Showing papers by "Hisashi Yamamoto published in 1986"

Chiral allenylboronic esters as practical reagents for enantioselective carbon-carbon bond formation. Facile synthesis of (-)-ipsenol.

Abstract: A stereospecific synthetic route to (-)-ipsenol is described. The synthesis illustrates a new asymmetric synthetic reaction using chiral allenyl boronic esters. The scope of the synthesis as a general route to either (R)or (S)-3-alkynol is further illustrated by several cases. Recently we had envisioned the synthesis of a number of natural products which contain arrays of stereocenters in an open-chain arrangement. The methods of creating these stereocenters in the particular relative configuration have been termed “acyclic stereoselection”.’ Of the many potentially useful methods to this problem, addition of chiral nucleophiles to carbonyl compounds should offer the advantages of widespread applicability to a unique degree.* Among them, the asymmetric addition of allylic nucleophiles to the carbonyl compounds is one of the most powerful and useful synthetic methods in modem synthetic chemi~ t ry .~ On the other hand, the propargylic reagent has never been developed to a useful level due to the lack of a satisfactory chiral system. The even greater versatility of propargylic systems4 compared to (1) General review: Morrison, J. D., Ed. “Asymmetric Synthesis”; Aca(2) Solladie, G., ref 1, Chapter 6, Vol. 2, and references cited therein. (3) Condensation of aldehydes with enantiomerically enriched allylboranes was shown to provide hornoallylic alcohols: Midland, M. M.; Preston, S. B. J . Am. Chem. Soc. 1982, 104, 2330. Herold, T.; Schrott, U.; Hoffmann, R. W. Chem. Ber. 1981, 114, 359. Pearson, N. R.; Hahn, G.; Zweifel, G. J. Org. Chem. 1982, 47, 3364. demic Press: New York, 1983; Vol. 1-4. 0002-7863/86/1508-0483$01.50/0 allylic systems encouraged us to study the former type compounds in detail. Whereas it is usually difficult to differentiate the two reactive centers of allylic system, it is relatively easy to achieve reaction specifically a t either one of the two reactive centers in a propargylic system.’ Prior to our work, efforts to find an efficient asymmetric synthesis using allenyl anion had produced very limited success. Thus, the reaction with carbonyl compounds has been extensively studied with magnesium: aluminum,’ zinc,8 titanium? and borong reagents with much discussion on diastereoselectivity. Although a cyclic mechanism has generally been proposed for such a re(4) Moreau, J.-L. In ”The Chemistry of Ketenes, Allenes, and Related Compounds”; Patai, S., Ed.; Wiley: New York, 1980; pp 363-414. ( 5 ) Ishiguro, M.; Ikeda, N.; Yamamoto, H. J. Org. Chem. 1982, 47, 2225. (6) Karila, M.; Capmau, M. L.; Chodkiewicz, W. C. R. Seances Acad. Sci., Ser. C 1969, 264, 342. Saniere-Karila, M.; Capmau, M. L.; Chodkiewicz, W. Bull. Soc. Chim. Fr. 1973, 3371. (7) Guillerm-Dron, D.; Caprnau, M. L.; Chodkiewicz, W. Tetrahedron Lett. 1972, 37. ( 8 ) Moreau, J.-L. Bull. SOC. Chim. Fr. 1975, 1248. (9) Favre, E.; Gaudemar, M. J . Organomet. Chem. 1975, 92, 17.

Epoxy silyl ether rearrangements: a new, stereoselective approach to the synthesis of .beta.-hydroxy carbonyl compounds

Abstract: Synthese de β-cetols par scission de trimethylsiloxy-1'alkyl-2oxirannes par TiCl 4 dans le dichloromethane

A Practical Synthesis of 1,3-Diene Using Allyltriphenylsilane and Titanium Tetraisopropoxide

Abstract: A practical method for the stereoselective preparation of 1,3-dienes by the use of allyltriphenylsilane as a key reagent is described.

A Conceptually Different Approach to the Asymmetric Synthesis of α-Substituted Carbonyl Compounds

Abstract: Synthese enantioselective d'aldehydes, cetones et acides carboxyliques a partir de l'addition de trialkyl-aluminium a des acetals α-insatures (bis-dimethylamides des acides alcene-1'yl-2dioxolanne-1,3dicarboxyliques-4,5)

Organoaluminium‐Induced Addition of Polyhalomethane to Olefins.

Abstract: Die Olefine (I) addieren die Tetrahalogenmethane (II) unter Katalyse durch Trimethylaluminium (III) und dem Pd-Phosphan-Komplex (IV) zu den homologen Tetrahalogenalkanen (V); Dodecen (VI) und CFZBrZ machen das Dibromdifluortridecan (VII) zuganglich.

Aldol Condensations Catalyzed by Organoaluminum Reagents.

Abstract: A new synthetic procedure for the practical synthesis of β-trimethylsiloxyketones from silyl enol ethers and aldehydes has been described which heavily depends on organoaluminum reagent as an effective catalyst.