Sulfone directed alkylative bridge cleavage of oxabicyclic vinyl sulfones with organolithium reagents (1)
Arjona, O. and Plumet, J.
Departamento de Química Orgánica I, Facultad de Química, Universidad Complutense, 28040 Madrid, Spain
Ars Pharm.36;(3);417-432, (1995)
Key words: Oxabicyclic compounds, Syn SN2', Exo conjugate additionAbstract
An efficient regio- and stereocontrolled methodology for the alkylative bridge cleavage of oxabicyclic vinyl sulfones is described. A range of 7-oxabicyclic [2.2.1]heptenyl and 8-oxabicyclic [3.2.1]octenyl sulfones has been found to undergo an overall syn SN2' opening when treated with a wide variety of organolithium reagents and lithium aluminum hydride. In this manner, highly functionalized cyclohexenyl and cycloheptenyl sulfones, versatile synthetic intermediates, are now available in high yields. The complete stereoselectivity encountered in the exo conjugate addition may be explained by chelation of the organometallic reagent with the oxygen bridge and steric factors. Furthermore, less-strained substrates allow for complete control of the addition and elimination stages.
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