Water → [5-(4-Hydroxy-2,6,6-trimethyl-1-cyclohexen-1-yl)-3-methyl-2,4-pentadienyl]triphenylphosphonium chloride

Participants

Reaction Steps

A suspension of 46.6 g of water-moist Raney-nickel and 518 mg of 1,2-bis(2-hydroxyethylthio)ethane in 1 l of methanol was pre-hydrogenated at 30° C. under normal pressure in a sulphonation flask provided with a gasification stirrer. Subsequently, a solution of 320 g of (4R,2E)-[5-(4-hydroxy-2,6,6-trimethyl-1-cyclohexen-1-yl)-3-methyl-2-penten-4-ynyl]triphenylphosphonium chloride in 2.1 l of methanol was added thereto and the mixture was hydrogenated at 40° C. and 1.1 bar of hydrogen. 15.6 l of hydrogen were taken up within 5 hours. The catalyst was filtered off and the filtrate was concentrated to a weight of 575 g. The product was crystallized by slowly pouring in 9.6 l of ethyl acetate. The suspension was stirred at room temperature for 2 hours and filtered. The crystals were washed with a small amount of methanol/ethyl acetate and dried at 60° C./0.01 mbar, there being obtained 272.2 g (84.7%) of [5-(4-hydroxy-2,6,6-trimethyl-1-cyclohexen-1-yl)-3-methyl-2,4-pentadienyl]triphenylphosphonium chloride (containing 97% of the (4R,2E,4Z)-isomer and 2% of the (4R,2Z,4Z)-isomer in accordance with HPLC) of melting point 211°-212° C. and [α]D20 =-26.2° (c=1, chloroform).

Provenance & Evidence