- Asymmetric Cross [10+2] Cycloadditions of 2-Alkylidene-1-indanones and Activated Alkenes under Phase-Transfer Catalysis
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Isobenzofulvene species are versatile synthons in organic chemistry, which have been employed in diverse challenging higher-order cycloaddition reactions. Here, the first chemoselective and asymmetric cross [10+2] cycloaddition reaction between activated 2-alkylidene-1-indanones and a variety of electron-deficient alkenes has been developed, relying on the in situ generation of dearomative 1-hydroxyl isobenzofulvene anion intermediates under the catalysis of a newly designed bulky cinchona-derived phase-transfer compound. An array of fused frameworks with multifunctionalities were generally furnished in excellent diastereo- and enantioselectivity, even at 1 mol % catalyst loadings.
- Yang, Yang,Jiang, Ying,Du, Wei,Chen, Ying-Chun
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supporting information
p. 1754 - 1758
(2020/02/11)
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- HandaPhos: A General Ligand Enabling Sustainable ppm Levels of Palladium-Catalyzed Cross-Couplings in Water at Room Temperature
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The new monophosphine ligand HandaPhos has been identified such that when complexed in a 1:1 ratio with Pd(OAc)2, enables Pd-catalyzed cross-couplings to be run using ≤1000 ppm of this pre-catalyst. Applications to Suzuki-Miyaura reactions involving highly funtionalized reaction partners are demonstrated, all run using environmentally benign nanoreactors in water at ambient temperatures.
- Handa, Sachin,Andersson, Martin P.,Gallou, Fabrice,Reilly, John,Lipshutz, Bruce H.
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supporting information
p. 4914 - 4918
(2016/04/26)
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- Substrate range of the titanium TADDOLate catalyzed asymmetric fluorination of activated carbonyl compounds
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The substrate range of the [TiCl2(TADDOLate)] (TADDOL=α,α,α′,α′-tetraaryl-1,3-dioxolane-4, 5-dimethanol)-catalyzed asymmetric α-fluorination of activated β-carbonyl compounds has been investigated. Optimal conditions for catalysis are characterized by using 5 mol-% of TiCl2(naphthalen-1- yl)-TADDOLate) as catalyst in a saturated (0.14 mol/l) MeCN solution of F-TEDA (1-(chloromethyl)-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis- [tetrafluoroborate]) at room temperature. A series of α-methylated β-keto esters (3-oxobutanoates, 3-oxopentanoates) with bulky benzyl ester groups (60-90% ee) or phenyl ester (67-88% ee) have been fluorinated readily, whereas α-acyl lactones were also readily fluorinated, but gave lower inductions (13-46% ee). Double stereochemical differentiation in β-keto esters with chiral ester groups raised the stereoselectivity to a diastereomeric ratio (dr) of up to 96.5:3.5. For the first time, β-keto S-thioesters were asymmetrically fluorinated (62-91.5% ee) and chlorinated (83% ee). Lower inductions were observed in fluorinations of 1,3-diketones (up to 40% ee) and β-keto amides (up to 59% ee). General strategies for preparing activated β-carbonyl compounds as important model substrates for asymmetric catalytic α-functionalizations are presented (>60 examples). Copyright
- Bertogg, Andreas,Hintermann, Lukas,Huber, Dominique P.,Perseghini, Mauro,Sanna, Maria,Togni, Antonio
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body text
p. 353 - 403
(2012/05/07)
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- Synthesis and reactivity of an unprecedented osmium(VIII) alkylidene
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The synthesis of a family of Os(VIII) alkylidene complexes, the highest oxidation state alkylidenes known to date, and their reactivity toward small organic molecules are reported.
- Martin, Véronique,Blakey, Simon
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supporting information; experimental part
p. 6800 - 6803
(2009/04/06)
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- Chemosensory performance of molecularly imprinted fluorescent conjugated polymer materials
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Fluorescent conjugated polymers are an attractive basis for the design of low detection limit sensing devices owing to their intrinsic signal amplification capability. A simple and universal method to rationally control or fine-tune the chemodetection sel
- Li, Jiahui,Kendig, Claire E.,Nesterov, Evgueni E.
