- Synthesis and stereostructure-activity relationship of novel pyrethroids possessing two asymmetric centers on a cyclopropane ring
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2-Methylcyclopropane pyrethroid insecticides bearing chiral cyanohydrin esters or chiral ethers and two asymmetric centers on the cyclopropane ring, were synthesized. These compounds were designed using a “reverse connection approach” between the isopropyl group in Fenvalerate, and between two dimethyl groups in an Etofenprox analogue (the methyl, ethyl form), respectively. These syntheses were achieved by accessible ring opening reactions of commercially available (±)-, (R)-, and (S)-propylene oxides using 4-chlorobenzyl cyanide anion as the crucial step, giving good overall yield of the product with >98% ee. The insecticidal activity against the common mosquito (Culex pipiens pallens) was assessed for pairs of achiral diastereomeric (1R*,2S*)-, (1R*,2R*)-cyanohydrin esters, and (1R*,2S*)-, (1R*,2R*)-ethers; only the (1R*,2R*)-ether was significantly effective. For the enantiomeric (1S,2S)-ether and (1R,2R)-ether, the activity was clearly centered on the (1R,2R)-ether. The present stereostructure?activity relationship revealed that (i) cyanohydrin esters derived from fenvalerate were unexpectedly inactive, whereas ethers derived from etofenprox were active, and (ii) apparent chiral discrimination between the (1S,2S)-ether and the (1R,2R)-ether was observed. During the present synthetic study, we performed alternative convergent syntheses of Etofenprox and novel 4-EtO-type (1S,2S)- and (1R,2R)-pyrethroids from the corresponding parent 4-Cl-type pyrethroids, by utilizing a recently-developed hydroxylation cross-coupling reaction.
- Taniguchi, Takashi,Taketomo, Yasuaki,Moriyama, Mizuki,Matsuo, Noritada,Tanabe, Yoo
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supporting information
(2019/03/26)
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- α-Arylation of Esters and Ketones Enabled by a Bench-Stable Pd(I) Dimer Catalyst
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A procedure for the α-arylation of α,α-disubstituted esters and ketones to generate quaternary carbon centers is described. The developed protocol is operationally simple and employs an air- and moisture-stable dinuclear Pd(I) complex [Pd(μ-I)(P t -Bu 3)] 2 to mediate selective α-arylation of aromatic C-I/Br bonds in the presence of aromatic C-Cl and/or C-OTf sites.
- Sperger, Theresa,Schoenebeck, Franziska
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supporting information
p. 4471 - 4475
(2018/07/02)
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- Synthesis and Applications of Unquaternized C-Bound Boron Enolates
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A general and facile method to prepare unquaternized C-bound boron enolates by a ligand-controlled O-to-C isomerization is reported. Using this protocol, C-bound pinacolboron enolates have been isolated in pure form for the first time, and have been fully characterized by NMR spectroscopy and X-ray crystallography. In contrast to the general perception, such C-boron enolates are stable without coordinative saturation at the boron. Moreover, C-boron enolates present reactivities that are distinct from the O-boron enolates, and their applications in C-O and C-C bond formations are demonstrated.
- Ng, Elvis Wang Hei,Low, Kam-Hung,Chiu, Pauline
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p. 3537 - 3541
(2018/03/21)
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- Synthesis, spectral characterization and biological evaluation of a novel series of 6-arylsubstituted-3-[2-(4-substitutedphenyl)propan-2-yl]-7H-[1,2,4] triazolo[3,4-b][1,3,4]thiadiazines
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On account of the reported anticancer activity of triazolothiadiazines, we have synthesized a novel series of 6-arylsubstituted-3-[2-(4-substitutedphenyl) propan-2-yl]-7H-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazines and tested for in-vitro cytotoxicity by trypan blue exclusion and MTT assay. These compounds were also evaluated for their in-vivo anthelmintic activity, as well as in-vitro antimicrobial studies. Amongst the tested compounds, the compound 7j was the most promising cytotoxic agent with IC50 value of 10.54 μM in MCF-7 cells. The compounds 7l and 7q exhibited excellent anthelmintic activity. The compounds 7d, 7f, 7j, 7l, 7o, 7p and 7r showed good antibacterial activity, whereas compounds 7e and 7k exhibited excellent antifungal activity. The structures of newly synthesized compounds were characterized by IR, 1H NMR, 13C NMR and LCMS analysis.
