- A Radical-Polar Crossover Annulation to Access Terpenoid Motifs
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A new catalytic radical-polar crossover annulation between two unsaturated carbonyl compounds is described. The annulation proceeds under exceptionally mild conditions and provides direct and expedient access to complex terpenoid motifs. Application of this chemistry allows for synthesis of forskolin, a densely functionalized terpenoid, in 14 steps from commercially available material.
- Thomas, William P.,Schatz, Devon J.,George, David T.,Pronin, Sergey V.
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supporting information
p. 12246 - 12250
(2019/08/27)
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- Synthesis and Reactivity of Reduced α-Diimine Nickel Complexes Relevant to Acrylic Acid Synthesis
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The aryl-substituted α-diimine (DI) nickel vinyl complex (iPrDI)Ni(CH=CH2) (iPrDI = [2,6-(iPr)2C6H3N=C(CH3)]2) was synthesized and structurally characterized. The complex is dimeric in the solid state and has a distorted-square-planar geometry at nickel. A combination of single-crystal X-ray diffraction, EPR, magnetic susceptibility, and NMR analyses was used to elucidate the electronic structure of the compound, and it is best described as a low-spin Ni(II) derivative with a singly reduced α-diimine chelate. Addition of CO2 to the nickel vinyl complex resulted in insertion into the nickel-carbon bond to yield the corresponding nickel acrylate (iPrDI)Ni(κ2-O2CCH=CH2). EPR spectroscopy coupled with DFT calculations established that the S = 1/2 product maintains the nickel(II) oxidation state with an α-diimine-centered radical. Addition of acrylic acid to (iPrDI)Ni(CH=CH2) induced rapid, net bimetallic reductive elimination to release butadiene and produced the metastable olefin-bound acrylic acid complex (iPrDI)Ni(κ2-CH2=CHCO2H). Over the course of 2 h at 23 °C, this complex underwent a net oxidation to produce (iPrDI)Ni(κ2-O2CCH=CH2), with concomitant loss of H2.
- Joannou, Matthew V.,Bezdek, Máté J.,Albahily, Khalid,Korobkov, Ilia,Chirik, Paul J.
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supporting information
p. 3389 - 3393
(2018/10/31)
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- Enantioselective Conjunctive Cross-Coupling of Bis(alkenyl)borates: A General Synthesis of Chiral Allylboron Reagents
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Palladium-catalyzed conjunctive cross-coupling is used for the synthesis of enantioenriched allylboron reagents. This reaction employs nonsymmetric bis(alkenyl)borates as substrates and appears to occur by a mechanism that involves selective activation of the less substituted alkene followed by migration of the more substituted alkene during the course of a Pd-induced metalate rearrangement.
- Edelstein, Emma K.,Namirembe, Sheila,Morken, James P.
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supporting information
p. 5027 - 5030
(2017/05/04)
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- Flexible syntheses of 5,8-disubstituted indolizidine poisonous-frog alkaloids via a Michael-type conjugate addition
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The efficient and flexible syntheses of 5,8-disubstituted indolizidine poisonous-frog alkaloids is described using a highly stereoselective Michael-type conjugate addition reaction as the key step. In this work, syntheses of the 5,8-disubstituted indolizidine poisonous-frog alkaloids (-)-231C, (-)-221I and the proposed structure for (-)-193E are reported.
- Zhou, De-Jun,Wang, Zhen-Hui,Zhang, Yan-Ru,Cui, Zheng-Guo
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- Synthesis of enantioenriched tertiary boronic esters by the lithiation/borylation of secondary alkyl benzoates
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Simple, secondary 2,4,6-triisopropyl benzoates (TIB esters) and secondary dialkyl N,N-diisopropyl carbamates have been reported to be resistant to deprotonation by strong bases. We have found that the combination of sBuLi (1.6 equiv) and TMEDA (6 equiv) in CPME at -60 C enables deprotonation of unactivated secondary dialkyl TIB esters, but not the carbamates. These carbanions were reacted with a range of neopentyl boronic esters which, after 1,2-metalate rearrangement and oxidation, gave a range of tertiary alcohols in high yield and universally high er. Further functional group transformations of the tertiary boronic esters were demonstrated (conversion to quaternary centers, C-tertiary amines) together with application of the methodology to the synthesis of the simplest unbranched hydrocarbon bearing a quaternary center, (R)-4-ethyl-4-methyloctane, validating the synthetic utility of the methodology.
- Pulis, Alexander P.,Blair, Daniel J.,Torres, Eva,Aggarwal, Varinder K.
