187950-48-7Relevant academic research and scientific papers
Intramolecular Cyclization of Vinyldiazoacetates as a Versatile Route to Substituted Pyrazoles
Drikermann, Denis,G?rls, Helmar,Kerndl, Valerie,Vilotijevic, Ivan
supporting information, p. 1158 - 1162 (2020/07/20)
Vinyldiazo compounds undergo a thermal electrocyclization to form pyrazoles in yields of up to 95percent. The reactions are operationally simple, use readily available starting materials, require no intervention of a catalyst, and enable the synthesis of mono-, di- A nd tri-substituted pyrazoles. With the ability to produce highly substituted pyrazoles and the flexibility in installing various types of substituents, this method constitutes a new entry to this valuable heterocyclic scaffold and may be of interest to all branches of the chemical industry.
An Enzymatic Platform for the Highly Enantioselective and Stereodivergent Construction of Cyclopropyl-δ-lactones
Chandgude, Ajay L.,Fasan, Rudi,Liu, Ningyu,Ren, Xinkun
supporting information, p. 21634 - 21639 (2020/09/23)
Abiological enzymes offers new opportunities for sustainable chemistry. Herein, we report the development of biological catalysts derived from sperm whale myoglobin that exploit a carbene transfer mechanism for the asymmetric synthesis of cyclopropane-fused-δ-lactones, which are key structural motifs found in many biologically active natural products. While hemin, wild-type myoglobin, and other hemoproteins are unable to catalyze this reaction, the myoglobin scaffold could be remodeled by protein engineering to permit the intramolecular cyclopropanation of a broad spectrum of homoallylic diazoacetate substrates in high yields and with up to 99 % enantiomeric excess. Via an alternate evolutionary trajectory, a stereodivergent biocatalyst was also obtained for affording mirror-image forms of the desired bicyclic products. In combination with whole-cell transformations, the myoglobin-based biocatalyst was used for the asymmetric construction of a cyclopropyl-δ-lactone scaffold at a gram scale, which could be further elaborated to furnish a variety of enantiopure trisubstituted cyclopropanes.
Synthesis of Allylboranes via Cu(I)-Catalyzed B-H Insertion of Vinyldiazoacetates into Phosphine-Borane Adducts
Drikermann, Denis,M??el, Robert S.,Al-Jammal, Walid K.,Vilotijevic, Ivan
supporting information, p. 1091 - 1095 (2020/02/15)
Cu(I) catalysts enable C-B bond formation via direct insertion of vinyldiazoacetates into B-H bonds of borane-phosphine Lewis adducts to form phosphine-protected allylboranes under mild conditions. The resulting allylborane-phosphine Lewis adducts can be used in the diastereoselective allylation of aldehydes directly without the need for removal of the phosphine. The allylation reaction proceeds with high diastereoselectivity and yields 5,6-disubstituted dihydropyranones after treatment with an appropriate acid.
Catalytic C-H Amination Mediated by Dipyrrin Cobalt Imidos
Baek, Yunjung,Betley, Theodore A.
supporting information, p. 7797 - 7806 (2019/05/22)
Reduction of (ArL)CoIIBr (ArL = 5-mesityl-1,9-(2,4,6-Ph3C6H2)dipyrrin) with potassium graphite afforded the novel CoI synthon (ArL)CoI. Treatment of (ArL)CoI with a stoichiometric amount of various alkyl azides (N3R) furnished three-coordinate CoIII alkyl imidos (ArL)Co(NR), as confirmed by single-crystal X-ray diffraction (R: CMe2Bu, CMe2(CH2)2CHMe2). The exclusive formation of four-coordinate cobalt tetrazido complexes (ArL)Co(κ2-N4R2) was observed upon addition of excess azide, inhibiting any subsequent C-H amination. However, when a weak C-H bond is appended to the imido moiety, as in the case of (4-azido-4-methylpentyl)benzene, intramolecular C-H amination kinetically outcompetes formation of the corresponding tetrazene species to generate 2,2-dimethyl-5-phenylpyrrolidine in a catalytic fashion without requiring product sequestration. The imido (ArL)Co(NAd) exists in equilibrium in the presence of pyridine with a four-coordinate cobalt imido (ArL)Co(NAd)(py) (Ka = 8.04 M-1), as determined by 1H NMR titration experiments. Kinetic studies revealed that pyridine binding slows down the formation of the tetrazido complex by blocking azide coordination to the CoIII imido. Further, (ArL)Co(NR)(py) displays enhanced C-H amination reactivity compared to that of the pyridine-free complex, enabling higher catalytic turnover numbers under milder conditions. The mechanism of C-H amination was probed via kinetic isotope effect experiments [kH/kD = 10.2(9)] and initial rate analysis with para-substituted azides, suggesting a two-step radical pathway. Lastly, the enhanced reactivity of (ArL)Co(NR)(py) can be correlated to a higher spin-state population, resulting in a decreased crystal field due to a geometry change upon pyridine coordination.
