Ring Expansion into Six-Membered Heterocycles

Valerolactones are obtained in the reaction of oxiranes with dianions produced from phosphorus compounds (Eq. 222). ° ° 

Perchloric acid hydrolysis of glycidonitriles leads to spirolactones (Eq. 223). Q /-----V Q- 

The reaction of oxiranes and isocyanides has been reported to give 1,3-oxazines (Eq. 224).  

Procedures involving the reduction of oxirane and ammonia in the vapor phase over an Al203-Si02 catalyst have been patented for the preparation of pyrazine, piperazine, and morpholine. The formation of quinoxalines is illustrated in Eq. 225.  

From the reaction of divinylketone monooxirane and HjS, thiopyranone is formed (Eq. 227).  

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