Latest News:

12/22/14 - Congratulations to Claire Filloux for a successful defense of her Ph.D. thesis.


10/31/14 - Congratulations to Kerem Ozboya for successfully defending his Ph.D. thesis. Kerem will be moving on to a post-doctoral fellowship position in the Nicewicz group.


09/22/14 - Congratulations to Jamie Neely for successfully defending her Ph.D. thesis. Jamie will will joining the Chirik group as a post-doctoral fellow.

RECENT PUBLICATIONS:


Enantioselective Rhodium-Catalyzed Isomerization of 4-Iminocrotonates: Asymmetric Synthesis of a Unique Chiral Synthon

Wen-Zhen Zhang, John C. K. Chu, Kevin M. Oberg, Tomislav Rovis

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, ASAP (2015)

                                                        

An enantioselective isomerization of 4-iminocrotonates catalyzed by a rhodium(I)/phosphoramidite complex is described. This reaction uses widely available amines to couple with 4-oxocrotonate to provide a convenient access to a central chiral building block in good yield and high enantioselectivity. Although the mechanism of this new transformation remains unclear, both Rh and the phosphoramidite play a central role.


Ligand design for Rh(III)-catalyzed C–H activation: an unsymmetrical cyclopentadienyl group enables a regioselective synthesis of dihydroisoquinolones

Todd K. Hyster, Derek M. Dalton, Tomislav Rovis

CHEMICAL SCIENCE, 6, 254-258 (2015)

                                                    

We report the regioselective synthesis of dihydroisoquinolones from aliphatic alkenes and O-pivaloyl benzhydroxamic acids mediated by a Rh(III) precatalyst bearing sterically bulky substituents. While the prototypical Cp* ligand provides product with low selectivity, sterically bulky Cpt affords product with excellent regioselectivity for a range of benzhydroxamic acids and alkenes. Crystallographic evidence offers insight as to the source of the increased regioselectivity.


Rh(I)-Bisphosphine-Catalyzed Asymmetric, Intermolecular Hydroheteroarylation of α-Substituted Acrylate Derivatives

Claire M. Filloux, Tomislav Rovis

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, ASAP (2014)

                                                        

Asymmetric hydroheteroarylation of alkenes represents a convenient entry to elaborated heterocyclic motifs. While chiral acids are known to mediate asymmetric addition of electron-rich heteroarenes to Michael acceptors, very few methods exploit transition metals to catalyze alkylation of heterocycles with olefins via a C–H activation, migratory insertion sequence. Herein, we describe the development of an asymmetric, intermolecular hydroheteroarylation reaction of α-substituted acrylates with benzoxazoles. The reaction provides 2-substitued benzoxazoles in moderate to excellent yields and good to excellent enantioselectivities. Notably, a series of mechanistic studies appears to contradict a pathway involving enantioselective protonation of a Rh(I)–enolate, despite the fact that such a mechanism is invoked almost unanimously in the related addition of aryl boronic acids to methacrylate derivatives. Evidence suggests instead that migratory insertion or beta-hydride elimination is enantiodetermining and that isomerization of a Rh(I)–enolate to a Rh(I)–heterobenzyl species insulates the resultant α-stereocenter from epimerization. A bulky ligand, CTH-(R)-Xylyl-P-Phos, is crucial for reactivity and enantioselectivity, as it likely discourages undesired ligation of benzoxazole substrates or intermediates to on- or off-cycle rhodium complexes and attenuates coordination-promoted product epimerization.


Catalysis Using Sustainable Metals - Part I

Matthew Gaunt, Tomislav Rovis, Hak-Fun Chow

SYNLETT, 25, 2715-2716 (2014)

                                                    

The discovery of new catalytic reactions involving the use of abundant, inexpensive and sustainable metal complexes has enjoyed a resurgence of activities in recent years. This Cluster, Part I of a two-part series, focuses on new research findings from several prominent research groups, highlighting the rich diversities of new chemistry that can be originated from the use of sustainable metals in catalytic reactions.


Enantioselective N-Heterocyclic Carbene-Catalyzed β-Hydroxylation of Enals Using Nitroarenes: An Atom Transfer Reaction That Proceeds via Single Electron Transfer

Nicholas A. White, Tomislav Rovis

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 136, 14674-14677 (2014)

                                              

A novel oxidative N-heterocyclic carbene-catalyzed reaction pathway has been discovered. Alkyl and aryl enals undergo β-hydroxylation via oxygen atom transfer from electron-deficient nitrobenzenes, followed by trapping of the resultant acyl azolium by the solvent. The proposed mechanism involves a single electron transfer event to initiate the reaction followed by radical recombination. This represents a profound mechanistic departure from the established two-electron disconnects in NHC catalysis.