The Study Of Allylic Oxidation Of Cholesterol-the Intermediate Product Of Vitamin D₃

Vitamin D₃ is a k(?)ind of fat-soluble vitamin,which plays an essential role in the maintenance of organic systems.As the population aging and the development of animal husbandry,the demand of Vitamin D₃ will keep rising.Nowadays,some of the vitamin D₃ used worldwidely are synthesized using the strategy including bromination,elimination,hydrolysis,and ultraviolet irradiation,in which,the using of a large amounts of bromine is unavoidable,thereby resulting in bromine-related corrosion and environmental hazard.In addition,undesired side products cannot be avoided in this process.Therefore,the production of vitamin D₃ by a halogen-free method is vital for the industry from an environmental point of view and has become a focus of scholastic interests.Herein,we present an innovative strategy for the synthesis of 7-keto-cholesteryl acetate,which is the key intermediate product of vitamin D₃.Our optimized N-hydroxyphthalimide(NHPI) system opens up a new and efficient access to Vitamin D₃.Molecular oxygen is introduced as oxidant,and only catalytic amounts of NHPI is used with a better yield,which has never been achieved before.This environmentally reliable and practical method holds promising application potential for chemical industries,particularly in the sythesis of vitamin D₃,for this easy method can substitute the bromination in the traditional route.In addition,a plausible reaction mechanism for the allylic oxidation of cholesterol catalyzed by NHPI and transition metal salts is shown in the paper.We explored the mechanism by using electron spin resonance (ESR) and UV-visible spectroscopy methods.