Research in the RajanBabu lab is focused on development of new methodology for stereoselective synthesis. Major research areas include:
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RajanBabu developed methodology surrounding C-C bond formation via metal-catalyzed hydroformylation. They reported several asymmetric examples through the usage of chiral phosphine ligand with a hemilabile coordinating group. This method was applicable using vinylarenes, 1,3-dienes and strained olefins as substrates. Applications of this chemistry include a new synthesis of (S)-ibuprofen and a new approach to controlling the exocyclic side-chain stereochemistry in helioporin D and pseudopterocins. Related to this methodology, RajanBabu also developed a tandem [2+2] cycloaddition/asymmetric hydrovinylation reaction to allow conversion of simple precursors (ethylene, enynes) to structurally complex cyclobutanes.
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The RajanBabu group developed methodology in the area of hydrocyanation, leveraging the reaction of vinylarenes with HCN in the presence of Ni(0) complexes. Based on the phosphorus ligands within the Ni complex, the reaction can be rendered asymmetric. The enantioselectivity could be further improved by tuning the electronics of the phosphine ligands to electronically differentiate the phosphorus chelates. Electronic tuning was accomplished, for example, using widely available sugars such as D-glucose and D-fructose.
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For further information on the Nugent-RajanBabu reagent, please see Bis(cyclopentadienyl)titanium(III) chloride.
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One area of interest to the RajanBabu group is catalytic multicomponent addition/cyclization reactions. This methodology allows for formation of carbocyclic and heterocyclic compounds from acyclic precursors including unactivated olefins and acetylenes. This method leverages the reactivity of bifunctional reagents (X-Y) where X-Y in above scheme can represent RSi−SiR‘, RSi−SnR‘, RSi−BR‘, RSn−BR‘, and trialkylsilicon- and trialkyltin- hydrides. The reactions are palladium-catalyzed, and incorporation of the X and Y species allows for vast diversification of the end products. Application of this methodology afforded syntheses of highly alkylated indolizidines such as IND-223A.
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RajanBabu has evaluated asymmetric aziridine openings with high enantioselectivity using yttrium- and lanthanide- salen complexes. The RajanBabu group has also developed water-soluble Rhodium(I) complexes, allowing for reactions to be run in aqueous media.