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OBJECTIVE Soluble oligomers of amyloid beta (Abeta), rather than amyloid fibrils, have been proposed to initiate synaptic and cognitive dysfunction in Alzheimer's disease (AD). However, there is no direct evidence in humans that this mechanism can cause AD. Here, we report a novel amyloid precursor protein (APP) mutation that may provide evidence to address… (More)
The sequential transformation of arynes into ortho-disubstituted arenes is achieved by a one-pot procedure using formamides and dialkylzincs. This reaction proceeded via a route involving the trapping reaction of the formal [2 + 2] cycloaddition adducts or quinone methides generated by the insertion of arynes into the C=O bond of amides.
Synthesis of dihydrobenzofurans was achieved by a route involving the insertion of arynes into formamides followed by trapping with zinc enolates of α-chlorinated methines. Benzofurans were generated from dihydrobenzofurans having a ketone group via the addition of an ethyl anion, the retro-aldol type reaction, and the elimination of an amino group.
The domino three-component coupling reaction of arynes with DMF and active methylenes or methines was studied as a highly efficient method for preparing heterocycles. Coumarin derivative 5 was formed when diethyl malonate (2) or α-bromomalonate (3) were used as a C2-unit. In contrast, dihydrobenzofurans 7a and 7b were obtained by using α-chloroenolates… (More)
In the presence of charge-transfer complexes between iodine and tertiary amines, the aqueous-medium atom-transfer radical reactions proceeded under visible light irradiation without the typical photocatalysts.
One-pot synthesis of xanthene derivatives was achieved by a route involving the cascade three-component coupling reaction of arynes with DMF and active methylenes followed by the SN2' reaction of three-component coupling products with thiols. The reactivity of three-component coupling products toward nucleophiles and the further conversion of oxygen… (More)
The utility of rhodamine B as a water-soluble organic photocatalyst was studied in the cascade radical addition-cyclization-trapping reactions under visible light irradiation. In the presence of (i-Pr)2NEt, the electron transfer from the excited rhodamine B to perfluoroalkyl iodides proceeded smoothly to promote the carbon-carbon bond-forming radical… (More)
Arynes, such as benzyne, are highly strained and kinetically unstable intermediates that have been widely employed in organic synthesis. In particular, since the initial report regarding the in situ generation of arynes under neutral conditions from ortho-(trimethylsilyl)aryl triflates and fluoride ions in 1983, numerous nucleophilic additions to arynes… (More)
The synthesis of 1H-benzo[f ]isoindole derivatives was achieved by the cascade radical cyclization–cyclization reaction of the active methine substrate having an allyl group and phenyl group as different two radical acceptors. This oxidative transformation proceeded by using iron(III) chloride FeCl 3 as a mild oxidant via the intramolecular radical addition… (More)