New heterocyclic materials

Abstract

The preparation of new heterocyclic systems by conventional ways is normally a hard work that implies many synthetic steps and expensive starting materials. Even more, many heterocyclic systems, being predictably stable, are impossible to be prepared because the synthetic approach simply does not exist. There is a very different approach to get new heterocyclic systems that uses simple organic starting materials (tertiary amines, alicyclic oximes) bearing a nucleophilic nitrogen which generates reactive intermediates, subsequently trapped by a inorganic reagent, disulfur dichloride (S2Cl2). In general, trapping of intermediates is followed by extensive dehydrogenation and chlorination to give new intermediates that can be trapped by selected nucleophiles on the way to stable final products.1-2 A good combination of reagents and reaction sequences permits the preparation of heterocycles that imply up to fifteen different steps all working sequentially in a one-pot reaction. The best example of this chemistry is the reaction of N-ethyldiisopropylamine (Hünig’s base), with disulfur dichloride.3-4 The first step is a slow oxidation of the amine to an immonium salt by a combination of disulfur dichloride and DABCO (diazabicyclo[2.2.2]octane).