- Preparation method of vitamin A acetate intermediate C15 and vitamin A acetate
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The invention provides a preparation method of a vitamin A acetate intermediate C15 and vitamin A acetate. The method comprises the following steps: taking 1-halogenated-2-methyl-4-acetoxy-2-butene asa raw material, preparing a corresponding Wittig reagent through a substitution reaction with triphenylphosphine or triester phosphite, then carrying out a Wittig reaction with beta-cyclocitral, hydrolyzing an ester group under an alkaline condition, acidifying to obtain a corresponding halide, and carrying out a substitution reaction with triphenylphosphine or triester phosphite again to prepareC15. The vitamin A acetate can be prepared by carrying out a Wittig reaction on the obtained C15 and 2-methyl-4-acetoxy-2-butenal under an alkaline condition. The method has the advantages of singlereaction type, easy operation and realization of reaction conditions, safe and environment-friendly operation, simple post-treatment and low cost; and the reaction activity is strong, the reaction selectivity is high, the atom economy is high, and the target product yield and purity are high.
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- Preparation method of vitamin A ester intermediate C15 and vitamin A ester
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The invention provides a preparation method of a vitamin A ester intermediate C15 and vitamin A ester. The method comprises the following steps: carrying out a halogenation reaction and a cyclizationreaction on 3, 7-dimethyl-3-hydroxy-1, 6-octadiene as an initial raw material, carrying out a substitution reaction on the obtained product and triphenylphosphine or triester phosphite to prepare a corresponding Wittig reagent, carrying out a Wittig reaction on the Wittig reagent and 2-methyl-4-acetoxy-2-butenal, performing acidifying, hydrolyzing and acidifying the obtained product, and carryingout a substitution reaction on the hydrolyzed and acidified product and triphenylphosphine or triester phosphite to prepare C15. The vitamin A ester can be prepared by carrying out a Wittig reaction on the obtained C15 and 2-methyl-4-R3 substituent carbonyloxy-2-butenal. The method has the advantages of single reaction type, easy operation and realization of reaction conditions, safe and environment-friendly operation, simple post-treatment and low cost; and the reaction activity is strong, the reaction selectivity is high, the atom economy is high, and the target product yield and purity arehigh.
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- Ionic Photodissociation of Polyenes via a Highly Polarized Singlet Excited State
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Several polyene acetates and polyene methyl ether were prepared.Upon direct excitation these polyenes undergo ionic photodissociation from their singlet excited states.Triplet-sensitization experiments on these polyenes revealed that the ionic photodissociation process is restricted to singlet excited states.The rationale put forward is that the polyene chromophore undergoes charge separation/polarization in the singlet excited state, which leads to ionic photodissociation.
- Reddy, A. Mahipal,Rao, V. Jayathirtha
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p. 6727 - 6731
(2007/10/02)
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