34944-05-3Relevant articles and documents
The Importance of 1,5-Oxygen???Chalcogen Interactions in Enantioselective Isochalcogenourea Catalysis
Cockroft, Scott L.,Elmi, Alex,Frost, Aileen B.,Ling, Kenneth B.,McLaughlin, Calum,Morris, Rylie K.,Pascoe, Dominic J.,Slawin, Alexandra M. Z.,Smith, Andrew D.,Smith, Terry K.,Willoughby, Patrick H.,Woods, Andrew M.,Young, Claire M.,de la Houpliere, Alix
supporting information, p. 3705 - 3710 (2020/02/11)
The importance of 1,5-O???chalcogen (Ch) interactions in isochalcogenourea catalysis (Ch=O, S, Se) is investigated. Conformational analyses of N-acyl isochalcogenouronium species and comparison with kinetic data demonstrate the significance of 1,5-O???Ch interactions in enantioselective catalysis. Importantly, the selenium analogue demonstrates enhanced rate and selectivity profiles across a range of reaction processes including nitronate conjugate addition and formal [4+2] cycloadditions. A gram-scale synthesis of the most active selenium analogue was developed using a previously unreported seleno-Hugerschoff reaction, allowing the challenging kinetic resolutions of tertiary alcohols to be performed at 500 ppm catalyst loading. Density functional theory (DFT) and natural bond orbital (NBO) calculations support the role of orbital delocalization (occurring by intramolecular chalcogen bonding) in determining the conformation, equilibrium population, and reactivity of N-acylated intermediates.
A C=O???Isothiouronium Interaction Dictates Enantiodiscrimination in Acylative Kinetic Resolutions of Tertiary Heterocyclic Alcohols
Greenhalgh, Mark D.,Smith, Samuel M.,Walden, Daniel M.,Taylor, James E.,Brice, Zamira,Robinson, Emily R. T.,Fallan, Charlene,Cordes, David B.,Slawin, Alexandra M. Z.,Richardson, H. Camille,Grove, Markas A.,Cheong, Paul Ha-Yeon,Smith, Andrew D.
supporting information, p. 3200 - 3206 (2018/02/22)
A combination of experimental and computational studies have identified a C=O???isothiouronium interaction as key to efficient enantiodiscrimination in the kinetic resolution of tertiary heterocyclic alcohols bearing up to three potential recognition motifs at the stereogenic tertiary carbinol center. This discrimination was exploited in the isothiourea-catalyzed acylative kinetic resolution of tertiary heterocyclic alcohols (38 examples, s factors up to >200). The reaction proceeds at low catalyst loadings (generally 1 mol %) with either isobutyric or acetic anhydride as the acylating agent under mild conditions.
FeCl3-Catalyzed Allylation Reactions onto 3-Hydroxy-2-oxindoles: Formal Total Syntheses of Bis-cyclotryptamine Alkaloids, (±)-Chimonanthine, and (±)-Folicanthine
Kinthada, Lakshmana K.,Medisetty, Sai Raghavendra,Parida, Amarchand,Babu, K. Naresh,Bisai, Alakesh
, p. 8548 - 8567 (2017/08/23)
An FeCl3-catalyzed efficient strategy for the allylation reactions of 3-hydroxy-2-oxindoles with allyltrimethylsilane has been developed. The reaction affords a variety of 2-oxindoles having quaternary center at the pseudobenzylic position in an operationally simple and inexpensive procedure. Control experiments using enantioenriched 3-hydroxy-2-oxindole show that the reaction proceeds through in situ generated 2H-indol-2-one (8). The methodology presents an efficient and concise access to the pyrroloindoline alkaloids (±)-deoxyeseroline (1a), (±)-esermethole (1b), (±)-physostigmine (1c), (±)-phenserine (1d), and (±)-physovenine (1e). Eventually, we extrapolated the scope of this methodology to the formal total syntheses of dimeric cyclotyrptamine alkaloids (±)-chimonanthine (3a), (±)-folicanthine (3c), and (±)-calycanthine (4).
