )-di- m -chlorobis-{2-[2-(4- tert -butyl)oxazolinyl]phenyl-C,N}dipalladium(II).” J. Organometal. Chem. 2002 , 654 , 66-73.

Liu, H.; Smoliakova, I.P. Stereoselective Synthesis of b - C -D-Glucopyranosides Using the Reaction of TMSCN and Grignard Reagents with Cyclic Five-Membered Sulfonium Salt Intermediates. Tetrahedron 2001 , 57 , 2973-2980.

Smoliakova, I.P.; Keuseman, K.J.; Haagenson, D.; Wellmann, D.M.; Colligan, P.B.; Kataeva, N.A.; Churakov, A.V.; Kuz'mina, L.N.; Dunina, V.V. “Direct ortho -Palladation of 2-Phenyl-2-oxazoline.” J. Organometal. Chem . 2000 , 603 , 86-97.

Smoliakova, I.P. "Synthesis of C -Glycosylic Compounds Using Three-Membered Cyclic Intermediates (Review)." Current Org. Chem. 2000 , 4 , 563-582.