Dongwei Cai

Simple and efficient resolution of l,1′-bi-2-naphthol

Abstract Acetonitrile is a crucial solvent for a simple and efficient resolution of l,l′-bi-2-naphthol using N -benzylcincbonidium chloride. Both enantiomers can be easily obtained with ≥95% yield and ≥99% ee.

Highly efficient synthesis of α,β-acetylenic aldehydes from terminal alkynes using DMF as the formylating reagent

Abstract The formylation of lithium acetylides with DMF led to α,β-acetylenic aldehydes in excellent yields (>94%). A reverse quench into a phosphate buffer (10% aqueous KH 2 PO 4 ,4 equiv) proved to be the key for this high-yielding reaction.

A STUDY OF THE LITHIATION OF 2,6-DIBROMOPYRIDINE WITH BUTYLLITHIUM, AND ITS APPLICATION TO SYNTHESIS OF L-739,010

Mono-lithiation of 2,6-dibromopyridine by n-BuLi is complicated by deprotonation of the pyridine ring by the resulting mono-lithium species. This problem can be eliminated by a reverse addition, but this causes formation of the undesired dilithio species. However, rapid lithium-halogen exchange between 2,6-dibromopyridine and 2,6-dilithiopyridine produces 2-bromo-6-lithiopyridine cleanly. Thus, using reverse addition, the mono-lithiated pyridine can be generated in 98% yield.

A conformational toolbox of oxazoline ligands

Abstract A toolbox of bis(oxazoline) and pyridinebis(oxazoline) ligands 6, 7, 8 has been used to probe conformational effects in Cu(II)-catalyzed Diels-Alder and Ru(II)-catalyzed cyclopropanation reactions.

Highly efficient and mild synthesis of variously 5-substituted-4-carbaldehyde-1,2,3-triazole derivatives

Abstract Synthesis of variously 5-substituted-4-carbaldehyde-1,2,3-triazole derivatives 2 was accomplished by reacting sodium azide with α,β-acetylenic aldehydes 1 in DMSO at room temperature. Therefore, the reaction remains basic avoiding the generation of the hazardous explosive HN 3 , resulting in a safe process. This mild and general reaction was instantaneous and was essentially quantitative.

Effects of triethylamine in asymmetric reduction using oxazaborolidine reagents

Abstract In the presence of triethylamine, the reduction of ketones using stoichiometric amount of oxazaborolidineborane complex (OAB·BH 3 ) shows increased enantioselectivity.

Effective lithiation of 3-bromopyridine: synthesis of 3-pyridine boronic acid and variously 3-substituted pyridines

Abstract By using toluene as a solvent, 3-lithiopyridine can be generated cleanly at −50°C. The addition of various electrophiles affords useful building blocks, such as the 3-pyridine boronic acid in 87% isolated yield.

Efficient synthesis of 6-mono-bromo-1,1′-bi-2-naphthol

Abstract Through mono-ester formation of 1,1′-bi-2-naphthol (BINOL) with pivaloyl chloride the selective mono-bromination was achieved cleanly on the other ring to afford 6-mono-bromo-1,1′-bi-2-naphthol in an efficient 86% yield.

An improved method for chiral oxazaborolidine-catalyzed reduction of 4-chromanone analogs and MK-0499☆

Abstract Addition of isopropanol to the stoichiometric reduction of ketones 4 – 8 using oxazaborolidine-borane complex 3 or the oxazaborolidine-catalyzed reduction of 4-chromanone analogs ( 1 , 7 – 9 ) enhances the enantioselectivity of the reduction.

AN IMPROVED AND PRACTICAL PROCEDURE FOR THE SYNTHESIS OF SUBSTITUTED PHENYLACETYLPYRIDINES

Abstract A general procedure for the synthesis of substituted phenylacetylpyridines in excellent yields is described using a Horner-Emmons condensation between α-aminoalkylphosphonates of pyridinecarboxaldehydes and benzaldehydes with cesium carbonate at room temperature.