The action of various silylating agents on mono-and polyvicinal 1,1-dihydroxy compounds has been investigated. Some of these reagents converted ninhydrin (2) and rhodizonic acid (17) into the corresponding geminal bis(trimethylsily1oxy) derivatives 1 and 20, respectively. Compound 1 readily fragments to form hexamethyldisiloxane and indantrione (4). The rhodizonic acid derivative 20 is, however, rather stable and even on pyrolysis at 500°C gives only traces of the tetraketone 21. With other silylating agents unexpected C-alkylation or C-amidation at the dihydroxy carbon is observed. Silylation of perhydroxycyclobutane and -cyclohexane leads to ring opened and contracted products. Hydratisierte Oxokohlenwasserstoffe, IV1) Silylierung von 1,l-Dihydroxy-Verbindungen Die Anwendung von verschiedenen Silylierungsreagenzien auf mono-und polyvicinale 1,l-Dihydroxy-Verbindungen wurde untersucht. Mit einigen dieser Reagenzien konnten aus Ninhydrin (2) und RhodizonsBure (17) die entsprechenden geminalen Bis(trimethy1silyloxy)-Derivate 1 und 20 gewonnen werden. Wahrend 1 leicht zu Hexamethyldisiloxan und Indantrion (4) fragmentiert, ist 20 thermisch relativ stabil, es gibt pyrolytisch bei 5WoC nur Spuren des Tetraketons 21 ab. Andere Silylierungsreagenzien bewirken unerwartete C-Alkylierung oder C-Amidierung am Dihydroxykohlenstoff. Silylierungen von Perhydroxycyclobutan und -cyclohexan fuhren zu Ringaufspaltungs-bzw. Verengungsprodukten.
In the course of our effort^^.^) to arrive at the elusive neutral cyclic oxocarbons of the type (CO), we now report our results on attempted "chemical" dehydration of appropriate gem-dihydroxy compounds using silylation and deoxysilylation by the sequence (1).
Results and Discussion
Applied to one of the simplest compounds of this class, ninhydrin (Z), which can also be successfully dehydrated by heating in vacuo, chemically by the reaction with thionyl chloride4) or borylation-deoxyborylation2), we observed that the products formed