- Synthesis and biological evaluation of cyclic derivatives of combretastatin A-4 containing group 14 elements
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Several tricyclic compounds inspired by the structure of combretastatin A-4 and bearing group 14 elements have been synthesized by homocoupling lithiated aryl fragments followed by ring-closing metathesis. These tricyclic compounds and their diolefin prec
- Blasco, Víctor,Murga, Juan,Falomir, Eva,Carda, Miguel,Royo, Santiago,Cu?at, Ana C.,Sanz-Cervera, Juan F.,Marco, J. Alberto
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- Double Functionalization of Styrenes by Cu-Mediated Assisted Tandem Catalysis
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The double functionalization of styrenes through Cu-mediated assisted tandem catalysis was developed. The reaction was initiated by Cu-catalyzed aziridination and the subsequent nucleophilic ring-opening, which was triggered by the addition of (NH4)2S2O8 as an oxidant of Cu-catalyst to form a variety of C–C and C–X bonds. The expansion to three contiguous catalytic cycles led to the synthesis of functionalized indolines by one-pot operation.
- Kawauchi, Daichi,Ueda, Hirofumi,Tokuyama, Hidetoshi
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supporting information
p. 2056 - 2060
(2019/03/13)
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- Intramolecular Crossed [2+2] Photocycloaddition through Visible Light-Induced Energy Transfer
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Herein, we present the intramolecular [2+2] cycloadditions of dienones promoted through sensitization, using a polypyridyl iridium(III) catalyst, to form bridged cyclobutanes. In contrast to previous examples of straight [2+2] cycloadditions, these efficient crossed additions were achieved under irradiation with visible light. The reactions delivered desired bridged benzobicycloheptanone products with excellent regioselectivity in high yields (up to 96%). This process is superior to previous syntheses of benzobicyclo[3.1.1]heptanones, which are readily converted to B-norbenzomorphan analogues of biological significance. Electrochemical, computational, and spectroscopic studies substantiated the mechanism of triplet energy transfer and explained the unusual regiocontrol.
- Zhao, Jiannan,Brosmer, Jonathan L.,Tang, Qingxuan,Yang, Zhongyue,Houk,Diaconescu, Paula L.,Kwon, Ohyun
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supporting information
p. 9807 - 9810
(2017/08/03)
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- Bis(1-cyanovinyl acetate) Is a Linear Precursor to 3-Oxidopyrylium Ions
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Herein we describe the first approach to 3-oxidopyrylium ions from a linear precursor. Heating bis(1-cyanovinyl acetate) in the presence of a trace amount of pyridinium p-toluenesulfonate results in a series of acyl group transfers and an intramolecular cyclization event to form a 3-oxidopyrylium ion that can be trapped by reaction with several dipolarophiles. When treated with dienes, the result is a sequential [5 + 2]/[4 + 2] cycloaddition reaction that provides sp3-rich products of high molecular complexity.
- Wilkerson-Hill, Sidney Malik,Sawano, Shota,Sarpong, Richmond
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p. 11132 - 11144
(2016/11/28)
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- A convergent, modular approach to functionalized 2,1-borazaronaphthalenes from 2-aminostyrenes and potassium organotrifluoroborates
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Azaborines are an important class of compounds with applications in both medicinal chemistry and materials science. The first borazaronaphthalene, 2-chloro-2,1-borazaronaphthalene, was reported in 1959; however, access to more highly functionalized substructures has been limited because of the harsh reaction conditions required to displace the chloride on boron. A convergent approach has been developed to synthesize disubstituted 2,1-borazaronaphthalenes from N-substituted 2-aminostyrenes and potassium organotrifluoroborates, where the potassium organotrifluoroborate is converted to the active R-BX2 species (X = Cl or F) in situ by addition of a fluorophile. Starting from aryl-, heteroaryl-, alkynyl-, alkenyl-, and alkyltrifluoroborates, a library of highly functionalized 2,1-borazaronaphthalenes were synthesized in one step under mild, transition-metal-free conditions.
- Wisniewski, Steven R.,Guenther, Courtney L.,Andreea Argintaru,Molander, Gary A.
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p. 365 - 378
(2014/01/17)
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- Syntheses of 3,4-benzotropolones by ring-closing metatheses
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Ortho-lithiated styrenes or ortho-lithiated benzaldehyde dimethyl acetals were added to 2,2-dimethoxypent-4-enals 7. The resulting alcohols were carried on to the aromatic dienones 10. These were ring-closed by olefin metathesis. Hydrolysis of the dimethyl ketal moiety and enolization provided the 3,4-benzotropolones 5. Overall, this access comprises 4-6 steps and totaled a 22-81% yield.
- Arican, Deniz,Brückner, Reinhard
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supporting information
p. 2582 - 2585
(2013/07/19)
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- CN-assisted oxidative cyclization of cyano cinnamates and styrene derivatives: A facile entry to 3-substituted chiral phthalides
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The asymmetric dihydroxylation (AD) of o-cyano cinnamates and styrene derivatives leads to efficient construction of chiral phthalide frameworks in high optical purities. This unique reaction is characterized by unusual synergism between CN and osmate groups resulting in rate enhancement of the AD process. The method is amply demonstrated by the synthesis and the structural/stereochemical assignment of the natural products.
- Reddy, R.Santhosh,Kiran, I. N. Chaithanya,Sudalai, Arumugam
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supporting information; experimental part
p. 3655 - 3661
(2012/05/31)
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- Microwave-assisted transition-metal-catalyzed synthesis of N-shifted and ring-expanded buflavine analogues
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Two novel and efficient strategies for the synthesis of hitherto unknown N-shifted and ring-expanded buflavine analogues are presented. Construction of the medium-sized ring system of the title molecules, a difficult task due to the high activation energy needed for the ring-closure with the additional rigidity imposed by the biaryl skeleton, was achieved by using Suzuki-Miyaura biaryl coupling and a ring-closing metathesis reaction as the key steps. The combination of a second-generation Grubbs catalyst and microwave irradiation proved to be highly useful in generating the otherwise difficult to obtain medium-sized ring system of the buflavine analogues.
- Appukkuttan, Prasad,Dehaen, Wim,Van Der Eycken, Erik
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p. 6452 - 6460
(2008/02/13)
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- Microwave-enhanced synthesis of N-shifted buflavine analogues via a Suzuki-ring-closing metathesis protocol
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(Chemical Equation Presented) A novel, microwave-enhanced six-step synthesis was devised for the synthesis of N-shifted buflavine analogues. Microwave-enhanced Suzuki-Miyaura cross-coupling and ring-closing metathesis reactions were used as the key steps. Microwave irradiation was found to enhance the ring-closing metathesis reaction to generate the otherwise difficultly obtainable medium-sized ring system of the target molecules.
- Appukkuttan, Prasad,Dehaen, Wim,Van Der Eycken, Erik
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p. 2723 - 2726
(2007/10/03)
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- The Addition of Organolithium Reagents to Quinone Silyl Methyl Monoketals. A Useful Expedient in the Synthesis of p-Quinols Having Acid-Sensitive Groups
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Acid hydrolyses of dimethyl ketals 4-alkyl- and 4-aryl-4-hydroxy-2,5-cyclohexadienones having an acid-sensitive functionality often afford low or no yields of the respective 4-substituted 4-hydroxy-2,5-cyclohexadienones (p-quinols).However, addition of me
- Stern, Alan J.,Swenton, John S.
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p. 2465 - 2468
(2007/10/02)
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