The reaction of cyclic CH-acids such as 5,5-dimethyl-1,3-cyclohexanedione, 1,3-cyclohexanedione, 4-hydroxy-6-methyl-2 H-pyran-2-one, or 4-hydroxycumarin with dialkyl acetylene dicarboxylates in the presence of tosylmethyl isocyanide (TosMIC) in polyethylene glycol (PEG-300) leads to new annulated highly functionalised 2-amino-4 H-pyrans at room temperature in good yields.
The reactive intermediate generated by the reaction of alkyl isocyanides and dialkyl acetylenedicarboxylates was trapped by 4-phenylaminocoumarin to produce dialkyl 2-cyclohexylamino-5-oxo-4 H,5 H-pyrano[3,2- c]chromene-3,4-dicarboxylates in good yields.