- Puthiyapurayil, Pushpan,Poojary, Boja,Chikkanna, Chandrashekhar,Buridipad, Sunil Kumar
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p. 407 - 416
(2013/01/15)
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- Synthesis and biological activities of a novel series of 3,6-disubstituted-1,2,4-triazolo-[3,4-b]-1,3,4-thiadiazoles containing gem-dimethylbenzyl moiety
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A novel series of 3,6-disubstituted-1,2,4-triazolo-[3,4-b]-1,3,4- thiadiazoles (6a-r) containing gem-dimethyl benzyl moiety were prepared by the condensation of 4-amino-3-aryl/aralkyl substituted-5-mercapto-1,2,4-triazoles (5a-c) with various fluoro substituted aromatic acids in the presence of POCl3. IR, 1H NMR, 13C NMR, 2D NMR (COSY), and mass spectral data confirmed the structures of all the synthesized compounds. All the compounds were also screened for their antibacterial, antifungal and analgesic activities. Compounds 6b, 6d, 6f, 6g, 6h, 6i, 6m, 6n, 6o, 6p, and 6r exhibited promising antibacterial and compounds 6a, 6d, 6f, 6g, 6h, 6k, 6m, 6o, 6p, and 6q showed significant analgesic activities.
- Puthiyapurayil, Pushpan,Poojary, Boja,Kumar, Sunil,Hunnur, Raveendra
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experimental part
p. 998 - 1005
(2011/11/06)
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- Arylation of esters catalyzed by the Pd(I) dimer {[P(t-Bu)]PdBr}
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Conditions for the coupling of bromoarenes with esters using a single base and catalyst with improved turnover numbers are described. These general conditions were made possible by using the Pd(l) catalyst {[P(f-Bu) 3]PdBr}2. Reactions of acetates, propionates, and isobutyrates are presented, and reactions of all three classes of esters on a 10 g scale are described.
- Hama, Takuo,Hartwig, John F.
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supporting information; experimental part
p. 1545 - 1548
(2009/04/07)
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- Palladium-catalyzed-arylattion of esters With chloroarenes
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Palladium-catalyzed α-arylations of esters with chloroarenes are reported. The reactions of chloroarenes with the sodium enolates of tert-butyl propionate and methyl isobutyrate occur in high yields with 0.2-1 mol % of {[P(f-Bu)3]PdBr}2/s
- Hama, Takuo,Hartwig, John F.
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supporting information; experimental part
p. 1549 - 1552
(2009/04/10)
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- Highly regioselective anti-markovnikov palladium-borate-catalyzed methoxycarbonylation reactions: Unprecedented results for aryl olefins
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(Chemical Equation Presented) A general, highly efficient and regioselective methoxycarbonylation, by means of a palladium-salicylicborate- catalyzed protocol, of terminal alkyl and aryl olefins is described. The substrates include aliphatic alkenes, allylbenzenes, and styrene derivatives. The yields are very good (60-92%) and the regioselectivity, in favor of the linear ester, is up to quantitative - unprecedented in the case of styrenes.
- Vieira, Tiago O.,Green, Mike J.,Alper, Howard
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p. 6143 - 6145
(2007/10/03)
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- Calcium salts of 1,5-benzodiazepine derivatives, process for producing the salts and drugs containing the same
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Provided are calcium salts of a 1,5-benzodiazepine derivative represented by the following formula (I): (wherein, R1 represents a lower alkyl group, R2 represents a phenyl or cyclohexyl group, and Y represents a single bond or a lowe
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- Efficient synthesis of α-aryl esters by room-temperature palladium-catalyzed coupling of aryl halides with ester enolates
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A catalytic amount of Pd(dba)2 ligated by either carbene precursor N,N′-bis(2,6-diisopropylphenyl)-4,5-dihydroimidazolium (1) or P(t-Bu)3 mediated the coupling of aryl halides and ester enolates to produce α-aryl esters in high yields at room temperature. The reaction was highly tolerant of functionalities and substitution patterns on the aryl halide. Improved protocols for the selective monoarylation of tert-butyl acetate and the efficient arylation of α,α-disubstituted esters were developed with LiNCy2 as base and P(t-Bu)3 as ligand. In addition, tert-butyl esters, such as those of Naproxen and Flurbiprofen, were prepared from tert-butyl propionate and aryl bromides in high yields in the presence of Pd(dba)2 and the hindered, saturated heterocyclic carbene ligand precursor.
- Jorgensen, Morten,Lee, Sunwoo,Liu, Xiaoxiang,Wolkowski, Joanna P.,Hartwig, John F.
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p. 12557 - 12565
(2007/10/03)
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