High atomic utilization conversion of ethers into furancarbaldehydes via an ether oxidation iminium-ion activation cascade strategy.

A novel organocatalytic one-pot cascade ether oxidation iminium-ion activation strategy for the synthesis of naphtho[2,1-b]furan-1-carbaldehyde and benzofuran-3-carbaldehyde from high atomic utilization transformation of aryl allyl ethers has been developed. Its synthetic application will provide a new ether oxidation iminium-ion activation cascade tool for the efficient synthesis of complex molecules.

Catalyst-Free α-Alkylation-α-Hydroxylation of Oxindole with Alcohols.

3-Alkyl-3-hydroxyoxindoles, a subclass of oxindole products, have antioxidant, neuroprotective, anticancer, and anti-HIV activities. In this study, a green and economical protocol for the synthesis of 3-alkyl-3-hydroxyoxindoles is developed for the first time via α-alkylation-α-hydroxylation of oxindole with benzyl alcohols without using any transition-metal catalysts in yields of 29-93%.

One-pot three-component access to 5-hydroxyindoles based on an oxidative dearomatization strategy.

A one-pot three-component reaction based on an oxidative dearomatization strategy has been performed to provide facile access to 5-hydroxyindole derivatives through a ZnI2-catalyzed tandem process. The multi-unit reactions for the construction of a new C-C bond and two C-N bonds are simple and efficient under mild conditions, and the yield of the target product is as high as 91%.

Pyridine-hydrazone-controlled cyanide detection in aqueous media and solid-state: tuning the excited-state intramolecular proton transfer (ESIPT) fluorescence modulated by intramolecular NHBr hydrogen bonding.

A new efficient pyridine-hydrazone-substituted naphthalimide receptor 4a-E has been synthesized as a selective colorimetric and fluorescent chemosensor for cyanide sensing in aqueous environments through a unique excited-state intramolecular proton transfer (ESIPT) mechanism. The addition of a Br group to the fluorophore skeleton at the ortho-position of hydrazone generates reference compounds (4b-E and 4c-Z). Interestingly, the potential intramolecular NHBr hydrogen bonding might compete with the anion-induced intermolecular NHA- hydrogen bonding, resulting in dramatic ESIPT suppression. The high emission of probe 4a-E and other control probes in solid-state is also investigated. Moreover, probe 4a-E preloaded on test papers, upon cyanide treatment, shows obvious changes in color which demonstrates that 4a-E is a writable platform. More importantly, it exhibits great potential application for the detection of cyanide in food materials and excellent performance in real-world water samples.

Addition of α-Cyanomethylpyridine to Naphthalimide via Trifluoromethyl-Directed CH Functionalization: Cyanide Sensing in Aqueous Media.

A colorimetric anion sensor based on the activated C-H group is described, and the selective and reusable detection of cyanide using the sensor is demonstrated. The system uses bromine to block isomerization and trifluoromethyl-directed C-H regioselective functionalization for direct C-C bond formation between a fluorophore and 2-(pyridin-2-yl)acetonitrile. Thus, this system provides a new way to develop activated CH-based anion receptors.

A reusable cyanide sensor via activation of C-H group: trifluoromethylcarbinol-directed meta-C-H cyanomethylation of naphthalimide.

A fluorescent and colorimetric anion sensor based on the activated C-H group has been developed, and its reusability and ability to selectively detect cyanides have been demonstrated. The system utilizes trifluoromethylcarbinol-directed C-H regioselective cyanomethylation for direct C-C bond formation between the fluorophore and acetonitrile. The present paper also describes a novel strategy for the enhancement of carbanion stability by a potential intramolecular C[double bond, length as m-dash]OH-C hydrogen bonding system, thus providing a new way to develop activated CH-based anion receptors.

Metal-free ß,γ-C(sp3)-H difunctionalization of propanols: DMP-initiated asymmetric spirocyclopropanation.

A DMP-initiated metal-free effective ß,γ-asymmetric spirocyclopropanation of propanols strategy using oxidative iminium activation is described. This process has been realized by a synergistic amine-catalyzed one-pot cascade oxidation-Michael addition cyclopropanation for "one-pot" access to various spirocyclopropyl propionaldehydes/propanols from diverse 3-arylpropanols and α-brominated active methylene compounds under mild conditions and with high enantioselectivity (ee up to >99%).

Asymmetric α-spirocyclopropanation of oxindoles and benzofuranones via dynamic kinetic resolution.

Chiral benzo five-membered heterocyclic spirocyclopropanes are an important class of parent core structures with pharmacological activity. A novel organocatalytic one-pot cascade ether oxidation iminium-ion activation strategy for the asymmetric spirocyclopropylation of benzofuran-2-ones and indolin-2-ones from allyl tert-butyl ethers/ pent-2,4-dienyl ethyl ethers with excellent enantioselectivity (ee% up to > 99) and diastereoselectivity(dr.% up to 91:9) has been developed. This process involves the successful dynamic kinetic resolution of racemic 3-bromobenzofuran-2-ones or 3-bromoindolin-2-ones. Its synthetic application will provide a new aminocatalytic cascade tool for the efficient synthesis of complex molecules.