2,2-Dimethyl-5-(5-R-2-furfurylidene)-1,3-dioxane-4,6-diones. 4. Synthesis, stereostructures, and properties of thiophene analogs
The reaction of 2-formylthiophenes with Meldrum's acid gave the corresponding thenylidenedioxanediones, which, in contrast to the furfurylidene derivatives, have an s-trans conformation of the mutual orientation of the thiophene ring and the exocyclic double bond. Thenyldioxanediones were synthesized by the selective hydrogenation of the exocyclic double bond.