Ring Formation Involving a Mononitrile Component

The heterocyclic syntheses that can be accomplished using a mononitrile are of the more conventional type where, generally, two organic components are combined to produce the ring. 

The first of these approaches stems from the Ritter reaction, whereas the second utilizes nitrilium salt intermediates. These reactions are probably different in degree rather than in kind since they are regarded as involving similar intermediates. 

In 1948 Ritter5 described a new reaction in which N-substituted amides were prepared from alkenes and nitriles in the presence of a 

One of the earliest heterocyclic applications of the Ritter reaction was to the synthesis of dihydro-1,3-oxazines.9 It was found that the reaction of the dialcohol (1) with nitriles leads to the oxazines (2) rather than the expected bis-amides (Table I). The yields are only fair 

The application of this approach to the synthesis of five-membered rings from 1,2-dihvdroxy compounds does not appear to have been 

---