5-Arylidene Derivatives of Meldrum’s Acid as Synthons in Pyrano[4,3-b]pyran Synthesis

The reactions of 5-arylidene derivatives of Meldrum’s acid with ethyl vinyl ether or N-vinyl-2-oxazolidinone yielded trans-trans-(2,4:4,7)-pyrano4,3-b]pyrans, cis-trans-(2,4:4,7)-pyrano4,3-b]pyrans, or diastereoisomeric mixtures of pyrano4,3-b]pyrans and reactions with 3,4-dihydro-2H-pyran afforded Michael adducts. The reactions of 5-arylidene derivatives of Meldrum’s acid with cyanoacetic acid derivatives do not provide appropriate pyrans.