Research Interests:
1) C–C Bond Activation. Our long-term goal is to greatly extend the regime of C−C activation to a wide range of organic compounds and enable synthetically useful transformations.
(a) “Cut & Sew”: Bridged/fused rings can be accessed by employing a transition metal to first regioselectively cleave a cyclic C–C bond, followed by an intramolecular insertion of an unsaturated bond, and finally, reductive elimination to afford the desired ring system. Such a “Cut & Sew” sequence would result in reorganization of bond connections and lead to novel molecular structures with high complexity. We expect that, by changing ring-sizes, linker-lengths and unsaturated unit-types, a great diversity of scaffolds that are difficult to access by conventional methods would be afforded using a single approach.
(b) Less strained ketones: Recently, progress has been made for C−C activation of common unstrained ketones, such as cyclopentanones, cyclohexanones and linear ketones.
(c) Cleavage of Unstrained Aryl-Aryl Bonds.We have developed a general approach for catalytic activation of the unstrained C(aryl)−C(aryl) bonds in 2,2’-biphenols.
2) Byproduct-Free Ketone Alkylation. Alkylation of carbonyl compounds is one very important way to form carbon-carbon bonds. Conventionally, toxic and expensive alkyl halides are employed as alkylating agents in combination with strong basic conditions, typically generating stoichiometric halogen-containing byproducts during reactions.We developed a bifunctional catalytic system that utilizes enamine-transition metal cooperative interactions to enable direct ketone alkylation with simple olefins as the alkylating agents.
3) Non-Directed β-Functionalization of Carbonyl Compounds. Conventionally, β-C−C forming reactions largely rely on conjugate addition of a soft nucleophile (e.g. organocuprates) to an α,β-unsaturated carbonyl substrate (e.g. conjugated enones) with or without a transition-metal (TM) catalyst. While effective, this approach typically requires unsaturated carbonyls and metalated nucleophiles. A Pd-catalyzed redox cascade approach has been developed, which can directly functionalize the β-position of carbonyl compounds. This approach merges Pd-catalyzed desaturation, C−X bond activation and conjugate addition.
4) Exo-type Directing Group for Site-selective C−H Activation. To achieve site-selective functionalization of unactivated aliphatic C−H bonds in alcohols and amines, we are exploring a new class of exo-type directing groups (DGs) that can be easily installed and removed from alcohol and amine substrates. In addition, we have illustrated the use of a temporary and catalytic exo-DG in direct γ and δ-arylation of free amines.
5) Palladium/Norbornene Catalysis.Palladium/norbornene (Pd/NBE) cooperative catalysis, also known as the Catellani-type reactions, holds promise for streamlining synthesis of poly-substituted arenes, as it can directly couple an electrophile as the ortho position and a nucleophile at the ipso position of arene simultaneously. In the past, the applicability of this method has been largely hampered by three constraints: 1) the type of electrophiles that can be employed as previously only alkyl and certain aryl electrophiles could be used; 2) the use of aryl iodides as substrates (as use of more readily available aryl bromides was generally not effective); and 3) the requirement of an ortho substituent on aryl-halides for mono ortho functionalization. Since 2012, efforts have been made here to address these constraints through in-depth mechanistic understanding, including discoveries of new classes of electrophiles, new ligand systems and new norbornene cofactors.
6) Total Synthesis and Drug Discovery. We have been interested in synthesis of structurally complex and biologically important natural products, specifically those with potent anti-cancer and immunosuppressive properties. Our long-term goal is to understand their mechanism of action and structure-activity relationship to ultimately facilitate drug discovery.
7) Polymer Chemistry. We have been interested in developing new polymerization approaches to prepare functionalized polymers. Utilizing the power of palladium/norbornene catalysis, we have developed an in situ-functionalization strategy, namely an A2B2C polymerization, for preparing poly-substituted aromatic polymers.
A bottom-up, simple “tri-aryl” approach has been developed for solution-phase preparation of atomically precise armchair graphene nanoribbons with tunable bandgaps.
Selected References
Zhou, Xuan; Dong, Guangbin* “(4+1) vs (4+2): Catalytic Intramolecular Coupling between Cyclobutanones and Trisubstituted Allenes via C−C Activation” J. Am. Chem. Soc., 2015, 137, 13715-13721.
Lim, Hee Nam; Dong, Guangbin* “Catalytic Intramolecular Ketone Alkylation with Olefins via Dual Activation” Angew. Chem. Int. Ed. 2015, 54, 15294-15298.
Xu, Yan; Yan, Guobing; Ren, Zhi; Dong, Guangbin* “A Unified Strategy for Diverse Functionalization at Alcohol β-Position” Nature Chemistry, 2015, 7, 829-834.
Thompson, Samuel J.; Thach, Danny Q.; Dong, Guangbin* “Cyclic Ether Synthesis via Palladium-catalyzed Alcohol-mediated Dehydrogenative Annulation at Unactivated Terminal Positions” J. Am. Chem. Soc., 2015,137, 11586-11589.
Ko, Haye Min; Dong, Guangbin* “Cooperative activation of cyclobutanones and olefins leads to bridged-ring systems by a catalytic [4+2] coupling” Nature Chemistry, 2014, 6, 739-744.
Mo, Fanyang; Dong, Guangbin* “Regioselective Ketone α-Alkylation with Simple Olefins via Dual Activation”,Science, 2014, 345, 68–72.
Dong, Zhe; Dong, Guangbin* “Ortho vs Ipso: Site-Selective Pd and Norbornene-Catalyzed Arene C–H Amination Using Aryl Halides” J. Am. Chem. Soc., 2013, 135, 18350-18353.
Huang, Zhongxing; Dong, Guangbin* “Pd-Catalyzed Direct β–Arylation of Simple Ketones with Aryl Halides”Journal of the American Chemical Society, 2013, 135, 17747-17750.
Xu, Tao; Dong, Guangbin* “Rh-Catalyzed Lewis Acid-Promoted Regioselective Carboacylation of Olefins: A C–C Activation Approach to Access Fused-Ring Systems” Angew. Chem. Int. Ed., 2012, 51, 7567–7571.
Ren, Zhi; Mo, Fanyang; Dong, Guangbin* “Catalytic Functionalization of Unactivated sp3 C–H Bonds via exo-Directing Group: Synthesis of Chemically Differentiated 1,2-Diols” J. Am. Chem. Soc., 2012, 134, 16991-16994.