Pyridazines. XXVI . A novel synthesis of pyrano[2,3‐ d ]pyridazines

A novel approach to the title ring system starting with conveniently available cinnamoylacetonitrile ( 1 ) is proposed. It involves the Japp‐Klingemann reaction of 1 followed by thermally induced cyclisation of hydrazones 2 and subsequent addition of the resulting pyridazine derivatives 3 to 2‐substituted cinnamonitriles 4a, 4b. The structures of the pyrano[2,3‐ d ]pyridazines 5a, 5b , thus obtained, were established on basis of spectroscopic data.