The first example of a highly non-symmetric ozonolysis of a sugar derived norbornene system
Sebastián A. Testeroa, Rolando A. Spanevelloa*, and Rakesh Kohlib
aInstituto de Química Orgánica de Síntesis, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario – CONICET, Suipacha 531, S2002LRK Rosario, Argentina
bMass Spectrometry Facility, Department of Chemistry, University of Pennsylvania,
231 South 34th Street, Philadelphia, PA 19104
E-mail:
[email protected]
Dedicated to Professor Edmundo A. Rúveda on his 70th anniversary and to Professor Roberto A. Rossi on his 60th anniversary
(received 31 Jul 03; accepted 09 Sep 03; published on the web 24 Sep 03)
Abstract
The completely regioselective fragmentation of the primary ozonide formed during the ozonolysis of an unsymmetrical substituted norbornene system in the presence of methanol appears to be controlled by remote substituents and affords a tetrasubstituted cyclopentane moiety as a unique product in an almost quantitative yield.
Keywords: Unsymmetrical ozonolysis, Diels-Alder, norbornene, substituted cycloalkene, polysubstituted cyclopentane
Introduction
Ozonolysis is a widely applied reaction in organic synthesis. It is used to cleave multiple carbon- carbon or carbon-hetero-atom bonds. Extensive investigation of the mechanism of alkene ozonolysis has confirmed the pathway originally proposed by Criegee.1 This process could be particularly interesting when an alkene is placed within a cyclic or polycyclic molecular structure. In this case the process could unveil a very useful functional group arrangement. A drawback that one could foresee is the generation of two similar functional groups, for example the ozonolysis of a cycloalkene would afford a dialdehyde or a diol upon treatment of the ozonide with methyl sulfide or sodium borohydride, respectively. From a synthetic point of view, the coexistence of two similar groups in a molecule could generate a serious problem for the subsequent regioselective manipulation of each of them. For this reason the possibility of
