Cyclic compounds cyclobutanes, synthesis

The substrate for the synthesis of cyclobutanes by elimination of molecular nitrogen is the 3,4,5,6-tetrahydropyridazine skeleton 1. The most important methods for obtaining these compounds are the hetero Diels-Alder reaction of suitable dienes with azo dienophiles followed by oxidative hydrolysis of the adducts, and the oxidation of six-membered cyclic hydrazines (see Houben-Weyl, Vol. E16d, pp 1-111 and ref 1). 

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