Tosylhydrazones ring closure with

Ring closure with tosylhydrazones 3,7-Transannular C—H-insertion... 

Another route to ring (7) involves introduction of the boron atom last, in the reaction between boron tribromide and an aromatic tosylhydrazone as exemplified in Scheme 26. The yields in the ring closure are not as high as those mentioned above but the main advantage with this method is the ready availability of the starting materials (78HCA325). 

Lithiation of -(benzotriazol-l-yl)-substituted tosylhydrazones 472 with butyllithium initiates the ring-opening and ring-closure reactions leading to 1,2,4-benzotriazines 473 (Scheme 247) <1997SC3963, CHEC-III(9.02.8.1)180>. 

An elegant route to pyrazoles, involves forming a ring closure precursor by Homer-Emmons condensation of a tosylhydrazone-phosphonate with an aldehyde, which becomes the 5-substituent intramolecular Michael addition and then loss of toluenesulfinate as the final aromatising step, completes the sequence. ... 

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