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With the aim of developing novel annulations via ketene intermediates, allenyl imide and alkynoates bearing good leaving groups are used for their function in a tandem conjugate addition-elimination reaction (SN2' type) promoted by nucleophilic phosphine catalysts. By utilizing thioamides as 1S,3N-bis-nucleophiles, [3+3] and [3+2] annulations have been established to allow rapid access to 1,3-thiazin-4-ones and 5-alkenyl thiazolones in high yields, respectively. Furthermore, the possible reaction mechanisms are proposed on the basis of deuterium labeling experiments and density functional theory calculations.

Benzidine was found to be a novel transient directing group to enable Pd-catalyzed direct selenylation of inert C(sp2)–H bonds of benzaldehydes. Diverse diarylselenides were readily constructed in ...

Air- and light-stable electrophilic difluoromethylating reagents, S-(difluoromethyl)- S-phenyl- S-(2,4,6-trialkoxyphenyl) sulfonium salts were successfully developed, and the introduction of intramolecular hydrogen bonds plays a crucial role for the stabilities and reactivities of these reagents. C-selective difluoromethylation of a broad range of β-ketoesters and malonates proceeded smoothly under mild reaction conditions to give good to excellent yields with excellent C/O regioselectivities.

A three-component Petasis-type gem-difluoroallylation reaction of using pinacol gem-difluoroallylboronates, aldehydes or isatin, and β-amino alcohols enabled by the neighboring hydroxyl group in amine is reported, affording various racemic and chiral gem-difluorohomoallylamine derivatives with good to excellent results. Based on the control experiment and stereochemistry of the product, a proposed reaction pathway is illustrated to clarify the origin of regio- and stereoselectivity under protic solvent conditions.

A practical synthesis of the orthogonally protected d- and l-β-hydroxyenduracididines (d- and l-βhEnds), the unique, nonproteinogenic α-amino acids found in mannopeptimycin antibiotics, is described. We appropriately applied d-lyxono-1,4-lactone derivatives as a starting template and investigated two transformations: (i) reduction of the lactone in a two-step sequence and (ii) regioselective ring opening of the benzylidene acetal. By careful evaluation of reaction conditions, multigram amounts of both orthogonally protected d- and l-βhEnds were successfully prepared.

A new kind of functionalized Janus dendrimer has been synthesized via a liquid-phase approach, which could easily be purified using a simple precipitation method without the need for chromatographic separation. Their use for liquid-phase organic synthesis has been achieved in the Pd-catalyzed Suzuki coupling reactions, giving biaryl products in excellent yields after cleavage.

In response to Berkeš's report revising the stereochemistry of HPA-12, an important ceramide-trafficking inhibitor that was discovered and synthesized and its stereochemistry determined in 2001, the synthesis and the stereochemistry were reinvestigated. A large-scale synthetic method for HPA-12 based on a Zn-catalyzed asymmetric Mannich-type reaction in water was developed. Single crystals of HPA-12 for X-ray crystallographic analysis were obtained from ethyl propionate/n-hexane, and the stereochemistry was definitely determined to be 1R,3S, consistent with Berkeš's revised structure.

The first chiral Lewis acid catalyzed enantioselective Friedel-Crafts alkylation of pyrroles with beta-CF(3) acrylates has been investigated, which afforded various types of chiral trifluoromethylated compounds in excellent yields (90-99%) with high ee's (up to 99% ee). With the aid of the Friedel-Crafts reaction adduct, optically active trifluorinated heliotridane was successfully constructed.

[reaction: see text] Phosphine dendrimer-stabilized palladium nanoparticles were synthesized and found to be highly effective for Suzuki coupling reactions, affording good to excellent product yields, high turnover number (up to 65,000), and excellent reusability (up to 9 catalytic runs). Furthermore, these Pd nanoparticles are efficient and selective catalysts for hydrogenations.