Zwitterion‐Catalyzed Amino‐Dibromination of Nitroalkenes: Scope, Mechanism, and Application to The Synthesis of Glycinamides

Gearing Effects on N-9-Anth-PyBidine-Cu(OAc)2-Catalyzed Asymmetric Direct Haloimidation Reactions of Alkylidenemalononitriles

A newly developed N-9-anthranylmethyl bis(imidazolidine)pyridine (N-9-Anth-PyBidine)-Cu(OAc)2 complex catalyzed asymmetric haloimidation reactions of alkylidenemalononitriles with N-bromosuccinimide and N-chlorosuccinimide, employing the succinimide moiety directly as a copper-bound nucleophile. The anthranyl substituent showed a gearing effect that produced a well-organized asymmetric sphere involving the N-H proton of the imidazolidine ring in the ligand. The gearing effect afforded hydrogen bonding-assisted copper-catalyzed haloimidation reactions with high enantioselectivity.

Incorporating azaheterocycle functionality in intramolecular aerobic, copper-catalyzed aminooxygenation of alkenes

Despite the maturity of alkene 1,2-difunctionalization reactions involving C-N bond formation, a key limitation across aminofunctionalization methods is incompatibility with substrates bearing medicinally relevant N-heterocycles. Using a cooperative ligand-substrate catalyst activation strategy, we have developed an aerobic, copper-catalyzed alkene aminooxygenation method that exhibits broad tolerance for β,γ-unsaturated carbamates bearing aromatic azaheterocycle substitution. The synthetic potential of this methodology was demonstrated by engaging a densely-functionalized vonoprazan analogue and elaborating an amino oxygenated product to synthesize a heteroarylated analogue precursor of the FDA-approved antibiotic chloramphenicol.

Trialkylphosphonium Oxoborate as C(sp3 )-H Oxyanion Hole Catalyst for Diels-Alder Reaction

We have developed a catalytic protocol for Diels-Alder reaction using trialkylphosphonium oxoborates as oxyanion hole catalysts. The reaction can be operated under ambient conditions. Dienes could easily polymerize under acidic condition. Nonetheless, these acid-sensitive substrates are compatible with the catalytic protocol and the reaction scope covers a wide range of substrates.

Trialkylphosphonium oxoborates as C(sp3)-H oxyanion holes and their application in catalytic chemoselective acetalization

The use of trialkylphosphonium oxoborates (TOB) as catalysts is reported. The site-isolated borate counter anion in a TOB catalyst increases the availability of C(sp3)-H to interact with electron donor substrates. The catalytic protocol is applicable to a wide range of substrates in the acetalization reaction and provides excellent chemoselectivity in the acetalization over thioacetalization in the presence of alcohols and thiols, which is otherwise hard to achieve using typical acid catalysts. Experimental and computational studies revealed that the TOB catalysts have multiple preorganized C(sp3)-Hs that serve as a mimic of oxyanion holes, which can stabilize the oxyanion intermediates via multiple C(sp3)-H non-classical hydrogen bond interactions.

Organobase-Catalyzed Umpolung of Amides: The Generation and Transfer of Carbamoyl Anion

A novel organobase-catalyzed umpolung reaction of amides was disclosed. This method provides an efficient method to generate and transfer carbamoyl anions. In this transformation, some of the inherent disadvantages of carbamoyl metal were avoided. The mechanistic analysis revealed that the reaction proceeds through polarity inversion of amide, and various carbamoyl anions were applied in the reaction. Moreover, a wide range of substrates was achieved with moderate to excellent yield.

Access to Bromo-γ-butenolides via Zwitterion-Catalyzed Rearrangement of Cyclopropene Carboxylic Acids

γ-Butenolides are useful structural motifs in many pharmaceutically relevant compounds. In particular, halogenated γ-butenolides are attractive building blocks because the halogen handles can readily be manipulated to give various functional molecules. In this study, a catalytic synthesis of halogenated γ-butenolides from cyclopropene carboxylic acids was developed using zwitterionic catalysts and N-haloamides as the halogen sources. The catalytic protocol could also be applied to the synthesis of halogenated pyrrolones by using cyclopropene amides as the starting materials.