Rare earth chlorides were used to catalyze the synthesis of 2-butoxy-3, 4-dihydro-2H-pyran (I) using equimolar acrolein and vinyl Bu ether. The cycloadduct is unstable which undergoes catalytic ring opening oligomerization. The way to stabilize the cyclo adduct has been studied, thus high yields of 90-95% were obtained.

Key words: BUTENE P, BUTOXY GROUP, PROPENAL, CHLORIDE, ETHER, DIHYDRO-COMPOUNDS, ETHYLENE P, BACTERICIDAL AGENTS, EUROPIUM COMPOUNDS, CYCLOADDITION REACTION