A copper(ii) perchlorate-promoted tandem reaction of internal alkynol and salicyl N-tosylhydrazone: direct access to isochromeno[3,4-b]chromeneElectronic supplementary information (ESI) available: Experimental procedures, analytical data for all products, crystal data and structure refinement of product 3a, copies of 1H and 13C NMR spectra of all products. CCDC 997620. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c4cc02862g

A copper( ii ) perchlorate-promoted tandem reaction of internal alkynol and salicyl N -tosylhydrazone provides a novel, concise method for constructing isochromeno[3,4- b ]chromene in 35-94% yields. The tandem reaction involves cycloisomerization, formal [4+2] cycloaddition and an elimination process. A copper( ii ) perchlorate-promoted tandem reaction of internal alkynol and salicyl N -tosylhydrazone provides a novel, concise method for constructing isochromeno[3,4- b ]chromene in 35-94% yields.