ABSTRACT
A new approach for real-time mass spectrometric analysis and identification of intermediates in confined, pressurized vessels is presented. The high-pressure reaction media is depressurized, mixed with a solvent, and fed directly to the atmospheric pressure electrospray ionization source of a tandem mass spectrometer. The method was applied to track product evolution for the dehydration of hydroxenin monoacetate, a commercially, important vitamin A precursor, and for the hydrogenation of 5-norbornene-2-carbonitrile with Pd/CaCO(3) as catalyst. Faster access but comparable results as by conventional off-line methods were obtained in every case.
ABSTRACT
A new method for the preparation of an E/Z mixture of vitamin A acetate from hydroxenin monoacetate is described. This two-step reaction was studied by changing the reaction parameters (reaction temperature, ultrasound power, and reaction time) and the alcohol used. This approach consists of the dehydration reaction of hydroxenin monoacetate under ultrasound irradiation in CCl4 and an aliphatic alcohol under an inert atmosphere. The formation of small amounts of HCl from CCl4 and an aliphatic alcohol under ultrasound irradiation is followed by the dehydration reaction of hydroxenin monoacetate. An E/Z mixture of vitamin A acetate was obtained resulting in the desired pentaenes. Some ethers derivatives were also formed as by-products, isolated and characterized. Study of the reaction mechanism is also reported here.