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supporting information
p. 16054 - 16057
(2013/11/19)
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- Asymmetric synthesis of tertiary and quaternary allyl- and crotylsilanes via the borylation of lithiated carbamates
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Tertiary allyl- or crotylsilanes have been prepared in high er and dr via the lithiation-borylation reaction of alkyl carbamates with silaboronates. Using a related strategy, quaternary allylsilanes could be accessed in similarly high er.
- Aggarwal, Varinder K.,Binanzer, Michael,De Ceglie, M. Carolina,Gallanti, Maddalena,Glasspoole, Ben W.,Kendrick, Stephanie J. F.,Sonawane, Ravindra P.,Vazquez-Romero, Ana,Webster, Matthew P.
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supporting information; experimental part
p. 1490 - 1493
(2011/05/12)
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- SULFUR-CONTAINING HETEROCYCLIC DERIVATIVE HAVING ?-SECRETASE-INHIBITING ACTIVITY
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The following compound is provided as an agent for treating a disease induced by production, secretion and/or deposition of amyloid β protein, for example,. a compound represented by the formula (I): wherein ruing A is an optionally substituted carbocyclic group or an optionally substituted heterocyclic group, R1 is optionally substituted lower alkyl or the like, R2a and R2b are each independently hydrogen, optionally substituted lower alkyl or the like, R3a and R3c are each independently hydrogen, halogen, hydroxy, optionally substituted lower alkyl or the like, or a pharmaceutically acceptable salt thereof, or a solvate thereof.
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Page/Page column 64
(2011/04/25)
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- Studies on the bisoxazoline- and (-)-sparteine-mediated enantioselective addition of organolithium reagents to imines
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The enantioselective addition of organolithium reagents to N-anisylaldimines promoted by chiral bisoxazolines and (-)-sparteine as external ligands is described. This reaction proceeds readily with a wide range of aldimine substrates (aliphatic, aromatic, olefinic) and organolithium nucleophiles (Me, n-Bu, Ph, vinyl) in excellent yields (81-99%) and with high enantioselectivities (up to 97:3.0 er). The external ligands can be used in substoichiometric amounts albeit with slightly attenuated enantioselectivities. A systematic evaluation of the structural features of the bisoxazolines revealed a primary contribution from the substituent at C(4) and a secondary influence from the bridging substituents. A computational analysis (PM3) provided a clear rationalization for the origin of enantioselectivity.
- Denmark, Scott E.,Nakajima, Noriyuki,Stiff, Cory M.,Nicaise, Olivier J.-C.,Kranz, Michael
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supporting information; experimental part
p. 1023 - 1045
(2009/05/30)
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- Methods of use of glycomimetics with replacements for hexoses and n-acetyl hexosamines
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Methods are provided for using a compound to treat, for example, endothelial dysfunction including vascular abnormalities. More specifically, methods are described for using an oligosaccharide compound or glycomimetic compound wherein a cyclohexane derivative is incorporated in either.
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Page/Page column 29-30; sheet 3
(2008/12/08)
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- Glycomimetic replacements for hexoses and N-acetyl hexosamines
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Compounds and methods are provided for obtaining oligosaccharide mimics. More specifically, compounds and methods are described wherein oligosaccharide mimics are obtained by incorporating or substituting in a cyclohexane derivative.
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Page/Page column 22-23
(2008/12/06)
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- INTERLEUKIN-1 AND TUMOR NECROSIS FACTOR-A MODULATORS; SYNTHESES OF SUCH MODULATORS AND METHODS OF USING SUCH MODULATORS
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Compounds are disclosed that have the chemical structure of Formula (II), (IIA) and (IIB) and their prodrug esters and acid-addition salts, and that are useful as Interleukin-1 and Tumor Necrosis Factor-a modulators, and thus are useful in the treatment of various diseases, wherein the R groups are defined in the claims.
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Page/Page column 164; 165
(2010/11/25)
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- Use of conjugated dienones in cyclialkylations: Total syntheses of arucadiol, 1,2-didehydromiltirone, (±)-hinokione, (±)-nimbidiol, sageone, and miltirone
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Functionalized hydrophenanthrenes can be prepared using a cyclialkylation-based strategy. These annulations are highly dependent on the directing effects of the arene substitutents and on conformational considerations. The utility of this methodology was featured in the syntheses of six diterpenoids.
- Majetich, George,Liu, Shuang,Fang, Jing,Siesel, David,Zhang, Yong
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p. 6928 - 6951
(2007/10/03)
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