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p. 15911 - 15918
(2008/09/21)
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- Phosphonamide ACAT inhibitors
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The present invention is directed to compounds useful for the regulation of cholesterol of Formula I, methods for using them and pharmaceutical compositions thereof, STR1 wherein Ar and Ar1 are each independently selected from unsubstituted or substituted phenyl which substituents are from 1-5 in number and are each independently selected from alkyl, alkoxy, hydroxy, halogen, nitro, trifluoromethyl, COOH, and COOalkyl; X is --NH--, --O--, --S--, or --(CH2)0-4 --, and R is hydrogen, alkyl, or phenyl.
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- N-acyl sulfamic acid esters (or thioesters), N-acyl sulfonamides, and N-sulfonyl carbamic acid esters (or thioesters) as hypercholesterolemic agents
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The present invention is directed to compounds useful for the regulation of cholesterol of Formula I, methods for using them and pharmaceutical compositions thereof, STR1 wherein X and Y are oxygen, sulfur, or (CR'R")n wherein n is 1 to 4; R is hydrogen, alkyl, or benzyl; R1 and R2 are phenyl, substituted phenyl, naphthyl, substituted naphthyl, an aralkyl group, an alkyl chain, adamantyl, or a cycloalkyl group.
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- Photocyclization of -(o-Tolyl)acetophenones: Triplet and 1,5-biradical reactivity
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Several ring-substituted α-(o-tolyl)acetophenones undergo photocyclization to 2-indanol derivatives in high quantum efficiency in solution and in high chemical yield as solids. The mechanism for reaction involves triplet state δ-hydrogen atom abstraction that generates 1,5-biradicals. Quenching studies indicate that the n.π* excited triplets of these ketones react, with rate constants >108 s-1. Variations in triplet reactivity are ascribed to conformational equilibria that populate reactive and unreactive geometries to different extents. The α-aryl ring eclipses the carbonyl in the lowest energy geometry, from which the most favorable geometry for reaction can be reached by small bond rotations. α-(2,4,6-Triisopropylpheny)acetophenone forms the relatively long lived enol as well as indanol in solvent-dependent ratios; deuterium labeling indicates that the 1,5-biradical disproportionates to form enol. This does not happen with α-mesitylacetophenone, so its 54% cyclization quantum efficiency is ascribed to an internal triplet quenching that competes with hydrogen abstraction. This internal quenching is presumed to be of the charge-transfer type and does not appear to lead directly to 1,5-biradicals. 1-Methyl-2-phenyl-2-indanol is formed from α-(o-ethylpheny)acetophenone with a Z/E ratio of 20:1 in benzene and 2:1 in methanol. The 1,5-biradical intermediates were characterized by flash spectroscopy; they have lifetimes between 15 and 45 ns, with those derived from α-(o-isopropylphenyl) ketones being twice as long-lived as those derived from α-(o-methylphenyl) ketones, and show only a small solvent dependence. Biradical lifetimes and the diastereoselectivity of cyclization are interpreted in terms of biradical intersystem crossing occurring preferentially along the reaction coordinate for cyclization, such that the two processes effectively occur concurrently. The applicability of this concept to other biradicals is discussed.
- Wagner, Peter J.,Meador, Michael A.,Zhou, Boli,Park, Bong-Ser
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p. 9630 - 9639
(2007/10/02)
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- Dipole-Stabilized Carbanions from Thioesters. Secondary α'-Lithio Carbamates and Tertiary α'-Lithio Thioesters
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The formation of 5 and 17, synthetic equivalents of the α-lithioalkylthio and α-lithiodialkylthio functions, respectively, by deprotonations of the corresponding carbamate 4 and thioester 16 are reported.The reactions of these formally dipole-stabilized carbanions with a variety of electrophiles and their use in synthese of 2,3-substituted thiiranes are demonstrated.The rearrangement of 17 to an α-thiol ketone is shown to be intramolecular by a double labeling experiment.Potentially chiral or conformationally isomeric α'-lithio thioesters are found to be racemized and equilibrated.Formations of secondary α'-lithio thioesters in medium chain, β'-dimethylamino, and allyl systems are reported while β'-alkoxy groups are shown to eliminate to give vinyl thio esters which undergo further metalation.The kinetic acidity of a methyl thioester is shown to be comparable to a propenyl thioester and greater then an ethyl thioester.
- Beak, Peter,Becker, Peter D.
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p. 3855 - 3861
(2007/10/02)
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