p-Toluenesulfonic acid → HCID 66770509, compound

Participants

Reaction Steps

2,5,6,6-Tetramethyl-cyclohexene carbaldehyde (64/7/29 trans 2-ene/cis 2-ene/1-ene isomers mixture) (1660 g, 10 mol., 1 eq.), ethylene glycol (1240 g, 20 mol., 2 eq.), cyclohexane (1660 g) and p-toluene sulfonic acid monohydrate (7.6 g, 0.04 mol., 0.004 eq.) were loaded altogether in a 10 liter schmizo type reactor equipped with a heating circulator, temperature probe, mechanical stirring device and a Dean-stark apparatus. The biphasic mixture was heated to reflux under vigorous stirring with azeotropic water removal from reaction mixture. After 8 hours reflux the reaction was then cooled down to room temperature. After decantation of the bottom phase containing excess ethylene glycol and p-toluene sulfonic acid the upper phase was concentrated under vacuum in order to remove cyclohexane and crude 2-(2,5,6,6-tetramethyl-cyclohexenyl)-1,3-dioxolane was obtained in 80% GC purity as a 80/7/13 trans 2-enyl/cis 2-en/1-enyl isomers mixture. Flash distillation afforded 1940 g of 2-(2,5,6,6-tetramethyl-cyclohexenyl)-1,3-dioxolane along with 60 g of residual heavy by-products formed during the reaction.

Provenance & Evidence