No abstract

Effi cient synthesis of an epothilone molecules fragment (15R)-C 13 -C 21 was carried out from D-mannitol through its conversion into methyl 2,3-O-cyclohexylidene-D-glycerate followed by the cyclopropanation of the ester group with ethylmagnesium bromide in the presence of titanium(IV) isopropoxide and the transformation of the obtained cyclopropanol into the corresponding 2-substituted allyl bromide. The coupling of the latter catalyzed by copper with 2-methylthiazolyl-4-magnesium bromide, the shift of a double carbon-carbon bond in the product obtained into the position, conjugated with the thiazole ring, and the common transformation of the protected 1,2-diol function afforded the target compound in 15% yield.

No abstract

A reagent combination of Ti(OiPr)4 and ethylmagnesium bromide generates low valent Ti(OiPr)3 which is readily used to transform carbonyl compounds into the corresponding pinacols. -(MATIUSHENKOV, E. A.; SOKOLOV, N. A.; KULINKOVICH*, O. G.; Synlett 2004, 1, 77-80; Dep. Org. Chem., Belarus State Univ., Minsk 220050, Belarus; Eng.) -Mais 19-032

No abstract

The composition of the gaseous products from the reaction of Ti(IV) isopropoxide with ethylmagnesium bromide in diethyl ether evidences the formation of subvalent titanium isopropoxide species in various oxidation states depending on relative amounts of the reactants. Reaction of titanium(IV) isopropoxide with one equivalent of the Grignard reagent gives presumably titanium(III) isopropoxide. The latter is generated as a result of disproportionation of starting Ti(IV) species and titanium(II) isopropoxideethene complex which is formed as a result of ethane extrusion from diethyltitanium(IV) isopropoxide. Titanium(III) isopropoxide prepared by this way transforms the aldehydes and the aromatic ketones into the corresponding pinacols in good yields.

Durch Oxidation der Nitroolefine (I) mit Perhydrol in wäßrig‐methanolischem NaOH bei.

Die Alkalisalze (I) von Cumylperoxid reagieren mit Kohlendioxid zu den Peroxycarbonaten (II).