More Like this

1. Diastereodivergent synthesis of 4-oxocyclohexanecarbaldehydes by using the modularly designed organocatalysts upon switching on their iminium catalysis

   https://doi.org/10.1039/D1CC01020D  

   Bora, P.; Jakkampudi, S.; Parella, R.; Sakkani, N.; Dai, Q.; Bihani, M.; Arman, H. D.; Zhao, J. C.-G. (January 2021, Chemical communications)

   null (Ed.)

   The cinchona thiourea moiety in the self-assembled modularly designed organocatalysts (MDOs) switches off the iminium catalysis of these catalysts. In this study, it was found that the inhibited iminium catalysis could be switched on by using an appropriate weak acid and that, once the iminium catalysis was switched on, these catalysts could be applied for the highly stereoselective and diastereodivergent synthesis of 4-oxocyclohexanecarbaldehydes via a domino reaction between ketones and α,β-unsaturated aldehydes. 

   more » « less
2. Stereoselective synthesis of chromane derivatives via a domino reaction catalyzed by modularly designed organocatalysts

   https://doi.org/10.1039/c8ob02677g  

   Jakkampudi, Satish; Parella, Ramarao; Zhao, John C.-G. (January 2019, Organic & Biomolecular Chemistry)

   A highly enantio- and diastereoselective method for the synthesis of functionalized chroman-2-ones and chromanes was achieved by using an organocatalytic domino Michael/hemiacetalization reaction of aliphatic aldehydes and ( E )-2-(2-nitrovinyl)phenols followed by a PCC oxidation and dehydroxylation, respectively. Using the modularly designed organocatalysts (MDOs) self-assembled from cinchona alkaloid derivatives and amino acids in the reaction media, the title products were obtained in good to high yields (up to 97%) and excellent diastereoselectivities (up to 99 : 1 dr) and enantioselectivities (up to 99% ee). 

   more » « less
3. Diastereodivergent Synthesis of Bridged Tetrahydroisoquinoline Derivatives Catalyzed by Modularly Designed Organocatalysts

   https://doi.org/10.1002/adsc.202000227  

   Jakkampudi, Satish; Konda, Swapna; Arman, Hadi; Zhao, John_C‐G (April 2020, Advanced Synthesis & Catalysis)

   Abstract The diastereodivergent synthesis of bridged 1,2,3,4‐tetrahydroisoquinoline derivatives has been achieved by using appropriate modularly designed organocatalysts (MDOs) that are self‐assembled in situ from amino acids and cinchona alkaloid derivatives. The domino Mannich/aza‐Michael/aldol reaction between (E)‐2‐[2‐(3‐aryl‐3‐oxoprop‐1‐en‐1‐yl)phenyl]acetaldehydes and ethyl or benzyl (E)‐2‐[(4‐methoxyphenyl)imino]acetates catalyzed by MDOs gives two different diastereomers of the desired bridged tetrahydroisoquinolines in good yields and excellent diastereoselectivities (up to 99:1 dr) and enantioselectivities (up to >99%ee). The diastereodivergence was achieved in the aldol reaction step. magnified image 

   more » « less
4. A One-Pot Intramolecular Tandem Michael–Aldol Annulation Reaction for the Synthesis of Chiral Pentacyclic Terpenes

   https://doi.org/10.1055/s-0039-1690521  

   Lu, Jianyu; Koldas, Serkan; Fan, Huafang; Desper, John; Day, Victor W.; Hua, Duy H. (October 2019, Synthesis)

   A chiral tricyclic terpene possessing a 6,6,6-tricyclic framework and a 3,3-dimethyl-7-oxooctylidenyl side chain undergoes a double ring-closing reaction to give two chiral pentacyclic terpenes in a ratio of 4:3 via an intramolecular Michael addition followed by aldol condensation under basic conditions. Three new stereogenic centers are introduced in the initial Michael annulation reaction. Stereoselective installation of an ethoxycarbonyl group at C17 of the two pentacyclic terpenes separately gives the corresponding highly functionalized pentacyclic terpenoids with seven stereogenic centers. The structures and stereochemistry of key intermediates and products are established through X-ray crystallographic analysis. A mechanism is proposed for explaining the stereochemistry in the Michael annulation reaction. 

   more » « less
5. Determining Michael acceptor reactivity from kinetic, mechanistic, and computational analysis for the base-catalyzed thiol-Michael reaction

   https://doi.org/10.1039/d1py00363a  

   Huang, Sijia; Kim, Kangmin; Musgrave, Grant M.; Sharp, Marcus; Sinha, Jasmine; Stansbury, Jeffrey W.; Musgrave, Charles B.; Bowman, Christopher N. (June 2021, Polymer Chemistry)

   null (Ed.)

   A combined experimental and computational study of the reactivities of seven commonly used Michael acceptors paired with two thiols within the framework of photobase-catalyzed thiol-Michael reactions is reported. The rate coefficients of the propagation ( k P ), reverse propagation ( k -P ), chain-transfer ( k CT ), and overall reaction ( k overall ) were experimentally determined and compared with the well-accepted electrophilicity parameters of Mayr and Parr, and DFT-calculated energetics. Both Mayr's and Parr's electrophilicity parameters predict the reactivities of these structurally varying vinyl functional groups well, covering a range of overall reaction rate coefficients from 0.5 to 6.2 s −1 . To gain insight into the individual steps, the relative energies have been calculated using DFT for each of the stationary points along this step-growth reaction between ethanethiol and the seven alkenes. The free energies of the individual steps reveal the underlying factors that control the reaction barriers for propagation and chain transfer. Both the propagation and chain transfer steps are under kinetic control. These results serve as a useful guide for Michael acceptor selection to design and predict thiol-Michael-based materials with appropriate kinetic and material properties. 

   more » « less