Hochstereoselektive Aldolreaktionen mit Metallbis- und Metallpolyenolaten zur Darstellung von Tetrahydropyran-2,4-diolen

Enolates of tetrahydropyran-2,4-diols with metals from group XIII were successfully
used to catalyse the domino aldol reaction. Further a series of reactions was performed to
obtain products containing 5 stereogenic centers. Optimising the reaction conditions enabled
isolation of one stereoisomer out of 16 possible isomers. Alkyl-, aryl- and alkoxy substituted
tetrahydropyran-2,4-diols were thus synthesised by the above mentioned strategy. Among the
group XIII metal enolates used indium tris enolate was found to be most effective. This is due
to various physical characteristics such as ion radius, electronegativity and charge density of
the indium(III)ions. A mechanistic model for the metal controlled domino aldol reaction was
deduced from the results obtained. The relative configuration of all the products was assigned
by NMR and in few cases by x-ray crystallography. Additionally first preliminary tests for
domino aldol reaction over two localseparated metal centers were performed.