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Volume 66, Issue 1
Displaying 1-10 of 10 articles from this issue
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[in Japanese]2008 Volume 66 Issue 1 Pages 2
Published: January 01, 2008
Released on J-STAGE: June 28, 2010
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[in Japanese]2008 Volume 66 Issue 1 Pages 3
Published: January 01, 2008
Released on J-STAGE: June 28, 2010
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Masanobu Uchiyama2008 Volume 66 Issue 1 Pages 4-16
Published: January 01, 2008
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSOrganometallic reagents having Lewis acidity (such as dialkylzincs) often form complexes with anion species (such as alkyllithiums) to generate ate complexes (such as lithium trialkylzincates). Since all of ligands coordinated to Zn are usually the same (homoleptic), these reactivities, i.e., the magnitude of the transference aptitude of ligands, are essentially equivalent. However, the reactivities of the ligands should be nonequivalent, if different ligands do coordinate to Zn (heteroleptic). Such heteroleptic zincates and their practical applications for organic transformations has been investigated and discussed theoretically based on computational methods.View full abstractDownload PDF (2884K) -
Katsukiyo Miura, Akira Hosomi2008 Volume 66 Issue 1 Pages 17-27
Published: January 01, 2008
Released on J-STAGE: March 01, 2011
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Mitsuru Shindo, Seiji Mori2008 Volume 66 Issue 1 Pages 28-38
Published: January 01, 2008
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSWe have developed the torquoselectivity-controlled olefination of carbonyl compounds with ynolates to afford tetrasubstituted alkenes. In the olefination of acylsilanes, α-oxy and α-aminoketones, and esters, the high selectivity and yield have been achieved under mild conditions. The E/Z selectivity is determined in the step of electrocyclic ring-opening of the β-lactone enolates (oxetenes) derived from cycloaddition of ynolates with carbonyl compounds. The theoretical calculations revealed that the several secondary orbital interactions are critical for the high torquoselectivity. The E/Z selectivity can be estimated by considerations of the electronic properties of the substituents of carbonyl compounds, wherein the electron-donating substituents would be traps to the carboxylate on the olefins and the electron accepting ones cis to it. This methodology is the novel olefination constructing multisubstituted olefins.View full abstractDownload PDF (2660K) -
Masanori Yoshida, Shoji Hara2008 Volume 66 Issue 1 Pages 39-49
Published: January 01, 2008
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSStereoselective synthesis of fluoroalkenes is described. The reaction of alk-1-ynes with p-iodotoluene difluoride under acidic condition gave (E)-2-fluoroalkenyliodonium salts stereoselectively in good yields. On the other hand, (Z)-2-fluoroalkenyliodonium salts were synthesized efficiently by Michael-type addition of hydrogen fluoride onto alkynyliodonium salts, which can be readily prepared from alk-1-ynes. By using the fluoroalkenyliodonium salts, a variety of fluoroalkenes were synthesized stereoselectively. For example, palladium-catalyzed cross-coupling reactions of the fluoroalkenyliodonium salts gave various fluoroalkenes . By treatment of the fluoroalkenyliodonium salts with potassium tert-butoxide at room temperature, 1-fluorocyclopentenes were synthesized in good yields via 1, 5-C-H insertion of α-fluoroalkylidenecarbenes, which were generated by α-elimination of the hydrogen atom and aryliodanyl group of the fluoroalkenyliodonium salts. Finally, the reaction of the fluoroalkenyliodonium salts with lithium diisopropylamide at low temperature generated α-fluoroalkylidenecarbenoids, which could be trapped with trialkylboranes to give 2-fluoroalkenylboranes stereoselectively. The fluoroalkenylboranes could be used for further fluoroalkene synthesis.View full abstractDownload PDF (2870K) -
Satoshi Shuto, Satoshi Ichikawa, Hiroshi Abe, Akira Matsuda2008 Volume 66 Issue 1 Pages 50-60
Published: January 01, 2008
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSDespite considerable progress and extensive effort, a general method for highly stereoselective glycosylation particularly for the 1, 2-cis-glycosylation has not yet been developed and therefore is required. The α/β-stereoselectivity in glycosylation can be affected by the steric and stereoelectronic (anomeric) effects around the anomeric center, which depend on the conformation of the glycosyl donor substrates. Therefore, we hypothesized that highly α- and β-selective glycosylation can be realized by employing conformationally restricted substrates. We showed that the α/β-stereoselectivity was significantly increased by the conformational restriction and was completely inverted by changing the substrate conformation from the 4C1-form into the 1C4-form in radical and nucleophilic C-glycosylation reactions as well as in O-glycosylation reactions. The conformational restriction of substrates also effectively facilitates the α- and β-selective radical cyclization reaction at the anomeric position. Using the method, C-glucoside trisphosphates designed as Ca2+-mobilizing agents were successfully synthesized.View full abstractDownload PDF (2614K) -
Masayuki Yamashita, Shunsaku Ohta2008 Volume 66 Issue 1 Pages 61-73
Published: January 01, 2008
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSWe found two novel skeleton rearrangement reactions. The one was the reaction from coumarin derivatives having an electron-withdrawing group at the 3-position with dimethylsulfoxonium methylide to cyclopenta[b]benzofuran derivatives. The other was the reaction from benzo[b]cyclobuta[d]pyran derivatives having an electron-withdrawing group at the 2a-position to tetrahydrodibenzofuran derivatives. Interestingly, the latter reaction proceeded stereoconvergently regardless of the stereochemistry at the 1-position in the cyclobutane compounds. Driving forces of these reactions would be attributable to release of the ring strain including in a cyclopropane ring and cyclobutane ring. These methodologies were applied to the total synthesis of linderol A, which is a constituent of Lindera umbellata (Lauraceae) and has a potent inhibitory activity on melanin biosynthesis, and the synthesis was performed in 14 steps, 34% overall yield. Furthermore, the uncertain absolute structure of linderol A was determined, and its asymmetric synthesis was also achieved.View full abstractDownload PDF (2702K) -
Takeshi Ohishi2008 Volume 66 Issue 1 Pages 74-75
Published: January 01, 2008
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSThe addition of a nucleophile to benzyne leads to the formation of an aryl anion that can be trapped with an electrophile. This mini review focuses on the new developments of benzyne chemistry via zwitterionic species. Direct introduction of different functional groups into the aromatic skeletons is briefly described.View full abstractDownload PDF (1494K) -
2008 Volume 66 Issue 1 Pages 76
Published: January 01, 2008
Released on J-STAGE: June 28, 2010
JOURNAL FREE ACCESSDownload PDF (188K)
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