Studies On The Photochemical Behavior Of Aryl Unsaturated Carbonyls And Their Derivatives

As a kind of important organic intermediates,unsaturated carbonyls are widely used in pharmaceutical,pesticide,spices,etc.Due to the conjugate structure of C=C and C=O,it can be employed in 1,2-and 1,4-nucleophilic addition,electrophilic addition,Diels-Alder reaction,Michael addition reaction.The difunctionalization of C=C is one of the most important reactions which can be achieved by a variety of ways,most of which are realized by transition metal catalyst and oxidation method.As a kind of clean method,photochemistry applied in the difunctionalization of olefins has the advantages of simple operation,quickly rate,environmently friendly.In order to further explore the photochemical applications,we designed and synthesized a series of aryl ?,?-unsaturated carbonyls and their derivatives,and subjected to the photochemical conditions.The trilfluoromethyl group plays a significant role in pharmaceuticals and agrochemicals because its introduction into drug candidates could strengthen chemical and metabolic stability,electronegativity,ameliorate lipophilicity,bioavailability,and enhance binding selectivity.We realized a UV light-mediated trifluoromethylation of aryl ?,?-unsaturated with a 450 W medium pressure mercury lamp as the light source,CF3SO2 Na as the CF3 radical source,anthraquinone(AQ)as the photosensitizer,which led to the antrone derivatives in 33-55% yield,which is prevalence in natural products with bioactivity.A series of aryl ?,?-unsaturated carbonyls were prepared to investigate the scope of the reaction.A control experiment by reaction with TEMPO(2,2,6,6-tetramethyl piperidine)for free radicals capture was conducted and with the theory of paramagnetic resonance(EPR)then a possible reaction mechanism was proposed,the CF3 free radical attacked C=C bonds and then followed by a intramolecular cyclization.The ester group is a kind of important intermediates in organic synthesis which can participate in decarboxylation,reduction,hydrolysis process into other functional groups.We explores the photochemical addition reaction process of aryl ?,?-unsaturated carbonyls and diethyl bromomalonate.By application of visible light induced strategy with the blue LEDs as the light source,Ir[d F-CF3-ppy]2(dtbpy)PF6 as the photocatalyst,the aryl ?,?-unsaturated carbonyls were reacted with diethyl bromomalonate by a radical addition and cyclization,leading to the ester substituted anthracene derivertives in yield of 85-90%.The scope of substituted of aryl ?,?-unsaturated carbonyls were explored on the influence of the substituent.The control reaction by TEMPO capture experiment showed that the reaction followed a free radicals pathway.The epoxy is a kind of lively reactive group that can be reacted by selective ring opening and functional transformation process produces.A series of aryl ?,?-epoxy ketones were prepared and subjected to the photochemical reactions.A UV light-mediated photorearrangment reaction was explored through a Norrish type ?reaction,leading to a variety of isochromanol derivatives,as the versatile synthetic building blocks of natural products.The photochemical reaction under UV irradiation was carried out under the condition of dried benzene as the solvent,without adding any other reagents.The photorearrangment reactions were affected by the electronic effect of the substitutants of the aryl ?,?-epoxy ketones,the electron-donating or donating groups leading to completely different results.As the photo products have isomers,we tried to add some chiral reagent or solid-phase photochemical reaction to control the stereoselectivity,while the r esults showed that the rearrangement reaction of free radical way was not affected by the external chiral selectivity.A plausible reaction mechanism was proposed that the carbonyl group inspiring by UV light to form biradicals,and thus followed by two hydrogen migration.EPR spectrum of free ridicals pathway was studied by TEMPO as the radical trap.