| Sumario: | The article discusses the stereocontrolled synthesis of spiroketals. It is observed that alternate nonchelated mechanisms are inconsistent with the observed stereochemical preference. Kinetic spiroketalization is Mediated cyclization of Ti(Oi-Pr)4 and MeOH-induced cyclization (C1-inversion) provide comprehensive access to systematically stereochemically diversified spiroketals. The exposure of the inversion spiroketal to the reaction conditions did not result in equilibration which shows that Ti(Oi-Pr)4-mediated spirocyclization is, kinetically controlled. Reduced stereoselectivity was observed when substoichiometric amounts of Ti(Oi-Pr)4 was used suggesting that the metal may remain coordinated to the product , although the complex is not responsible for the stereochemical outcome of the kinetically reaction.
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