Stereoselective Ring-Opening of gem-Difluorocyclopropanes: An Entry to Stereo-defined (E,E)- and (E,Z)-Conjugated Fluorodienes
Specklin, Simon,Fenneteau, Johan,Subramanian, Parthasarathi,Cossy, Janine
supporting information, p. 332 - 336 (2018/01/17)
The ring-opening of gem-difluorocyclopropyl acetaldehydes producing selectively (E,E)- and (E,Z)-conjugated fluorodienals is described. Two stereo-divergent methods are presented to access both stereoisomers from a common precursor, in high yield and selectivity. The mechanistic aspect of these transformations is discussed.
Alkene Dioxygenation with Malonoyl Peroxides: Synthesis of γ-Lactones, Isobenzofuranones, and Tetrahydrofurans
Alamillo-Ferrer, Carla,Karabourniotis-Sotti, Marianna,Kennedy, Alan R.,Campbell, Matthew,Tomkinson, Nicholas C. O.
supporting information, p. 3102 - 3105 (2016/07/13)
Treatment of homoallylic alcohols or carboxylic acids with malonoyl peroxide 1 provides a stereoselective method for the preparation of tetrahydrofurans, γ-lactones, and isobenzofuranones in 44-82% yield and up to 27:1 trans selectivity. Application of this simple and effective heterocyclization in the synthesis of the antidepressant citalopram is also described.
Total synthesis and biological evaluation of fluorinated cryptophycins
Weiss, Christine,Bogner, Tobias,Sammet, Benedikt,Sewald, Norbert
, p. 2060 - 2066 (2013/02/22)
Cryptophycins are cytotoxic natural products that exhibit considerable activities even against multi-drug-resistant tumor cell lines. As fluorinated pharmaceuticals have become more and more important during the past decades, fluorine-functionalized cryptophycins were synthesized and evaluated in cell-based cytotoxicity assays. The unit A trifluoromethyl-modified cryptophycin proved to be highly active against KB-3-1 cells and exhibited an IC 50 value in the low picomolar range. However, the replacement of the 3-chloro-4-methoxyphenyl-substituent in unit B by a pentafluorophenyl moiety resulted in a significant loss of activity.
Highly regioselective palladium-catalysed oxidative allylic C-H carbonylation of alkenes
Chen, Huoji,Cai, Congbi,Liu, Xiaohang,Li, Xianwei,Jiang, Huanfeng
, p. 12224 - 12226 (2011/12/14)
Pd-catalysed direct oxidative carbonylation of allylic C-H bonds with carbon monoxide was first described. This new procedure shows that the inherent requirement for a leaving group in the Tsuji-Trost palladium-catalysed allylic carbonylation can be lifted, which provides a new route for accessing more synthetically useful β-enoic acid esters with high regioselectivity. The Royal Society of Chemistry 2011.
A highly selective and general palladium catalyst for the oxidative heck reaction of electronically nonbiased olefins
Werner, Erik W.,Sigman, Matthew S.
supporting information; experimental part, p. 13981 - 13983 (2010/12/24)
A general, highly selective oxidative Heck reaction is reported. The reaction is high-yielding under mild conditions without the need for base or high temperatures, and the selectivity is excellent, without the requirement for electronically biased olefins or other specific directing groups. A preliminary mechanistic investigation suggests that the unusually high selectivity may be due to the catalyst's sensitivity to C-H bond strength in the selectivity-determining β-hydride elimination step.
A Stereospecific Access to Allylic Systems Using Rhodium(II)-Vinyl Carbenoid Insertion into Si-H, O-H, and N-H Bonds
Bulugahapitiya, Priyadarshanie,Landais, Yannick,Parra-Rapado, Liliana,Planchenault, Denis,Weber, Valery
, p. 1630 - 1641 (2007/10/03)
Rhodium-catalyzed decomposition of α-vinyldiazoesters in the presence of silanes, alcohols, ethers, amines, and thiols have been shown to produce the corresponding α-silyl, α-hydroxy, α-alkoxy, α-amino, and α-thioalkoxy esters in generally good yield with a complete retention of the stereochemistry of the double bond of the diazo precursor. An extension of the process in homochiral series has also been devised using either a chiral auxiliary attached to the ester function or achiral α-vinyldiazoesters and Doyle's chiral catalyst Rh2(MEPY)4. In the former approach, pantolactone as chiral auxiliary gave diastereoselectivities of up to 70%, while the second approach produced the desired allylsilane with ee as high as 72%. On the other hand, Rh2(MEPY)4-catalyzed insertion into the O-H bond of water led to poor or no enantioselectivity in good agreement with recent literature reports.
