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1. Origins of Periselectivity and Regioselectivity in Ambimodal Tripericyclic [8+6]/[6+4]/[4+2] Intramolecular Cycloadditions of a Heptafulvenyl-Fulvene

   https://doi.org/10.1021/acs.jpca.3c05656  

   Sengupta, Arkajyoti; Houk, K. N. (September 2023, The Journal of Physical Chemistry A)
2. Huisgen's 1,3‐Dipolar Cycloadditions to Fulvenes Proceed via Ambimodal [6+4]/[4+2] Transition States

   https://doi.org/10.1002/anie.202005265  

   Liu, Fang; Chen, Yu; Houk, K. N. (June 2020, Angewandte Chemie International Edition)

   Abstract Huisgen's 1960 announcement of the concept of 1,3‐dipolar cycloadditions was published the year before Alder's study of the reaction of diazomethane and dimethylfulvene. The diazomethane reaction was studied again in 1970 by Houk et al. and shown to give a [6+4] adduct. Padwa's nitrile ylide cycloaddition to dimethylfulvene (1978) gave [6+4] and [4+2] adducts. We performed computational studies of these reactions with density functional theory (DFT) and show that they involve ambimodal [6+4]/[4+2] transition states that can lead to either type of cycloadduct from one transition state. We dedicate this paper to the extraordinary life and humanity of Rolf Huisgen, and to the undying influence of his discoveries on chemistry. 

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3. Catalytic Enantioselective Hetero-[6+4] and -[6+2] Cycloadditions for the Construction of Condensed Polycyclic Pyrroles, Imidazoles, and Pyrazoles

   https://doi.org/10.1021/jacs.8b13659  

   Bertuzzi, Giulio; Thøgersen, Mathias Kirk; Giardinetti, Maxime; Vidal-Albalat, Andreu; Simon, Adam; Houk, K. N.; Jørgensen, Karl Anker (February 2019, Journal of the American Chemical Society)
4. Crystal structure of 2-(2,2,6,6-tetramethylpiperidin-4-yl)-6-[(2,2,6,6-tetramethylpiperidin-4-yl)amino]-1 H -benz[de]isoquinoline-1,3(2 H)-dione

   https://doi.org/10.1107/S2056989022010374  

   Pollock, Alicia A.; Huther, Holly A.; Birch, Cole M.; Reinheimer, Eric W.; Lewis, David E.; Gerlach, Deidra L. (December 2022, Acta Crystallographica Section E Crystallographic Communications)

   The structure of the title compound, C30H42N4O2, has orthorhombic (Pbca) symmetry. This compound comprises a 4-amino-1,8-naphthalimide core with a 2,2,6,6-tetramethyl-4-piperidinyl substituent bonded to each nitrogen atom. The structure displays N—H...O hydrogen bonding. The structure exhibits disorder of the main molecule. 

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5. LixSiON (x = 2, 4, 6): a novel solid electrolyte system derived from agricultural waste

   https://doi.org/10.1039/D0GC02580A  

   Zhang, X.; Temeche, E.; Laine, R. M. (October 2020, Green chemistry)

   A set of LixSiON (x = 2, 4, 6) polymer precursors to a novel solid-state electrolyte system were synthesized starting from rice hull ash (RHA), an agricultural waste, providing a green route towards the assembly of all solid-state batteries (ASSBs). Silica, ∼90 wt% in RHA, can be catalytically (alkali base) dissolved (20–40 wt%) in hexylene glycol (HG) and distilled directly from the reaction mixture as the spirosiloxane [(C6H14O2)2Si, SP] at 200 °C. SP can be lithiated using controlled amounts of LiNH2 to produce LixSiON oligomers/polymers with MWs up to ∼1.5 kDa as characterized by FTIR, MALDI-ToF, multinuclear NMR, TGA-DTA, XRD, XPS, SEM and EDX. XPS analyses show that Li contents depend solely on added LiNH2 but found N contents are only ≤1 at%. NH2 likely is removed as NH3 during sample preparation (vacuum/ overnight). In contrast, MALDI indicates N contents of ∼5–30 at% N with shorter drying times (vacuum/ minutes). 7Li NMR positive chemical shifts suggest that precursor bound Li+ ions dissociate easily, ben- eficial for electrochemical applications. The 7Li shifts correlate to Li contents as well as Li+ conductivities. 1H, 13C and 29Si NMRs of the Li6SiON precursor show fluxional behavior implying high Li+ mobility. Dense microstructures are observed for Li4SiON and Li6SiON pellets heated to 200 °C/2 h/N2. Impedance studies suggest that ionic conductivities increase with Li content; the Li6SiON precursor offers the highest ambient conductivity of 8.5 × 10−6 S cm−1 after heating to 200 °C/2 h/N2. 

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