Síntese de 1,1,1-tricloro-4-metoxi-3-alquen-2-onas com cadeias graxas e suas derivatizações para isoxazóis e alcoxicarbonil-1H-pirazóis graxos

Abstract

This project presents the acylation methods of acetals applied for chemoseletive synthesis of greases 1,1,1-trichloro-4-methyl-3-alquen-2-ones derived from alkyl methyl ketones and dialkyl ketones, including those with unsymmetrical substituents, for example, the octan-3-one. The synthesis of dimethoxyacetal was conducted in the manner already established, providing yields, 82-90% after isolation. The acetals were acylated with trichloroacetyl chloride , as already described, called acetal acylation method and allowed the regiospecífic synthesis of 1,1,1-trichloro-4-methoxy-3-alquen-2-ones. Seven 1,1,1-trichloro-4-methoxy-3-alquen-2-ones, were obtained being six unreleased ((Cl3CCOCR2=C(OR)R1, R1 = C2H5, C4H9, C5H11, C6H13, C7H15, C9H19, C11H23, C13H27 ; R2 = H, CH3, C3H7, C4H9; R = H, CH3), in yield between 9-91%. It was observed that some of 1,1,1,-trichloro-4-methoxy-3-alquen-2-ones were obtained together with the respective trichloromethyl-β-diketone, probably due the hydrolysis during the isolation process which involves the use of aqueous acidic solution. The products obtained from the acylation of dialkyl acetals (R2 = alkyl) ketones derivatives were only the trichloromethyl-β-diketones, derived from the complete hydrolysis of 1,1,1-trichloro-4-methoxy-3-alquen-2-ones. This is probably due to thermodynamic issues involving the accomodation of the four substituents on the double bond plane of 1,1,1-trichloro-4-methoxy-3-alquen-2-ones with R2 = alkyl. It was also observed for these trichloromethyl-β-diketones, with R2 = alkyl, that exist in solution preferably in the keto form. The 1,1,1-trichloro-4-methoxy-3-alquen-2-ones and/or respective trichloro- methyl-β-diketones reacted with hydroxylamine chloride and hydrazine chloride to obtain the unprecedented series of the respective 5-trichloromethyl-5-hydroxy-4,5-dihydro- isoxazoles and carboxyalquil 1H-pyrazoles with greases substitutes. The 5-trichloro methyl-5-hydroxy-4,5-diidroisoxazóis were obtained in yields 28-95%. The carboxyalquil -1H-pyrazoles were obtained in yields of 30-97% range. It s important accentuate the structural similarity between the carboxyalquil-1H-pyrazoles and esters of grease acids, these represent a functionalized form of conventional grease acids. It was also realized in these project the transterification of vegetable oils (soya, canola and olive) with trimethyl trietilortoformatos under p-toluenesulfonic acid catalysis. And to emphasize the possibility of direct esterification of the free acid were also made the esterification reaction of grease acids (stearic, oleic and linoleic) under the same transterification conditions. This method proved to be efficient from the synthetic point providing from commercial oils used as from free grease acids and their methyl ethyl esters. This method proves important, given the high profile of biodiesel in the context of biofuel production, because it provides from transterification products under mild conditions under acid catalysis and also promotes the esterification of the free acids portion contained in vegetable oil. Making it an attractive possibility for the case of recycling vegetable oils now used for cooking, rich in free acid.