Stereoselective Ring Opening of Bicyclic Nitroso Diels-Alder Cycloadducts with Carbon Nucleophiles

Bicyclic oxazines are attractive compounds and valuable synthetic intermediates as they can be easily obtained by hetero Diels-Alder reactions between cyclic dienes and nitroso dienophiles. In particular, the more strained case (i.e. the [2.2.1]-cycloadduct) represents an interesting powerful combination of stability and reactivity as it can be transformed into highly densely functionalized cyclopentene derivatives by a variety of ring-opening reactions. Aim of this article is to summarize the methods used by various chemists for opening of bicyclic oxazines by the formation of a new carbon-carbon bond, to give highly substituted ring systems containing multiple stereocenters. Particular emphasis will be given to regio- and stereoselective procedures, including the most recent developments on less strained [2.2.2]-cycloadduct.