88082-89-7Relevant academic research and scientific papers
Synthesis of Substituted Aromatic Compounds by Diels-Alder Reactions of Alkoxycyclobutenes Produced via Photocycloadditions between Vinyl Ethers and 1,3-Dione Enol Esters
Barker, Andrew J.,Begley, Michael J.,Birch, Alan M.,Pattenden, Gerald
, p. 1919 - 1923 (1983)
The adducts (5) obtained from photocycloaddition of ethyl vinyl ether to the 1,3-dione enol acetate (4) rapidly loses acetic acid producing the ethoxycyclobutene (7).On being warmed in the presence of a dienophile, the ethoxycyclobutene (7) undergoes electrocyclic ring-opening to give the ethoxydienone (8) followed by cycloaddition to produce Diels-Alder adducts ; elimination of ethanol from (10) gives the dimethyl phthalate (11).In a 'one-pot' reaction, heating a solution of (5) with 1,4-naphthoquinone in xylene containing aluminia leads to the substituted anthraquinone (12) in 95percent yield.On storage at 0 deg C for a few days the ethoxycyclobutene (7) is converted into the crystalline dimer (9) via the transient ethoxydienone (8); the structure of (9) followed from X-ray measurements.An analogous dimer (14) was produced during attempts to effect an intramolecular Diels-Alder reaction from the bicyclic ether (13).
