Wen-Chung Shieh

Large scale microwave-accelerated esterification of carboxylic acids with dimethyl carbonate

An environmentally friendly process for the esterification of carboxylic acids with dimethyl carbonate can be accelerated by employing a combined strategy: using 1,8-diazabicyclo[5,4,0]undec-7-ene (DBU) as the catalyst (chemical means) and microwave as the energy source (physical means). This approach provides synthetic advantages, niches, and upscalability.

DABCO- and DBU-accelerated green chemistry for N-, O-, and S-benzylation with dibenzyl carbonate

Abstract An environmentally friendly process for the benzylation of nitrogen, oxygen, or sulfur atoms with dibenzyl carbonate has been developed. Catalytic amounts of DABCO or DBU can accelerate this ‘green’ alkylation.

Accelerated benzylation reaction utilizing dibenzyl carbonate as an alkylating reagent

Ionic liquids can effectively accelerate slow N-benzylation reactions utilizing dibenzyl carbonate as an alkylating reagent. By applying microwave irradiation in the presence of the same ionic liquid, additional rate enhancement was accomplished.

Asymmetric reduction of ortho-substituted benzophenones with B-chlorodiisopinocampheylborane: A convenient synthesis of enantiomerically enriched benzhydrols

A very efficient synthesis of chiral benzhydrols from ortho-substituted benzophenones is described which presumably utilizes a heteroatom-directed, intramolecular asymmetric reduction of ketones with B-chlorodiisopinocampheylborane.

A SIMPLE, RECYCLABLE, POLYMER-SUPPORTED PALLADIUM CATALYST FOR SUZUKI COUPLING—AN EFFECTIVE WAY TO MINIMIZE PALLADIUM CONTAMINATION

ABSTRACT To address the challenges encountered in homogeneous catalytic processes, such as the minimization of metal contamination and the recycling of the catalysts, a polymer-supported palladium catalyst for Suzuki coupling was developed. The application of this heterogeneous palladium catalyst to the synthesis of a novel, amino-tetralin type, pharmaceutical ingredient led to a very low residual palladium content (<1.1 ppm).

A Scalable Synthesis of an Azabicyclooctanyl Derivative, a Novel DPP-4 Inhibitor

A practical synthetic strategy to a chiral azabicycclooctanyl derivative (1), a potent DPP-4 inhibitor, starting from a commercially available nortropine is described. The stereogenic center of 1 was established employing a modified protocol of Ellmans diastereoselective addition of a benzylic nucleophile to tert-butanesulfinimine. Other key steps include Corey-Chaykovsky reaction, Meinwald rearrangement, and CDMT-promoted amide bond formation involving a sterically hindered amine 2.

An enantioselective synthesis of (R)-4-piperidinylglycine

Abstract An efficient process for the synthesis of ( R )- N - t -Boc-4-piperidinylglycine 8a , an unnatural amino acid, via enantioselective rhodium-catalyzed hydrogenation of the Cbz-enamide 5a is described. Subsequent deprotection of 8a affords unprotected ( R )-4-piperidinylglycine 9 in good yield.

A novel kinetically-controlled peptide synthesis—Dramatic increase of chemical yield with retention of chiral integrity

Peptide synthesis empolying the highly selective reaction of isobutyl chloroformate at the carboxyl group of the N-protected amino acid, almost to the exclusion of the amino group of the C-protected amino acid, is described. This one-stage, kinetically-controlled strategy remarkably affords peptides with excellent optical purity in high chemical yields.

A Facile and Green Synthesisof a Naphthyridine Derivative: A Novel Hedgehog PathwayModulator

A green and highly efficient synthesis of a naphthyridine derivative, a novel hedgehog pathway modulator, in high yield and purity from inexpensive starting materials is described. The key step involves an acid-promoted aryl amination reaction of aniline with naphthyridine halides.