REGIOSELECTIVITY OF PHENOL ALLYLATION REACTION WITH ALLYL ALCOHOL OR ALLYL ACETATE

• Main Author: Pebriana, Rian
• Format: Dissertations
• Language: Indonesia
• Subjects: Kimia analitis
• Online Access: https://digilib.itb.ac.id/gdl/view/32173
• Institution: Institut Teknologi Bandung

various biological uses of economic value. For example, estragole is a major component of palm oil flower essential oil that is attractant to the Elaeidobius kamerunicus Faust beetle. The beetle has been identified as an efficient pollinator of palm oil. In the chemical industry, estragole is the raw material for producing anethole. Anethole is an additive compound used in food products, alcoholic beverages, in oral hygiene product formulations, and as an intermediate compound essential for synthesizing pharmaceutical compounds and perfume chemicals. Another example, eugenol which is a major component of clove oil, is useful as a flavour, aromatherapy, herbivorous antifeedant, nematocide, fungicide, and bacteriocide. A simple phenylpropanoid, 4-allylphenol (chavicol), is a demethyl derivative of estragole and is a component in betle oil (Piper betle). This compound is less volatile than its O-methyl derivative, estragole, but due to its position as an intermediate for various phenylpronoid derivatives, 4-allylphenol becomes an attractive target in the synthesis of phenipropanoid derivatives. Various methods have been developed in the synthesis of 4-allylphenol, which included stoichiometric reactions, homogeneous catalyzed reactions, and heterogeneous catalyzed reactions. Stoichiometric reaction methods included Friedel-Craft reactions, dealkylation reaction of 1-allyl-4-alkyloxybenzene, and organometallic reactions with organozinc. Examples of homogeneous catalyzed reactions included the allylation reaction of allylphenylboronate pinacole ester with hydrazone-palladium catalyst, phenol allylation reaction with allyl tosylate using rhodium catalyst, and phenol allylation reaction with allyl bromide using an ?- cyclodextrin catalyst. Another example was the allylation reaction of phenol with allyl alcohol using a water-soluble palladium catalyst. Furthermore, examples of heterogeneous catalyzed reactions were phenol allylation reaction using a mordenite zeolite catalyst with an allyl alcohol substrate and a phenol allylation reaction using an H-? zeolite catalyst with an allyl acetate substrate. Another method that can be used in the synthesis of 4-allylphenol was the Claisen and Cope rearrangement of the allyl phenyl ether substrate. However, the methods have not been satisfactory, either from the side of the yield or the regioselectivity aspect, so an alternative method is needed in synthesizing this compound. This research aimed to examine the regioselectivity of phenol allylaltion reaction with allyl alcohol or allyl acetate to synthesize 4-allylphenol by various methods, which included: 1) 4-allylphenol synthesis by stoichiometric reaction with the mediation of thionyl chloride reagent, 2) synthesis of 4-allylphenol by the watersoluble palladium-catalyzed reaction, 3) synthesis of 4-allylphenol by the rearrangement of allyl phenyl ether using zeolite catalyst, and 4) synthesis of 4- allylphenol by the rearrangement of allyl phenyl ether using water soluble palladium catalyst. The reaction product of the experiments were analyzed by GCMS-EI, GCMS-CI, and GC-FID methods to determine the optimum conditions associated with the yield and reaction’s regioselectivity. The one-pot synthesis of 4-allylphenol through the phenol allylation reaction with allyl alcohol using thionyl chloride reagent was significantly influenced by the amount of thionyl chloride, reaction temperature, reaction time, and stirring rate. The optimum condition of the reaction resulted in a conversion of 62% and a regioselectivity to 4-allylphenol of 75%. The regioselectivity mechanism is determined by the presence of an allyl phenyl sulphite intermediate compound which may undergo further rearrangement to the para position of phenol compound. The synthesis of 4-allylphenol through the allylation reaction of phenol with allyl alcohol using a water-soluble palladium catalyst was significantly affected by Zn powder as co-catalyst, the amount of sodium hydroxide, the volume of water, reaction time, and temperature. The optimum condition of the reaction resulted in a conversion of 47% and a regioselectivity to 4-allylphenol of 60%, which were better than the previous study, i.e. 8% and 45%, respectively. The regioselectivity mechanism was suggested because of the solvation by the water and the participation of the zinc metal in the transition state of the palladium catalytic system. The synthesis of allyl phenyl ether by the allylation reaction of phenol with allyl acetate using water soluble palladium catalyst was significantly affected by reaction time and temperature, the amount of catalyst, base, and air atmosphere. Under optimum condition, the reaction can produce allyl phenyl ether with 100% conversion. The rearrangement of allyl phenyl ether with zeolite catalysts was significantly affected by the reaction time and temperature, the Na-ZSM-5 zeolite, and the amount of Na-ZSM-5 catalyst. The optimum condition yielded 2- allylphenol with a 52% conversion. While the isomerization reaction of allyl phenyl ether with a water soluble palladium catalyst was directly influenced significantly by the amount of phenol and Na-ZSM-5 zeolite. The optimum condition resulted in 92% conversion and no other product formation. But the regioselectivity to 4-allylphenol was still about 48%. The isomerization reaction of allyl phenyl ether with water soluble palladium catalyst by synthesizing allyl phenyl ether in situ proceeded in 2 steps, i.e. the first step was allyl phenyl ether synthesis from phenol and allyl acetate and the second step was isomerization of allyl phenyl ether. This reaction was significantly influenced by the amount of phenol, reaction time, the amount of catalyst, sodium hydroxide, and volume of water. The optimum condition resulted in a 99.8% conversion with a regioselectivity to 4-allylphenol of 53%. The presence of solvation played a role in regioselectivity, but this solvation mechanism had no significant control to enhance further regioselectivity. Based on the results of the experiments it can be concluded that the selectivity of C-allylation was significantly influenced by the mediation of thionyl chloride reagent, the use of allyl alcohol as an allylation reagent, and the water solvation. Meanwhile, selectivity to O-allylation was significantly influenced by the reactivity of allyl acetate reagent. The reaction regioselectivity to 4-allylphenol was significantly affected by the mediation of thionyl chloride reactant, the participation of the zinc as co-catalyst, the amount of phenol, and the water solvation. While the use of Na-ZSM-5 zeolite suppressed the formation of byproducts in isomerization reaction of allyl phenyl ether. Factors determining both the selectivity of C-allylation and the reaction regioselectivity to 4- allylphenol such as the water solvation and the amount of phenol are in agreement with the previous study, while other factors are new contributions from this study.