20965-10-0Relevant academic research and scientific papers
PHOTOCHEMICAL ARYLATION OF FURANS AND THIOPHENES
D'Auria, Maurizio
, p. 419 - 434 (2007/10/02)
The photochemical behaviour of furan and thiophene is discussed with special attention to photoarylation of thiophene.The irradiation of 5-bromofuran-2-carbaldehyde, 41, in benzene gave good yields of the corresponding 5-phenyl derivative 42.The reaction 41--->42 has been studied considering the photochemical behaviour changing both the position of the halogen on the furan ring and the effect of the solvent.Kinetic and spectroscopic data are in agreement with the formation of a transient triplet exciplex in this type of reactions.The use of both the iodo derivative 50 and acetonitrile as solvent allowed the conversion to be optimized.On the contrary, the irradiation of 41 in diethyl ether or in an amine furnished the dehalogenation product 53.Photoarylation can be extended to thiophene derivatives and aromatic or heteroaromatic donors.The reaction also occurs with halothiophenes or thiazoles as donors, or by using halothiophene carboesters as acceptors.On the contrary, halothiophene carbonitriles are unreactive under similar conditions.Some applications to the synthesis of naturally occurring polythiophenes are reported.The target compounds were obtained through photoarylation and subsequent reaction with alkynes in the presence of palladium(0) complexes as catalysts.The role of polythiophenes in the environment is discussed.The hypothesis that the bioactivity of these compounds is related to the capability to be singlet-oxygen sensitizers is supported by the finding that all the bithiophenes synthesized are singlet-oxygen sensitizers.
Photochemical Synthesis of Phenyl-2-thienyl Derivatives
Antonioletti, Roberto,Auria, Maurizio D',Onofrio, Franco D',Piancatelli, Giovanni,Scettri, Arrigo
, p. 1755 - 1758 (2007/10/02)
The irradiation (in benzene solution) of 5-bromo- and 5-iodo-thiophene-2-carbaldehyde or the corresponding methyl ketones furnishes the corresponding 5-phenyl derivatives.The same reactivity for other halogenothiophenes is reported: 3,5-dibromothiophene-2-carbaldehyde furnishes the 3-bromo-5-phenyl-2-thienyl derivative while the corresponding di-iodo compound yields 3,5-diphenylthiophene-2-carbaldehyde.In contrast, 5-acetyl-2,3-di-iodothiophene furnishes only the photosubstitution pruduct at C-5.Generally the iodine-containing compounds are more reactive and more stable under the reaction conditions than ones bearing bromine, in agreement with previous reports on the corresponding furan photochemistry.
Enamines from Iodine Oxidation of Trialkylamines. 1. Electrophilic Capture by Cationic Heterocyclic Rings
Wadsworth, Donald H.,Detty, Michael R.,Murray, Bruce J.,Weidner, Charles H.,Haley, Neil F.
, p. 2676 - 2681 (2007/10/02)
Simple enamines derived from acetaldehyde, acetone, and propionaldehyde were generated in situ by iodine oxidation of triethylamine, N,N-diisopropylmethylamine, and tri-n-propylamine, respectively.The enamines were captured by a variety of cationic substrates including trityl, indolizinium, dithiolium, pyrylium, thiapyrylium, selenapyrylium, and tellapyrylium cations.The use of a second equivalent of iodine (or excess) oxidized the initial products of enamine capture to various iminium dyes.These dyes were easily hydrolyzed to heterocyclylidene aldehydes and ketones.Cyclic amines such as N-methylpyrrolidine gave enamines derived from ring oxidation. 2-Cyano-N,N-dimethylethylamine generated a cyano-substituted enamine under the reaction conditions.
